STANFORD ARTIFICIAL INTELLIGENCE PROJECT Memo No. 14

June 15, 1964

COMPUTER CONTROL OF A MACHINE FOR EXPLORING MARS

by John McCarchy Computer Science Division

Stanford University

Abstract: Landing a 5000 pound package on Mars that ,,,auld spend a year looking for life and making other measurements has been proposed . We believe that this machine should be a stored program computer wi th sense and motor organs , and that the machine should be mobile . We discuss the following pOints :

1 . Advantages of a computer controlled system.

2. What the computer should be like .

3. ,,!hat we can feasibly program the machine to do given the present state of work on artificial intelligence.

4. A plan for carrying out research in computer controlled experiments that will make the Mars machine as effective as possible.

The preparation of this memo has benefited from discussion with E. Fredkin, J. Lederberg and M. L. Minsky.

The research reported here "'as supported in part by the Advanced Research Projects Agency of the Office of the Secretary of Defense (SD -183)

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COMPUTER CONTROL OF A MACHINE FOR EXPLORING MARS

by John McCarthy Computer Science Division

Stanford University

In 1969 or 1971 we can land 5000 pounds on Mars. The machine we land can have 300 watts of power, can communicate from 10,000 to 100,000 bits per second back to earth according to the distance between earth and Mars. The machine should be able to operate for a year. These facts were taken from a General Electric study called Beagle after the ship that took Darwin around the worldo The Beagle study does not discuss the possibility of making the machine mobile, but we believe this can and should be done even if the power limitation makes it go very slowly. We shall follow G. E. 's lead and call the machine the Beagle.

The Beagle should obtain as much information as it can about Mars and radio it back to earth. Naturally, the most interesting question is whether there is life on Mars and if so what it is like. Therefore, we can set forth three goals.

1. To carry out as thorough a search for life as possible, i.e., to maximize the probability that if life exists on Mars, Beagle will find it.

2. If life exists to find out as much as possible about its chemistry, physiology, and ecology. Chemistry will be emphasized because the same means that detect life may also be used to study its chemistry.

3. To find out anything about the environment of Mars that will help future exploration, especially manned exploration.

Why Computer Control of the Beagle:

Up to now space probes have consisted of a collection of separate experiments sharing propulsion power supply and telemetering. We believe that Beagle will be much more effective if it is a computer with sense organs and motor organs and the experiments are represented by computer programs each of which uses the sense and motor organs in a co-ordinated way. Beagle differs from previous space experiments in a number of ways that are relevant to this preference.

Ie A large number of sense and motor organs can be included in a 5000 pound machineft

2. Many of the experiments can use common facilities of manipulation, picture recognition, etc~

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30 If Beagle works for a year the results of the early experiments will make changes desirable in later ones o

These needs of the Beagle mission can best be met by a computer controlled system. A brief statement of the reasons follows:

10 The control circuitry of each sensory or motor device can be reduced to a minimum if the whole system is computer controlled.

2. The strategy of each experiment can be chosen freely by writing suitable programs even after the hardware decisions have been made.

30 New programs can be written and transmitted from the earth even after Beagle is on Marso

The Computer and Its Programming:

In this section we shall discuss the features that the Beagle computer should have.

10 It should be light, compact, fast, have a large memory, and be reliable. We shall not discuss how these features can be achieved in this paper, but many companies are working on the problems involved, and we are quite sure a suitable computer will be available.* Suit­able parameters might be

1.1 weight - 100 lbs. 102 volume - 2 cu~ feeto 1 .. 3 memory cycle 1 !-L sec _. add instruction 2 !-L sec -

floating multiply - 10 ~ sec. 1.4 power consumption - 40 wattso 105 memory 130,144 - 48 bit words3

If these goals are too hard to meet, some compromises are possible, but even higher performance might be helpful ..

2. If possible, the system should nat use mechanical secondary storage, e.g. tapes or drums. They make reliability difficulto

3. The system must be able to recover from programming errors in programs that carry out particular experiments" Otherwise, it will be impossible to allow the wide variety of programs necessary to make use of the flexibility of a computer based system" In particular, it would be difficult to allow the revision of programs from the earth on the basis of preliminary experimental results if an error in such a revision could cripple the whole machine ..

* I donlt want to suggest that reliability will come automatically, only that I donYt have anything important to say about ito

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The ability to recover from programming errors can be achieved by the same devices as one beginning to be used to make time-sharing monitor systems proof against user errors~ The necessary features are avail­able on the Digital Equipment PDP-l and PDP-6 computers, on the IBM 360 computer and partially on the IBM 7090 and 7030 computerso In fact, the Beagle computer should be operated with a time-sharing system, although the Beagle monitor must differ substantially from time-sharing systmes oriented towards computation centerso The important features of time-sharing systems are the follow.ing:

10 The system has a user mode and an executive modeo When in user mode the use of input-output instructions is inhibited and attempts to change memory outside an area reserved to a particular program leads to interrupts to the executive programo

20 A clock leads to an interrupt of the executive every so often anyway 0 (Say, every millisecond)., The executive then decides what program should be executed next for a quantum of ti.me 0

;0 Input or output devices generat.e i.nterrupts to an appropriate part of the executive program whenever input becomes available or an output device is ready for more o

The core of the execut.ive program must be absolutely debugged, but protection can be provided against errors in large parts of the executive (eogo, the programs that handle input-output devices) by allowing earth generated interrupts to a part of the executive that can be instructed to make changes in the rest of ito

We envisage the program to be dlvided into four partso

10 The time-sharing executive - divides the time among the application programso

20 Housekeeping prqgrams" Handle communication wi.th earth, temperature control management of the energy and supply, control of the motion of the machineo

;0 Programs for operating deviceso Used as subroutines by the pro­grams that run experimentso Normally contain checks to make sure the devices are not damagedo

40 Programs for running experiments 0 These are written under the supervision of the experts in the field in which the experiment is performed., The time-sharing system permits them to be wri.tten inde­pendently of each othero

Mobilitx::

The effectiveness of the Beagle will be greatly enhanced by mobilityo There are two difficulti.eso }i'irst, a'1 average power of 250 watts will not

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move a 5000 lb. vehicle very fast, and not all the power is available for that purposeo Second, the motion cannot be directly controlled from the earth because the response delay varies from a little over six minutes to almost 25 minutes 0

The first difficulty can be overcome by accepting very slow progress (e.g., 10 cm/sec to 100 cm/sec depending on terrain) at times when the experiments and information transmission require very little energyo The second problem rmst be solved by developing computer programs capable of steering the vehicle past obstacles over different terrainso

Mobility is important for the following reasons:

10 Beagle might land in an unsuitable place, e.g. on bare rock or in a ditch.

20 Beagle should be able to look for high points from which to transmit pictures of the landscape 0

3. Features that looked interesting in pictures could be examined at close range 0

40 The search for life will be more effective if Beagle can go look for ito

Artificial Intelligence:

Research labelled artificial intelligence is aimed at making computers perform tasks that require intelligence when performed by humans 0 The exploration of Mars involves many such tasks. If the artificial intelligence problem were completely solved we could expect to send a computer to Mars with no control from earth and have it send back all the information that could be acquired by a large manned expedition. In fact, it is very unlikely that results comparable to manned exploration will be achievable by computer controlled machines within the next twenty years. However, many of the subsidiary tasks are within or near the present state of the programming art especially if the machine can be instructed from the earth if it gets stucko

Some of the tasks are:

10 Controlling the telemetering so as to submit information at the maximum rate compatible with the orientation of Mars and the distance from Mars to earth. Information of lower priority can be saved for later transmission at times when high priority messages have to be sent.

2. Compression of informationo Sending only deviations of an instrument reading from its expected value based on previous readings. Picture compression is more difficult but some results have been achieved.

30 Picture recognitiono In various forms, picture recognition is required for a number of Beagle's tasks. Some of these are:

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301 Recognizing types of terrain and obstacles so that Beagle can obey orders to moveo

302 Recognizing the lands of materials it has been ordered to collect for analysis o

303 Co-ordinating the devices that pick up samples and subject them to analysiso

40 Motor co-ordination, co-ordination of the IIhands" and wheels and IIlegsffo

50 Other experimental strategieso

The assumption that the computer can be programmed to achieve the above goals relies heavily on the ability to reprogram it from the earth when unexpected conditions are encounteredo We do not expect the state of work in artificial intelligence by 1970 to make the following feasible.

10 To put in the program our concepts of what is interestingo

20 To define life well enough so that the machine would recognize any form of ito

30 To make the program adaptable to any terrain without further instruction. eogo, swamps or mountainso

Projects:

The problem of making good use of a 5000 pound payload is very difficult 0 A number of investigations should be started right away if the Saturn V rocket is to be used when it becomes available 0 Some of these projects are:

10 Design of a suitable computer 0 We assume that the work on small, light, reliable and fast computers with low power consumptions is pro­ceedingo We are less confident that the computer companies will come up with system designs suitable for the sophisticated programming that would be required. The Stanford Computer Science Division would be interested in helping with the order code, input-out structure, and system program design for such a computer~

20 Artificial Intelligenceo Anything that can be learned about how to make machines behave intelligently will eventually be of use in unmanned planetary exploration~ The most critical problem for Beagle, however, is the visual pattern recognition necessary for selecting and picking up samples and for steering a vehicle past obstacles to a goalo The more we can achieve in general purpose manipulation the less it is necessary to rely on Rube Goldberg contr&ptions for raising antennas, picking up s~mples, righting the machine after landing, etc.

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30 A qample cqllector~ The mechanical engineering of a device for picking up and breaking and crushing samples should be undertaken soon.

40 A vehicleo The low power that is likely to be available calls for a special vehicle designo For example} a crab that uses the same organs.for mobility and for picking up things may be appropriate.

We believe that work aimed at a prototype Beagle that can be tried out on earth should be started as soon as possibleo We are eager to help with this~

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,s.

THE SEARCH FOR EXTRATERRESTRIAL LIFE

-A Program for the Biological Exploration of Mars-

I'. Summary of Report; Outline of Proposed National Program.

II. EXOBIOLOGY

IIa. Preamble; Outline of the Area of Inquiry (Lederberg, Pittendrigh)

lIb. Summary of Present Knowledge (Sagan. Shneour)

IIc. Major Goals in the Biological Exploration of Mars (Vishniac)

III. PURSUIT OF THE ANSWERS

IlIa. Theoretical Constraints (Lederberg)

IIIb. Astronomical and Engineering Constraints (Sagan; Levinthal; Lederberg; Rea)

IIIc. Sterilization and Quarantine Constraints (Atwood)

IIId. Approaches to a Comprehensive Program (Sagan; Levinthal)

IIIe. The Proposed Program.

IV. THE PROGRAM IN PERSPECTIVE: Costs and Justification

IVa. The Scientific Justification (Horowitz; Pittendrigh)

!Vb. Costs and Political Justification (Lederberg)

!Vc. The Inherent Political Hazards (Pittendrigh)

V. ANTHOLOGY OF SELECTED LITERATURE; and BIBLIOGRAPHY (Shneour)

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. II. EXOBIOLOGY

IIa. Preamble; "and Outline of the Area of Inquiry (Lederberg, Pittendrigh)

II. EXOBIOLOGY

lIb. Summarv of Present Knowledge (Sagan, Shneour)

(i) Planetary Systems; origins of; frequency of; chemical evolution of planets and their atmospheres

(ii) Inorganic Syntheses of complex molecules

(iii) Theories of the origin of life

(iv) Potential homes of life in the solar system Environmental limits for life Provisional exclusion of all but Mars

(v) Mars as an abode for life Chemistry of; Temperatures; Atmosphere; seasons, etc., etc.

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II. EXOBIOLOGY

IIc. Major Goals in the Biological Exploration of Mars (Vishniac)

1. In general the testing of hypotheses about chemical evolution and the origin of life

- and particularly the significance of a demonstration that life has arisen twice independently in one solar system

2. Further knowledge of the Martian environment

- i~portant for significance of possible negative answer to (4.) below

3. What level of chemical evolution has the Martian surface attained?

4. Are there living organisms on Mars?

5. If there are, then: ~fuat genetic system lVhat energy transfer system etc., etc.

- towards a general comparative study with terrestrial organisms; especially as this bears on the question of the independent origin of Martian life.

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.... . --;

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III. PURSUIT OF THE ANSHERS

IlIa. Theoretical Constraints (Lederberg) (cf."Signs of Life")

Problems in definition of, and operational criteria for the detection of life

- including, e.g., possibilities of non-carbon bas~d life, etc.

Entropy approach; chemical complexity and abundance.

Optical Activity

Macromolecules Structural Functional

) ) criteria

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III. PURSUIT OF THE .ANSHERS

IIIb. Astronomical and Engineering Constraints

IIIb-i. Martian opportunities (Sagan, Haughey)

IIIb-iio Available and Foreseeable Vehicles (Levinthal, Haughey)

The vehicles Their payloads

costs time-table of availabilities

11Th-iii. Instrumentation and Detection Hethods

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1. Some comments on 111etrology" (Lederberg)

2. Available methods (Rea) e.g., spectroscopy, etc.

3. Available and foreseeable exobiological instruments and probes (Levinthal)

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III. PURSUIT OF THE ANSWERS

IIIe. The Sterilization and Quarantine Constraints (Atwood)

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II I. PURSUIT OF THE ANSli7ERS

IIId. Approaches to a comprehensive program (Sagan, Levinthal, Brown)

(i) Evaluation of potential yields from:

i-I. The available instrumentation and methodology (Sagan)

i-2. Balloons and Terrestrial Orbiters (Sagan) e.g., Better data on Mars

i-3.

i-4.

i-S'.

i-6.

i-7.

Evaluation of instrumentation by scrutiny of the know'n conditions on earth.

Planetary Fly-By (Sagan)

Planetary Orbiters (Sagan)

Planetary probes; Hard Landers (Levinthal)

Planetary Soft-Landers; unmanned (Levinthal)

Planetary Soft-Lander; manned (Levinthal)

Evaluation cost vs yield in each case; hO,\=1 far will the yield from the simpler approaches cont~ibute to better design and success of the more complex and expensive approaches; it is conceivable 'V7e should dispense with the simpler approaches and invest all in large landers.

(ii) Evaluation of the Uniqueness and Urgency of the 69-71 Opportunities (Brown)

Do '\'7e go all out for 69-71? Hhat hazards (especially political) are involved in adopting a IJ crash" approach? If we adopt it - 1vhat vehicles, etc?

~fuat hazards (e.g., Russian contamination) and what advantages are there in rejecting ,the crash, approach, ignoring the uniqueness of 69-71, and going more slowly?

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III. PURSUIT OF THE ANSHERS

IIIe. The Proposed Program

The development of this section is of course the main task of the Study; and the following notes are intended as nothing but suggestions and indi­cations of the kinds of things we will have to include.

1. Ground-Based Hork

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a. Support of theoretical and experimental vlork directed to the problems of the origin of life.

b. Sterilization and quarantine methods; 't·]hat still needs to be done; hOvl to do about it.

c. Continuing studies of engineering, instru­mentation, and payload design problems; specified as fully as we reasonably can; how these studies should be organized; fixation of responsibilit~for sustaining the program. Should thergbe Summer Study in the next, and succeeding, years on purely engineering detail and payload design?

d.. l"'!eteorite work?

e. Other?

2. Flight Program

A likely conclusion is that 't'le cannot attain any of the major goals itemized under IIc. (p. [I-) 'tvithout a ¥~rs landing mission.

We must then consider: vlliat is the minimum lander mission? Hhat is the optimal lander mission? iihat arrays of experiments should be included? l'lhen and in what sequence should possible

landers be attempted? lVhat recommendations do we have on preliminaTY

non-landing missions?

The most important aspects of the recommended program will be its size and the timing of it; how much, hov7 fast? And in fixing on these features we shall have

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III. PURSUIT OF THE ANSHERS

IIIe. 2. Flight Program (continued)

we shall have to bear in mind the political aspects alluded to in section IV. We shall have to face the questions: Do '\-7e now have, or can '\ve confidently foresee, a sufficit2i::.t number of clean cut questions to which answe.rs are obtainable with available methodology to justify the cost of proposed landing missions, and the risk of co~amination before a definitive judgment on the pr~sence of life can be made.

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'''' IV. THE PROGRAH IN PERSP~CTIVE

The following notes ~?-re not intended to outline the organization of this section; but-rather to indicate the range of topics to be handledo

(a) The Scientific Justification (Horowitz, Pittendrigh)

1. E.g~, address ourselves to the Simpson type argument: given the accepted (even Simpson) possibility of life on Mars the issue becomes: are 'tole pessimistic conservatives

or do we seize the challenge and insist on the sense of adventure in science.

2. Some further comment (really insistance) on the scientific significance (especially of the positive answer about - ) life on Mars.

3. The general yield to biology of all that is involved in pursuing the goal - even if no life is found.

E.g., instrumentation development - the stimulus to theorv; about nature and origin of life.

4. Groundwork for any later exploitation of Mars.

(b) Costs and Political Justification (Lederberg)

1. Ackno't'rledgment of (and estimate of) ~.igh cost - but the problem of estimating true cost in deciding to go ahead; e.g., fact that the Space Program is already a given national policy decision; the rockets will be built anyway

2. The political naivity of complaint that the money would be better spent on: hospitals" professorships (Harren 'Heaver); systematics (~ Simpson); water table problems (Kusch), etc.

3. Only very brief al~usion to: The econowics of disarmament and the economic significance of the Space Program; and the question of deflection of scientific ma.npower.

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IV. THE PROGRlU1 IN PERSPECTIVE (continued)

(c) The Inherent Political Hazards for (a) science in general (b) attainment of our own goals

inherent in premature, half-baked attacks on the problems; and in the danger of e~rly negative results.

(d) Relative Merits of Exobiology vis-a-vis other aspects of Space Program.

v. ANTHOLOGY OF SELECTED LITERATURE: and BIBLIOGRAPHY (Shneour)

Your list of what you consider important papers and reports (with exact references)~will be greatly appreciatedo

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Space Sc1enco Board ExoblolW;y SUll"u"ner Study

DRAFT

S I.GNS OF L I FE

A Survey of the Detection Problem In Exobiology

by •

Joshua Lederberg Department of Genetics, Stanford University. Medical School

Introduction

I The maturation of exobiology calls for increasing attention to the systematic statement of its theoretical basis and its operational methods. Very little sci ence Is tota 11 y i rre 1 evant to I t and the policy-maker faces the danger of utter confusion in reacting to a flood of Isolated proposals for the development of spaceflight experiments. The stakes of such a large enterprise even demand

· Investment In new methodologies requiring further emphasis on the choice of valid goals, rather than available means which are tolerable bounds to more In­dividualized efforts In other fields. A system should help dispel this confusion and rationalize the division of labor, the only means of reducing a complex problem to manageable parts.

As a target Mars takes first place In our present thinking, yet our premlssed information Is only (I) terrestrial biochemistry, (2) the Inferences from labelling Mars as a "terrestrial planet", and (3) a very small body of definite observational data. Thus the choice of our first experiments must take account of a wide range of theoretical possibiliti es. Our speculation will be narrowed

'and therefore simplIfIed by any tangible Information about Mars, even much that may seem to fall outside the domain of biolo~y • . Such Information is IncreasIngly valuable If (as most global studies overlook) It encompasses .the variability of the ' planet's features In space and tIme.

, Evol utlonary Stages

" Fundamental to all biological theory, eso- or exo-, Is the evolutionary principle. As Is now commonplace, we name the following stages In the Earth's history,

A. · Chemogeny (Organic Chemistry)

The productIon of complex organic compounds by a variety of ~-repllcatlve mechanisms - the primitive cosmic aggregatIon, photochemistry of insolated atmospheres, thermal, Inorganic-catalyzed, and spontaneous reactions of previously formed reagents.

B. Blogeny (Biology)

The replication of a specifIcally ordered polymer, e.g., DNA, whIch speci­fies the · sequence of its own· replicates, and of RNA and proteins, from which cells and organisms are fashioned. Random experiments of error In

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'repllcatlon, and natural selection of theIr developmental consequences, result In the panoply of . terrestrial life.

t. Cognogeny (History)

'The evolution of the mechanisms of perception, computation and symbolic ex­pression whereby Interpersonal communication can occur and traditIon can accumula~e" I.e'. cui ture.

Mars must be supposed to have had an earlier history similar to Earth. Our ques­tion Is then, how far has Its chemogeny gone; how like and how unlike the Earth's; has Its evolution passed through the biogenic (ordered macromolecular) stage? Then through the cognogenic?

1n evaluating a complex set of possibIlIties It Is helpful to fl.nd a classifying parameter that can be scanned systematIcally, If sometimes only Implicitly, to generate a probabIlity space. In this case" the evolutionary princIple furnishes the parameter: chemIcal complexity_ Of all chemical possibilitIes" terrestrIal 11 fe compr I ses a set of cho 1 ces: to \o/hat stage of complex I ty has Mart I a 1 evo 1 u­tlon progressed, and at what levels has It diverged from the terrestrial?

For other planets, for example Jupiter" the hypothesis of ultimate divergence Is more plausible than for Mars. If only to evade perplexity how to deal with a totally unspecified' situation, we state" but pass over the posslbllty of a non­aqueous or non-carbonaceous system" that Is we postulate that Martian life Is predicated on chemical linkages, predominantly -e-e-, -C-O-" -e-N-, and -O-P-"

: that are barely stable In aqueous medium. We leave to hypothesis the extent to whl:h the constructions from these radicals emulate terrestrIal biochemistry 'at each level of complexity. '

;qq~mogeny generates a vast mix of products through the level of random macro-• mOl ecul es. Whether or not I t had progressed to b logeny Mars must have nurtured ,'such chemistry. A negat Ive assay for organl c material s woul d precl ude blogeny, but would properly be ~lamed on defIciencIes In the particular sample. The positIve assay" If It told something of the concentration and composition of

,organic molecules" would add' to our understanding of Mars' development" and would contribute to our judgment of the life-detection problem. But It would not answer It. On tbe other hand, once life has appeared on'a planet, It would dominate Its organic chemistry - most carbon compounds would be witnesses of bIogenic (or cognogenlc) specificity_ The description of organic molecules has at least

I the 'second-most priority In exobiology.

A scan of chemical en~ltJes poInts up many conceivable data hard to reconcile 'with chemogeny" and thus Imply blogeny, or co¥nogemy., ,The simplest example: Suppose a specimen of water contained ,pure H (to the exclusion of. deuterium).

,Such samples do exist on Earth, but'the probability that a randomly chosen sample wll1 have such a striking artifact Is small", smaller stt.ll If we prefer not to take account of the products 'of cognogeny.

, The ehemlcal scan

·To publish a complete scan th~ou9h chemIcal complexity mlght be as witless as It Is pretentious for' anyone person to attempt. However~ segments q,f such a scan

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; are challenges to the imagination of the special tstl as t~e scrutiny of the first , e~emfnt" hydrogen" already hopefully suggests. Just what discrepancies In the H IH ratIo In a Mars sample would be beyond simple (chemogenlc) explanation? How would one Interpret such a finding from a terrestrial foray? What are the simplest Instrumental means of makIng such a measurement? What are the ranges of biogenic, of cognogenlc systems that might be expected to generate discrepant samples? \~ha,t Is the probabl,llty of detecting such a sample?

Intuitively we judge this probabIlIty very low, but this Is a tentative Judgment mainly based on terrestrial experience (the market price of pure protlumJ)., We

: cannot formally prove the Im~osslblllty of natural fractionatIon processes as an 1 alternative to blogeny, without specifying the local circumstances.

