An origin of life on Mars

Abstract

Evidence of past liquid water on the surface of Mars suggests that this world once had habitable conditions and leads to the question of life. If there was life on Mars, it would be interesting to determine if it represented a separate origin from life on Earth. To determine the biochemistry and genetics of life on Mars requires that we have access to an organism or the biological remains of one-possibly preserved in ancient permafrost. A way to determine if organic material found on Mars represents the remains of an alien biological system could be based on the observation that biological systems select certain organic molecules over others that are chemically similar (e.g., chirality in amino acids).

Figure 1.

Liquid water on another world. Mars Global Surveyor image showing Nanedi Vallis in the Xanthe Terra region of Mars. Image covers an area 9.8 km by 18.5 km; the canyon is about 2.5 km wide. This image is the best evidence we have of liquid water on Mars. Photo from NASA/Malin Space Sciences.

Figure 2.

Diagram of the proposed explanations for the origins of life on Earth. Any of these explanations would work on Mars as well as on Earth. From Davis and McKay (1996).

Figure 3.

Maps showing crater distribution, ground ice, and crustal magnetism on Mars. The suggested target site for deep drilling to search for evidence of ancient life on Mars is the region between 60° and 80°S at 180°W, where the ground is heavily cratered, crustal magnetism is preserved, and ground ice is present. Figure from Smith and McKay (2005).

Figure 4.

Conceptual comparison of the distribution of molecules in organic matter of biological and nonbiological origin. The ordinate “type of molecule” represents in a general way the size, structure, chirality, and all other features of the molecule. Nonbiological processes produce uniform distributions of organic material, illustrated here by the curve. Biology, in contrast, selects and uses only a few distinct molecules, shown here as spikes (e.g., the 20 l-amino acids on Earth). Alien life might have similar selectivity but based on a different set of molecules (McKay 2004).