NEEP602 Course Notes (Fall 1997)
Resources from Space

Lecture #16: Little Green Persons!

Title: Life on Mars?


View from Viking lander (NASA Photo)

Major Stages of Martian Evolution (Synthesized largely from material presented by Munch, 1976; Carr, 1984 and 1996, and the cratering age estimates of Soderblom, 1988)

1.BEGINNING---------------------------------------------4.57 b.y.
2.MAGMA OCEAN/PLANETARY DIFFERENTIATION-----------------4.5-4.4(?) b.y.
3.CRATERED UPLANDS/CLAY SOUP ---------------------------4.4(?)-4.2(?) b.y.
4.LARGE BASINS------------------------------------------4.2(?)-3.9 b.y.
5.PLANETARY VOLCANISM ----------------------------------3.9-2.0(?) b.y.
6.MATURE CRUST/ATMOSPHERE-------------------------------2.0(?) b.y.-PRES.
If life comparable to simple forms present on Earth were to devlop on Mars, the critical period of Martian evolution would be those between Stages 2 and 5, above. The discussion notes below are added within the context of the more general notes of Lecture 14.

3. Cratered Uplands/Clay Soup - 4.4(?)-4.2(?) b.y.
  • Highly cratered crust similar to lunar highlands.

Cratered highlands (NASA Photo)

  • Formation of a megaregolith to about 10 km similar to the 25 km thick megareglith of the Moon.
  • Probable dense, moist, CO2 rich atmosphere with significant CH4, CH4 derived areosols, and NH4 (Sagan and Chyba, 1997, and Kasting, 1997)
    • Note: The nature and evolution of the Martian atmosphere through time consists of many uncertainties, including the following (see Carr, 1996, Chapters 5-7):
      • Initial composition
      • Potential of a late infall of water-rich (cometary) material [not likely based on comparison of D/H rations of Earth's water with that measured for comets Hale-Bopp and Hyakutake (Owen ,T., and Meier, R., 1997, reported in Science, 277, 318)]
      • Variability of obliquity of rotational axis to orbital plane
      • Changes in insolation
      • Changes in composition due to core fromation and evolution of hydrogen and other volatiles from the interior
      • Changes in composition due to weathering of the megaregolith
      • Changes in composition due to magmatic and hydrothermal activity
      • Amount and stability of greenhouse gases (NH4, CH4, CO2, H2O) through time
      • Degree of CH4 derived organic aerosol formation by photolysis (Sagan and Chyba, 1997, and Kasting, 1997)
      • Amount and rate of surface regolith carbonate decompostion due to UV radiation (Mukhin, et al, 1996).
      • Degree of impact erosion through the Large Basin Stage, see below.
      • Degree of hydrodyamic entraining by high rates of hydrogen escape.
      • Strength of the magnetic field, if any.
      • Degree of solar wind erosion (sputtering) (Kass and Yung, 1995, and Johnson, and Liu, 1996)
      • Degree of water and carbonate capture and recycling in the megaregolith
  • Probable creation and continual impact stiring of a soupy mixture of water, clay , carbonate, hydrocarbons and other atmospheric and crustal components (WCCS).
    • Note: This probably is the most likely period for the "evolution" of complex organic molecules as precursors to replication life (possibly self replicating RNA (see Ekland and Bartel, 1996, and Science, 1996, 273, 870-872) for the following reasons:
      • Terrestrial isotopic fractionation of biological origin has been dated at 3.850 b.y. (Mojzsis, et al, 1996) and the development of molecular precursors must significantly predate this date.
      • Clay mineral sturctures (montmorillonite, illite, and hydroxylapatite) have been shown to serve as templates for complex organic molecules (Ferris, 1996)
      • Necessary phosphate compounds can be produced and preserved during impacts into relatively cool crustal materials like a clay soup and also have been found in the Muchison meteorite along with other organic compounds (Science, 1996, 273, 870-872).
      • Aqueous slurries of coprecipitated NiS and FeS, possible hydrothermal mineral species in reducing crustal environments such as deep sea smokers on Earth, converted CO and methanethiol (CH3SH and detected in volcanic and ancient gases on Earth) through several steps to methyl thioacetate (CH3CO(SCH3) plus H2S. With its C-C bond, methyl thioacetate resembles acetyl-coensyme A which is a candidate for a primordial initiation reaction for a chemoautotrophic origin of life (Huber and Wachtershauser, 1997, and Crabtree, 1997)
      • Impact shock in a CH4, H2O, CO2, N, and H2S containing, attmosphere produces a variety of organic compounds (see McKay and Borucki, 1997)
4. Large Basins - 4.2(?) - 3.8 b.y.