The entroey argument

, More Important than the particular nuggets that we mIght hope to find by a systematIc scan are the generalizations that Impatience or weariness might Impel •

. :, GIven the evolutionary continuity of life and our understanding of the organism : as a chemical machine, t~ere can be no absolutely distinctive signature of life. , Some conjunctions - like a planetary depot of protium - would be so unaccountable - to our present model of chemIcal behavlos· that we would feel obliged to postulate

the operation of a goal-directed system (blogeny or cognogeny) rather than accept the Improbability of such a conjunction by chance. This choice plainly depends on our freedom of choice of models. For example, our present knowledge of chemo­geny permits a wide latitude of hypotheses as to the range of molecular species

; t~at atmospheric photochemIstry mIght generate. Further developments In our , knowledge of chemogeny or of the available chemical and physical resources of M~rs might confer useful constraints on the-date that might be "explained away" Sf chemogeny, and thus cannot make a critical contributIon to our search.

,~m terrestrial experience we Judge that the occurrence of any of a number of compounds In hIgh purity Is a sign of life. Such deposits at a microscopic level are even more likely to signify cognogeny - a smelter, a chemical laboratory, a communications cable, than biogeny - organic structure usually being built of microscoptcally defined components. Pockets of entropy are not unique to life, however, and only the details of experience or confident use of avaIlable theory

I can decide whether the eddy has a chemical-kinetic explanation or a blo- or cogno~ genetic one. Lacking our experIence, a MartJan visitor might credit the assocl­atlon of diamonds to some mysterious bIogenetic func,tlon, Inh'lblted by V chromo­somes; If he were cleverer, to the General Electric Company. He would need very special knowledge of 'the Earth to predict they would be, found in the ground.

: The entropy argument can be generalized further to Improbability values In an open system.' Thus the acc~mulatlon of kinetical'y unstable materials (tn the' context of local chemIcal and physical conditions) would also call for a special explanation. For example, an accumulation of photo'sensltlve pigments (witness terrestrial chlorophyll) requires special attention to the magnitude of, plausible', synthetic processes'(atmochemlcal vs. blogenlc)-by which their steady-state con­centration could be maIntaIned. Analogous reasoning would apply to compounds that are thermolabile in relation to the ambient te~perature, or chemIcally un­stable species that should reach equll Ibrl,um with oxlda,nts and other reagents.

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Optical activity

:' The discrimination of optical Isomers Is the most promising entropy pocket turned up by the chemicai,sca~. In fact~ for any carbonaceous (more generally, tetravalen~) system, s~,bs~antlal net optical asymmetry is virtually equivalent

,to biogeny_ Our, fund~mental definition of blogeny Is the well-ordered macro-I rnol~cule (we have stl1 l, to'dlscuss a direct approach, to its detection). \~hen tet~a~alent carbon Is Incor,porated into macromolecular structure, each carbon sta~ds a re~sonable risk of being asymmetric, of having a distinctive substit­uent on each of its four vaJences. Such an atom is subject to stereo-(optical) 'Isomerism, and its orlentat~on.l' 0- or L-, must be specified If the macromolecule is tQ be ordered, more concretely, if it Is to have a well-defined three­dlme~lonal shape. Conversely, biogenetic macromolecules, having ordered asym~tric centers, have the necessary information to discriminate among the isome"s of monomeric substrates. It Is less obvious why only L-amlno acids are used tor terrestrial proteins. The Intercalation of a 0- amino acid would be a newt~lentent of versatility_ We may know better when the rules of polypeptide

, confo~atlon are better known. Or the answer may be in the details of evolution of amino acid anabolism and problems of discrimination of analogs. Howbeit,

, optical Isomers will not'occur at exactly the equivalent concentrations In any biogenic system. The theory has ample support from terr~strlal experience. The ratio of D-glucose to L-glucose on the Earth must be better'than 1015:'1.

, In addition to the theoretical generality and historical tradition of the 'Pastorlan principle, the criterion can be applied to any organic molecules or an aggregate of them. Paradoxically, optical actIvity Is Instrumentally a weak measure and Its historical preeminence mIght do 111 service by obscuring the basic criterion: a statistical pr~ference beyond chance or weak chemical effects, among asymmetry Isomers. The matter Is dIscussed further und~r Instrumentation.

Signals

The main tack of search for cognogeny Is the scrutiny of radIation emanating i from the planet rather than from Its chemIcal composItIon. But sImilar consider­

atIons apply to the ,detection of Intelligent signals: If the coherence or mono-I chromaticity or modulation pattern or other regularity of the signal defeats

our efforts to attrIbute It to some naturalme~hanlsm, we ,have only the alter­native of purposive behavior. ,The spontaneous emissIon of a prime number series; even more, an Intelligent reply In dIalogue are extreme examples, but stIll fall within this crIterion. '(A codIng theorem remtnds us,' however, that the most efficient communication of Information Is by defInitIon" IndIstinguishable from noIse to the unbr,lefed eavesdropper.) , , '

Flyby or orbiter mIssions may be more efficIent at, detecting the radIation signals and 1~rge-scale topographic modIficatIons expected of cognogeny. Landers may well be planted on Mars before there has been extensive surveillance to settle this question, and sImple assays for "anlmal", especially cognl tlve life should not be overlooked. These mIght range from Ideographic descriptions or the origin and scIentIfic purposes of the experiment" and InstructIons how ,to modulate the 'telemetry; "Martians" please press the black button, do not press the red oneil, to nIght-lights" mIcrophones, and acceleratIon detectors.' The lattE,t '.In parti­cular should be able to discrIminate between some classes of ,physical 'events -for example, sudden Impacts -,from those eharacter:-t'stlc'of manipulation by an

'. anImal. With the'suggestlon that this problem ~as not received t~e attention

4

It deserves" we leave Its f~rther consideration ,to other occasions.'

Macromo 1 ecu I es

, Macromolecules of well-defIned, Information carrying order bound chemogeny from . blogeny. The replIcatIon of such macromolecules (genes) and the posslbl'llty of

random error (mutatIon) opens the door to natural· selection and the evolutIon of more and more complex forms of lIfe. The most direct challenge of exobiology Is the assay of InformatIonal macrorrDlecules. A random polynucleotide Is not life; routes to Its photochemIcal synthesIs from sImple ga~ses and Inorganic phosphate are in sight. But',we might find evidence of Its replIcation" either by dl~ect observation" or by finding a sIgnificant concentration of replIcas of the same sequence. The sequence need not be the gene Itself. Macromolecular sequencing Is also manifest In gene products, RNA and proteins. It Is Important that the sequence Imply ordering from a template whIch selects from an abundance','

: of kinetically equivalent choices" not merely a pattern Inherent In the chemistry : of the monomer" as In crystallizatIon.

: The main methodological problems of contemporary molecular biology are exac.tly , those which face this area of exobtologlcal work. ·Thls challenge gives us' the

groundwork for exobiology and assures the full utilizatIon of any Instrumental advances. But It Is a chastening note that biochemIstry has - as of now -perhaps barely reached the point of affIrmatIon that antIbody gamma globulin answers these crIteria In any detail. Indeed" ·some workers dispute that thIs prote1n Is synthesized by the general rule of Information trans~er'from DNA •.

, That this question concerning an abundant and Important.molecule can stIll be 1n dIspute at the present time warns us of our limitatIons 'In answering analogous questions concernlng macromolecules on another planet.

How do we detect Informational macromolecules?

A. Compositional Analysis

1. Demonstration of macromolecules In t~e sample.

2. DemonstratIon of composition and nonrandom ordering In such macromo 1 ecul es. '

1. The most evident approach to A" and the foundation of blochemlstrYI Is the Isolation of macromolecular species from the samp1el and t~etr . . purifIcatIon before attempts at analysis. Practical methods ~re mostly' empirIcal" far from general prln.clples of .wlde application -. various regimes of extracdon and precIpitatIon ~ which does not preclude their usefulness If the sample collection and proceSSing equipment permit.

More rational techniques mainly rely on diffusional propertles.of large molecul es.. free dt ffus Ion .. · sedimentation, dial ys Is" molecul ar' sieves" and electrophoresis" In prlnc1.ple also vapor phase dlffus10n (to remove monomers) -molecular dlstll1atlonl gas chromatography" and mass spectro­metry. Solution chrornatogr.aphlc methods may also rely on the coincidence of functIonal groups on one mol~culel e.g."a polyelectrolyte.

SImilar princIples underly non-separative methods of detectIon ~hleh have not ~eenextens Ively de~~l~ped to date. .Rotatlonal relaxatIon times

: .' .

5

. I

can be measured by flow or electric btrefrlngence~ or the analogous polarization of fluoroescence. Polyfunctlonallty Is tested by Inter­molecular Interactions of adsorbed dyes (e. g. optical shi fts .I'n acridine orange on DNA) or the monomeric units with one another In special cases (hypochromic,ty of DNA" diagnosable upon heat-denaturation). More direct chemical tests for poiyfuncttonaltty also suggest themselves •.

2 •. The previous methods, Insofar as they lack perfect generallty~ may give some clue as to the composl!lQn of the macromolecule~ as well as Its molecular sIze. At the other extreme" \'1e \';01.11 d seek the complete primary structure to emulate the recent tours-de-force of chemical technique. Reasonable Inferences might be drawn from less complete evidence of structural IndIviduality" hard to evaluate In advance: homogeneity In molecular weIght or endgroup analysis, crystal 1 tnlty~ or sharp fraction­atIon by any other.procedure. A sharp X-ray dlagram'of a heteropolymer sample could Imply Its Individuality long before It had yielded to full: ana I ys I s. . ' '. .' '! \

Other partl.al measures. of great utility Include the scission of the polymer by specific reagents, especlallyenzymes~ to give a pattern of zharacterlsttc fragments (the polypeptl~e "f.lngerprlnt") •.

. B.' Functional AnalysIs

. ! i

The uses that blogeny has discovered for macromolecules furnish other avenues for their detection. These functions are all reduclble'to the stereospecifi­city of the polymer In complex formation., The chemical spec,flclty of complex formation then becomes the argument for the structural Individuality of the'" pol ymer.

Function

Auto-Replication

Hetero-Repllcatlon

Morphogenests (Flbers6 Ma~branes, ~eslcles)

Enzyme

Neutraltzlny (In~u~lble " antibody)

Transpor.t (e-g. serum albumin)

Complex with

Incipient polymer (same species) and polymer building monomer Incipient polymer (different species) and polymer bull dl ng monomer _

Formed polymer6. similar specIes

Substrate - catalytic effect Cofactors to form holoenzyme Analogues - co~plexes Inaettve~ qua enzyme

Antigens

HormoneSI ~oxlns

6

" ','

In this list .. the enzymatic functions are partlc~larly promising In, light of their : specificity and amplifying capability. Many enzymes have turnover numbers of 10li­o. substrate molecules per second per enzyme molecule. 'If suitable precursors , .. (nutrients) can be deflne~ .. enzyme ~equences .. , e.g. respiration or, photosynthesis" : ,extend the versatility ,of this approach. Finally .. rep'lcatlon" be It of mole- !

I .,cul~s or eells, offers the larges~ampllflcatlon - a 'sl'ngle bacterl~m could grow' , " Jnt~ tonnage,masses In a few days, ,but might be the most exactIng of the envlron-:' ment.". I. '

Metabolism

'This '\15 an extension of the j:Oncept of testing for enzymatic activity •. Under certain conditions the test,for a sequence of enzymatic reactions, the metabolIc syste~, can exploit the tmprqbablllty of Its simulation by a non-biogenic' process.

i "On th4. other hand" the same condl tlon al so decreases the a priori probablll ty :' tha~ the entire sequence wIll be represented In an.extraterrestrlal specIes. ;, ThIs a priori probability will be greatest, of course, the sImpler the level at ! which the metabolic reactIons are tested: for example" the assimilation of ele-; mentary nutrients, e.'g_ C, N" 0 or p' Into organic molecules. At the next highest ; l~vel of chemIcal complexity, molecules such as H,eO" C02' and 02 and NH3 are among 0' the ~st pervasive metabolites of terrestrIal lIfe, and the choice among them

for search I ng for ev I dence, of the I r convers Ion I nto other compounds will depend mainly on Instrumental considerations. In gene,ral,' the 'more complex the meta­bollte.belng 'tested, the less assurance we would have that It was part of an

I extrater,re,strJal bIogenic system. '

'nstrumentat lon'

! The classification of existing Instruments" or those proposed for analytical pur-! poses Is a task as difficult as It Is urgent. The real aim, • classification of

possible Instruments, requires a total knowledge of physics. However, If human lImitation precludes perfectIon, some system may be better than none" and we can 0

lay one out even If w. cannot exhaustively analyze It. A proposed scan parameter' I s tb~f energy 1 eve I of the trans I t Ion by wh I ch the mo 1 ecu I e I s recogn I zed. , ' .. Fur~her parameters Include whether photons are tn~roduced or emitted, whether " chemJcal'reagents are employed, Including auto-reactions, whether the displacement of· .. ~tate (Including position) of the analysand or the probe Is d~agnosttc" and

, ,lor radiation probe~, whether power, polarization, phase, wavelength, or ~ :/ vector of the probe Is altered as an, Index of the analysis. /

)

Empirically, radiation probes have limited selectivity" but may be of special t value In conjunction with chemical reagents. Absorption (power loss) measure­

ments have dominated Instrumental analysis. But,conventlonal methods rarely stabilize or measure Input power better than 1: 1000, wIth corresponding limita­tions to detectlvlty. For example, optical molar absorptivity rarely exceeds 10' so that 10-8 molar solutions (6 x 1012 molecules In a 1 em3 cell) would gIve the lowest useful signal under the most favorable conditions. By contrast, fluoro-. metric measurement (whIch can exploit shifts In wavelength, flux vector, polarl- . zatlo~ and phase) can easily measure 108 molecules and can probably be extended to l()Afo under favorable condItions. The delicacy of excttatlon methods (whIch could also Include chemIcal" nucleonic and thermal excitation) stems from the measurement of'8 signal against a,nolse bac~ground rather than agaInst the power fl uetuattons of, th~ ,pro,be. "' . . '

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Optical activity is usually ~easuredvia power loss (attenuatIon of polarized light by a crossed ,analyzer): the molar rotations are relatively small" present ". detectlvlty being abou.t" 1015 molecules., " "

". : The mo~t sens.itlve approaches to analysts are "two~stage mechanisms: the "select1ve" displacement of the analysand, then a sensitive detection. In pr"'nclple" such

"methods might detect a single molecule" as In mass spe~trometry: ,m/e 'dlsplace- , ment followed by accelerated Ion detection. The reasoning behind this recommen- " '_ datton can be Illustrate~ by Its applicatIon to optical activIty (ster~o-asymmetry) on a Mariner-type mission. " ,

We assume capture of a dust sample of" say" 100 mg" containing at most 100 ""g of organIc matter" perhaps 1 ""9 (about 10 'nanomoles) of a partIcular species •

. Direct measurement of optical actIvity of such a dl1~te sample Is far beyond, present technique., Typl.cal of the analytical problem Is a very sma] 1 sample

, which" however" has a marked ~Ias" In the .molecular proportions." It m.lgflt contatn, or be converted" Into,,' say 10 molecules' of P-lactlc acid" plus only 'l~ of L~lactlc. DiffusIon technIques can be devised to separate such species" chroma­tography on an active adsorbant" diffusion through an active membrane - even more certaInly after complexlng with an optically active ligand (say Rl R2 R~ 51-) 'gIvIng chemically dIstinct dlastereolsomers. These tactics transfer the pro&lem to the much smaller dImensions of chemIcal Identification.

A scIence of metrology" the orderly study of methods of measurement, remains to be developed. T~e preceding classtffcat'lons" lacking such a thought out theor­etIcal framework" are untIdy" and thus lend less confidence as to their complete­ness than would be desired.

8

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Repor'G oi'

. . :" TEE _l!:.0 EOq ~'JOPJffi~G GROD? ON

!~.ns :S:COLOGIC_!\.'[, ORBITERS

Enl~ard CollegG ObS~l~atory and Smithsonian Astrophysical Observato~~

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Participants: ·Dr" Cu:::;'l S.o.c:;o.u:; Cbei:tms.:o. B.1rv8.rd College 01)8 e1"ve:i~o!"'J·· .

end. Sr.li-tbsOlli8.:J. i}.s·:::...~c-ob.YE:ica.l G~:, ·~e:::ve:ho ... r:y Camb:Cid.[;e, 1.f9,sC2.cb.uSE/G'C,6 - .' \' :

Dr.. FraliJ( D" Drake Space Sciences Divisio~ Jet Propulsion Labora.tory National 11.eronautics and Space Ad.:r~:;::'1istr2.tio!l Pasadena, California

Dr (> Ri chard 14. Goody Blue Hill Netcorological Obse::<y.::cor-y·· Birvard University Cambridge, ~~ssachusetts

~~o Donald Po Hearth Office of Space Science & A:991ico:tic"!s National Aeronautics ana. S})2.CG A&lJi:::J.istJ:'a-;:;ic:1 Hasnington, D .. Co . Mr" John l~~rtin Space Sciences Di ":ris:Lon Jet Propulsion M "'0:; oY:a::..o":{'y National Aerona.utic3 and Sne.C0 _4.dn1inist~..:,.!ci.,)n

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Pasadena, California

Dr .. Hilliam No> Sinton Lm·lell Observatory Flagstaff, _~izona

Nr .. 1,T 0 G" St.:::oud Goddard Space Flight C(;r.:-'c~::· Nationa.l Aeronautics 8.20:0. 8:9':'::;3 }_clrJi:u.is·~::::·,,~·C~·.o:!'

, Greenbelt, J M3.~Jland

Dr .. Andre1'! To Young R9.rvard College Observ.::;i:;o:::-y Cambridge) 1~ssachuBetts

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The l'IlGcting WOoS hGld at the req,v.est of Dro I

Or~ ReJnoldo; of the Eio-t ~. ~

science Proe;rams Division, l'YA8..i\. Rcndqu.arters.1 'lio. discuss DOS si.'ble sc:_erltii'ic

.missions of biological'relevance to be perfo:i.--n:cd. :(:'o:n project2c. 1-:.::.rs o::biters)

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sidel"'ed u..'rllikelYJ but there are promising possioflities i'or c..etermini::J.3

physical :parameters of biological relevance &13 bourJ.;:2E.:ry C01:c.i:::::ions or: the

ecology of Ms.rtian organisms; a.nd elso} for' clE:teeojing surface J?henome~

1-Thien may be due directly to the CJ~ti vities of 1:&trtie.:.'l orG8.nisr.cs 0

i969-19,,"(1 time period is especiully f'oNore.ble) boJeu because o-Z '::::J.12: moder2.te

energy requirements of the 'Gr.ajector~e3J and. bec2..use the so:.:r~~!:lcr!l lle::li-

sphere i·Ta ve· of cl8,rkening 1·1111 1~0e.ch its Ti.JC'.:r:irm.L'11 e)~~ci.1"G lrithin e. rei.! :rcol1t~hs

The princiIlal 2.dv.:lrrt:lGC:~) C.S fS.l" 2.~ "jiclo[:;icc.lly :eel:;;. vant e:<-::pe:cimen.ts

are concerned) of a i<".s.rs ol~bi-cer a:ce (J.) tiSh -co:9ographic9.1 l·esolutiou;

detect seasonal changes on l-t..:cs ~

Because of .Iche im;?o:··ta~ce ;)f "uDe 580.3 C;'lJ.l cn:.;.nS(;. .... :J a lons s cien:~i:fic I

/ lifetime of the orb:L·t;E:~ is highly clesil~c.b~~:,:' e. 3-rnonth lifeci:.:Je being: per-

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haps the minimutJ 8.(;(:~:9t3.blG valvo'::) D.nd a :fo· •. n· .... -to six-month life:-ci:::.Je

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being preferable,. In ordel" to ir;,v8s'tiga"ee t:te 'Y:s.ve of' c...:.:cke:o.i~[;; in its

photometric; polarime-eric) an.a possibly spect.:'''ome'tric v.spect,s, it is im ....

'- portant that the spacecra.ft l)e l.U orbi'G 2.n.d i'unct,iolling 1ihcn ~·:z.TS :::":3 8.t

nearly· ideal ./.cbi ter is one 1-ibich f'ur.ct.iona .I

on helioeentr .c longitude lOou

f'o:;:- c 6-sonth period>. cen'~ered. . \' ", . ' , ~ \'

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2

It is recognizGd that 0. trade-off exists D.wong t'he lifetime of the

orbiter.., the vTeiglTG o.vailal)le io~C' scientific eXl1c:!:'imen.ts, and the de.tu rate

'for cormuunice:tion back "to E8.r-~hc If any of these -three :DP.:':·3.~1;C"Gerc can be "

improved by ·the dovelopmcrrG of fu:ctb.-b9.58d facili"Gie?.7 this improve:neni?

should be strongly encouragcdu

cost of a single spacecruft) very lc.l"ge i:;:;jproVC!TI(;D."bD in g~"oui1c.:.0e.8e.d COIlJ-

munication facilities can be made" it UP"oears t,ha:G i'o~ . ... _ J; . • . .'

''tlnich give u 20'N folcl imJ?roY~ment in the data rate obto.:Lnc.ble from any

given spacecraft in "cne vicinity of 1,1~trG" ThUD.i 1-/ith such a facility) a d.2.t:::..

rate of 30 bits per second rece:i "led lTith cUX':i.:'0U"c::"y-}?lannec 8Cj,u:"r:>:::.z:nt cc.u

be increased" t,o ·600 bits ~er second" I~ sny,Gerious tnought is to be

It is also Teco~n:"Lzed t:t·:.::c ·c1-:.;:; demund. for a circu12::'"' o:cbi t requirl2s

a smaller scientific·puyloaCL ..

orbit im}?lies, elliptical o:;.:·b:~ts .a:ce co:nGj.(;"0~:;:e\l c.cceptablz v

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A polar orbi'~

'\-lith a sielli~icant p:c'Gces!;ion of t:'lc lin(: 'oi' D.l?sides clur:"ng ';:'1:-2: o::-c:.=.:te::-' s

scientific lifetilGG is S(;ielrGi:;:·ic:.:.~ly lli"t.:ch mo:::-c c.I.esirable than au (;<lu2."c,orie.l

orbit becD.:'J.se,·· am one; othel'" 1'8'::';:0:,;;':::;, of :c12e great; biological interest of tb.e

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In the follm.fing discussion 0:1." ponsible scien't~ific illztru.TLe~~ts for

.1.., 969 n""".:.d J.. .. 971 }"b-J."r.:. o""'b-_', ~-,r..'!~r::J 'i 'G' 'l~ - 1 "Dc. ,. .... -;. .1.- , t~ iJ b' ., '.~' "" ... ~ .I. ....... - .l. ... \.0_ - - ,'.L.l._ ~ o.:.:): .. d.d;}-.;u. ~n:J."G .ne avo. G. _E:: sCl:en·c,~lJ..C

'payload is in the range 50-·200 pounds) a:'2Q that the e}):Co. re:te lies i:;, the

I

"rI.~":,,, j;!~- o (;collcl 0 l:i.ic-~:l.:~e 8.CCG},jt~.ljlc

:periapsis is useful from many }?o1.nts of 'vie:,,! 0

~o"m some experiments '\-Then the o:l'biter is if this can

tend the useful life of the orbite~o

Io ULTR..\ VIOLE"E SPECTROSCOPY .P.lfD ?EO'i'OESfl1Y

(a) dete:r-mi::-:at:'o:-;. of' tl:c ultraviolet flux at 'Cnc l::s.rt:':"an su.rf"ace

SE:u::-"ch fo::' ·C':':o3 ~.~ -: ...... r,-i ..... ~ .: "o,. co -": -n -; .~.. '~J _().1_ -r.\ C 0 D..l...O .. ~I..'u-I,..;,-, .. :..~.; .. :..:..G!"-.J...J·c ...... -~ t:.<.::."'" 2

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S. g3.S Gusl?ect.ed f:::'uc: i:::',_':Ca.::-20.. s'cuciies) anCi possibly

:relE:!vanJ~ t.o l':::,i.<~j.2.w. biologic2.1 c.cti vit.:Lcs

It~ '·las our opinion thD:C 5UC.:1 e:':-,gerinK:u-'Gs of l)ioJ..og:L c:;:.l i=..terest can be

performed almost as 'Hell, and l:J).Cl'i soon8r:; by i

.,/ mical Observatories; 01" by oth(;::.' t.echniGL'.E:S E.-'C, - .. ,'

l"ockets and. DY Orbiting Astrono-

)?articular) a searcb for c.cetaI.dE:ilyde can "oe pe:;:forroE.:c \·;ri'lj2l higher reliability

in the i.:J.frared, if high Slje(;'~roscopic resc,Lu:tion or e .. l1 ~:9?ro?:::iat,e

• a bsorpt.ion gas cell f'ilter cali"ol"a.-cion is 't: )ed 0 The sea.;ccb. :to:- oxygen car. oe

~a~~ in the infrared and in

A computation of the ult:::avlol,:;;-'.j ::'lux 2.t t: 8 surf'e.ce of 2&rs :,er_l...~J...r8s sp~ctral

meisurements of mcder~tcly,biEh to~oGTaphi:1\1 Tesolutio~) but only relatively

poor spectroscopic resolutiono

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scientific payload of' l~rG or"bi"t,81"S late ill the decade co Spcctror;1C;ters can

,be launched from sto.-bilized plutfo:::ms by modest rocketa such aD the; Aero~)ee"

,-Orbiting As-~ronomical Obscrv.:toriE!.G 2.J?:geur to bave Cluit,e aG.~y'uc.te c::.:p.?b:!.liti(;!~

fOl" the above ultruviolet obse1~vations of the :!?lr.:.~:.e·G ~::J.rz" T'~is is particu-

larly. true fo~ the Goddard scanning sp3ctrOGctcr plann~d for OAO-2~

is recommended thut D. firm cO~1litm~:rt for the f61-! :"1QUrs: ;ccquired observing .,-

time of i{!D.rs be obtai:::.ed at an ee.,:!'ly date ..

