Microsymposium 36, MS035, 2002

1

DDS-BIOMARKER HYPOTHESIS IS SUPPORTED BY WATER DATA OF MARS ODYSSEY.A. Horváth (1,2), T. Gánti (3), Sz. Bérczi (4), A. Gesztesi (1), E. Szathmáry (3,5), (1) Budapest Planetarium of Society forDissemination of Scientific Knowledge, H-1476 Budapest Pf. 47, Hungary, (2) Konkoly Observatory, H-1525 Budapest Pf. 67,Hungary, (3) Collegium Budapest (Institute for Advanced Study), 2 Szentháromság, H-1014 Budapest, Hungary, (4) EötvösUniversity, Dept. G. Physics, Cosmic Mat. Sp. Res. Gr. H-1117 Budapest, Pázmány 1/a. Hungary, (5) Eötvös University, Dept.of Plant Taxonomy and Ecology, H-1117 Budapest, Pázmány 1/a. Hungary (planet@mail.datanet.hu)

AbstractIn the analyses of several thousand Dark Dune Spots (DDSs)on Southern Polar Region of Mars from MGS MOC imageswe could determine the shape, the pattern and the sea-sonal/annual dynamics of these spots. The time sequence ofDDSs was interpreted as a process resulting from possiblebiological activity [1, 2] of putative Mars Surface Organisms(MSOs). MSOs heat up by the absorption of sunlight, growand reproduce through photosynthesis and generate in parttheir own living conditions. The lifecycle of putative MSOscan explain the dynamics of DDS morphogenesis. As weearlier predicted in this model H 2O ice is a important compo-nent of the frost and the dark soil [2]. New water observa-tions of Mars Odyssey spacecraft on the Southern PolarRegion’s of Mars well support our predictions [12, 13].

IntroductionDark Dune Spots (DDSs) and their clusters are interestingobjects with seasonal frost cover transformational dynamics.They were observed on the Mars Orbiter Camera (MGSMOC) narrow angle images of the Mars Global Surveyorspacecraft [3] from the years of 1998, 1999 and 2001. Frostcover appears during winter and gradually changes latewinter and early spring forming spots of defrosting on thedark dunes. On other surfaces the frost disappears duringspring, but on the dark dunes the frost persists until latespring or even early summer [4]. Various authors [4, 5, 6]studied the whole defrosting process from winter untilsummer of the southern hemisphere and they concluded thata complex process of CO2 sublimation and re-precipitation(function of season and local temperature, under the controlof the surface and interior geophysical properties of thedunes) may couse the defrosting process.

Observations of the DDS transformation with 4 actorsWe studied the transformational process according to ahypothesis which describes the observations on dark dunespots morphology, the patterns of DDSs, the formation andtransformation of DDSs by using other components andactors, than that of [4-6]. Namely: over the Dark Dunefields’ material and its frost cover , new actors as the water(embedded in the hypothetically porous dark dune soil) andthe putative Martian Surface Organisms (MSOs) were alsoinvolved as agents in the defrosting process.

Individual DDSs exhibit a characteristic spot structurewith inner dark region, transitional grey peripherial ring andthe frost cover surrounding the structure (Fig. 1A) [1, 2, 8].On slopes the spots are elongated downwards: they occur inellipsoidal or fan-shaped forms and sometimes streams flowout from these spots (Fig. 1B) [1, 2]. We also observed thatDDSs are shallow crater-like holes in the frosted layer andthe DDS formation process is triggered from the bottom ofthe frost (Fig. 1C) [2, 7]. We also observed seasonal andannual variation and recurrence of DDSs patterns, too (Fig. 1

D and E) [2, 7]. The shape, location, development and otherfeatures of the DDSs prompted us to suggest that some fluidphase must be invoked in their explanation, which under thegiven circumstances cannot be anything else but liquid water.

Fig. 1 Dark dune spots (DDSs) characteristic events: inner ringstructures (A), fan and flow-shaped forms (B), shallow holes-form(C), seasonal (D) and annual (E) dynamics. Sun in all figuresilluminated from upper left, north is up.