Large basin formation largely in present northern hemisphere.

Note: multicell life forms would probably not survived these large events, but the complexity of their precursors may have been enhanced by the energy, shock chemistry, and material introduction.

Present rotational dynamics and variability established.

Note: These established an inherently extreme variability to climate variations unlike that experienced by Earth. Such variability may have inhibited the survival of some replicating forms but may have acted as a forcing factor on "speciation" of others.

Much of megaregolith concentrated in southern hemisphere.

Note: Clay-related synthesis of complex organic molecules may have made the Uplands a reservoir of organic building blocks for more complex evolutionary activity in flooded basins (see below).

Remelting of the warming mantle beneath the large basins may have been triggered by the release of lithostatic pressure.

Upland valley networks (see Carr, 1996, Chapter 4) formed late in this stage.

  • Note: valley networks appear to have formed by ground water sapping in the upper megaregolith (Carr, 1996), possibly sustained by increasing hydrothermal activity in response to remelting of the mantle under the Uplands. Such sapping and the accompaning mass wasting of the upper megaregolith downstream would have carried any organic compounds toward the basins. The movement of magmas into the weathered megaregolith would potentially recycle meteoric water and CO2, producing much hydrothermal activity and recycling of atmospheric volatiles thus counteracting atmospheric losses.

Organization of complex organic molecules into replicating life forms, if it occurred on Mars, probably happened at or near the end of this stage for the following reasons:

  • Terrestrial isotopic fractionation of biological origin has been dated at 3.850 b.y. (Mojzsis, et al, 1996)
  • Complex, evolving, single cell life forms known as fossils on Earth at 3.55 b.y. (Schopf, 1993)
  • RNA appears capable of at least some self replication (Ekland and Bartel, 1996)

Summary arguments for early life
  • Great age (>3.55 billion years) of earliest one cell life forms on Earth and of isotopic evidence of biological processes (3.850 b.y.).

Figure: Apex Chert microfossils (NASA Life on Mars #31)

  • Evidence of an environment that allowed surface subsurface water to exist.
  • Implications of the model for lunar evolution on the nature of the surface environment of terrestrial planets when self replicating organic compounds (life) first formed, that is, intense cratering with production and weathering of fine-grained and glassy material in a water and carbon dioxide rich megaregolith, addition of extraplanetary material, and repeated peaks of high thermal energy.
  • Other planetary systems apparently capable of retaining liquid water, such as, 70 Virginis in the constellation Virgo (Science, v 271, 449-450)
  • Various experimental results increasingly suggests complex organic chemistry is possible in potenial Martian environments between 4.4 and 3.8 b.y.

  • Questions to be answered
    • For how long and how frequently did surface water exist?
    • What overall environmental conditions existed at that time?

Arguments against present life on Mars
  • Some Viking analyses gave no suggestion of biological metabolism occuring in Martion soil. (Horowitz, 1988)
  • Present surface environment incompatible

Arguments for present life on Mars

One Viking analysis was consistant with poistive results of the same experiment in the dry valleys of Antarctica (Levin, 1988)

Potential ecological niches related to permafrost, subsurface weathering, and active hot springs, if present.

Relevant terrestrial niches (see Ghiorse, 1997, Fredricson and Onstott, 1996, and Monastersky, 1997)

Algae in brines of Antarctic pack ice (Arrigo, K., 1997)

Bacterial in----500 meters below the surface in South Carolina (Wobber, F.J., et al, 1989, reported in Science News, 151, 192)

Bacterial in old bearing conglomerates at 60oC, 3.5 km below the surface in South Africa (Onstott, T. C., reported in Science News, 151, 192)

Bacteria in sedimentary rocks 600m below the surface (340 m.y.)