II. TE:LEVISION

Pot.ential e)::periments of bioloGical revelc.nc..:; includo (c.) a detailed

characteriza.tion of' :;.u.clc:!. in the 1-f3.rtie.n

. ',f darkeninr:; .. ,.

obt~in8d 'Ilir08 (_. ~l.Oo bi' .- "GS per

i:1dicates

that ~he reliable cletermin[;.t:Lo~1

a difficult undert,ak:!.;.:~_

li·fe on IVers by tE:l',:;v~:3io:1 p:Lctl.":.:c(:fj j a mini:·,:t::'.J ~cesolu:t.ion of ::.. meter seems I

indicated ... Such :r'0so1utio:ls do not Deem lJl"O~cticulforan orbiter in oIGhe 1969

and 1971 missionsg 1·Ti:.cth8l" more t::'actc.ble :cesolutior;.s in the 30-meter r:2.nge

- are biologically Si@1ifican:G J.S ~e ?otG~tiel gains

may concei va'bly be very high; 0' .. tbe other' kr..o.) t,~e cOS'c, in -c,erms or data

transnission rate is also very hiCho It .;i.s ~, li,",;.E:stio;'1 of· c.sse:ss~s::.:t, 0:':: a

p~io:!:'i probabilities;! r~=.c.) as 8.:'1'cici)?8.tea..lI the group 1·lD.S divided on this

issue"

Television is nO-'G required, in o::'c1e::' to p:,"ovide a :firm to:9ogru:pb.icc.l

localization for other kinds b~ observations for e:·:e.mple, ini'rared.

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s}?ectrosco-pyo The e.x]?ccted tODOC .... ·~pll:LcD.l resolution. of infro.red spectra ....

met;ric observD..JGiol1s i}3 comparul)lc -GO the visilJle 'topog:caphic3.1 resolution"

graphic features crs.tel"'S :m::'e;ht be

If .Jche fa.ctor of 20 im}?X'over.1ent in c1.a:'ca .Jcransrassiol'l :ca.te by cons~ruc"'Gion 'II

of large grouL"1.dbased contllul1icO."cion f'acili tics ~s o~Dtaille(rJ 'Chen roJ 2000 bi t~1

:per second becomes feasible from. the 'v'icinity of Mars 0

x 108

bits per day, and :L"""D.plies ';;hat ,...., 100 Ir::"ros-quality J?b.otogr:: .. J?b.s or

of a.eter.:rln:bg .

'\-lith fairly h=iu1. :.-(:;solu:tion. ~cc:;.LLc;,x· and. :3·:';c.so110.1 chal1ges in the :fine struc-

'.A statistical s.nalysi:3 o~~· "'cl';.8 :.L_·c~::::..sitf co::..~:'elation of 'che l'iTl8S 'wi l! give -'

sCu"ne indicat::Lon of the sc~~.r::)~:·=:.l :J.:.G.cl s·~cu.lo..r variations of: 'i;hesurface

featuxes in two cl:I..'ii1ensioll~J"

.,.... r'" It ..!-h- .:. ~D' c- ~, " ~ - .,.. ~ .,. 0_';>· +"_~_,,;:, ·:",~'o'\_:.,o""" ... !-·ea."' Cv"'" _",' 0 1' '..l:.ne grau:p :..e v'::'v C! ';;';'I.A..;;~ ..l""V!j I.; v"v _......., _

~ -~-- ':'0 'oe p-'yc1"o-)"'\r~-iolO~'~c<:>1 '~'1 O""'~(""~'t"l .q·~.l.Cl-l')· ..... ~c:::>~'~u:l o .. ·:~. -;~"J.-.!.;" ··1 ........ ·!~_·' ... ·;·;.,<::~_7(> .;..:.p]?t:a .. r.: v ~, J-J. .1:'l.J- b..... G..I. .:. ........ ..i...t_ .I. ':-6.w.J.) -l.' _ _~_'"' _ _ ... -u._ _

I:£L OY2ICAL POLARIIyf8TKi

, -.. --..:- ....... -- ..... , ._-------~~~~~~~~==~~==~.~-~-.~ .. ~-==-=-====~===~~~~~-~~~~~=~~= .. ~-~-~-~-.~~------------~-------------------------------------

.'

~ ...

-6-

l\~ian d.o.rk. areas 0 T:'1is last c::.::;m.b-i 1 i ty TnE.y be directly ~'~le. tee::!. to the

presence of organisms on 1>1ar3 <> PoJ..:;,rimetr'J at vizible m1.Q. at micrm'rave

;fl"equencies appears to be ·!::''-1.e only prac-cic[!.ble method of remotely d8~cec-Gins

'Phe et:f~cts. of indiv.Ldrp, 1 smull orC;3.l1.is:ms on l·f2.rs clirect~ly;; alJchough even.

here;; the hypothetical orc;anisms c~"1 only be dete·cted end11£:.::;se o ~'----

Because of the l1.,ecessi·ty of positioning inter:ference fr:L."1ges over t'.t.l:·:

disk of Mars, ordip~rily onl~ vcrf poor topogra~hical resolution ~an oe

oOta:L."1.ed from Earthbased visual pola.rimetr.f; and astronor.'lical Useeingi: lir.1-

its the resolution of photographic or photoelectric polar:im~t;i."Y G T'D..e ilnpr,?ve-

ment or resolu"Gion o btai.i'1.a-nle from an or;';i"ter is 1r.:.ore tha..'l'l an order ot I!U':.g ...

l1..itude o

:s.:tension OT the

-' 2I'2.y :prov-lc.e a. discri:n-

. has suggested that :L:r a cCllp:i.ete extension or the :polarization curve to 1800

is for same reason im?ossiblc) observations at 90° .sh~uld be a signifi~t

composition discrirr~~anto I ,/

A modest improve.lnent i..'r'l exiDting :polar-';m.eters 1\'ould :permt :m.eas'\.l.:"e:nent

not merely of in':ojensi'~Y a:n.d J_inear polarization.., -nut ins .Jee2..d" 0-':;''' ali four

stokes parameters 0 T'ne u.sef'Ul.."'less of suc:1. a stol-:es :mcter could be SUbS':02..Uti-

areas is high, and the effec"i:riife SCD.t.lcer-ii.:.g :t.:~l '!Ghe a.l;jmcspnere negligiblej in I

the blue, \-lh~re the M8.rl~ial1 blue h2.ze ~·lilJ.. dQlli.t'"late; e.:."ld. in the yello1'l ~ .~ l

A polarimeter or .stokes meter ie' an espec;:'8.l.ly" e;t;tractive'.ins-cr:l.I:lent -·iI, •

. ,

" .

. \.

-7-

'_l":>or e. i-A'nr~ O-J."}..';t~"I"') ~oec<:l'u~e .j +. 3.. ~ l·r r~}-,'Iv' _"l,T,,::>"_'1 rttht).. . • • ~ . ... v...o. - :..I .... ..,;.;'" v. - oJ..... - _...,,u,l'h ... l;r' COl'lservo:i.~~ ve ~~ a.a:GD., J.:'e..te

..z. •• ~ , -., ura.:'1S1ll.l.SSl.on; }?err arms mcasuremcn:"Gs 1{n:LCn ~anJ u..71iquely, be performed o~

. vrganisL'ls the.il1selves 0 A deter.rr2..:..'lD:Gio:l 0:1:" ]?9..rticular ar~a.s O~ i·:.:.ro l;hich

undergo especially

ant in site selection for eyentUD.l lanc1ing lllis B ions 0 .'

TV .... ·.0

dete~ing "s1.lX:face temperatures 0 Loncer 1'layele~-ths (around.' 20 ;.1) are

temperature -t:iJne

they are related to the condens8.tion and concer.!..1~:'8..tio~: of 1-::;!.-~er at the Slll"­

face of the planetc) ~--

.An ·fn'?r.:.recl bolome.!Ger in the~ 8-13 !.!. ~~~Cio~ ulso has

~he capability of' detecti.."rlg 110-'0 spots on l'~e..rs J 'if' they occupy c. sizable

fraction of the fj cIa. of ",rIc1-! 0

frost layero -Such localCG are ~resumptive ~oci cf jI~digenous biological

a.ctivity ~ alld are tneref'or~ l~eley.::.r:..t to s:I:te selectiop. for eVeU':C'U.2.1 la."1c1.:L.%

missions 0

\ . merJ.t, su,:,h a devIce shouJ.d .llever'(he18Ds be conSidered, e's:peci~.1y

orbiter :?$.yload. is SlJ-w.J.lo - '. \"

-8-

It is also possible) by obsel"Va-ciorls of' the satre area of the planet

a/I,j differen.t local tim:::s of day) that detailed in.forma:~ion of high topo-,"

graphical resolution can be obt2.:tn'2;d 0:0. the tb.e~mal r-~.~op-~rtie3 of.' the l/;3.rlian·

surface. Ecuever) similax in.form.:~:~ion co.n also be obta1~ ..... ~. by micrc'tvD.ve

