The Exploration of the Moon and Planets:A New Perspective on Earth

James W. Head, IIIDepartment of Geological Sciences, Brown University

Providence, Rhode Island USA

50th Anniversary of NASA

Inhabiting the Space-Time Continuum

Inhabiting the Space-Time Continuum

Most people

Inhabiting the Space-Time Continuum

Solar System

Billions of Years

50 years of explorationhas brought us out here!

Mariner 10

VenusExpressCassiniGalileoMagellanVega 1,2Venera 15,16Venera 13,14Venera 11,12Pioneer12,13Venera 9,10Mariner 10Venera 7,8Venera5, 6Mariner 5Venera 4Mariner 2

Chang-e-1KaguyaSMART-1Lunar ProspectorClementineGalileoLuna 21,22,24Luna 17,19,20 Zond 8Luna 16Zond 5,6,7Luna 14Surveyor 5,6,7Lunar Orbiter 4,5Surveyor 3Lunar Orbiter 3Lunar Orbiter 1,2Luna 11,12,13Surveyor 1Zond 3, Luna 9,10Ranger 7,8,9Luna 1,2,3

Apollo 17Apollo 16Apollo 15Apollo 14Apollo 12Apollo 11Apollo 10Apollo 8

Phoenix 2007 Mars Recon. Orb. Opportunity, SpiritMars ExpressMars OdysseyMars PathfinderMars Global SurveyorPhobos 2Viking 1,2Mars 4,5Mariner 9Mars 3Mariner 4,6,7

Cassini-HuygensGalileoVoyager 1,2Pioneer 10,11

HayabusaNEARGalileo

Bepi-Colombo 2011

Venera D

Jupiter Orb Probe 2011

Future studies

Past and current Only successful missions

Stardust 2004-2008Deep Space 1GiottoSuisei, SakigakeVega 1,2ICE

Rosetta 2004-2011

Japan manned 2025US Moon Base 2020Chinese sample return 2017Chinese lander 2012Luna Glob 2011Lunar. Recon. Orb. 2008Chandrayaan-1 2008

New Horizonsto Pluto

Comet sample return 2010?

Mars 2018, 2020Scout/Mars Sample Return 2016Mars Sample Return/Scout 2013Scout 2011Fobos Grunt 2009Mars Science Laboratory 2009

Messenger

1958

Professor Thomas A. (“Tim”) Mutch

OUR JOB IS TO THINK OUR WAY

TO THE MOONAND BACK

Apollo 15

Hadley-Apennines

Earth: Exploration

• When did plate tectonics start?• How and when did continents form?• What was the early atmosphere like?• When, and where, did life originate?

• We needed an understanding of the major processes operating inthe first half of Solar System history.

Earth: What is the history of the formative years?

Comparative Planetology

• Where is the record of the major processes operating in the first half ofSolar System history?

• Planets and moons were soon to join Earth as objects of geologicalinterest and analysis.

• We were on our way to a Grand Experiment:The field of Comparative Planetology was born.

Luna 9 – first soft lunar lander

Luna 13

Portion of Luna 13 TV panorama

1966

Lunar Ranger1961 - 1965

Ranger 7: July, 1964Ranger 8: Feb., 1965Ranger 9: Mar., 1965

Soviet Union-US Space Race to the MoonCold war period flights to the Moon

USSR Attempts 48

Successful 21

USA Attempts 31

Successful 22

From Huntress, Moroz, Shevalev, 2003

Moon: Exploration

Moon: Exploration

Apollo 15

Hadley-Apennines

Moon: Exploration

Lunar rock typesMaria

Highlands

Lunar ages

MariaHighlands

HighlandsYoung craters

Origin of the Moon: Giant Impact Hypothesis

The Moon was formed due toaccretion of the impact ejecta

in orbit around the Earth.

Mars-size body

Proto-Earth

Moon: Insights into the formative years of planetary history.• Ancient age of lunar crust.• Magma Ocean: Concept of wholesale melting.• Linkage of geological observations and accretionary theory.• Moon formed from impact of Mars-sized object into early Earth.• Lunar Interior: Crust, lithosphere and thermal evolution.• Differentiation, segregation instability and overturn.• The Moon as a “one-plate” planet in contrast to Earth.• Impact cratering is a fundamental geological process.• Cometary volatiles may accumulate near poles.• The Moon is a record of the first half of solar system history.