Bacteria (Bacillus infernus) in volcanic springs at 75oC in Yellowstone National Park and in deep ocean vents

Bacteria 2.7 km below the surface (Phelps, T.J., et al, 1996, AGU December meeting reported in Science News, 151, 192)

Bacteria in basalt 1.5 km below the surface in Washington living on carbon dioxide and hydrogen from weathering of basalt (80-160 m.y.) (Stevens and McKinley, 1995)

Figure: Columbia River Basalt nanobacteria(?) (NASA Life on Mars #29)

Bacteria in sandstone and shale in New Mexico (DOE team, 1997, Nature, March 6)

Bacteria and archeaea in granite 207m below the surface in southeast Sweden ((Pedersen, et al, 1997)

Various in hydrothermal vents in the deep sea

Figure: Hydrothermal deep sea "black smoker" (NASA Life on Mars #30)

Bacterial spores (Bacillus sphaericus) in amber encased bee (25-40 m.y.) (Cano and Borucki, 1995)

Chemoautotropic bacteria in a limestone cave ecosystem living on carbon and H2S in southern Romania (Sarbu, et al, 1996)

Bacteria on bottom of sea ice at the poles (Staley, J.T., as reported in Science News, 149, 126)

Fungi, if evolved, and lichen colonies both have proved on Earth to be geologically resilient in the extreme (Visscher, 1996, and Levin, 1988)

Search for evidence of life on Mars (see Gould, 1994)

Figure: Lake sediments (NASA Life on Mars #4)

Figure: Chaotic terrain, possibly with carbonate/water associations (NASA Stones, Wind, and Ice #25)

Figure: Polar layered ice and dust (NASA The Red Planet #22)

Figure: Elysium Mons (evoved magma) (NASA Volcanos #14)

Figure: Area of valley networks in Uplands (NASA Life on Mars #5)


Evidence for large volumes of water and water ice (Carr, 1996, Chapter 7)

Figure: South Polar Cap in summer (NASA The Red Planet #21)

Figure: South Polar Cap in winter (NASA The Red Planet #20)

Figure: Comparison with Earth Polar Caps (NASA The Red Planet #23)

Figure: Clouds around Olympus Mons (NASA The Red Planet #18

    Figure: Viking 1 vs winter CO2 frost at Viking 2 (NASA A Spacecraft Tour #17 and 18)

Other potential resource concentrations on Mars besides water

Composition of the soil

In this diagram, preliminary Pathfinder APXS analyses of soils (yellow dots) extend the range of Viking soil analyses. The analysis of Yogi appears to be contaminated by dust adhering to the rock's surface. The rock composition can be estimated by subtracting a portion of dust; the resulting Yogi composition is very similar to that of Barnacle Bill (we assumed 50% dust having the composition of drift analysis A-5 and used a linear mixing model to subtract the dust which is only strictly valid if the dust, where present, is thicker than the APXS penetration depth). Barnacle Bill is also contaminated by dust, but to a lesser extent.  

APXS analyses of Martian soils are compared with Viking soil analyses. Each element is normalized to silicon in this diagram. The yellow boxes representing Viking data include all analyses and their analytical uncertainties reported by B.C. Clark and others (1982) Journal of Geophysical Research, vol. 87, p. 10,064. Although the first APXS soil analysis (A-2) was reported to be almost identical to Viking soils, ssubsequent analyses demonstrate some variability and a few significant differences from Viking analyses. Specifically, soils at the Pathfinder site generally have higher aluminum and magnesium, and lower iron, chlorine, and sulfur. Scooby Doo, which appears to be a sedimentary rock composed primarily of compacted soil, also exhibits a few chemical differences form the surrounding soils. Analysis A-5 represents a deposit of windblown dust (called drift), whereas the other soil analyses may be cemented materials.

Figure: Martian rust (iddingsite) (NASA The Red Planet #38)

The figure summarizes what we know about the evolution of Mars and appears to be consistent with the best information and ideas availabe to date. Stay tuned!


1. Discuss the rationale, if any, to assume that simple life forms developed on Mars and that they may have evolved to survive in some ecological niches to the present time.

2. Where would you go to search for fossils and current life forms on Mars and why?


Mars environment material

Carr, 1996, Chapter 8.


Ahrens, et al, 1989 Formation of atmospheres during accretion of the terrestrial planets, in Origin and Evolution of Planetary and Satellite Atmospheres, S.K. Atreya, et al, editors, University of Arizona press, Tucson.