obs~.::.'vations 0 .... "

~~~D SPECTROSCOP[

Infrared spectroscopy is potentially an e:~rep~ly useful technique for

observations from e. YJ.3.rS orbiter 'Hhich are biologically siguificant ..

f'ollolling obscrvs:tions ca:J.; i:c. -principle)" b~ obtained: (a) c.n improVeiT.Zut

tribution or the 8i:o:'002:L -oe..r:.C.s attrib-..:..'~ed. -~0 orL:2.~ic matte 1" en. Mars 0 If the

be the CC.C8, then this featu.:cc shoulc. r:...::;ve2.~ be oose::cved mo~e than. a. 1"81·r .:J

3.69 \.1 feature 1-'ould. t..:,;:'::'d. tc ·~!:!.npoi::':::c t'b.e sites of [;.cetaldeb.yc.e productioll.

I .. ) D' .. . .... .~ 1 l' .. \ D e~el"ml.na~J..on, 0:1: 1I0:3S:'D e S8C·.SODa_ or SeCU.Lar i::J. the

intensity or 1-ravelengtb.. di6·~::i·Dution of such bands:; again 1·rith ·l.:.igb. topo-I

graphical resoluGion~ Season.c.l variations in the iIltensi"cy of" the Sinton

Da.ne_s correlated \·rith the .. ·raY~ of de.:ckening \.;oulcl :91"ovicle much stro:.:ser

evidence for life on l-/$"'3 than have at the present,

1fe..velength regio:2~ E8.1 .. t::ibased. 6r,servations of tIle Sinto:::J. b8.nds) because

of t~.3ir 10i'T ~GO?OG".rD.phical resolut.ion, are ect..ually an irrtagration of

cOlltributio~s ~rorn Co large a:rec. of tb.e Martian disk. ~heTefore, relatively "

underabund.ant o::gauic molecules \·ri11 he.V0 their sp.=!ctral features diluted..

Rigll topographica.l xcooll'[cio;:). ru:..y permit, such underabuui2.D.t·· .coleciilar si..')acies \

to be observed 0

I

.-=",::""-'-~. ~~~--------------------

.'

-9-

(d) Observc;;tiions 1-lith high topog:ro.phico.l resolu.tion _ ... for exu:m.plc:;

over the disl\: of Mars 0

of' dD..rkenir.t.g is as the rcs}?onse of l.fo.J::>-Gian o::-GD..lliSl11S to 0. disco:'1:(jinu01.1.S in ...

1'lhile

':~here arc :pla.usibili.!I.iY ergunents for this; it is, at the px'csent time,

llO.!~ k.rJ.own "lnether the \'l2..ye oi' darl-:cl1ing :Ln ~e.t(J.il fOJ.J..Oi'';; the front of' the

ll:'l.Ve of 1'late:: ,raIlor sus:gected to 'be 't;ro:v81ing frc.::!l "tre vD.}?orizi:c.e "bo the

(e) A searc...f). for orC;8..::~i(; i\:c.:1ctio:c.o.:~ :;:::'1)\).:)8 oti:.8r 'chan. hycl:cocarboD. or

8..'l'J.d surface orga:a.i::; D.:fld, C~,",.:.:O C8.:.1 b~ o.etec'ted}

IJe 'Hill be :1.mpOX"!~lt to .:J

variations of -cl"~ese l)3.11cls) to dcter:mi.n0:; for eXC:(ffi:ple:; 1>lnec:l<::x' 'Glle ort:3.i.'1ic

.matter on :Mars is uni:for:mJ..y distributed over the disk, and. lfllether some

(f) A search for other ~':':~il.os:p:c.e:cic c.:(,ses of bioloJic~:.l SiQl'i -?ice..::'lce II

C"'lil and CO arc lihotodccoya':'Jos:.t:Lon products or e.cGtald.cnyc.0: v ..;.

cation, localization~ m:d s~8.::;on3~ varic.;tion may be relevant 'co l\'!a.rtian.

oiological activities u

It is cleax· froE. "the pr'eceili.r.:,t; char-ac-cerizo.tion tha.t infra:c'ed. z::;}8ctrc ...

S CpTlY holds great :poten"t;ial fox' orbiter ol)~ervatiol1S or l'J!ars Q Ti.J.ere are

several types of' trspeciirOL'leters tI 1:hich ti.rc conceiva.ble ... TheDe' ir.:.cl1J.de

\,

-:-:====:~====-========-.. =--......." .. -... _ .... _--

.....

-10-

urrays) we c1ge s ) D.nd cOl1vc:ntior..al grat~"1.g m1u prism s}JC!ctrome-ters 0

but still useful. :ce.:c..:;e is 204, to 30 8 ~ 0 1.llle spcc-t;roscopic rCGolutio:a. rc ...

quired is ~oO~, or 0 0 05 ~ c:'0 3 .. 5 l-1.? and may deteriore::;e ,to e..iJou:t OCll !J. at 5

If. ~ characteristic orbitsl velocity is -1 2 kill. sec ) fu"1d spect::,'a of c.:"-eas

100 la;n. on a. side are desi:.~ed) then sca.'I1 ti:m.es < 50 seconds are acceptable.:. ,

Since the abunCla-"l1ces of rare substances are being souJ;ht) t~1e dev:i..ce zhol;.lcl

. "00 ca":'"l..q"ole 0_'::>' d:.J'ec':-,· ~ r' 1" c."e~"'" • 0- • .: 1 I • .... r:- e .... - V.l...L~ P 1/~ essJ.. .L.!.S ~n ':;_"1.e con'GJ.nuu:.1o S:L"Ylce seasor...al

Zt is :903sio1e

bra.tion SOl) .. :~ce ...

and 'Hater.1 it iz :r'c;co:;:;rnellclecl t,haJtj selective absorption gas CG~ .filter c2.li-4

oratio!l.s be ccnsidered) first from Earth-based. e:.;:pe:i.. ... :ilT~C::nts} ~~.=. then }?ossibly

from Iv1ars oroiters 0

the lOTl..g-terra. relia-oil:I.ty o~ Q(;;tecto:cs other spectrometer components in

It also must De dete~ined I

1-lhetherhigh sig:'1.al-to-noise ratios C8.;."1. De 90ts.:L.i.ed 'by ~"'3.clia:tion cool:ing ~""l

1'1ars orbit"

ir~ systems is necessaTJQ .'::) .. ~ Because of the conc:::.leraO.Le

Sea.rches :for molecul~r oxygen on 1;-1.8.:;'''3 CB-J.""l. .\; ll1D.cle by observations of

such forbidden transitions as

\ i \ .

the ulBnct. 'ner;~1i ttir...g I

"'" \.7 .J;'

\ '

\

- ..... ..,=':'::.=--=--.-.,="""=' .... ----------------,.,..-------

-ll ...

a detern-2nation of' t,otal o'x:ygc~~. aou..."1dance not conveniently obtained a.t ultr-

violet frequencies o Such observat:..o:.1.S o·? Jyb,l"o C3...."'1.also us:fully be per-I"

i'r.,::,.uled from the v-:i.cinity of tile Ea.rth"

VIo ACTIVE .lUr.D Ef.\..SSIVE £l:ICROH:1\ VE Rl\})IO:V1ETRY PjI;l) POLA.RTI.fETRY

Passive observations at seYeral micrm·l8.Ve \"aveleng-c,:o..s s.~e cauable of ." . -'.'

determining \·~ith high ..cco'pogra]?hice..l resolution (a) the brightness t;em:f)eratu.re

at several different :)..evels "beneath the :/')l"'"~ia..'11 sm"face 0 By detennining the

variation in -i 'l1.tensi ty of the t-;·,ro }?lc.D.2.-]olo,1:,ized co..ll:90nen.!;js as a :function

1:ne

roughness ~~d its seas-

onal variation, and,7 throucih the diele c"i:;ric const~.l'lt,7 of (eL) the surf'a.ce

compositiono

Because of the i:::".!.clCJ.i:e:.-.:.cy of tlle ~,,::::;.:::-tia.:!'l surf'a:;e environment) a detailed

characterization of the ii'Tllliec.ic.:G(;: J:fu:ct.i2.::.'1 si .. fosu.::·i'ace enVirop..ment d01m to a

depth of about one meter is of biological relevsnce~ Measurements of' the

temperature on the dark sic.e 'Hould ]?er.nri:'~ 3. ;direct c...::teminatio:l of ·;;hat ,/

parameter for the first time,? ~d in c..ddition) such a s"~~ey ms.y 'U:'1.cover hot

s:pots 'Vlhich are or :pOssi·ble 'biolosical s.:',;::ificar.l.ce for the reasons ne:1.tioned

'orbiter e;reatly e}:ceecls that ;'{:.ich ca.:."1 be obtaiL'1.ed. from the Es.:::-tho

Active radar ObSel"'yc.tio":.s :miGht be. t·lrought useful in searchinz for t~e

sus~2cted subsurface 'DerrlJ.8/;'~"oS t - I

layer; nO"ileVer, s"ince the dielectric constant I

., oe

(

made" conveniently a:t 1."'15..C'J/),,{·1D..V8 f':r'eCluE:J.1.cies .. Radar 8..1:'~:G'[~etry could als 9. be

j usef'uJ.. in character:Lzi.n£ i the tOIlogre.};:--;y of the lvI::1rtian su.rface ..

J , .

\

._ .. __ .. , -~-~ .. ---:-------~----------.

.. -12 ....

. EO'Hever) the potentia.l retu:n1s from active ra6.a.r seem to be so D:u1;).ll)

compared to the very large pOi'ler and 1"eigll.lc require.rn.ents) _that it is not

reco!mIlendcd ·~h8:t :':"2~a.ar be i'lm·Jn on G3.J:'ly lV'J.a::-s orbiter ~~issions 0 Cb. the

o·liher ha..."1d, i?he 'Hide range of ]!ossible ·h,.f'orJJ19.tion oots.ina-ole from a

:passive !ilicro"lave device lr18.kes it eo :oromising ins"trtlIr;e:o...1G,. A large antenna.

is necessary) but its weight ca:1'l b~ smail" T;.1.e :m.icr01-lO.v~ eCJ.~rment itself

C8.!.'1. be com.]?S.rable to that used :i.n the l,~ariner 2 rn...issio:o. o It s!locld be

:po:L'Tlted out that since the :passive polarizat;ion measurements can determine

some index of.' surface rou.g'P.,l1ess) seasonal varia:l:iions i.J.'1: surface rc-c.g..."'trr:.ess

should also be detectable v Such obse:cV;;1"C·ions ca:l cOl1ceivably be :;:-e~ted

directly to Ma...~ia:n. biological act.i'vi.ty -j • ., .l,:;:J.G cCl1t:L"Uetc:c size range 0

VITo CONCLUSIONS

Significant experime::'lts rclev<:4'1.t ':co ~!)io:.ogy can bci' }?erfor.med from a.

Tllese experiments) for

various reasons} C3..'l'L."10"C "be :ge~":-o:c:r£led fro:n. the' .,icinity of the. Earth) Ol~

from !vIars flybys" lL'I1. orbiter has an intl":i..t"1.sic capability for high topo-

graphical resolution over a signific8..J."lt f':co,ctj,)n of the '\.,rhole planetal ..... .r

SUl':face; for observations of seasonal ,chc.:lJ.e;es~ and for measurE:..yUents at

large phase anglesQ Eeloi·! .s~:re four suggested (·.cperimentc.l pacl;:z.ges agreed

upon by ':che Working G;coup :m.e:::.bc::."s) in oro.eJ.'" of i '~creasing '\'Teight, data rate

..... nificant set' of oroit8r eXJjcrim.ents for: a·'scienti::.c p3.ckage in. the 20-pound

:i.niprove:Glent in groundbased co:mnu:.'1ica;tion j;·:::.cili-'cies, '.s !.Q.8.c..e·,iI . }j:. ... ov-.:.c..es a ~·!ide-

. - \. variety of sigD..if'icant experirn.ents;) a:.l'ld still we:L~'1r '; m the l50 ..... }?oU,.."1d ~~e 0

\.

......

Payload 1:

Pa.yload 2l

Payload 3:

Payload 4:

Optical pol~r~n8ter 2-1ine optical CCD.l1..."ler

~1rarea bolometer

Optical polar~nctcr 2-1ine optj.c2-1 S CG':Ciller

Inf'ra~ced oolc!Ileter ~1rared spectrometer

Optical polarim0tcr 2-1ine optical scunner Inf'rare d. s pe ctro1il8 ter

. lUCr01'lo.ve radicmeter

Optical polarimcte::." Ir~rared s~ectrc~e~er l/; 0rOi'1!:lve '("0 (1 ~ ""h~(':"-:' ".':'" . • 1-'-6 <.;N - &;,.;... ... ~c ............ u\.:..:_

10 bit-per-}?ictu:cc:: .!~eleYisicD:

"

.. '

In order to L'"_s.zi.L'1lize 'C[.LC scientific O??~:.:'t-..u:..ities :for 1969-1971 Nars·

oroiters, i':c is recoIru'Tlendcd ~G.:.}.8:C early i'lstrumental c..::.:Yelo!),.lle:n.t and nea:--

Earth test fligll"t~ of these 6.Ci.r1..c.:cs he per:fo:crc.edo In e.dc.ition, the :follow'l.ng

und.ertaldngs are st:l:·onc;J.y ::.~eco:~~·u::ndecl so th2:~ t!1e scientif":'c retu--rns :from

·l~s orbiter missions C2.n i)e rr~::::.rllize6.:

(1) the develornent; of l;:;.T2;c) gl'ound.based) :phased-a::ray c.e8::? s'}?ace

comrn.tL."1ication facilities to j:.nprove data. tra.."1smission rates frc::n. the v:Lcin:i.ty

of L-lars

(2) the perfor.f:2...r."'1ce of 1: tsh angular l~esolution ultre.:v'iolet 5}!3ctroscopy

of Ma.rs :from. the vic:L.'J.ity of ',"he Eart:-Ll) p2.r0icule.rly from roc~':ets \'!ith ste.-oil-

:l.zed :platf'orms and :fro:.:n. -the O:i' )iting Ast;ro:nomical Observatories

(3) o-oser-vc.tions of gurs 'lith ga.s cell :filter calibratio::l to check the

(l~) a search i.."I"). the near .',ura:red fqr ~;101ecuI:.::.::- o~gen or:. l·~ars"

\

2101 CONSTITUTION AV ENU E

WA5H I NCTON 2~, 0 , C.

NATIONAL ACADEMY OF SCIENCES NATIONAL RESEARCH COUNCIL

OF TH E UNITED STATES OF AMERICA

Reply to

SPACE SCIENCE BOARD

SUMMER STUDY 1964 800 Welch Road

CABLE AD DRESS : NARECO WASH I NGTON, D . C .

Palo Alto, California 94304

October 30, 1964 ACTION REQUIRED

MEMOR~~UM TO: Participants, Exobiology Summer Study

FROM: J . P. T. Pearman, Executive Director, Exobiology Summer Study

SUBJECT : Las t wo rds from Palo Al to.

This is the final transmission of late working papers and amendments. The revised t able of contents, also included, replaces all earlier ver sions . Other contributions to the report may be avai l able for dist r ibution at the next meeting . Please be sure to bring all your Study papers with you to New York .

The Palo Alto office will close on 2 November. Please address all communic a tions about the Study to me at:

Space Science Board Nat i onal Academy of Sciences 2101 Constitution Avenue, N. W. Washington, D. C. 20418 Telephone: 202 -96 1- 1385

Dr. Shneour may be r eached at :

Department of Genetics Stanford Medical Center Palo Alto, California Telephone : DA 1-1200 ext . 5239

The foll owing briefly recapitul a tes arrangements for the next meeting :

Da tes : 6, 7 and 8 November Time: 9 :00 a . m. Place: Room IB Caspari Hal l

Rockefell er Institute 66th and York Avenue New York City,

Telephone : LE 5 - 9000

October 30, 1964 Page -2

Hotel reservations, for those who have requested them, at:

Beekman Tower Hotel Telephone: EL 5-7300 3 Mitchell Place (First Avenue at 49th Street) New York City,

with effect from the evening of 5 November.

May I remind you again to bring the Summer Study papers with you to New York - - extra copies will not be available.

enclosures

" ,

lfemDrlU!dum: To member. of the Ex.obiology (SWlIII!e1:) Study Group.

From: C.S. Pitteudrtgh

SlIbjeet: !be aecond plenary :session, Ncm York City, Now. 6, 7, and 8, 1964.

i'hia ~aMISI! will bring Y«I up to date on the pl'ogresB of the atudy SDd

plana for ita completion ~, as a COllll!Jelltary OIl the agenda, contribute to 211

affic1eut use of our tuJ clurill8 the New York plenary session next 'feek.

(1) The SteaM Coanittee's Proarecs Report

As JOU alreaq know the Steering c-ittee thought it advisable to renae detailed

plana in July, apec1ff..cally to postpOne the second plenary sess.1on until considerably

more progrellS h&4 beeD m&de ~m completion of a firat dnft of our report.

1h8 Auauat clates initially set aside for a plenary session ~ere used for meetings

of smaller _rk1Dg srouPS that addressed tbemsel-.,e8 to particular seetiOllS of the

zeport eo which l.ea.et ~s had then beeD made. Other similar small workiDg

. groups bave met 8iOl:e then. !be result. of all these seaai<JD$ are _Used by the

li8t of _ available c10cuments eacloDed.

WheD it became clear (late July) that our origiaal Khe1"1e for completion hal

been too optimistic, the Steering Committee decided. it _ld be sl.'PlrOpriate to submit

a progreas report to thlll Space Scieuce Board. Aa you may lmow the Board vas then

preparing. paper for trallilmittal to Mr. Webb stating ita reell!!!!!ewfatioJUI GIl wat the

aatioll'. program in spHI! ucience should be during the 70's and 80's. If the eKObiology

Summer Study was to make 81\Y useful input 1:0 the Board'e deliberations it had to be

IIIIIde then, or at 1atat by september. Giveu the EeVised program of plenary seae1OD11,

it was clear that the working group as a \thole could ~ contribute a report in time.

It was belie1Ped that suffiCient agreement naftrtheless aiateG on _ral very general

points to juatify the SteHina Committee submittiDg a Prosreu Report.

It 1e emphaIsized ~t the EellU1UDg paper did not have the authority of the wele

working group'. opiDiOil _4 approval; aDd it he been submitted atZ'ietly as a P'rogrese

Report from the Steering Commit~. It is being mailed to you under separate cover

;

•

• 2 -

from the Palo Alto effiee.

It 80 happena th& 1ft fG'"t'llIUlating it:a main r~ions the COOII!!ittee had

the benefit of diseusaiOll with _)" other: workillg group 1I!l!!!l!bI!rs wo t:Zere in Palo

Alto from August 16 - 18 for other meet:iDSS. Attendance at the Steer1.1!!g ColZllllil:tee

meetiDg which approved the Pro~eaa Report ~1.lS as follClm:

(a) SteeriD,g Committee Members

P:l.ttendr!gh, Lederberg, Ierrl.nth81, Nwiek, Schneoul.", and Z'e&l."l!l!IIt.

(b) tIorkiug GrIlIl.'P !!'emIMn's

Gll3Sel', Gross. Mccarthy, Hiller, HinDley, Oro, Rich~ Stryc£'.

There is eridenc:e that the hogRSS l!e~rt cUd ~ .!l useful purpose. And its

timiDg haa rezooved p1re8mae for completion of our final ,epo!:!: in a hanL~l atmasphere

of haste.

(t) Goals and Apda for the NIi!lJ York Plenar;y Session

The plan 1a still to c:aD!!'lete th~ study in 1964. It is bel1.eved we shall not need

a third plenary session, but \::hat can only be deeic!ed at the elQse of the New York

meeting. All agemia for that meeting is attached to this mIl!iIIn'andum.

our goal at the Ne!:1 'fork meetiDg is to ;reach agreement on fClUr Uems as fo11OO3:

(a) 'l'he general ab'uCture of the final report

(b) !'roc:edw:es for 14;" completion

(e) The outline of a Swmna~ statement that will introduce the rep07.t

(d) ikacOIJDDenaations for a I\I1ticmal progr4m in exobiology

· '.

(3) Structure of the Final ReDOrt

It i~ clear now that .~ &mount of editing and connecti~eAti86ue-~ie1ng could

weld the existing ~rking papers into a single useful statement. It is p~poaed that

with a minim!lm of edUing they be reproduced in their present form as supporting

papers justifying or ezplicating pOints made in the single S~r.r Statement ~hich

will ints» duce the report.

The Summary Statement is envisaged as a 20-30 page article that aill ex~lain our

mission, state the ares of study, sW!!I!Iarlze wat _ IOlfS, xmat _ can reasonably

expect to find out in an ~biology pr~&m, and What ue believe that program should be.

lt will strive to be short enough to be read but long enough to do justice to the

various faeeta of the study end i1:8 proposals. It will uae the fuller t:'O!:king papers

as supporting documents cited tihe~~r voasible.

If this appro&dl is accepted at (the begirming of) the 1'1enal:Y Sesliliou, the

Report will c01lllist of three volumes Q) foll_a:

Vol. 1

(8) suneary Statement, including iteeommaud&tions foz a Program

(b) Supporting papers .

Vol. 2

Bibliography and Anthology.

Vol. 3

Proceedingll of Cad Sagan's Meeting on the iiemote Im;estiga;;~ of !-~rtian Rio logy.

A .ll.!!!:. of the availcble tfo!!'k:!.ng (o!' "eu'pG!'ti!!g") l'sre!.'s !!:'r Yol~ 1 ".:!E~ 0 ",

mailed to you under separate cover from the Palo Alto office. A regrouping of them

i nto a rational sequence of sections will be made at the Plena~ Session.

Outlines of the p~8ed Summary Statement with its recommendaticns fOL a national

program will also be available at the beginning of the Plenary Session.

• " - 4 -i

(4) SUggested Procedures for Completion of the Report

AaSt!ll1ing u<! reach agreement in r~etg York on (a) the geaeLal otructure of the

Report and (b) an outline of the SUIIIIIlllry Statement with itG progzanomal:ic t'ei:Omrnendationll ,

a third plenary B~sion would be wmecaSS2.ry if you funhe:!:' approve the follewing

procedures for completion of the report:

1) That an editOrial group (Pittendrigh, Viflhniac, Pearman) be charged with:

(s) Writing the Summary Statement on the basis of its approved outline;

and (b) EKeze1sing tihatevcr editorial authority is neCeS$3ry to bring the other

papers to publication readiness.

ii) ibat their uersion of the Summary Statement be mailed to the wole Working

Group for mail response on two iasues:

(a) Reject or accept in principle

(b) If accept - ws!;. specific suggestions (if any) for revision

1ii) That the Steering Committee then decide wic:h of the propcsed revisions be

accepted and 80 instruct the editorial group

iv) 7bat the resulting revisions be Qent to the~king group for mail response

on two items:

(a) Accept

(b) lejec:t and vote for a third plenary session

v) That a thi!':'d plenary session be called unless there is a 90% aeeeptanee 1:0 lv.

(5) A Note on the Gez!erali!:Y of rec"ftm!il?Udaticms ue should eifel'

'l'he Steeriug Committee DOW believes tore should restrict our prliJgra=tic recommen­

dations to a very general l€roel --- CCJmpSrable to that dGll'eloped in the Progre&&

Report. 'lileir reasous are as folIet.s:

(a) He eamwt hope ~ go beyond that level and mainUlin a schedule for complei:1on

in 1964.

'\

• - 5 -

(b) In any case it is probably m&er not to jeopardize the eucCE!as 0;;; major

pointa em wieh we S!!l ag?:ee by inclusion of detaillS ,.ohic:h at this jtmetulre

would necezsarily not be unanimous and certainly inauffieient:ly studied.

One proposal He might: well offer is e8tabl11lhm2nt of e mcne pe=ent study group

thai: would c:ontmue where ~ h£l7e left off and addrGSs itself to the details \'6& have

fwnd bi!}lODd our ctlII!petenee in the time available.

Comments on paper 2d

5 Nov€(Qlber 1964

1'0 6 line:2 t1P

]ic)t'-l' does one defend ~we mltst ap;:roaoh this problem fro'm the ststJdpoillt

of the origin of the ee.,,:t.hM

(aie)? :!~v not b~' baolt-eAtrapollltiol"l 1'il@Jll

livUlg th~s'?

Problems c@..n be a~proa~hed ill !lany Hc\YS 5,) not :nt#C~Bss\..1"11y those

limited 'bJ' the !)!'01;Jonsrlts of one a?proacho

p~ 12 . line 9 ·up

The ld~a is not dlffieult to aooept3 the Qliu:lar-tiou llrTithout more

eonvinolna proof is <lifftot.ut to acoe}.Jto

While BLome :flrg~)!1ie oor.n:po'U!lo.s !1l:i.ght be pr'~du(\ad i.uh1szhest yield

htem ftreducinso atmospheres ~ ths Sl'gl;U1!Sltlt 'ba.s~ on sme.11 yield 1$ faT

from ri,go:rcuso L1.fe n~~d. mt have startecl mora thJA11 oncet :nor ill large

po 14 Table I

The vmlue for '1'o1.ct.;'X).o®s is £l!SWll-2£.o Sxoept for sadi!IH~l'ltary l'&eks p

muoh or most of' the crtlst ot the Earth is of baea.lt1e ori~in\) eego, ths

Great ~]Grthwest Plateau (seir. .~uJ.l®.rd.~ VolOillWas p U:ni'l'ersitty of Texas

Press, 1962l !l 0 55) )'71'2 i en h&~i. 8.:'1 ,~:rea. 0 f ~?o i) !) () () 0 squar e ~il es; and

represents hund:red12 ·:;f flows su:?erpoOJed one upon ~~othal"o Acoordh1glYg

thermal zones llartg e.r ... t~rl.s:lveo cnly one n.atu.ral therme.l eZ!?erimer1~ wasp

th.eoret1oallyo Y.r.<Bcef"S~.:ryo 11~bul~"l..t1on of c~U':re:r.rc l~nfa:r'gie3 is not relevant

2

po 15 lilte a up

statement may be inCO!TeCt.a Heyris 9 !:ialterSr and f4eyar ob~cQined

n1mhrdr~POslt1ve produots by e100t~io disoharge in presence of

~;:··~9 .N2, ~ 02°

line :3 ,

. po 11 line 4

tfl1at about the suthor/) s 2.5 un1de.n.tlfi$d rr.mino acidS (by ninhya.r1n?) 0

i o Sa ~. ~~ no 23.51 (1955)0

line 17

Na tube of alum:tne wssusedo The tubs '.9 Qf' V'y'oo:r gle.6U!3 in semi!

~ents the bed mater1al was alumina. I •

Aspartic aeid.t' glutamic Stoidt! and sar111~ Yn:t"'e a100 'PY.'92ent Ii in ,

l~"'le 5 up

Considerable Her·: lm~ pl'Oduoed £1lll with ~11,~i2).e as b~~d mater1e.lo

?his synth6sis is les~ e/ctl."a1lti''tre since only 4 emiylO ;..1.0id$ ~'?er61 produc.edo

wbereas 14 protG}inaoeoua amino aoitis 6tZld 1lO nonp?OteinaotaOuRl? amino acids

w.ere torm~d in the synthee 1s th:rcu~.).1 s ilioso

18 Q line If, up

po 21 line 2

~pcrt ~or this state.aent? Some gsologists postuLated a primitive

aeld Hartho Reaction ot phosphorio aoid Oll largely cooled basalt mu1d

sive poln>hesphorle aoido Caloium phosphate premotes amino acid

OG!3tleuat1c.!lo

po 21 lin®, up

This statemant would be; mada only in 9.A"1 arbitrarily rest rioted

~exto Only 9. small amOUl'lt p generated as needed by a feT:-7 orgardsmst)

would be req'tti.ratftc

po 22 line 10

ID ord9.r to o·btainl at all, any; polypeptides containing aome or each

pre'elnao8OUs amino aeid 9 with molecular weights ot m9~ thousendo

])~ 22 line 11

Amino aoids do not them.al.ly decompose rapidly 11'1 the preSetl08 of

sufficient asparti0 acid~ glutamio ecid9 or lys1n~~ The propar l~~h

of time for ~ocopol..vmerlzat1o.n is about three ho\U"so One nead not

be oeJ'jcal~ed with, sago!) thousands of yaars p onl;V' a fe~: hourso In less

t1m6 than that, suoh therew~ po].y-(\-amil'lo aaids fom ~ ~~1ater vast l-lWllDerS

of mlorQsphsres in the l"9..l'lgs of size of the ooc.elo 'l'hese oan 00 made to

diT14e by rals1~ the pH~ are stable eno'lJ.3.b to be sectioned for electron

mieroseopy I) and some of th~ ooUl'lc.aries are bl1am.tllelar 0 U:nd.el" these

ooDiltions the ateps froa prilnol'dU]. gases to amino 8<.;ids to formed

m1eropartlcles requires less than ten hourso fhe org~kl~c ~ter~~s of

the mlol1&part1elas would then be protected from destruotion by over-

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• >.

VOLUHE I

0, SUMMitRy STftrG'Mt?,vT

I. 'DIE SCliBfDlC JW::aaoUND.

a. What is Life? b. '!he Origin of Life. c. 'Zhe Solu S:ptem 88 an Abode of Life.

II. 'DIE KltPLOllAt'IOH OF lfAi8.

1lI. ""

a. 'lbe Goals of Martian Ixploration. b. AwDues of Approach. c. Terrestrial hograms. d. PllIJIetary lI1asiOllll.

i. 'lhe Stertliaation Problem

8B 'lbe Available 'ehicles Immel! Opportunities

1 Fly-bya and Orbiters • Atmospheric Probes • UmMmed Landers

1. IecogD1tion of Life

November 5, 1964

2. A lle9iev of Current Devices for Life Detection 3. '!he Concept of aD Automated Biological Laboratory 4. Potential ADalytical Tec:bn1quea for an AutOlDllted

Biologicsl Laboratory !filmed Flights

e. 'milet:ablea; hoapecta.

VOLmJE III

Il1DDl'B IBVISTIGAnOlS or !fAJ.TIAH BIOLOGY: Proc.:eediugs of a SJmposium in 1964.

· 0

I. 'DIE SCIENTUIC BACmBOUND

a. &hat i8 Life?

i. Signs of Life

ii. Search for btraterreatrial Life

b. 'l'he Origin of Life

1.. !he Origin of Life

c. '!be Solar System as an Abode of Life

i. '!he Solar S)'8tem as an Abode of Life

- 2

Lederberg

Brown

Miller

Sagan

U. 'DIE EXPLOIATION OF MARS

a. the Coals of Martian hp loration

1. 'l'he Coals of Martian EKploration 'f1shn1ac

b. Avenues of Approach

A br1ef statement or1ent:i.ng the reader to what follCJW8 in the nat of II. lUll! l1sting:

1. B1olog1cal Laborator)' work H. Aatronom:i.cal observstor1es; terrestrial

observator1es, balloons, rockets and terreatr1al orb1tera.

iii. PlaDetar)' I'l)'-b)'s. 1v. Planetar)' Orb1tera v. Planetary aboospheric probes

vi. PlaDeury Laaders; unmanned. v11. Planetll17 Landers; manned.

c. Terreatri.&l Programs

1. CRUnd Laborator)' Work l!Iov1ck

U. Terrestrial Observator)' Work Rea, Sagan

111. Orb1tf.ng astronomical observatOries, balloou .00 rockets Sagan

" "

II . 'mE EltPLOllA1'1ON C1F MAIlS (continued)

d . Planetaq Missions

i. !be Sterlli&ation Problem

1. !be need for sterilization; the nature of the problem

Z. Standards for Spacecraft Sterlli&ation

3. Spacecraft Steril1ution

11. !he .. &lIable Yeh1cles

Hi. Lmmeb Opportunities

1. I.auueh Opportunities

iv. Fly-bys and Orbiters

1. ILemDte Imrestigationa of Mars

1. !he Recognition of Life

- 4

Atwood

Sagan. Coleman

Horowita

Sagan

Sagan

a. ProviaiOllsl focus on cerbon-water systema.

b. A Model of Martial Ecology Yillhniac c. EBotic Biochemical Syatems Pimentel d. Living l'botoebemical

Beactions on Mara Gaff1"OD e. !he Use of Hartian Materials

in the Seareb for Martian Life IU.ch f . Optical Activity Stryer g . Kac:romoleculea Lederberg. h. Mol'phology (1) Schwartz i . MorpbolOS)' (2) Conger j. Higher Organisms Sagan k. Criteria of Life :rem

Z. A Jl.evi _ of Current Devices for Life Detection Bruch

et al.

1 ...

II. 'lHE EXPLORATION O'P MARS (continuold)

vi. Unmanned Landers (continued)

3. !he Concept of an Automated Biological Laboratory

m S

a. Some principles for tile design of an Au~nated BioLogical Laboratoxy Glaser

b. Computerized LaDoratol:ies Glaaer, McCarthy andM1nsky

4. Potential Allalytical TecbniquelJ for an Automated Biological Laboratory Rea, et ale

(For detailed contenl:s see Octoher 29 List of WorkiDg Papers, Section 9.e.)

vii. HaMed Plights

1. Prospects for Hauned lIJ.ieeiDn8

2. '!he Iq»aet of Mmmed Sl)8CSCraft on the Exobiology Program

e. Timetableaj Prospects.

Levinthal

Horowitz

DRAFT 13 January 1965

Biology and the Exploration of Mars

Synopsis and Index of Papers

Preface: Purpose of the study: origin, arrangements and terms of reference.

1. Summary: Short account of chief arguments and findings; explana­tion of principal conclusions and recommendations advocating a thorough scientific study of Mars with primary emphasis on biologi­cal questions.

2. The Scientific Background

Definition of life: difficulty in rigorous definition. Significance of extraterrestrial life for planetary evolution, origin and nature of life.

Existence and evolution: role of the environment. Chemical evolu­tion; origin of organic matter in planetary formation and develop-mente ~

Habitability of planets of the solar system: Martian characteristics and biological hypotheses; goals of Martian exploration.

Observational and experimental recognition of life: terrestrial precedents - optical activity, morphology, remote observation, microorganisms, soil biochemistry. Variant biochemistries, ecological implications of Martian environment, morphological and chemical simulation, experimental use of indigenous materials.

Papers:

2.1 What is Life? 2.2 The Origin of Life 2.3 The Solar System as an Abode of Life 2.4 The Goals of Martian Exploration 2.5 The Recognition of Life

2.5.1 General Considerations Signs of Life

Mazia Miller, Horowitz

Sagan Vishniac

Lederberg

3.

2.

2.5.2 The Terrestrial Precedent Optical Activity Stryer Horphology I Schwartz Norphology II Conger Terrestrial Orbiters Sagan Soil Biochemistry . l-lcLaren Soil Chemistry and Sampling Cameron

2.5.3 Extrapolations Exotic Biochemistries Pimentel Model of Martian Ecology Vishniac Development of Rigorous Tests for

Extraterrestrial Life Fox Use of Martian Materials in the

Search for Martian Life Rich Higher Organisms Sagan

PreEarations for the EXEloration of Mars.

Methods, and limitations, by which further information about Mars and particularly about the search for life may be obtained - from the Earth (surface and near vicinity); by means of spacecraft; vehicles for the purpose and opportunities for their use.

Laboratory work on the chemistry of the origin of life; effects of (simulated) Martian environment on terrestrial organisms; studies of possible biochemical systems of special relevance to the Martian environment.

Papers:

3.1 Introduction, including a survey of possible avenues of approach Pearman

3.2 Terrestrial Programs 3.2.1 Astronomical Studies: use of terrestrial,

balloon, rocket-borne and orbiting observatories Sagan

3.2.2 Meteorite Studies Arnold and Urey 3.2.3 Biological Studies

Non-Biological Syntheses Miller Simulation of Planetary Environments Ponnamperuma Exotic Biochemistries Pimentel

3.3 Vehicles for Planetary Missions Levintha1 3.3.1 NASA Studies of Planetary

Mission Possibilities Hearth 3.4 Launch Opportunities for Planetary Missions Sagan

4.

3.

The Sterilization Problem.

Avoidance of contamination of }1artian environment 'tvith terrestrial organisms an essential condition. Discussion. of present arrangements and standards; precautions not limited to superficial contamination. Unsolved problems and need for energetic program; consequences of neglect.

Papers:

4.1 The Nature of the Problem 4.1.1 Spacecraft Sterilization:

The Present Situation 4.1.2 Spacecraft Sterilization

4.2 Standards for Spacecraft Sterilization

4.3 Internal Contamination of Spacecraft Components

Atwood

Hall (JPTP) Horowitz Sagan and

Coleman

Brown

5. Nissions for Remote Observation of Bars