Mercury

Mercury: Exploration• Earth-based observations.• Mercury, slightly larger than the Moon, but containing a

core of lunar size; What would the geology look like?

• Mariner 10 - 1973.

Mercury: Lunar-like surface, Earth-like interior

• Mercury is Moon-like!• Impact craters and plains dominate the surface.• Are the plains volcanic or impact?• Tectonic one-plate planet, but with huge tectonic scarps.• Magnetic field: Is the core liquid and convecting?• Mariner 10 raised more questions than it answered.

Mercury: Lunar-like surface, Earth-like interior• What is the origin of Mercury's huge core?• Recent Earth-based measurements are consistent with a molten core:

Implications?• Does Mercury have crustal magnetic anomalies?• What is the origin of the smooth plains: Does Mercury have surface volcanism?• What is the cause of global-scale contraction early in its history?• Does significant global contraction inhibit extrusive volcanism?• Are the radar reflective materials in polar crater interiors water ice?

• MESSENGER and BepiColombo will explore the half of Mercury unobserved byspacecraft, and address these questions. MESSENGER M-1 1/08; M-2, 10/08!!

???????

Departure NAC Mosaic 2(DEP_NAC_MOSAIC_2)

•Acquire 15x13 NAC mosaic, to cover northernhemisphere, including M10 gore + "new" territory nearlimb portion. Resolution is from 140 - 300 m/pixel.

Departure NAC Mosaic 2(DEP_NAC_MOSAIC_2)

•Acquire 15x13 NAC mosaic, to cover northernhemisphere, including M10 gore + "new" territory nearlimb portion. Resolution is from 140 - 300 m/pixel.

Individual frames acquired

Departure NAC Mosaic 2(DEP_NAC_MOSAIC_2)

•Acquire 15x13 NAC mosaic, to cover northernhemisphere, including M10 gore + "new" territory nearlimb portion. Resolution is from 140 - 300 m/pixel.

Mosaic produced

MESSENGER Second Flyby, October 6, 2008

Mars

Mars: Exploration

The Geological RecordOf Climate Change

Hydrological Cycle and System:Surface and Near-Surface Reservoirs

MARS

Study of Extreme Climate Change

Latitude-DependentIce-Related Deposits

Latitude-dependent layer found above 30º North and South latitude.

(Mustard et al., 2001; Kreslavsky and Head, 2000, 2002; Milliken et al., 2003; Head et al., 2003)

Lineated Valley Fill:Debris-Covered

Valley Glacier Systems.

Plateau Icefields?

Mars Earth

Dickson, Head and Marchant, Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases, Geology (2008).

- Heavy impactbombardment.- Valley

networks.- “Warm/Wet”

early Mars?

-Volcanism.- Outflowchannels.- Oceans?- Southcircumpolardeposits.

- Low impact rates.- Tharsis volcanism continues.- Outflow channels continue.- Late-stage polar caps.- “Cold/Dry” late Mars.

Water and Climate on Mars: Relation to Geologic History

Open Basin LakesN=210 (~65% newly

recognized)Fassett and Head, 2008a,b

Noachian Valley Networks and Open Basin Lakes

Mars: Moon/Mercury with Water and Climate

• Mars similar to the Moon and Mercury in many ways.• Tectonics: No signs of plate tectonics: A one-plate planet.• Significant record of early impact history and volcanism

preserved in its crust.• But Mars differs in fundamental ways!

Mars: Moon/Mercury with Water and Climate

Differences from the Moon and Mercury:1) Global crustal dichotomy:2) Tharsis and Elysium topographic rises.3) Volcanic activity extends up to the geological present.4) Mars is a "water" planet: Rivers, lakes and oceans.5) Extreme oscillations in spin-axis obliquity characterize Mars.6) Huge crustal magnetic anomalies.7) True polar wander may have occurred.8) An early "warm and wet" Marsis a likely habitat forthe formation and evolution of life.

• Mars may be the true Rosetta stone ofEarly Earth history, filling in the missing transition.