Horváth, Gánti, Bérczi, Gesztesi, Szathmáry:DDS-BIOMARKER HYPOTHESIS IS SUPPORTED BY WATER DATA OF MARS ODYSSEY

2

Biological interpretation of DDS-formation by 4 agentsWe interpret the sequence of DDS formation as a

accelerated process of sublimation combined with melting ofwater and some kind of biological activity of putativeMartian Surface Organisms acting on, or in, the material ofthe dark dunes 1, 2, 7, 8 .

We sketched the following life cycle of MSOs: in winterthe first rays of sunlight activate the MSOs, they start towarm up H2O component and evaporate the CO2-frost coverfrom bottom. Later MSOs begin to grow and reproducethemselves in the water melted by them. Defrosting of the icecover stops shielding the MSOs and water immediatelyevaporate, too, on the unprotected region. The completeevaporation of liquid water stops the life conditions of MSOsand they desiccate.

All these events happen in the upper layer of the darkdune soil. In our model we suggest that the four componentsact together in a life-cycle and in a desiccation cycle,alternately following each other seasonally and annualy.Therefore, despite the adverse conditions, the hypotheticalMartian Surface Organisms could dwell below the surfaceice, in the upper water-rich layers of the dark dune filed.

Water observation of Mars Odyssey on South PoleMGS MOLA data indicate that the southern frost cover is0.1--1 meter thick [9]. These are average values, from whichsignificant deviations may occur locally. The frost cover mayconsist of three components: frozen carbon dioxide, carbondioxide clathrate and water ice [10, 11]. Unfortunately, wedo not have any data on the relative composition and internalstructure of the frost.

Latest data provided by the Gamma Ray Sensor on theMars Odyssey spacecraft after 55 days of mapping by theAmerican Neutron Spectrometer (NS) and the Russian HighEnergy Neutron Detector (HEND) indicate deficits of highenergy neutrons in southern highlands of Mars. The deficitsof high-energy neutrons indicate that hydrogen is concen-trated in the subsurface. Modelling suggests that water-icerich layers with tens of centimeters in thickness provide oneof the best possible fit to the data. In this case the subsurfacematerial has water ice concentrations of 60% ice by volume[12, 13].

This prevalence of water ranges from the South Pole upto 60ºS, surprisingly coinciding with the region of the DDSs(Fig. 2 A and B). From this data we may deduce that water insome form is relatively abundant in this region of the DDSs.

ConclusionsMeasurements by the HAND and NS instruments of MarsOdyssey observed the presence of water ice abundant in theupper 1--3 meter thick layer of the Southern Polar Region’sbetween 90°S--60°S latitudes [12, 13], as we predicted in ourDDS-MSO model [1, 2].

These new water observations of Mars Odyssey alsosupport evidences to our DDS-MSO hypothesis on the recentlife on Mars.

AcknowledgmentsAuthors thank for the use of MGS MOC images of NASAJPL and Malin Space Science Systems [14] and for use ofMars Odyssey data of I. Mitrofanov and W. V. Boynton.

Fig. 2 Water observations by the Neutron Spectrometer (A) andHigh-Energy Neutron Detector (B) of Mars Odyssey spacecraft inFeb.-Apr. 2002 on the South Polar Region of Mars during thesummer and places of dark dune spots (white filled circle).

References[1] Horváth et al. 2001, LPS XXXII, # 1543. [2] Gánti et al.(2002-3) OLEB in print. [3] Albee et al. 2001, J. Geophys. Res.106 E10, 23291. [4] Malin M., Edgett K. 2001, J. Geophys. Res.106. 23429. [5] Bridges et al. 2001, LPSC XXXII, # 2126. [6]Reiss, Jaumann 2002, LPS XXXII, # 1606. [7] Horváth et al.2002a,b, LPS XXXIII, # 1108, 1109. [8] Horváth A. et al. 2002c,Antarctic Meteorites XXVII, 37. Tokyo, [9] Smith et al. 2001,Science 294, 2141. [10] Hoffman 2000, Icarus 146, 326. [11]Carr 1996, Oxford Univ. Press. [12] Boynton et al., ScienceExpress Report.1073722, May 30, 2002. [13] Mitrofanov et al.Science Express Report.1073616, May 30, 2002. [14]http://www.msss.com/moc_gallery/ .