Martian fly-by and orbiter: capabilities for environmental determina­tions, preliminary reassessment of oiological and physical hypotheses for Martian phenomena, study of seasonal changes, cartography, selec­tion of sites for surface studies, and selection of apparatus for inclusion in landed spacecraft. Strong preference for orbiter as precursor to landing missions without adding unnecessarily to risk of contamination.

Paper:

5.1 Potential Yields of Biological Relevance from Remote Observations of Hars

6. Nartian Landings: Unmanned

Sagan

Final need for landing missions for identification and especially for characterization of life and environment (even if detected by other means). Single experiments insufficient to avoid ambiguity; large array of instruments required with coordinated control over programming and sample manipulation. Single large lander required rather than many small ones. Concept of an automated biological laboratory. Review of analytical methods of potential application and instruments in development.

Papers:

6.1 The Ultimate Necessity of Landing Missions 6.2 Large vs. Small Landers

6.2.1 Practical Considerations in Spacecraft Development

4.

Stroud 6.3 The Concept of an ABL

6.3.1 Some ?rinciples 6.3.2 Computerized Laboratories 6.3.3 Analytical Methods for Landers* 6.3.4 Review of Available life-Detectors**

Glaser McCarthy and Minsky

Rea (Bruch)

7. Martian Landings: Manned

Need for direct human observation; experimentation, exploration, and specimen collection ultimately indispensable, but not until­the usefulness of unmanned devices has diminished and the need to avoid contamination has passed. Special problems in the treatment of Martian samples returned to Earth and control of contamination if microorganisms are found on Mars.

Papers:

7.1 Prospects for Manned Missions 7.2 The Impact of Manned Spacecraft on the

Exobiology Program 7.3 (~uarantine and Back-Contamination

8. A Program: Conclusions and Recommendations

9. Appendix I: Analytical Hethods

10. Appendix II: Available Life Detectors

* Summary and General discussion) with a tabulation. Details in Appendix I.

** Summary and discussion. Details in Appendix II.

Levinthal

Horowitz Brmm

Rea

Bruch

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MEMORANDUM:

To:

From:

Subject:

NATIONAL ACADEMY OF SCIENCES NATIONAL RESEARCH COUNCIL

OF THE UNITED STATES OF AMERICA

SPACE SCIENCE BOARD

15 January 1965

Working Group Members, Exobiology Summer Study

C. s. Pittendrigh

Summary and Conclusions of the Summer Study

CABLE ADDRESS: NARECO WASHINGTON, D. C.

I am enclosing a draft of the paper which the editorial group was commissioned to write summarizing the study, its conclusions and recommendations. It has not been an easy piece for us to write and there are portions of it that clearly need tightening - especially in the section on landers. Nevertheless it is close enough to what we intend to justify our submitting it to you for scrutiny and comment. The bottom of p. 21, all of pp. 22 and 23 have been struck out; the material is all part of the conclusions and recommendations.

The Steering Committee meets in Palo Alto on February 1 and 2 to consider your reactions and recommendations for revision. To be useful - and to be acceptable! - your comments must reach Peter Pearman by January 25. This means your mailing dealine is January 23. We ~egret the pressure.

You will of course immediately see that we have "substantially reworded the conclusions and recommendations you approved in New York City. We have however nowhere violated their spirit. The most substantial change is omission of explicit reference to small landers.

I assume responsibility for that change and offer the following in explanation. (1) There was in fact by no means a real unanimity behind the recommendation. (2) It was clear to me that no explicit recommendation for or against a small lander in 1969 could ever gain truly unanimous approval. (3) The rewording I have made covers both points of view and in any case faces the realities of the situation: what. is flown in 69-73 will depend entirely on what.is possible between now and then in the way of engineering development. (4)" B~ig thfn"gs have happened since our November meeting. By this I mean the NASA· Program which is now public - courtesy of "Missiles and Rockets". The point is that the Voyager missions are now an approved program in the technical sense of

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"program". This is what we were all working for and there is no doubt (for so I am told) that the Summer Study played a useful role in affecting the decision.

Two Saturn lB-Centaur shots will be flown at each opportunity: 69, 71 and 73. TIle work of specifying their payloads is .now imminent and makes the convening of a Standing Committee urgent. There is an explicit intention on NASA's part that landers be included in the program. How big or small is something they cannot specify at present - and nor can we. In terms of the booster they could carry as much as 1/2 ton of scientific payload.

The wording of the lander recommendation was made in light of this news: it is intended to leave initial lander size open to further discussion and the realities of engineering development.

Many of you will find the distribution of emphasis and the extended attention to the probabilities of life on Mars surprising and tedious. I was deliberate in the emphasis I gave to the question of probabilities. The audience - especially of the summary - will look precisely for these evaluations: Commoner, as you have doubtless read, has charged we have ignored the matter.

Sincerely yo~~

~ V{~~. Colin S. Pittendrigh

P. S. A revised outline - by chapter - of the main document is also included.

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Summary and Conclusions

of the

Space Science Board's 1964 Summer Study

on

BIOLOGY AND THE EXPLORATION OF MARS

I. Introduction

II. The Origin and Nature of Life

III. The Possibility of Life on Mars

IV. The Scientific Aims of Martian Exploration

V. Spacecraft Sterilization: the overriding mission constraint

VI. Avenues of Approach to the Exploration of Mars

VII. The Timing of the Explorations

VIII Conclusions: Recommendations

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I. Introduction

Until recent years the origin of life and its possible occurrence elsewhere

in the universe have been matters for speculation only. The rapid growth of

molecular biology since 1940 has, to be sure, Changed ~e discussion of life's

origins into far more precise and explicit terms than were possible earlierj

and the subject entered a new, experimental, phase in 1953 with Miller's

first successful inorganic synthesis of tmportant bioChemical substances in

a simulated atmosphere of the primitive earth •. But the real transformation

which the subject haa undergone s tema from the spectacular growth of space

technology in the last decade. The possibi1i~ of life's origin and occurrence

on planets other than ours is no longer limited to idle speculation: it has

entered the realm of the testable, of science in the strict sense. Given t~e

rockets now available and especially those available by 1969 it has become

'fully realistic to consider plans for the biological exploration of Mars.

the Summer Study. which this report summarises was convened in June, 1964,

by the Space SCiencer'Board of the National Academy of Sciences to examine

this possibi1it,y. The working group consisted of 36 people representing a

broad spectrum of scientific disciplines: evolutionary biology, genetics~

microbiology, biochemistry and molecular biology, animal physiology, soil

"Chemistry, organic Chemistry, planetary astronomy, geochemistry, and theoretical

physics. The membership also included individuals with no prior committment

to the biological exploration of the solar system.

Our task was to examine the scientific foundations and merits of the

proposal to undertake a biological exploration of Mars. What were the potential

scientific yields? How valuable, if attained, would they be? What~ in fact,

is the p088ibilit)' of life occurring on Mars? And of our detecting it with the

available ad fonaeeable technology? . What c~ld be achieved by further astro-

nomic,l voEk f~ earth! ., Martian fly-by mi8siona? "by Martian orbiters?

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and Martian landers? What payloads would we recommend for planetary missions?

What timing and overall strategy would we recommend for Martian exploration

were we to consider it worthwhile at all?

In brief the overall purpose was to recommend to the Space Administration,

through the Acad~'8 Space Science Boardl on whether or not a biological

exploration of Mars should be included in the nation's space program over the

next few decades; and, further) to outline what that programlif any, sho~ld be.

We emphasize that our conclusions were rea~hed on strictly scientific

grounds; that we recognize a muCh wider'array of considerations bear on any

ultimate decision to undertake Martian exploration. As a body we were not Charged

with nor did we attempt the broad over-view that entails these o"ther considera-

tions. We predicated our discussion on the continued vigor of a national

space program. ~e did notl for instancel address 'ourselves to the question of

whether the ve~ large cost of developing the Saturn boosters could be justified ~

on scientific grounds. Nor should we~ the development of the Saturn boosters

is already firmly committed for other reasons. The questions we faced were

whether the application of suCh boosters to the biological exploration of the

solar system - of Mars in particular - can answer well-framed and important

scientific questions; and what priorit,y these questions merit within the space

program.

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II. The Origin and Nature of Life

The modern, naturalistic view of life's origin dates from Darwin. Implicit

in his evolutionary treatment of life is the proposition that the first appear-

ance of organisms was only a chapter in the natural history of th~ planet as

a whole. Oparin later made this notion explicit in his view that the origin

of life was a fully natural, perhaps inevitablel step in the ontogeny of the

Earth. Systems capable of self-replication and controlled energy transfer -

living organisms - had their origin in the sequence of chemical changes that

were part of tbe planet's early history.

The tractability of this great inductive step to further d~scussion has

been enhanced by the progress of cellular biology and biochemistry over the

last few decades. What has emerged from that progress is a picture of life's

uni~ at the subcellular and chemical levels comparable to the unity at higher

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levels whiCh so largely influenced Darwin. Not only is there an essentially uni-

versal pattern to the structure of cellular organelles - its membranes, t:t/

mitoChondria, nuclear apparatus1 etc. - but still more surprising unity is

found in its molecular constituents. Eve~ere the essential catalytic

functions a;a disCharged by proteinsl energy transfer effected by ATP1 and

the synthesis of proteins by an elaborate nucleic acid system. The same

enzymatic cofactors are found in organism after organism; particular metabolic

pathways recur from cell to cell; and eve~ere the' fundamental functions of

information storage and replication are assigned to the nucleic acids.

To a significant extent the discussion of life's origin must concern

the origin of these molecular types that are crucial in cellular organization:

the origin of nucleic acids, of proteins l of carbohydrates, and so on.

Beginning with Miller's now classical experiment of 1953 in which he

synthesized amino acids from a simulated atmosphere of the primitive earth

using electric discharge as the energy sourcel a long series of workers has

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succeeded in synthesizing - inorganically - virtually every major category of

molecules from which the cell is built. The list includes: amino acids and

simple polypeptides; purines and pyrimidines, nucleotides and simple poly-

nucleotides; carbohydrates; and even adenosine triphosphate (ATP) on which

the cell's energy traffic depends.

The credibility of the naturalistic, evolutionary view of life's origin

as an exploitation of previous chemical evolution on a sterile Earth is greatly

heightened by these results: the great chemical complexity of its molecular

constituents does not, in last analysis, require the.intervention of the cell

itself. {

The general tenet that life involves no qualitative novelty - no elan vital -

goes hand in hand with the more explicit proposition that it is the molecular

organization, as such, of living things that alone distinguishes them from the

non-living. The central issue in discussing origins now concerns not so much

the prior evolution of complexity in molecular constituents as the attainment

of their organization into a system that is alive. It is here we lack any

sure guides - save one - on the contingency involved; on how improbable it all

was. That one lead comes from the great and well-known advances of molecular

genetics in the past ten years.

The essence of organization in one sense is its improbability, its dependence

on specification or information. And the most characteristic feature of living

organizations - organisms - is their capacity to store and replicate the infor-

mation on which their existence depends. The high point of our biochemical

advance has been identification of the molecular basis of these defining charac-

teristics. It is an astonishing fact that we know and to a large extent under-

stand the manner in which the information underlying life's organization is

encoded in molecular structure; that we understand how that molecular structure

is replicated; and further that simple polynucleotides have been synthesized

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from completely inorganic sources - without the intervention of the cell at all.

To a significant degree the origin of organization itself is again a question

of evolving molecular complexity.

It remains unclear, of course, what precise sequence of ~vents exploited

the opportunities afforded by the purely chemical evolution of the earth's

surface and atmosphere. Nor, were we to know the precise sequence, would we

be able to define a single boundary between the living and non-living. That

boundary must have been as fuzzy as it often is hetween species and for essentially

the same reasons - the evolutionary process is fundamentally a continuum. To

a large extent the recognition of boundaries depends on the concepts in terms

of whiCh we discuss it. But at some point in the unknown sequence a community

of molecules would have been fully recognizable to us as a living as against

a non-living thing: it would have been bounded from its environment by a mem-

brane, capable of controlled energy expenditure in fabricating more of itself

and endowed with the capacity to store and replicate information.

We cannot fully know the preCise course of the earth's early chemical

evolutionl and the degree of contingency involved in the subsequent transition

to a living organization of molecules; and for these reasons we cannot fully

assess just how probable or improbable life's origin was at the outset of our

own planet's evolution. Nor can we estimate to what extent the emerging pic-

ture of a single chemical basis to life on Earth reflects a physical necessity

for living organization as against a mixture of physical sufficiency and •

historical accident. Is it so that the catalysis essential to chemical organ-

ization can only be effected by proteins containing the 20.amino acids we ~~

encounter in cells; andl\the nucleic acids are the only polymers, for physical

reasons l that can carry molecular information satisfactorily? Or are these

and other empirical generalizations about life on earth - like its optical

activity - merely a reflection of the historical contingency that gave such

molecules first access to living organization, thus preempting the field;

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precluding realization of other physically sufficient molecular foundations

for life.

To the extent we cannot answer these questions we lack a true theoretical

biology as against an elaborate natural history of life on thi's planet. And

to the extent we cannot estimate how much contingency in general was involved

in life's origin hereJ we cannot take the ,great inductive step that tempts us

20 on learning from the astronomer that there are probably some 10 planetary

systems elsewhere in the universe which must have had a history comparable to

our own. One thing is clear - for life to be unique to our planet the probability

of its origin must be almost unimaginably low. If on the other ~and the proba-

20 bility is at all reasonableJ life must be abundant in the 10 planetary

systems that fill the sky.

What is at stake in this uncertainty is nothing less than knowledge of

our place in nature. It is the major reason why the sudden opportunity to

explore a neighboring planet for life is so immensely important.

We emphasize that the act of discovery itself would have this great scien-

tific) and for that matter philosophical) impact. But it is also important

that discovery wouldJ in another way) be only the beginning. The existence

and accessibility of Martian life would mark the beginning of a true general

biology whose subject matter would be life as a class of living organizations -

a class in which the terrestrial case would be a single member. We would

have a unique opportunity to shed new light on the meaning of that astonishing

molecular similarity in all terrestrial organisms. Is it there as a physically

necessary basis for liDb~ Or is it - physically sufficient but not necessary -

a historical accident in the sense that in another instance of planetary

evolution a different basic chemical complexity could equally well have

emerged and preempted the local opportunity for life?

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III.' The Possibility of Life on Mars

No biologist will disagree with out assertion on the scientific importance

of life elsewhere in the solar systa~. It is however another matter to conclude

that search for it should proceed at once. The exploration will be costly in

money and other resources. To undertake it we need ~ assurance it is not

folly from the outset.

Interest immediately focuses on Mars for two reasons: it is relatively

close to us and is the most earth-like of all the other planets in the solar

system. Its year is long (about 600 days) but the length of its day is curiously

similar to that of earth, a fact that to considerable degree ameliorates an

otherwise ve~ severe environment.

Mars has retained an atmosphere although it is thin; current measurements

of pressure range from 10 to 80 millibars. Its only certainly identified con-

stituents are carbon dioxide (accounting for 5-30% of the total) and water

, -3-2 vapor present in very much smaller amounts (2 x 10 gm cm ). Oxygen has been

sear~~ed for and not detected; it cannot be present in pressures greater than

0.25 millibars. Nitrogen and argon are believed to constitute the bulk of the

remainder. The absence3 or at best3 ~ry low concentrations of oxygen imply

that in turn ozone is absent and that flux of ultraviolet radiation at the J\

Martian surface must be high.

Temperatures are 1~4t that ve~ different' from' o~ own: at some latitudes

and seasons they range from a daily high of +300 t~nightly low of _400

: A A

diurnal range of about 1000 is probably typical.

There are two white polar caps Whose composition has been the subject of

some controversy. The evidence now is clear that they are ice, or rather hoar

frost. They undergo a seasonal waxing and waning which is probably accompanied

by an atmospheric transfer of water vapor from one hemisphere to another.

Our knowledge of what lies between the polar caps is limited to the

distinction between the so-called "dark" and "bright" areas and their seasonal

changes. The latter, usually considered "deserts", are an orange-ochre or

buff color. _>T'ne former are a neutral grey. It is likely that early descrip­

tions of the dark areas as green result from a physiopsychological effect due

to contrast from the orange "bright" areas.

Hiological interest nevertheless continues to center on the "dark"

areas. In several respects they exhibit the kind of seasonal change one would

expect were they due to the presence of organisms absent in the "bright"

(desert) areas. In spring the recession of the ice cap is accompanied by

development of a dark collar at its border, and as the spring advances a

wave of darkening proceeds towards the equator and, in fact, overshoots it

200 into the opposite hemisphere.

Polarographic studies suggest that muCh of the Martian surface may be

covered with small (0.1 millimeter) particles; and in the dark areas (but

not in the bright) the curve on which this inference is based shows a seasonal

displacement. The dark areas, too, are the place w.lere infrared spectroscopy

has produced evidence - the so-called Sinton band~ - suggestive of chemical

bonds we would associate with life on our own planet.

Needless to say, none of these principal facts about the Martian dark

areas and the Sinton bands demands the presence of organisms for their explan­

ation. Indeed the question is lllether the Martian environment could support

life at all; and furth-er whether its history would have permitted its loeal.

origin. These are clearly different questions.

We are agreed on an unequivocal answer to the first question: we find no

compelling evidence that Mars could not support life even of a kind essentially

similar to our own. Were oxygen present to the small limiting extent current

measurements allow, a fully aerobic respiration would be possible. But even

its total absence would not of itself preclude life. poe of our more rewarding

exercises has been ~he challenge to construct a Martian ecology assuming the

most adverse conditions indicated by present knowledge: it posed no insuperable

problem. Some terrestrial organisms have already been shown to survive . . freeze-thaw cycles of the kind a +300 to -400 c environment implies. Others

cope with extremely low humidities and derive their water supply either meta-

bolically or from atmospheric water vapor. There are many conceivable ways

of coping with a strong flux of ultraviolet (and. even of exploiting it as an

energy source) •. rne history of our own planet provides plenty of evidence

that, once attained, living organization is capable of evolving adjustments

to very. extreme environments. And1 finally, we are reminded that the evidence

we have on Martian conditions is very coarse-grained, a sort of average that

takes account of almost no local variations dependent on topography. Within

~ ~~~J this range ~ must exist ~, - as here - there will be places, probably I ..

abundantly, where the ~xtremes of temperature, aridity, and adverse irradiation

are markedly ameliorated. Even presence of water in the liquid phase is far

from unlikely) if only transientlYl by season, in the subsoil.

A measure of our judgment that niches in the contemporary Martian environment

could support life even comparable to ours is provided by the emphasis we

place on spacecraft sterilization as a fundamental prerequisite to landing:

we are deeply concerned with the danger of inadvertantly conta~inating Mars

with terrestrial organisms. We shall return to this problem later.

The other question - waether life in fact is there - depends on our judgment

of ho* probable its origin on Mars has been. This is precisely the question

we cannot answer even for Earth and the principal rea8on~Sidering exploration A

in the first place.

Our judgment given all the facts is that the presence of life on Mars -I J

and hence its origin there - is reasonably high. It is certainly high enough

that, given the rewards at stake1 we cannot escape the conclusion that

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exploration, if it is possible, should proceed.

Given the same facts other scientists may incline to a more conservative

position. But "conservative" has not always been synonymous with "correct" in

the history of science. What judgment would a conservative observer equipped

with our current knowledge of the physical sciences have made ~n the probability

of life's origin in the early millenia of ear~~rs history; or, given the first

simple self-replicating system, on the probability of human civilization?

The history of life on earth certainly tempers qp'70ur~o~ervative inclinations.

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IV. Tne Scientific Aims of Martian Exploration

We approach the prospect of Martian exploration as evolutionary biologists.

Tne origin of organisms was a chapter in the natural history of the earth's

surface. Our premise is a generalization from that single cas~: the origin of

living organization is a probable event in the evolution of all planetary

crusts that resemble ours. We thus conceive the over-all mission as a systematic

study of the evolution of the Martian surface and atmosphere: has that

evolution included, in some niches of the planet, chemical systems with the

degree of complexity and organization we would recognize as "living"?

Our aims in sumnary form are:

(1) Tne determination of the physical and chemical conditions of the

Martian surface as a potential environment for life,

(2) the determination of whether or not life is present on Mars, and

(3) the characteristics of that life, if present.

Tnis formulation emphasizes that as biologists we have as much interest

as the planetary astronomers in a thorough study of the meteorology, geochemistry,

geophysics, and topography of Mars. Whatever the outcome of directly searching

for life, its full meaning will escape us unless the findings can be related to

the prevailing environment.

v. Sp~cecraft Sterilization; the Ov~~ng Mission Constraint

Before proceeding to the more programnatic aspects of the undertaking,

we are concerned to single out the task of spacecraft sterilization from the

many and diverse problems that Martian exploration will enta~l. We believe

that many of our non-biologist colleagues have still not fully grasped either

~~e magnitude or the fundamental importance of this issue. .

Conta~ination of the Martian surface with terrestrial microbes could

irreversibly destroy ~~p~~a~ a truly unique opportunity for man~'ind)

to pursue a study of extraterrestrial life. Thus, ltlile we are eager to press

Martian exploration as expeditiously as the technology and other factors permit,

we insist that our recommendation to proceed is subject to one uncompromising

qualification: the attainment of effective spacecraft sterilization.

The avoidance of impact or the sterilization of the payload is thus the

boundary condition on all approaches to Mars. The teChnical proble~ preci-

pitated by this demand include the control of trajectories to an accuracy

sufficient to prevent the accidental impact of unsterilized payloads, the

development of sterilizable spacecraft cqrnponents for vehicles intended fo~

landing, and the development of sterilization procedures which will prevent

the introduction of microorganisms to predictable levels of confidence. It

is clear that as the number of landings on Mars increases, counting launChings

and landings on a world-wide scale, the probability of viable organisms

surviving on anyone payload must decrease. Since we have not as yet succeeded

in sterilizing a space vehicle, the problem must be considered unsolved.

An energetic program for the development of sterilization procedures of

space vehicles and their components must be implemented immediately tn=o=dar

if we are to take advantage of the opportunities Which will arise between 1969

and 1973. It cannot be emphasized sufficiently that standards of sterili~

are not subject to negotiation or compromise, that any retreat from this

position ~eans the loss of biologically significant information on Mars for

all time. We must guard not only against accidental neglect of all safeguards

but also against political pressures designed to place the pr~stige value of

space explorations above its scientific significance.

VI. Avenues of Anproach to the Exploration of Mars

For convenience wa distinguish four categories of work that can contribute

to attaining our goals: (a) laboratory work needed to develop techniques for

planetary investigations and the knowledge needed to interpret their findings;

(b) earth-bo~nd astronomical studies of Mars; (c) the use of spacecraft for

the ra~ote investigation of Mars; and (d) a direct study of the Martian

surface by landing missions.

(a) Laboratory work

Tne consideration of the evolution of life on Mars raises many

problems w~ich can be studied in earth-based laboratories. Such studies are

in fact essential to provide the background against ~ich the results of ~

planetary missions must be interpreted. Tne work includes the chemical analys~s

of meteorites, especially with respect to their content of organic compounds

and the extension of studies on the spontaneous formation of organic molecules

and their aggregation into larg~Units. Tnese investigations may reveal to

us the mechanism by which not only the materials essential for living organisms