Venus

Venus: Exploration

Venus Atmosphere P surface = 93 barT = 470 Cat 6052 km radius

CO2 major component N2 admixtureO2 and H2O traces

Three cloud decksat 45 – 70 km altitudeConcentrated H2SO4

Strong zonal windsfrom E to W ~100 m/s at the clouds level

Light from the sky isorange

Soviet Union Venera 13 Color Panorama

Volcanism on Venus

Venus: An Earth gone astray?

• Venus exploration has revealed a planetary surface that, like the Earth,has no remaining morphological record of the first two-thirds of SolarSystem history.

Venus: An Earth gone astray?

• There is no ancient heavily-cratered terrain.• The surface is predominantly volcanic in origin.• Tesserae: Intensely tectonically resurfaced terrain.• Impact cratering record is sparse.• Average age of the surface < a billion years.• Crater population nearly completely spatially random and the vast majority of

the craters have not been modified.

Mikhail Ivanov, Vernadsky Institute, RAS

• Venus must have undergone a global-scale resurfacing in its recent history!!• This resurfacing must have been geologically rapid!• What could have caused such a configuration and event?• Among the hypotheses are:• 1) transition from mobile lid to stagnant lid lithospheric regime,• 2) episodic plate tectonics, and• 3) catastrophic overturn of a depleted-mantle layer.• Could similar processes lie in Earth's past or future?

Venus: An Earth gone astray?

Comets

Asteroid belt

Comet nuclei

Black arrow shows place

of impact

Outer planets and satellites

Satellites and Rings of Saturn

Satellites of Uranus

Oberon

Ariel

UmbrielTitania

Miranda

Puck

Miranda, D = 480 km

Impact cratersand

Tectonicstructures“coronae”

ρ = 1.2 g/см3

Composition:ice Н2О +silicates

Voyager 2 image

Young icy surface of Europa

“Rafted terrain – ice layer thickness <10 km,Below water to ~ 100 km, volcanism on the floor?Chemogenic life like at “black smokers” on Earth??

Search for extraterrestrial life, Europa

July 14, 2015

The Sun!

The Critical Role of the SUN inPlanetary Evolution

• The Sun: The “King Kong” of planetary climate evolution!• SOLAR INSOLATION: The fundamental input parameter to

the nature/evolution of climate systems.• The Sun: A VARIABLE STAR at many timescales!

– Sunspot cycles.

– ~500 year CMEs.

– Faint young Sun.

– Changes in solar activity andluminosity on scales for whichwe are totally clueless!!

Earth -The Home Planet

Inhabiting the Space-Time Continuum

Solar System

Billions of Years

50 years of explorationhas brought us out here!

Earth: Returning to the HomePlanet!

• We now have perspective on the missing chapters in the first half of Earth history.• Impact cratering is a fundamental planetary geological process:• 1) Proto-Earth was hit by a Mars-sized projectile.• 2) Huge impact basins in early Earth history.• 3) Throughout history: Negative influence on existing biota, mass extinctions.• Density inversions of internal layers and global resurfacing: Could such events

initiate plate tectonics on Earth?• Radical climate change and Snowball Earth: What are the lessons from Mars?• Life: New perspectives on hospitable environments.

NASA at 50 Years

• No longer do we view the Earth in isolation. Earth is now a member of afamily of terrestrial planets that have shared similar events and phasesin their histories.

-We look to the geological record of one-plate planets tounderstand the role of impact cratering with time.

-We look to Venus to understand how tectonism and volcanismmight appear during the Earth's Archean period, billions of years ago.

-We observe the thermal evolution of different terrestrial planetsand wonder what the distant future holds for Earth.

-We look to Mars to understand radical climate change.-We look to the Moon to understand how our crust formed.-We look to Mars, Europa and beyond to understand life’s origins.-We look to Pluto because it is there!

Ongoing Lunar Missions

Chang-e 1, China

Kaguya, Japan

Mars ARES

Answers to these fundamental questions lie in the results of space missions tobe undertaken in the next 50 years of Solar System exploration!

51 Years Since Sputnik:The Next 50 Years of NASA

Comparative Planetary Systems

The Next Fifty Years