Prebiotic Chemistry on Mars

If life arose on Mars, it would have been preceded by a period of prebiotic chemistry in which the molecular building blocks of life were formed and self-assembled into replicating systems. Implicit in the view that Martian life could have emerged in a warmer wetter climatic era is that many of the same prebiotic processes operated there as they did on early Earth. For both planets, which processes and environments were on the critical path to the origin of life remain unclear. Earth-like surface conditions on early Mars translate into the presence of an atmosphere and bodies of liquid water, volcanism and hydrothermal activity, surface temperatures roughly bracketed by the freezing and boiling points of water, predominantly solar and internal energy sources, an impact flux declining over time. In this context the first order task is to estimate how much abiotic organic matter might have been produced on Mars. Although the uncertainties are daunting, it is possible to scale estimated production rates of organic syntheses on the early Earth to Mars. Atmospheric photochemistry and electric discharges should scale according to solar flux. Impact related syntheses and contributions of organic matter from meteorites and IDP can be scaled to estimates of the Mars/Earth flux ratio . There may also have been a role in prebiotic synthesis for hydrothermal systems analogous to that suggested for the prebiotic Earth. Survival of prebiotic organic matter would have been enhanced by rapid sequestration/lithification and subsequent preservation against metamorphic effects of tectonic and impact origin and oxidation by a later oxidizing atmosphere. The concentration of organic matter in the Martian regolith or lacustrine sediments would have depended on the thickness and rate of accumulation of soils and sediments, all of which are poorly constrained. While less profound in significance than the discovery of evidence of past or present life, the discovery and characterization of prebiotic organic matter on Mars would be a major advance in understanding prebiotic chemical evolution on a terrestrial planet.

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Last Modified August 21, 1996