ware first formed, but a~so the origin of reactions and mechanisms that led to

the formation of organized structures and their self-perpetuation. At the same

time a serious effort must be made to investigate possible alternatives to the

carbon-water system of biochenistry, or at least to obtain an estimate of the

likelihood of such alternatives~ We attach special importance to experim~nts

in whiCh Martian and other planetary environ~ents are simulated. While some

of w~ese simulated environments may allow terrestrial microorganisms or enzyme

systems to function, others may be more conducive to the activity of reactio~

systems based on alternative biochemistries.

It will become clear later that considerable work remains to be done in

defining sche~es for life detection and in developing the instrumentation to

exploit th~~.

(b) Earth-bound Astronomical Studies of }~rs ------- ---Tne observation of Mars from terrestrial observatories enjoys the

advantages of economy, absence of weight and size limitations, and high data

rate. It is however limited by the terrestrial atmosphere in attainable

resolution and spectral range and further constrained by daylight and waather.

Nevertheless much valuable work could be conducted at a cost which is low

compared to that of space programs if the nation's large inst~~ents ware made

available during prime seeing time for the observation of Mars. The use of

120" and 200" telescopes could rapidly extend our knowledge of the Martian

atmosphere and in particular our knowledge of the intriguing Sinton bands

described earlier.

(c) ~ne use of Spacecraft for Remote Observation of Mars

Some of th~ observational limitations imposed by the terrestrial

environment can be overcome by balloon-borne observatories but since they are

severely restricted in size and observation time their usefulness is limited.

Tne projected Earth-orbiting astronomical observatory (OAO) overcomes some of

these limitations and we believe the observation of Mars should be given a

substantial priority in the plans for its use.

It is, however, from Martian fly-by missions and, in particular, from

~~rtian orbiters that the remote observation of that planet is best undertaken.

We hope to obtain our ~i~st close-ap informat~.~n ,"on ~?-~. Martian surface from

the visual scan to be carried out by Mariner IV and gain additional knoN~edge

of atmospheric density by the occultation of the telemetry signals.

Fly-by missions are, however, severely limited in the time available for '

observation; they provide at best a fleeting glimpse of the planet.

Martian orbiters will be technically possible for·the opportunities of

1969 through 1973. They offer an unparalleled opportunity to scrutinize the

planet at comparatively short range. We have'examined in some detail

J0 potential orbiter payloads and have defined optimum instrument mixes for a

range of payload sizes. The largest we list would be well within the capacity

of a Saturn IB - Centaur syst~n to ~lace in orbit: It would carry instruments

for (1) optical polarimet~j (2) infrared spectro~etry; (3) mi~rowave radio~etryj

and (4) infrared and television mapping (106 bit per picture). These sensors

w~uld yield iT~formation on temperatures, atmospheric composition, topography, .

etc. and, most important of all, perffiit a sustained scru~iny.through a full

cycle of seasonal change.

(d) Martian landing missions: ABL's small and lar~

It is barely conceivable that the findings of a Martian orbiter could

confirm the presence of life on the planet. We are in any case convinced that

landing missions are a !!E£ qua ~ for adequat~ Martian exploration. Our

most difficult and least completed task has been the attempt to define lander

payloads.

Tne design is to some extent dependent on our knowledge of the structure

of ~~e Martian atmosphere. Tne size of the payload that can be deposited

depends, for instance, on whether tIle use of a parachute is feasible or

~~ether the density of 'the stmosphere is so low as to require the use of

retrorockets. An economical way of studying the Martian atmosphere is by the

use of non-survivable atmospheric entry probes. Such probes can be launched

either from Earth or from space vehicles, either fly-bys or orbiters. An

entry probe can transmit infonuation on atmospheric pressure, scale heig~t,

composition, winds, and surface conditions. Since· their design is not dependent

on atmospheric density, such probes are probably the most useful device for

obtaining the advance information needed for the successful soft landing of a

larger instrument package.

However, if we had a complete knowledge of these prerequisites for a

successful soft lander, our principal design difficulty would remain:

it concerns the problem of life-detection. t~1at minimal~~_~t~~~~~~

p~rmit us to conclude ~~ether living organi~~ist on Mars, or not? This

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question has been debated for the past six years and the absence of any clearcut

answer is in itself a significant fact.

To look for life we must know what it i$. And knowing what it is wa must

still translate our definitional criteria to operationally useful instrumental

assays. .The difficulties of an adequate definition of life are wall-enough

knoNn; L~ey include the problem, alluded to earlier, of transitional states

of organization between the fully living and the non-living. Probably the

nearest to a consensus we can hope for would be a definition that'focused on t

the organization of constiuent:molecules and - implicit in that focus -"

stressed infonnation storage and replication functions. That stress, in its

turn, implies the capacity for evolution. Such a definition is clearly

functional and were we to attempt to make it concrete we would be restricted

to the ~~emical basis of the o~ly organization and associated informational

system wa knoN - our own terrestrial case. Right here the difficulties become ~ ..

clear. Unless we commit ourselves to the view that Martian life has chemical

basis similar to ours, we are limited to functional assays; but the functional

assays - like detection of :expextrgR"RX exponential growth and reproduction -

are impossible witho~t knowledge of a suitable medium.

We cannot recount here all our deliberations on the life detection problem.

We have sought the most generalized criteria; among these is net optical

activity ~ich is almost surely the result of steric restrictions imposed by

a historical accident in the origin of life. Another is the presence in wl~Lf.A cal'\..

assays of exponential features ~.~ only be ascribed to growth and

reproduction. And we have reconciled ourselves to the fact that early missions ~. r . .:::

sho~ld assume a carbon-water type of bioc.~emistry .-is the most likely basis

to any Y~rtian life. On that assumption enzymes that should be widespread _

like p~osp~atases - can be, sought for and growth hopefully provided for by

very generalized media.

TIle fact remains, and dominates any attempt to define landers for

detecting life, that no single criterion is fully satisfactory, especially

in the meaning of its negative results. The reliability of ev~ry individual

assay is so contingent on the existence of particular conditions that wa

cannot be sure prevail on Mars wa must employ as mixed a strategy as possible, V\'\oou.:.' :':'.: I ..... :·'

as broad a spectrlli~ of assays as possible. Finally, we apply them to samples I,

in as logical a sequence as possible. (The logic of that sequence is, however,

a formidable fraction of what remains to be clarified.)

Discussion throughout our study has returned repeatedly to the conclusions

that We w..:>uld not be convinced by negative answers from single "life-detectors",

that given the hazards of any chanical or metabolic assay we should ensure some

direct visual inspection by television, and that the lander program must

ultimately involve ~at We came to call an Automated Biological Laboratory (ABL).

The ABL concept is not yet wall defined: it involves provision for the

multiplicity and divers1ty of chemical analytical tecnniques and biological

assays that our aims call for; it involves, too, the idea of an on-board ,

computer by means of which a variety of pre-programmed assay sequences can ~

initiated contingently on the results of prior steps; it involves the idea of a

sustained discourse between the computer and investigators on earth. It is,

in short, an ambitious concept. But our preliminary scrutiny of the ABL idea

suggests that tho·ugh a'llhitious it is fully possible with even the current

technology.

In the long run we believe that the return of Martian s~ples to the earth

and the sending of manned missions will become involved in the work. Neither

1<6

of these ar~ urgent considerations but surne of our readers will be as surprised

as we were to discover that manned Martian missions will probably be feasible

in the 1980 I s. Certainly neither the return of samples nor the send·ing of men

to Mars will be scientifically justifia~le until unmanned landings have

exhausted their great potentialities.

Iq

2·0

-VII- The Tir:linq and::Ovcr.:t11 S.t:.ra.tegy~ of.· Exploration

All of us would in principle prefer a gradualistic approach to the ultimate

goals of landing a large ABL on }~rs and) eventually, or returning samples for

study here. It is clear on all grounds - of economy) and scientific prudence _

that we should exhaust the possibilities of further progress using earth-based

observations and non landing missions to Mars.

There is, for instance, a strong majority of our opinions that believes

a successful orbiter program must precede a landing. The orbiter promfses an

i~ense extension of our knowledge of the atmosphere (its density and chemical

composition) and surface of Mars. Its capability for sustained ~easonal

~t~,;::~v observation and extensive topographic mapping will t a thorough re-evaluation

"" '4 of the several Martian features that have been considered suggestive of life.

And it will permit a far better informed selection of landing site for the

ultimate ABL missions. It has the further merit of effecting this substantial

step forward with minimum risk of contaminating the surface.

Constraints to proceeding in a completely unhurried, stepwise fashion arise

from several sources, however. They are a combination of~~~ex~~ab~eT astro-

nomical fact and the nature of space science in general. Any space experiment

takes years of preparation and budgetary committmentj the preliminaries to

actual flight involve years of experimental design, spacecraft development, and

the coordination of effort among large numbers of people in a wide range of .

disciplines. The scientific investigator no longer has the total freedom he

usually enjoys to make tentative starts) to explore hunches without full com-

mittment, to stop and follow another course o He is further plagued by the

prospect of investi.ng years of work only to encounter a mission failure or

cancellation in which it is all lost - at least until a new opportunity

arises perhap~ years hence. He may chafe under these circumstances but he

must accept them if he wishes to proceed at all. The goal of a Martian

l~nder will be by far the most complex and difficult spacecraft we will have

built) involve an even wider range of disciplines and instrumentation to be

coordinated.

to develop.

And it will be,for these reasons/the most costly and time-consuming

A Martian orbiter is itself a much larger undertaking than any space-

craft so far flown. The point is that we are confronted with the necessity

of near-comrnittment many years ahead of flight time; and the opportunities

for flights to Mars are by no means always at hand. The orbits of Earth and

Mars are such that these opportunities are limited to brief windov.Ts ~,*.ic~ ,::,ccur

every second year but undergo a further approximately 17 year cycle of favor-

ableness. Our attempt to develop a systematic and gradualistic program is I C' )

thus constrained to some extent dUe~ the fact that while favorable opportun-

ities occur in the 1969-73 period they will not return before 1984-5.

We have concluded that the 1969-1973 opportunities can be and should be

a~~loited for a substantial program of planetary missions. By that time the ), '4 '" .,.

Saturn booster system will be available, and a four to five year lead time is h'\.tA.h' :J-i~

evidently adequate for the development of ~ spacecraft. -------------_._-_.----_._--_._----_._---_. __ . ----- { The more' detailed planning of planetary missions for 69-73 is for the most (

part outside the scope of this Study's competence and commission: the decisions I concerned involve engineering and many other elements.~fJVl.~ ~,d'\.. w-~ ~4 wY:~r.;t!·

I

Neverth~ess scientific considerations do ju/stifY the f/OllOWin,/g )omments/o~,

the 69-73 missions. ~/I (1) ! large Martian orb 0 ter should be injUded for t?e reajns spetle~/out

earlie~' ~ this secti.on". "large" we mean f sCientifi/payload that woujd , I~u / / / .I":

inC1Ujl! instrumentat10n (a) optical PJ1arimetry;jb) in;rared spect1;ometry;

(c) microwave radiome and (d) infrared and teYZ1VOSion mapping (l~it per

Pi~ure). The success of this mission~ll depend on th/~vailabil/~ty of a / / /

Saturn class boos~er and a substantial improvement in currently available I

communications facilities.

~ .

(2) We deliberately omit an explicit recommendation in favor of any

fly-by missions additional to those already executed or planned for the 1964

and 1966 opportunities. They yield at best a fleeting glimpse of the planet,

and unless they are already so large that they could as well have been orbiters, /

/

the array of sensors ~ey carry is small •. Given t~ooster power adequate to

deliver it" an orbiter is overwhelmingly prefera~le. It may well be" however, /

I that strictly engineering considerations will demand some preliminary flights

/ in 1969:'and if these are undertaken their eJq>loration as fly-bys could yield

/ worthwhile information. /

(3) Some Martian lander should also be included preferably. to follow the

orbiter and exploit its findings; the'first lander must therefore be attempted

no later than 1973 and by 1971 if possible. ,,­

/

It is not possible for/~s to outline now what·the contents of a j' /

first lander should be interms' as specific as those used to describe the orbiter. /

The central point on which ~ll agree is that the mission ulti'-tely demands a

large lander, which we hay': come to call an ABL (Automate/niolOgiCal Laboratory). ,/

M1Ut is unclear at presont is how fast such a really large lander can be

designed and developed/from biological and engineeri~g viewpoints. It is.1 / i

I

however, clear that/its development, both as con,c'eptual design and engineering /

reality~ must be an evolutionary process; an~/that it is unlikely the evolution

of an ABL will be complete by 1971. /

In recommending a lander for 1971 we are therefore proposing something

/ s~ort of what is ultimately possible and desirable. We are certain, however,

/ I

that by 1971 b lander with a suffic,iently diverse array of inst4Ul1entation will I

/ be possible to justify its flight: And it may be that a sufficiently vigorous

ABL development will surprise.us in what in fact proves possible by that time.

(4) The task of designing an AnL should be initiated immediately as a

continuing project. The contents of landers in 1971 and 1973 will be an

incidental product of this continuing undertaking.

(5) The brief history of space science has already attested that space-

craft must be designed and evolved in relation to a particular'booster system;

the switch to new and larger boosters can ,render previous spacecraft

evolution obsolescent. It has also pointed up the dangers of designing

spacecraft to the limit of booster capacity. For these rea~ons~ and /.

further, because adequate orbiter and landing missions mu'st ultimately utilize ..'

large rockets of the Saturn class which will be available by 1969~ we

rcco~end that the entire Martian program be based on them from the outset~

if possible.

(6) Tne problems associated with the biological exploration of Mars

are div~rse, and the task of implementation raises challenges; in lnany respects

wholly novel. Orbiter and lander missions alike will involve many different

eA~erimenterse The evolution o~ an optimum scientific payload will require

a continuing dialogue among all potential investigators and the 'engineers ,

responsible for implementing their scientific goals. The u}ldertaking we are /,/

/

recommending cannot proceed without some provision for organizing and sus­/

/

'taining that dialogue on a continuing basis. As th~'program develops other devices

may become more appropriate but at the

of the Space Science Board will be the

\

,/'

outset we/believe a standing committee /

./ simplest adequate provision. ~t should

be charged with: (1) a continuing surveillance of progress from a scientific

viewpoint; and (2) the responsibility of giving advice on request to the

Space Administration.

VIII. Co~clusions and Reco~endations

The following surrmary of our conclusions and recom~endations is extracted

fro~n the foregoing pages:

(1) L'1e biological exploration of HaT$ recommended.

The biological exploration of Hat's is an undertaking of tne greatest

scicntif~c significance. Its realization will be a milestone in tne historJ

of hu~an acnieva~ent. We are unanimous in the assertion that its importance

and the consequences for biology which may 'stem from it justify the highest

priority ::,.vng all objectives in space science -- indeed in the space progra:n

as a wilole.

NO:le of us find the probability of life so lo'W' that exploration now would

be folly. On the other hand, most of us regard the probability of life on Mars

as reas':>nably hign; and all of us find it hign enough that given the immense

importance of a positive answer wa cannot escape the clear conclusion tnat tne

undertaking snould be carried forward.

(2) ~e Scientific Aims of the Exploration

We approach the prospect of Hartian exploration as evolutiona't'Y biologists.

Liv~ng systems have emerged as a cnapter in the natural history of the eartn's

surface. ~~r fundamental pr~~ise is a generalization from that single case: the

origin of living organization is a probable event in the' evolution of all

planetary crusts that resa~ble O'Jrs.

We thus conceive the over-all mission as a systematic study of the

evolution of the Hartian surface and atmosphere: has that evolution included,

in SO-.:le niches of the planet, Chemical syste.~s tvith the degree of complexity

and organization wa wo'~ld recognize as "living"? ~~r specific aims are:

(a) The determination of the physical and che~ical conditions of

the Martian surface as a potential environment for life,

(b) the determination of whether or not life is presen~ on Mars, and

(c) the, Characteristics of that life, is present.

//' (3) :~l i~~~diate start to_~oi~ the 1969-1973 opportunities.

A major effort should be initiated irnm~diately to exploit the particu-

larly favorable opportunit~es of 1969 thro~gh 1973.

~'7~ are here concurring 'vith the Space Science Board's vie"ls that planet'::::7

exploration snould be the major aim of the nation's space science efforts in

the 1970's and 1980·s; and, further~ that the biological exploration of Mars

be the priwary focus of the pro6ra~.

(4) 222~f~~erilization: a major mission constraint.

Before proceeding to other aspects of the undertaking, w,~ are concerned

to sin6le out tne task of spacecra~t sterilization from the many and diverse

probl~:ns that Hartian exploration 'tvill entail. He believe that ffi.3.ny of our

non-biologist colleagues have still not fully grasped either tne magnitude 'or

tne f~nda~ental importance of tnis issue.

Co~ta~ination of tne }~rtian surface with terrestrial microbes could

irrevocably destroy a truly uniqye opportun~ty for mankind to p~rsue a study

of extraterrestr~al l~fe. Tuus, WJ1~J..e vla are eager tv press Mart~au. explorat~uu.

as exped~tJ..ouS1Y as the technology and other factors permit, W~ insist that

o~r recom:nendation to proceed is subject to one uncompromising qualification:

the attaiThuent of ieffective spacecraft sterilization.

5.1 Every opportunity for remote observation of Mars by earth-

bour~ or balloon-borne instruments should be exploited to the maxLuum

,possible extent. A vigorous progr~ here can yield a very substantial

increase in our knowLedge of Y~rs before the major program of planetary

~issions begins in 19690

5.2 The brief his tory of sp:.ce science 1'..as already a:ttes ted that:

sp~cecraft t:lUS t 'be designed and evo:!. v~d in :cela.tion to a particular

boos ter sys te~; the switch to new l~rger boos'ters can render previous

,"

s?~cccr~£c evolution obsolescc~t. It l1..:1s also pointed up the dangers

of desizning spacecraft to the licit of booster capacity. For thcse \

-.. ' . rc.:sons,>·furthcr, because adequate orbiter and landing missions I:lust

ult:~-:..:lt:ely utili;:e large rockets of the S~turn class which will be

availa~le by 1969, We reco~~nd th~t ~he entire ~~rtian program be

b~~cs ou t~~ from the outset, ~= possiblco

5 1.3 We deliberately omit an explicit recommendation in'favor of

~ny fly-by oissions additional to thoc~ already executed or planned

for ~hc 1964 and 1966 opportunities. They yield at best a fleeting

Zli=psc of the 'planet, and unlc~s they are already so large that they

could ~s well have been orbiters) the array of sensors they carry is

s~llo Given the ~oostcr power adequate to deliyeT it, an orbiter is

overwhelminglY preferable. It may well be, however, that strictly

c~zincering considerations will d~uand some preliminary flights

in 1969 and if these arc uneertakcn their ~~ploration as fly-bys

could yield worthwhile inforwation.

5.4 Every e£fo=t should be ~de to achieve a large orbit~ng :"':":'-J __ <;

~:'ssion I(~Y 1971 at the latest)". This mission should precede the

first l(luder. By "large" we wean a n1-i-:li.-i1U:ilo scientific payload-&:€

~t-20Q-pvund& that would include instrumentation for: (a) optical

polarimetry; (b) in~rared spectrometry; (c) microwave radiometry; . , . '. t- vr :1.- r".~ ~-(" '*"

~~d (d)! television mapping (106 bit per picture) 0 The success of r...

:his oission will depend on the availability of a Saturn class

booster ~nd a substantial improv~nt in currently available co~uni-

cations facilities.

~ . i

, . . ..

5.5 The first landing mission should be attempted no later than

1973 and by 1971 if possible.

It is not possiblo for us to outline now what the contents of

.. first 1andc~ sV\ utl~ be in terms as -spec'ixrc i's:':ih~se used to

describe the orbiter. The central point on which all agree is that

the mission ultimately demands a large lander, which we have come to

call an ABL (Automated Biological Laboratory). What 1s unclear at

present is how fast such a really large lander can be designed and •

developed from biological and engineering viawpoints. It.!i, however.-

clear that the development, both as conceptiull design and engineeri~g.

really, must be an ev~lutionary process; and that it is unlikely the

evolution of an ABL will be complete by 1971. .. :

In recommending a lander for 1971 we are therefore proposing

something ahort of what is ultimately possible and desirable. We

are certain, however, that by 1971 a lander with a sufficiently

diverse array-of instrumentation will be possible to justify its

flight. And it may be that a sufficiently vigorous ABL development

will surprise us in what in fact proves possible by that time. I _)

, ,5.6 The task of designing an ABL should be initiated

~diately as a continuing project. The contents of landers in-

1971 and 1973 will be an incidental product of this continu1ng .

u~ertaking.

"

(.

:1 ,

~

1 \

5.7 The problems associated with the biological exploration task

of ~rs are diverse and the t--~ of implementation raises challenges

in many respects wholly novel. Orbiter and lander missions alike

will involve many different exper~enters. The evolution of'an

optimum scientific payload will require a continuing dialogue among

all potential investigators. and the engineers responsible for

icplementing their scientific g~als. ~he undertaking we are recom-

~nding cannot proceed without some provision for organizing and

sustaining that dialogue on a continuing basis. As the program·

develops other devices may become more appropriate but at the outset

we believe a standing committee of the Space Science Board will bee

the siQplest adequate provision. It should be charged with: (1) a

continuing surveillance of progress from a scientific'viewpoint; and

(2) the responsibi1~~ of Siving advice on request to the' Space

AdQinistration.

~ .. -.. ltI

2101 CON"'STITUTION AVENUE WASHINGTON 25. D. C.

CABLE ADDRESS: NARECO WASHINGTON. D. C.

Memorandum

To:

From:

Subject:

NATIONAL ACADEMY OF SCIENCES NATIONAL RESEARCH COUNCIL.

OF THE UNITED STATES OF AMERICA

SPACE SCIENCE BOARD

21 February 1965

Exobiology Study Participants

J. P. T. Pearman, Executive Director

Summary Chapter - Final Review

The Summary, previously circulated~has been revised by the Steering Committee on the basis of comments received. The revised text (but without preface, title page and table of contents) is enclosed for your final review.

Please advise me of any major points you find unacceptable at your earliest convenience. If we do not hear from you by Febru­ary 26, we shall assume concurrence. Please do not hesitate to telephone or wire collect, if necessary.

I trust you will excuse this note of urgency - we wish to make the report available with the least additional delay.

I. Introduction

Until recent years the or~g~n of life and its possible occurrence elsewhere in the universe have been matters for speculation only. The rapid growth of molecular biology since 1940 has, to be sure, changed the discussion of life's origins into far more precise and explicit terms than were possible earlier; and the subject entered a new, experimental, phase in the 1950's with successful abiogenic synthesis of impor­tant biochemical substances in conditions simulating the presumptive environment of the primitive earth. But the real transformation which the subject has undergone stems from the spectacular growth of space technology in the last decade. The possi­bility of life's origin and occurrence on planets other than ours is no longer limited to idle speculation: it has entered the realm of the testable, of science in the strict sense. Given the rockets now available and especially those available by 1969 it has become fully realistic to consider plans for the biological exploration of Mars.

The Study which this report seeks to interpret was convened in June, 1964, by the Space Science Board of the National Academy of Sciences to examine this possibility. The vlorking group comprised 36 people representing a broad spectrum of scientific in­terests: evolutionary biology, gene' lCS, microbiology, biochemistry and molecular biol­ogy, animal physiology, soil chemistry, organic chemistry, planetary astronomy, geo­chemistry, and theoretical physics. The membership included some with considerable prior involvement in problems of space exploration and others with none. Advice was also sought outside the group of immediate participants on the potentialities of selected analytical methods for the experimental study of extraterrestrial life and its environment. More than 30 individuals contributed in this fashion written assessments of techniques in which they were particularly well versed.

Our task was to examine the scientific foundations and merits of the proposal to undertake a biological exploration of Mars. What were the potential scientific yields? How valuable, if attained, would they be? What, in fact, is the possibility of life occurring on Mars? And of our detecting it with the available and foreseeable technol­ogy? What could be achieved by further astronomical work from earth? by Martian fly-by missions? by Martian orbiters? and Martian landers? What payloads would we recommend for planetar~,r missions? What timing and overall strategy would we recommend for Martian exploration were we to consider it worthwhile at all?

In brief the overall purpose was to recomm~nd to the Government through the Academy's Space Science Board, whether or not a biological exploration of M~rs should be included in the nation's space program over the next few decades; and, further, to outline what that program, if any, should be.

We emphasize that our conclusions were reached on strictly scientific grounds: that we recognize a much wider array of considerations bear on any ultimate decision to undertake Martian exploration. As a body we were not charged with nor did we attempt the broad over-view that entails these other considerations. We predicated our discussion on the continued vigor of a national space program. We did not, for

•

instance, ~d(.r0ss ourselves to the question of whether the very large cost of developing the Saturn b,)Qsters could be justified on scientific grounds. Nor should we have; the dl!vcl(lpl:1Cnt (:f the Saturn boosters is already firmly connnitted for other reasons. The questions we faced were whether the application of such boosters to the biological ex?loration of the solar system - of Mars in particular - can answer well-framed and in~?ortant scientific questions; and what priority these questions merit within the space prograo.

II. The Origin and Nature of Life