Arrigo, K., 1997,Science, 276, 394

Bowring, S.A., and Housh, T., 1995, The Earth's Early Evolution, Science, 269, 1535-1540.

Cano, R., and Borucki, M.,1995, Science, 268, 1060.

Carr, M.H., 1984, Mars, in M.H. Carr, et al, The Geology of the Terrestrial Planets, p207-263.

Carr, M.H., 1996, Water on Mars, Oxford University Press, New York, 229p.

Crabtree, F.H., 1997, Where smokers rule, Science, 276, 222.

Ekland, E.H.and Bartel, D.P., 1996, Nature July 25 as reported in Science News, 150, 93.

Ferris, J.P., 1996, Nature, May 2, reported in Science News, 149, 278.

Fredricson, J.K.,and Onstott, T.C., 1996, Microbes deep inside the Earth,, Scientific American, October, 68-73

Ghiorse,W.C., 1997, Subterranean Life, Science, 275, 789-790

Gooding,, J.L., 1992 Soil mineralogy and chemistry on Mars: Possible clues from salts and clays in SNC meteorites, Icarus, 99, 28-41.

Gould, S.J., 1994, A Plea and a Hope for Martian Paleontology, in Neal, Valerie, editor, Where Next Columbus? The Future of Space Exploration, Oxford University Press, Oxford, 107-128p.

Horowitz, N.H., 1998, The Biological Question of Mars, in D.B. Reiber, editor, The NASA Mars Conference, AAS Science and Technology Series, v 71, 177185.

Huber, C., and Wachetershauser, G., 1997, Activated acetic acid by carbon fixation on (Fe,Ni)S under primoridal conditions, Science, 276, 245-247.

Johnson, R.E., and Liu, M, 1996, The loss of atmosphere from Mars, Science, 274, 1932.

Kass, D.M., and Yung, Y.L., 1995, Loss of Atmosphere from Mars Due to Solar Wind-Induced Sputtering, Science, v 268, 697-699.

Kasting, J.F., 1997, Warming early Earth and Mars, Science, 276, 1213-1215.

Levin, G.V., 1988, A Reappraisal of Life on Mars, in D.B. Reiber, editor, The NASA Mars Conference, AAS Science and Technology Series, v 71, 187-208.

McKay, C.P., and Borucki, S.J., 1997, Organic synthesis in experimental impact shocks, Science, 276, 390-392.

Monastersky, R., 1997, Deep Dwellers, Science News, 151, 192-193

Mojzsis, S.J., et al, 1996, Nature 384, 55.

Mukhin, et al, 1996, Nature January 11 reported in Science News, 149, 21

Munch, T.A., et al, 1976, The Geology of Mars, Princeton University Press, Princeton, 400p.

Pedersen, K., et al, 1997, Evidence of ancient life at 207 m depth in a granitic aquifer, Geology, 25, 827-830.

Sagan, C., and Chyba, C., 1997, The early faint sun paradox: organic shielding of ultraviolet-labile greenhouse gases, Science, 276, 1217-1220.

Sarbu, S.M., Kane, T.C., and Kinkle, B.K., 1996, A chemoautotropically based cave ecosystem, Science 272, 1953-1956

Schopf, J.W., 1993,Science, 260, 640,

Smith, D.E., and Zuber, M. T, 1996, The shape of Mars and the Topographic Signature of the Nemispheric Diochotomy, Science, v 271, 184-188.

Soderblom, L.A. 1988, The Geology of Mars, in D.B. Reiber, editor, The NASA Mars Conference, AAS Science and Technology Series, v 71, 43-53.

Stevens, T.O. and McKinley, J.P., 1995, Science, 210.450.

Swindel, T.D., 1997, Jounrnal of Geophysical Research-Planets as reported in Science News, 151, 210.

Treiman, A., 1996, To see a world in 80 kilograms of rock, Science, 272, 1447-1448.

Visscher, H. 1996, Proceedings of the National Academy of Sciences, March 5.

Back to Syllabus

University of Wisconsin logo

University of Wisconsin Fusion Technology Institute  · 439 Engineering Research Building  · 1500 Engineering Drive  · Madison WI 53706-1609  · Telephone: (608) 263-2352  · Fax: (608) 263-4499  · Email:

Copyright © 2003 The Board of Regents of the University of Wisconsin System. For feedback or accessibility issues, contact
This page last updated August 21, 2003.