The modern, naturalistic view of life's origin and evolution dates from the foundations of modern biology a century ago. Implicit in the evolutionary treatment of life is the proposition that the first appearance of organisms was only a chapter in the natural history of the planet as a whole. Oparin later made this notion explicit in his view that the origin of life was a fully natural, perhaps inevitable, step in the ontogeny of the Earth. Systems capable of self-replication and controlled energy transfer - living organisms - had their origin in the sequence of chemical changes that were part of the planet's early history.

The tractability of this great inductive step to further discussion has been enhanced by the progress of terrestrial cellular biology and biochemistry over the last few decades. What has emerged from that progress is a unified picture of life at the subcellular and chemical levels, underlying the unity at higher levels which so largely influenced Dan-lin. Not only is there a common pattern to the structure of cellular organelles - membranes, mitochondria, nuclear apparatus, etc. - but a still more surprising unity is found in its molecular constituents. Everywhere on Earth the essential catalytic functions are discharged by proteins, energy transfer effected by ATP, and the synthesis of proteins today controlled by an elaborate nucleic acid system. The same enzymatic cofactors are found in organism after organism; particular metabolic pathways recur from cell to cell; and everywhere the fundamental functions of information storage and replication are assigned to the nucleic acids.

To a significant extent the discussion of life's origin must concern the or1g1n of those molecular types that are crucial in cellular organization: the origin of nucleic acids, of proteins, of carbohydrates, and so on.

In the 1950's a series of experiments was initiated in which the synthesis of biologically important compounds was accomplished by application of energy to pre­sumptive primitive environments. The list includes: amino acids and their polymers; carbohydrates and fatty acids;purines and pyrimidines; nucleotides, including adenosine triphosphate (ATP), and oligonucleotides - every major category of molecular sub-unit of \vhich the cell is built.

The credibility of the naturalistic, evolutionary view of life's origin as an exploitation of previous chemical evolution on a sterile Earth is greatly heightened by these results: the great chemical complexity of its molecular constituents does not, in last analysis, require the intervention of the cell itself.

The general tenet that life involves no qualitative novelty - no elan vital -goes hand in hand \-lith the more explicit proposition that it is the molecular organi­zation, as such, of living things that alone distinguishes them from the non-living. The central issue in discussing origins now concerns not so much the prior evolution of complexity in molecular constituents as the attainment of their organization into a system that is alive. It is here we lack any sure guides - save one - on the cont­gency involved; on how improbable it all was. That one lead comes from the great and

well-known advances of molecular genetics in the past ten years.

The essence of organization in one sense is its improbability, its dependence on specification or information. And the most characteristic feature of living organ­izations - organisms - is their capacity to store and replicate the evolving informa­tion on which their existence depends. The high point of our biochemical advance has been identification of the molecular basis of these defining characteristics. It is astonishing how much we have recently learned about the manner in which the informa­tion underlying life's organization is encoded in molecular structure; that we under­stand how that molecular structure is replicated; and further that simple polynucleo­tides have been synthesized in cell-free systems.

It remains unclear, of course, what precise sequence of events exploited the opportunities afforded by the purely chemical evolution of the earth's surface and atmosphere. But at some point in the unknown sequence a community of molecules would have been fully recognizable to us as a living as against a non-living thing: it would have been bounded from its environment by a membrane, capable of controlled energy expenditure in fabricating more of itself and endowed with the capacity to store and replicate information.

We Catlnot fully-know the precise course of the earth's early chemical evolution, and the degree of contingency involved in the subsequent transition to a living organ­ization of molecules; and for these reasons '''e cannot fully assess just how probable or improbable life's origin ,,,as at the outset of our ml1n planet's evolution. Nor can we estimate to what extent the emerging picture of a single chemical basis to life on Earth reflects a physical necessity for living organization as against a mixture of physical sufficiency and historical accident. Is it so that the catalysis essential to chemical organization can be effected only by proteins containing the 20 amino acids we encounter in cells; and that the nucleic acids are the only polymers, for physical reasons, that can carry molecular information satisfactorily? Or are these and other empirical generalizations about life on earth, such as optical activity, merely a reflection of the historical contingency that gave such molecules first access to living organization, thus preempting the field; precluding realization of other physically sufficient molecular foundations for life.

To the extent we cannot answer these questions we lack a true theoretical biology as against an elaborate natural history of life on this planet. We cannot prejudge the likelihood of life's appearance on Earth; therefore we cannot confidently take the great inductive step when "t"e are told by astronomers that there may be 1020 planetary systems elsewhere in the universe '''itb histories comparable to our own. One thing is clear - for life to be unique to our planet the probability of its origin must be almost unimaginably 1m". If, on the other hand, the probability is.at all reasonable, life must be abundant in the 1020 planetary systems that fill the sky.

Hhat is at stake in this uncertainty is nothing less than knowledge of our place in nature. It is the major reason why the sudden opportunity to explore a neighboring planet for life is so immensely important.

He emphasize that the act of discovery itself 'vould have this great scientific, and for that matter philosophical, impact. But it is also important that discovery would, in another way, be only the beginning. The existence and accessibility of Martian life would mark the beginning of a true general biology of which the terrestrial i~ a special case. l~e ,,,ould have a unique opportuni ty to shed new light on the meaning of that astonishing molecular similarity in all terrestrial organisms. Is it there as a physically necessary basis for life? Or is it - physically sufficient but not

necessary - an historical accident in the sense that in another instance of planetary evolution a different basic chemical complexity could equally well have emerged and preempted the local opportunity for life?

III. The Possibility of Life on Mars

No thoughtful person will disagree with our assertion on the scientific importance of life elsewhere in the solar system. It is however another matter to conclude that search for it should proceed at once. The exploration will be costly in money and other resources. To undertake it 'ole need !.2.!!!£ assurance it is not folly from the outset.

Interest immediately focuses on }lars. The nearest and most earth-like of the planets in the solar system are ~lars and Venus,but the surface of Venus has been tentatively excluded as a possible abode of life, because of the probably high surface temperatures. The ~lartian year is long (687 days) but the length of its day is curiously similar to that of Earth, a fact that to considerable degree ameliorates an othenoJise very severe environment.

Mars has retained an atmosphere, although it is thin; current estimates of pressure range from 10 to 80 millibars at the surface. Its only certainly identified constituents are carbon dioxide (accounting for 5-30% of the total) and water vapor present in very much smaller amounts (2 x 10-3 gm cm- 2). Oxygen has been searched for and not detected; the sensitivity of such measurements implies a partial pressure not greater than 0.25 millibars. Nitrogen and argon are believed to constitute the bulk of the remainder. The flux of ultraviolet radiation at the Martian surface may be high, but this is not yet certain. Hmyever, some models of the composition of the atmosphere allow for effective shielding.

The surface temperatures overlap the range on Earth: at some latitudes and seasons they have a daily high of +30°C with a diurnal range of about 100° c.

There are two 'o1hite polar caps '''hose composition has been the subject of some contt·ovcrsy. The evidence now is clear that they are ice, in the form of hoar frost. They undergo a seasonal 'vaxing and waning which is probably accompanied by an atmospher­ic transfer of water vapor from one hemisphere to another.

Our knowledge of what lies between the polar caps is li~ted to the distinction bet'oJeen the so-called "dark" and "bright" areas and their seasonal changes. The latter, usually considered "deserts", are an orange-ochre or buff color. The former are much less vividly colored. It is likely that early descriptions of the dark areas as green result from an optical illusion due to"contrast with the orange "bright" areas.

Biological interest nevertheless continues to center on the "dark" areas. In several respects they exhibit the kind of seasonal change one would expect were they due to the presence of organisms absent in the "bright" (desert) areas. In spring the recession of the ice cap is accompanied by development of a dark collar at its border, and as the spring advances a Have of darkening proceeds towards the equator and, in fact, overshoots it 20° into the opposite hemisphere.

Polarimetric studies suggest that much of the Martian surface may be covered with small sub-mi llimeter sized particles. The curve on \o1hich this inference is based shows a seasonal displacement in the dark areas, but not in the bright. Infrared absorption features have been at. ributed to the dark areas, suggesting abundant H-C bonds there -more recent analysis throws great doubt on his interpretation, leaving us with no definite information, one way or the other about the existence and distribution of organic matter.

Needless to say, none of these inferences about the Martian dark areas demands the presenc~ of organisms for their explanation.

Ind(;eo, the question is \o1hether the Bartian environment could support life at all; and furi:l::er, 'tolhether the history 1,·;rould have permitted the indigenous origin of life. These are clearly different questions. Our answer to the first question is that we find no compelling evidence that Mars could not support life even of a kind chemically sir.:ilar to our m·ln. Here oxygen present to the small limiting extent current measurements allow, a fully aerobic respiration would be possible. But even its total absence would not of itself ?~~clude life. One of our more rewarding exercises has b(;cn the challenge to cons t ruc t a ~·lal·tian ecology assuming the most adverse conditions indicated by present knowledge: it posed no insuperable problem. Some terrestrial organisms have already been shown to survive freeze-thaw cycles of +30 0 to -70°C. Others arc known to cope with extremely low humidities and derive their water supply metabolically. There are many conceivable ways of coping with a strong flux of ultraviolet (and even of exploiting it as an energy source). The history of our own planet provides plenty of evidence that, once attained, living organization is capable of evolving adjustments to very extreme environments. And, finally, \ole arc reminded that the evidence \o,le h.::ve on Nartian condi tions is very coarse-grained, a sort of average that takes account of almost no local variations dependent on topography. Within the range of conditions represented by our present numerical estimates it is likely that there exist, perhaps abundantly - as on Earth -places where the extremes of temperature, aridity, and adverse irradiation are markedly ameliorated. Even the presence of water in the liquid phase is perhaps not unlikely, if only transiently, by season, in the subsoil.

A measure of our judgment that niches in the contemporary Martian environment could support life of a sort comparable to that of Earth is provided by our over­riding concern \o1ith the danger of inadvertently contaminating Mars with terrestrial organisms. We shall return to this problem later.

The other question - \'lhether life in fact is there - depends .on our judgment of how probable its origin on Mars has been. This is precisely the question we cannot answer even for Earth and the principal reason for considering exploration in the first place.

Given all the evidence presently available we believe it entirely reasonable that Mars is inhabited with living organisms and that life independently originated there. However, it should be clearly recognized that our conclusion that the biological exploration of Mars will be a rewarding venture does not depend on the hypothesis of Martian life. The scientific questions which ought not to be prejudged are:

a. Is terrestrial life unique? The discovery of Martian life \vould provide an unequivocal ~ answer.

b. Hhat is the geochemical (and geophysical) history of an Earth-like planet undisturbed by living organisms? If \oJe discover that Mars is sterile \ve· m~y find answers to this alternative and highly significant question.

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IV. The Scientific Aims of Martian Exploration

We approach the prospect of Martian exploration as evolutionary biologists. The origin of organisms was a chapter in the natural history of the Earth's surface. The hypothesis to be tested is a generalization from that single case: the origin of living organization is a probable event in the evolution of all planetary crusts that resemble ours. We thus conceive the over-all ndssion as a systematic study of the evolution of the Martian surface and atmosphere: has that evolution included, in some niches of the planet, chemical systems with the kind of organization we would recognize as "living"?

Our aims in summary form are:

(1) ThE~ determination of the physical and chemical conditions of the Martian surface as a potential environment for life,

(2) the determination whether or not life is or has been present on Mars, (3) the characteristics of that life, if present, and (4) investlg.ati.C?n of the pattern of chemical evolution without life.

This formulation emphasizes that as biologists we have as much interest as the planetary astronomers in a thorough study of the meteorology, geochemistry, geophysics, and topography of Mars. Whatever the outcome of a direct search for life, ·its full meaning will escape us unless the findings can be related to the prevailing environment.

v. Avoiding the Contamination of Mars

Before proceeding to the more programmatic aspects of the undertaking, we are concerned to single out the task of spacecraft sterilization from the many and diverse problems that Martian exploration will entail. We believe that many of our non­biologist colleagues have still not fully grasped either the magnitude or the funda­mental importance of this issue.

Contamination of the Martian surface with terrestrial microbes could irreversibly destroy a truly unique opportunity for mankind to pursue a study of extraterrestrial life. Other future uses of Mars are not evident to us now; whatever they are, they may be clumsily destroyed by premature and uninformed mistakes in our program. We are eager to press Martian exploration as expeditiously as the technology and other factors permit. However, our present sure knowledge of Mars is very slim and so our recommen­dation to proceed is subject to one rigorous qualification: that no viable terrestrial microorganism reach the Martian surface until we can make a confident assessment of the consequences.

In operational context this means that the~robability of a single viable organism reaching the Martian surface be made small enough to meet scientifically acceptable standards. These standards, already established provisionally* ~hould be continually reexamined in the light of all new information. Moreover, every effort should be made to ensure the continued acceptance by other launching nations of the recommended confidence levels for protection of Mars. against contamination. The technical problems precipitated by this demand include the control of trajectories to·

., .. .. S:: * Report of COSPAR Seventh Meeting, Florence, Italy, May 1964, Resolution 26.

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an accuracy sufficient to prevent the accidental impact of unsterilized payloads, the development of sterilizable spacecraft components for vehicles intended for landing, the development of procedures which will prevent the introduction of microorganisms and the means for establishing the reliability of the entire program. Since we have not yet succeeded in sterilizing a space vehicle, the problem must be considered un­solved.

An energetic program for the development of sterilization procedures of space vehicles and their components must be implemented immediately if we are to take advan~ tage of the opportunities which will arise between 1969 and 1973. We must guard not only against accidental neglect of necessary safeguards but also against placing ephemeral considerations of prestige above enduring scientific significance and utilitarian value of our exploration of space.

VI. Avenues of Approach to the Exploration of Mars

For convenience, we distinguish four categories of work that can contribute to attaining our goals: (a) laboratory work needed to develop techniques for planetary investigations and the knowledge needed to interpret their findings; (b) Earth-bound astronomdcal studies of Mars; (c) the use of spacecraft for the remote investigation of Mars; and (d) a direct study of the Martian surface by landing missions.

(a) Laboratory work

The consideration of the evolution of life on Mars raises many problems which can be studied in Earth-based laboratories. Such studies are, in fact, essential to provide the background against which the results of planetary missions must be inter­preted. The work includes the chemical analysis of meteorites, especially with re­spect to their content of organic compounds, and the extension of studies on the spontaneous formation of organic molecules and their aggregation into larger units. These investigations may reveal to us the mechanism by which not only the materials essential for living organisms were first formed, but also the origin of reactions and mechanisms that lead to the formation of organized structures and their self-perpetua­tion. Other possibly interesting lines of effort include alternatives to the carbon­water system of biochemistry and simulations of Martian and other planetary environ­ments. While some of these simulated environments may allow terrestrial microorganisms or enzyme systems to function, others may be more conducive to the activity of reaction systems based on alternative biochemistries.

It will become clear later that considerable work remains to be done in defining schemes for life detection and in developing the instrumentation to exploit them.

(b) Earth-bound Astronomical Studies of Mars p

The observation of Mars from terrestrial observatories enjoys the advantages of economy, absence of weight and size limitations, and high data rate. It "is however limited by the terrestrial atmosphere in attainable resolution and spectral range and further constrained by daylight and weather. Nevertpeless, much valuable work could be conducted at a cost which is low compared to that of space programs if the nation's large instruments were made available during prime seeing time for the observation of Mars. The use of 120" and 200" optical telescopes and of the largest radio telescopes and interferometers could rapidly extend our knowledge of Mars. We support the

. recommendations of another co~ttee of the National Academy of Sciences· on the

• Ground-Based Astronomy, A Ten-Year Program, National Academy of Sciences Publication No. 1234, 1964.

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development of ground based astronomical facilities. For such facilities to play a significant role in the planning of 1969-73 Mars missions work on this program must be begun early.

(c) The use of Spacecraft for Remote Observation of Mars

Some of the observational limitations imposed by the terrestrial environment can be overcome by balloon-borne observatories but since they are severely restricted in size and observation time their usefulness is limited; it is also restricted by absorption in the Earth's atmosphere. The projected Earth-orbiting astronomical obser­vatory (OAO) overcomes some of these limitations and we believe the observation of Mars particular in the ultraviolet should be included in the plans for its use.

It is, however, from Martian fly-by missions and, in particular, from Martian orbiters that the remote observation of that planet is best undertaken. We hope to obtain our first closeup information on the Martian surface from the video scan to be carried out by Mariner IV and gain additional knowledge of atmospheric density by observation of the telemetry signals during occultation of the spacecraft.

Fly-by missions are, however, severely limited in the time available for observa­tion; they provide at best a fleeting glimpse of the planet.

Martian orbiters will be technically possible for the opportunities of 1969 and thereafter. They offer an unparalleled opportunity to scrutinize the planet at comparatively short range. Potential orbiter payloads have been examined by another group and compositions of such payloads have been suggested for a range of instrument, weights up to 200 lbs. (which is within the capability of the Saturn IB-Centaur).For !

example, a modest payload which any of several vehicles could place in orbit might include instruments for (1) infrared and television mapping; (2) microwave radiometry;

, (3) infrared spectrometry; and (4) optical polarimetry. These sensors would yield information on temperatures, surface and atmospheric composition, topography, certain characteristics of surface structure, etc. and, most important of all, permit a sus­tained scrutiny through a full cycle of seasonal change and over a major fraction of the Martian surface.

(d) Martian landing missions: ABL's small and large

While it is conceivable that the findings of a Martian orbiter could establish the presence of life on the planet, we are in any case convinced that landing missions are essential for adequate Martian exploration. The definition of lander payloads is . a complex and demanding task which we have only begun to explore.

Their design is to some extent dependent on our knowledge of the structure of the . Martian atmosphere. The size of the payload that can be deposited depends, for in­

stance, on whether the use of a parachute is feasible or whether the density of the atmosphere is so low as to require the use of retrorockets - this is especially critical for small payloads. In this connection, we note the possibility that the density profile of the Martian atmosphere will be .determined by astronomical means, or by Mariner IV, with sufficient precision for the purpose of designing a landing system. A more direct method for studying the Martian atmosphere involves the use of non­survivable atmospheric entry probes that could transmit information on atmospheric density structure and composition. Such probes could be launched from either fly-bys' or orbiters. Since their design is not dependent on atmospheric density, these are useful devices for obtaining advance information if needed, for the survivable landing of an instrument package. The view has also been presented that a small surviving

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capsule: \olould have even more value, in that it might determine not only the density profile of the atmosphere, but also its composition at the surface, wind velocity and other data th.'::lt would enhance the probability of success of a large lander.

However, if we had a complete knowledge of these prerequisites for a successful survivable lander, our principal design difficulty would remain: it concerns the problem of life-detection. What minimal set of assays will permdt us to detect Martian life if it does exist? A debate on this question for the past several years

, bas yielded a variety of competing approaches. Each of these is directed to some manifestation of life according to the cues of terrestrial biology. Needless to say,

. visual reconnaissance, from mdcroscope to telescope is one of the most attractive of these for it offers the expectation that many recognizable hints of life would immediately attract our attention. However, we can easily imagine circumstances in which

... this type of observation would be inconclusive. Many other suggested procedures seek :!;.~. '. 'to identify, at the outset, the more fundamental biochemical structures and processes r;:' that we would, in any case, explore in depth. No one of these analyses, however,

:W' whether photosynthesis or respiration, DNA or proteins, growth, enzymes or metabolism, or, in a figurative sense, fleas or elephants, can be sure of finding its target and reliably reporting on it under all circumstances, nor would any single approach satisfy all the particular interests that motivate different investigators in their search

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We cannot recount here all our deliberations on the life detection problem. We have sought the most generalized criteria; among these is net optical activity, which is almost surely the result of steric restrictions imposed by an historical accident in the origin of life. Another is the presence in assays of exponential features which can only be ascribed to growth and reproduction. And we have reconciled ourselves to

. the fact that early missions should assume an Earth-like carbon-water type of bio­chemistry as the most likely basis to any Martian life. On that assumption enzymes that should be widespread can be sought; growth could hopefully be provided for by generalized media.

The fact remains, and dominates any attempt to define landers for detecting life, that no single criterion is fully satisfactory, especially in the interpretation of some negative results. To achieve the previously stated aims of Martian exploration \~e must employ as mixed a strategy as possible.

Discussion throughout our study has returned repeatedly to the conclusions that \~e would not be convinced by negative answers from single "life-detectors", that given the hazards of any chemical or metabolic assay we should ensure some direct visual inspection by televiSion, and that the lander program must ultimately involve an Automated Biological Laboratory (ABL). The ABL concept is not fully defined: it involves provision for the multiplicity and diversity of chemical analytical techniques and biological assays that our aims call for; it"'involves,too, the i,dea of an on-board· computer by means of which a variety of programmed assay sequences can be initiated contingently on the results of prior steps; it also involves the idea of a sustained discourse between the computer and investigators on earth. It is, in short, an ambitious concept. But our preliminary scrutiny of ~he ABL idea suggests that, though ambitious, it is realizable with the current technology.

In the long run we believe that manned expeditions and the return of Martian samples to the Earth will be part of the exploration of the planet. Neither of these is immdnent, but some of our readers will be as surprised as we were to discover that manned Martian missions will probably be feasible in the 1980's. Certainly neither the return of samples nor the sending of men to Mars will be scientifically justifiable until unmanned landings have pr~pared the way.

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VII. The Timing and Overall Strategy of Exploration

All of us would in principle prefer a gradualistic approach to the ultimate goals of landing a large ABL on Mars and, eventually, of returning samples for study here. It is clear on all grounds - of economy, and scientific prudence - that we should exhaust the possibilities of further progress using Earth-based observations and non-landing missions to Mars.

For instance, a strong majority of the Working Group believes a successful orbiter program should precede a landing. The orbiter promises an immense extension of our knowledge of the atmosphere. (its density and chemical composition) and surface of Mars. Its capability for sustaining seasonal observation and extensive topographic mapping will permit a thorough re-evaluation of the several Martian features that have been considered suggestive of life. And it will permit a far better informed selection of landing site for the ultimate ABL mdssions. It has the further merit of effecting this substantial step forward with minimum risk of contamdnating the surface.

Constraints to proceeding in a completely unhurried, stepwise fashion arise from several sources, however. They are a combination of celestial mechanics and the oper­ational realities of space research. Any space experiment takes years of preparation and budgetary commitment; the preliminaries to actual flight involves years of experi­mental design, spacecraft development, and the coordination of effort among large numbers of people in a wide range of disciplines. The scientific investigator no longer has the total freedom he usually enjoys to make tentative starts, to explore

,!. hunches without full commitment, to stop and follow another course. He is further t"',.. plagued by the prospect of investing years of work only to encounter a mission failure /;. or cancellation in which it is all lost - at least until a new opportunity arises

.: ,:;'.:.;. . . Dp.rhaps years hence. He may chafe under these circumstances but he must accept them :j'}~~~r-if he wishes to proceed at all. The goal of a Martian lander will be by far the most 'J.::: complex and difficult spacecraft we will have built, involve an even wider range of 1'.:-· disciplines and instrumentation to be coordinated. And it will be, for these reasons,

., the most costly and time-consuming to develop. A Martian orbiter is itself a much larger undertaking than any spacecraft so far flown. The point is that we are con­fronted with th~ necessity of near-commitment many years ahead of flight time; and the opportunities for flights to Mars are by no means always at hand. The orbits of Earth Rnd Mars are such that these opportunities are'now limited to brief windows

--which recur about every second year but undergo a further approximately 17 year cycle of favorableness. Our attempt to develop a systematic and gradualistic program is thus constrain~d to' some extent by the fact that while favorable opportunities occur in t~~_1~6~~73 period they will not return before 1984-5.*

We have concluded that the 1969-1973 opportunities can be and should be exploited

* For these reasons an alternative strategy has been discussed: it would allow the early use of landing probes, always providing that reliable decontamdnation systems will have been developed and authenticated. A udnority opinion holds that small landers may provide environmental information useful in the design of other spacecraft and may succeed more readily than orbiters. According to this view the way should be left open to their use - even though the results obtained may well be less comprehen­sive.

for a substantial program of planetary missions. By that time the Saturn booster system will be available, and a four to five year lead time is evidently adequate for the development of initial spacecraft.

The more detailed planning of planetary missions for 1969-73 is for the most part outside the scope of this Study's competence and commdssion: the decisions concerned involve engineering and many other element~ with which we did not cope.

VIII. Conclusions and Recommendations

(1) The Biological Exploration of Mars Recommended.

The biological exploration of Mars is a scientific undertaking of the greatest validity and significance. Its realization will be a milestone in the history of human achievement. Its importance and the consequences for biology justify the highest priority among all objectives in space science -- indeed in the space program as a whole.

(2) The Scientific Aims of the Exploration

We approach the prospect of Martian exploration not only as biologists but as scientists interested in evolutionary processes over the broadest range. Living systems have emerged as a chapter in the natural history of the Earth's surface. We wish to test the hypothesis that the origin of life is a probable event in the evolu­tion of all planetary environments whose histories resemble ours.

We thus conceive the over-all mission as a systematic study of the evolution of the Martian surface and atmosphere: has that evolution included, in some niches of the planet, chemical systems with the degree of complexity, organization and capacity for evolution we would recognize as "living"? Our specific aims are:

(a) The determination of the physical and chemical conditions of the Martian surface as a potential environment for life,

(b) the determination whether or not life is or has been present on Mars, (c) the characteristics of that life, if present, and (d) investigation of the pattern of chemical evolution, in the

absence of life.

(3) An Immediate Start to Exploit the 1969~1973 Opportunities

A major effort should be initiated immediately to exploit the particularly favorable opportunities of 1969 through 1973.

l~e arc here concurring with the Space Science Board's views that plane~ary ex­ploration should be the major aim of the nation's space science efforts in the 1970's and 1980's; and, further, that the biological exploration of Mars be the primary focus of the program.

(4) Avoiding the Contaudnation of Mars: a Major Mission Constraint

Before proceeding to other aspects of the undertaking, we are concerned to single out from the many and diverse problems that Martian exploration will entail, the task of prevention of contamination.

Contamination of the Martian surface with terrestrial microbes could irrevocably

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destroy a truly unique opportunity for mankind to pursue a study of extraterrestrial life. Thus, while we are eager to press Martian exploration as expeditiously as the technology and other factors permit, we insist that our recommendation to proceed is subject to one rigorous qualification: that no viable terrestrial microorganisms reach the Martian ~~urface until we can make a confident assessment of the consequences.

(5) Programmatic Recommendations

5.1 Every opportunity for remote observation of Mars by Earth-bound or balloon and satellite-borne instruments should be exploited. A vigorous program here can yield a very substantial increase in our knowledge of Mars before the major program of planetary missions begins in 1969.

5.2 It has become evident that an adequate program for Martian exploration cannot be achieved without using scientific payloads substantially larger than those currently employed in our unmanned space research program. 'Although predominantly engineering considerations may incline to early use of smaller payloads, we see very substantial advantages in the use, from the outset, of the new generation of large boosters which are expected to become operational toward the end of the present decade. These advantages include: the possibility of avoiding spacecraft obsolescence due to a change in booster; the potential for growth in the versatility of scientific pay­loads and the relief of pressure on the engineer to design spacecraft to the limit of booster capacity.

5.3 We deliberately omit an explicit recommendation in favor of any fly-by missions additional to those already executed or planned for the 1964 and 1966 opportunities. They yield at best a fleeting glimpse of the planet, and unless they are already so large that they could as ,~e1l have been orbiters, the array of sensors they carry is small. Given the booster power adequate to deliver it, an orbiter is overwhelmingly preferable. It may well be, however, that strictly engineering con­siderations will demand some preliminary flights in 1969 and if these are undertaken their exploitation as f~y-bys could yield worthwhile information.

5.4 Every effort should be made to achieve a large orbiting mission by 1971 at the latest. This mission should precede the first lander. (A dissenting minority view supports the simultaneous use of small landing probes.) By "large" we mean a scientific payload that would include instrumentation for: (a) infrared and television mapping; (b) microwave radiometry; (c) infrared spectrometry; and (d) optical polari­metry. The success of this mission will depend on the availability of a large booster and a substantial improvement in currently available communications facilities.

5.5 The first landing mission should be s~heduled no later than 1973 and by 1971 '~~ if possible.

We have not yet outlined what the contents of a large lander should be in terms as specific as those used to describe the orbiter~ The central point on which all agree is that the mission ultimately demands a large lander, which we have come to call an ABL (Automated Biological Laboratory). What is unclear at present is how

::' fast such a large lander can be designed and developed from biological and engineering viewpoints. It is, however, clear that the development, both as to conceptual design and engineering, will go through several generations. It is hoped that the first generation of an ABL could be used for the 1971 opportunity.

The lander we are recommending for 1971 is something short of what is ultimately possible and necessary but could have a sufficiently diverse array of instrumentation

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to answer Some of the scientific questions we have posed.

5.6 The task of designing an ABL should be initiated immediately as a con­tinuing project The contents of landers in 1971 and 1973 will be products of this continuing unde~taking.

S.7 The problems associated with the biological exploration of Mars are diverse and the task of implementation raises challenges in many respects wholly novel. Orbiter and lander missions alike will involve many different experimenters. The evolution ~~ an optimum scientific payload will require a continuing dialogue among a". ~otentia1 investigators and the engineers responsible for implementing their scientific goals. The undertaking we are recommending cannot proceed without some provision for organizing and sustaining that dialogue on a continuing basis. As the program develops other devices may become more appropriate but at the outset we believe a standing comrndttee of the Space Science Board will be a useful provision. It should be charged with: (1) a continuing surveil'.ance of progress from a scientific viewpoint; and (2) the responsibility of giving advice on request to the National· Aeronautics and Space Administration.

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REPORT OF THE COMMITTEE ON fllARI'IAN lAiiJDERS

The Committee to consider Mars landers consisted of A. Douglas

¥~cLaren, vance Oyama, George Hobby, Gerry Soffen, Edward Evans,

and was ~haired by Wolf Vishniac. Jerry stuart contributed addi­

tional information. The Committee considered two landing vehicles,

one containing up to fifty pounds scientific payload, and the other

a scientific payload between 100 and 300 pounds. The Committee

considered payloads which would be most economical: the largest

amount of information that could be obtained in the smallest

~rray of apparatus, as well as the largest amount of useful

information that was, likely to be obtained per number of bits.

The Committee also considered the logical sequence in Which

such experiments might be carried out, the coherence of the

investigation carried out by any one payload, and the 'contribution

that information so obtained might make to future investigations.

Ideally, the complement of anyone experiment should be available,

sterilizable, amenable to automatic programming, and be applicable

to the study of soil samples.

The following pages are a brief surr~ary of the detailed dis­

cussions vhich were held, and it is clear that each item requires

congiderabl~ amplification. The payloads described on pp. II' and 12

are the unanimous recommendation of the Committee, the suggested

sequence of operations was drawn up later by the Chairman. The

specific recommendations listed in the discussion section also

have the Committee's unanimous support.

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SAMPLING

We viewed the sampling as the single most important problem

that confronts the design of an unmanned lander. The performance

of anyone investigation is strictly dependent on the availability

of a sample and on its size. This dependence upon the availa­

bility of a sample which must be obtained regardless of the

nature of the surface on which the lander may light places

a considerable demand on the sophistication of the sampling

equipment.

A sampling device must obtain a sample with high reliability,

.regardless which technique may be employed (sticky surfaces, suction,

either alone or with abrasives, coring, drilling, explosive fragment­

ation, or scooping). Ideally the sample should consist of small

particles or be sufficiently friable to permit chemical processing.

Since there are limits below which one cannot perform satisfactor,y

chemical analyses the size of the sample will determine the nature

of the experiments that may be performed upon it. vIe have conside·red

as the example of the most difficult soil to work with a terrestrial

desert soil which may contain 0.1% organic matter or less. Of

such soil 10 grams would be a lower limit for extensive analytical

procedure~, while a desirable sample would be in the order of 100

grams to 1 kilogram. In addition to obtaining a sample, ancillar,y

equipment should be able to measure the sample and parcel it out

to various experiments that may compete for the same sample. A

metering of the sample will give us not only the basis for any

quantitative measurement, but will also tell us whether or not any

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sample has ~een introduced in anyone experiment, so the experiment

will not go through the programmed motions without a sample having

been int~oduced.

Each landed instrument package should contain several sampling

devices so chosen that at least one of them should be successful.

venturi suction deVices, although capable of the induction of

sizable samples in suitable soil, are bound to be successful at

least in ~he milligram range. Even smooth rock has enough dust

or sandy material on it which could be collected by some such

device.. Devices for obtaining larger samples ",ould have to

find a suitable substrate on which to operate. It is therefore

desirable that at least the largest sampling device (100 grams to

1 kilogram) be equiped with sufficiently sophisticated sensors to

allow it to tell whether it rests on rocky surface or on loose

SOil. This would preclude the sampler from exhausting its power

supply or suffer mechanical damage on a rocky surface. Some roving

capability should be built in, so that the sampler could reach

out and test for surfaces of various hardness and begin its sampling

on the pTo-per ground. Roving ca})llbili ty is also ir.:po=-tant to

escape ~he burned area 'should ~~trorockets be used and to avoid

splinters of wood if balsa is used as an impact limiter. The im-

portance of sampling devices is such that the Committee feels justi-

fied in aSSigning a large fraction of the lander weight to the sampling

operation. Since at present the only devices available work reliably

in the milligram range, the Committee recommends strongly that larger

iampling devices be developed.

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The subsequent sections discuss the performance of a landed

complement of instruments in terms of the sample required for each

experiment. We' list the measurements that may be performed without

any solid sample, with samples' of one or more milligrams, 1 to 10

grams, apd with amounts over 100 grams.

ENV1RONMENTAL MEASUREMENTS REQUIRING NO SOLID SAMPLE

Humidity. Relative humidity should be measured immediately

above the surface as well as below. Such measurements could be

carri~d out for instance with an A~03 detector in which conductivity

is a function of water adsorption. MeastrEments below the surface

of the soil could be carried out by the incorporation of such a

detector in a probe which will penetrate the soil. This same

probe woUld include some of the measuring devices or attachment~·

mentioned below. The measurement of humidity below ground would

not be a measure directly of the water content of the soil but of . '

the water in equilibrium with the gas phase in the soil. Humidity .~

should be measured at intervals for a full Martian day in order to

obtain the diurnal variation.

Temperature. A temperature measu~ment should accompany the

humidity measurements ~oth' .~bove ground and below.

Pressure. A single measurement of atmospheric pressure should

be carried out.

Atmospheric' Composition. We suggest a gas chromatographic

analysis' of the gases found in the atmosphere and below the Boil.

Of particular interest is the determination of oxygen. The sensi-

tivity'of the oxygen ~easurement should be sensitive to a value at

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least 2 orders of magnitude below the nominal maximum value for

oxygen ( 0.025 mb = 10-6mols/liter). Should gas chromatography

not be sufficiently sensiti~e we suggest an exploration of methods

such as the use of kryptonate or fluorescence quenching. Other

gases that may be detected and measured by gas chromatogr.aphy

would include a confirmation for the values assigned to carbon

dio~de, and a search for gases of potential biological significance

such'as H2S, NH3, CH4, CO, oxides of nitrogen such as N20, NO, and

N02, and HCN. In terrestrial biology these gases may be metabolic

end products as well as substrates. Some of these gases may con-

ceivably occur at higher concentrations in the atmosphere underground.

Radiation. It:Ls of interest to determine the flux of ultra­

violet light between 1850 and 3000 l.. This could either be measured

by a broad band determination or by resolving it into about 100 o A bands. A series of filters and a thermopile are suggested as

one typ~ of detector. The determination of ionizing radiation

has been considered only for secondary missions.

Surface s:tructure. A study of the mineralogical structure

and chemical composition of the surface could possibly be obtained .

by x-ray diffraction, infra-red reflectance 'spectroscopy, and alpha

scattering.

EXPERIMENTS WITH MILLIGRAM SAMPLES

Organic Matter. Milligram amounts of soil can be pyrolyzed

and volatile material condensed on a flat plate. A small non-

specific uv source and a non-selective detector of visible light

could determine the rormation of fluorescent material which is

fonned from all, organic matter during pyrolysis.

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Growth ~ Catalytic Activity. Milligram samples can be us~d

to detect chemical activities such as the evolution of gases or

change in pH. . The~e experim~nts may take the form of pro­

viding labeled organic substrates and looking for the evolution

of radioact-1ve gases or a determination of the increase of par-

ticles in either distilled water, salt solutions, or in the

presence of organic compounds. Gas evolution, which can· be

detected either by measurement of radioactivity or by gas chroma­

tography, may take place eithe:r in solution or in soil samples

barely moistened with the appropriate reagents. The increase

in particles can be measured only in a liquid medium by ,light scattering

which may detect 103 particles.

The organic substrates might be sterilizable carbon compounds

in such combinations that some of them might be used by micro-

organisms, or one that is easily decomposed such as urea. Urea

is commonly found and decomposed in the soil, but it may also

have a non-biological origin and therefore be found even in the

absence of living organisms. Its .decomposition could be detected

by observing the evolution of ~~onia and carbon dioxide. Various

salt solutions may be designed to support organisms that could

occupy the ecological niches expected on Mars, and should make

allowance for the possibility that high salt concentration is

a Yartian device of water preservation.

EXPERIMENTS WITH GRAM SAMPLES

Soil Composition. In addition to the experiments described -above which can be performed on milligram. samples, larger samples

of Martian soil can be heated to obtain volatile gases which are

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driven off under these conditions. After driving off H20, and possibly

NH3 and 'C02, ,the heating can be continued until pyrolysis occurs.

The fragments'ot w~t may have been organic compounds may then be . ;; .

passed through a gas chromatograph into a mass spectrometer_ The

combination of ' the gas chromatograph and mass spectrometer for the

study of pyrolyzed soil samples is ~commended on the basis of its

operational Simplicity, versatility, and scope. It is limit~d by

the data capability. It is recommended that despite this limitation

this technique can be valuable since suitable programming may

select fOr the trans~ssion of a few peaks of major interest. The

t~nsmission of a full GC/MS scan will have to wait for the strength-

eniIlt$ ,Of the data link.

Compounds·of High Molecular Weight. It is of interest to deter-

mine the occurrence of compounds .of high molecular weight. Such

compounds may be organiC compounds and be of biological significance,

either as the products of living organisms or as the accumulation

of some prebiotic'chemical events. From the point of view of the

origin and ~yol~tion of l~~e the occurrence of any compound of J>~" , If' ~

molecular weig~t'above 500 br 1000 InfJ.y be of interest, even if it , '" .j.' ,

is Dot a carbon~compound. The techniques that have been proposed

for such studies, such as dialys'is and dye absorption (J-band) do

not distinguish adequately between high molecular weight organic

compounds and colloidal c~ys such as bentonite. We recommend

that the use of a molecular sieve technique of which sever.al have

been developed in recent years and are capable of determining

molecular weights in ranges of interest to biologists (Sephadex,

derivatives of agar, and polyamides such as Bio-Gel)-

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Ident.ifica.tion of Amino Acids and Their Optical Isomers. Amino ------- -- -- --- ----- ---acids may occur in soil either as the result of biological activity

or may arise in prebio~ic chemical events. Amino acids may there­

fore occur in·~rtian soil regardless whether living organisms

exist or not. ,In that event it is of interest not only to identify

the amino acid but. to determine whether one optical isomer pre-

dominates. A technique which is capable of doing both again

exploits the capabilities of the gas chromatograph. If one

optical isomer of an optically active alcohol is used to esterify

the amino acids, gas chromatography can distinguish the optical

isomers of the amino acids. An extension of this technique

promises to carryou~ sim~lar operations with esterified optically

active carbohydrates. Such an instrument would be useful not

only in analYsis of soil but i~ the analysis of Martian organisms

should it have been possible to cultivate them in a growth experiment.

Fluorimetry. An examination of soil. samples by spectral fluori­

metric techniques may identify several classes. of organic compo~ds

of potential biologic~l significance. The use of two monochromators,

or at least of two sets of filters, allows the selective use of various

wavelengths of exciting light in addition to a measurement of the

~mission band. Such examination would ·reveal compounds related

to photodynamic pigments, porphyrins, phenazines including flavins,

quinones, proteins, nucleic acids, and others.

Elementary Analysi~. We recommend the development of apparatus

capable to carry out a chemical elementary analysis of the major

soil constituents. Although no such automatic apparatus exists

at the moment we believe that this and other wet chemical techniques

. are amenable to automation.

• I

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EXPERIMENTS WITH 100 GRAM - 1 KILOGRAM SAMPLES

Soil Respiration. In addition to,all the analyses that have

been mentioned above, large samples of soil lend themselves to

measurements of acti vi ties observed in the total soil; A large

sample may be monitored for gas exchanges, paying particular atten-

tion to carbon dioxide and ammonia. Such gas exchanges may be

monitored on the original sample and upon the addition of water or

various solutions of minerals and organic compounds. An alternative

to carrying out experiments with large samples in the instrument

capsule might be an experiment performed in situ. Possibly a section

of soil might be suffiCiently isolated by a suitable shroud to

carry out such measurments without necessity ~f removing the sample

from its location.

The availability of large samples of soil suggest growth experi-

ments in which the medium is ,an aqueous extract of such soil. The

preparation of a Martian soil extract and its use as a growth

medium may turn Q.ut to have many advantages over whatever might , :

be supplied in th~ ~~~,trument capsule. ~.~

, Photosynthesis. Since all life depend~'~~~~n the energy conversion •. '. r

-r~'

from radiant energy to chemical energy it wO~9L/,~e desirable to test ; .,,;~, \ 'I

, ~~) .. for the occurrence of photosynthesis. The only/d.~fini te experiment

,'/' "'( included in these reconnnendations i~ part of t~e:growth experiment

in which the occurrence of light dependent growth may be tested.

The Committee feels it desirable to see a procedure developed

which would search for photosynthesis in a sensitive and more

direct fashion. Light dependent C02 fixation appears promising

and can he made sensitive by the use of c1402, but since C02

4

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fixation.is not a necessar,y, though likely, concomitant of photo-

synthesis, the development of another approach.may be desirable.

Pending such development we recommend an experiment in which C02

fixation is meas~red as a function of light.

PICTURES

Although pictures of Mars would be extremely desirable their

demand on the communication link are such that their transmission

at present would interfere with the transmission of data from

other experiments. The Committee feels very strongly that the

amount of information obtained, f.:rom pictures is small on a per

bit basis compared tc;> what can be learned from many other experi-

ments, and that pictures should therefore be assigned a secondary

priority. Given the choice, tpe Committee feels that the various

analytical experiments ~hat have been proposed will provide us

with more valuable information than pictures are likely to do.

Nevertheless, efforts should be made to improve the communi-

cation link to the point where the transmission of an occasional \ 7 , ....

picture (10 bitsl,wOt4d not interfere with other experiments. Should

it be possible to obtain such pictures the following observations

appear desirable: ~~,to see an experiment in which growth may have

ta~en place, .either~~~roscoPically or microscopically; b) to ob­

serve the enviromnent in which the spacecraft is operating and

elroe'cially in which the sampler is collecting Martian soil; and

c) to observe a sample being taken in a close-up picture. The

.----- observation of a mechanical device obtaining a soil sample may

Q

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give us a strong, visual impression of the Martian soil. It is

strongly recommended that all efforts be made to improve the

communication link, including the development of better or larger

transmission antennae and power supplies. In this' connection

we urge NASA' to request from the AEC the development of RTG or

similar devices that will extend the availability of energy both

in level and time.

SUGGESTED PAYLOAD CONFIGURATIONS

Two payloads are considered here, one including 50 pounds

of scientif.ic instruments, not counting the data processing equip­

ment, a~d the other approaching 300 pounds.

Fifty-Pound Payload

1. Detection of water in the atmosphere 1 pound· _

2. Gas chromatograph for atmospheric analysis, 7 pounds

3. Measurement of atmosphe!ic pressure 1 pound

4. Photomet·ry of ultraviolet light 3 pounds

5'. Probe f9 r soil examiIlSltion which will " '

include waterde~ection and other devices 6'pounds

6. Temperature. measurement for inclusion in 5 and

1 1 pound

7 • Gas intake f.or soil probe to lead to gas

chromatograph

8. Sampl~ng devices from milligram range to

10 gram ~nge

1 pound

15 pounds

9. Fluorimetric detection of organic compounds 5 pounds

10. Combustion device for t~e detection of carbon,

hydrogen, nitrogen, sulfur in gas chromatography 5 pounds

·~

.' --- -12-

11. Growth eJq>enment, "biological amplification

of sample", incl. "enzyme" 5 pounds

TOTAL 50 pounds

263 Pound Lander

Items 1-10 above 45 pounds

12. Sampler' for 100 gram to 1 kilogram range, . .

including roving capability and soil testing 40 pounds

'13. Sample processing (sifting, distribution,

extraction, measurements of pH and conductivity) 15 pounds

14: Detection of amino acids and separ.ation of

optical isomers 25 pounds

15. Fluorimetri'c examination of soil 15 pounds

16. Growth experiment, more sophisticated than

Item 11 above 15 pounds

17. Detection of catalytic activities ("enzyme

experiments") 3 pounds

18. Soil respiration measurements on large sample 10 pounds

19. Detection of high molecular weight compounds

and molecular s~eving 5 pounds

20. ~ss spectroscopy to follow gas chromatography 25 pounds

21. Photosynthesis detection 10 pounds

22. x-ray diffractometer 15 pounds

23. Measurement of alpha scattering 30 pounds

24. Elementary analysis 10 pounds

TOTAL 263 pounds