THE SEARCH FOR LIFE’S ORGANIC CARBON IN RETURNED SAMPLES FROM MARS.

Abstract

Evidence of habitability and habitation of Mars may be forthcoming by returning samples to Earth [1]. Clear objectives and associated choices of samples is essential to maximize the opportunities presented by returned samples. In the context of the solar system, the relative similarity of Earth and Mars generates an expectation of biochemical harmony for Earth and Mars. We can confidently predict that any biochemical scaffolding on Mars would be based on carbon and any biochemical solvent would be based on water. To expect otherwise would require planetary conditions and chemistries [2] that differ dramatically from those of either Earth or Mars. Reduced carbon is therefore a beacon for the potential discovery of evidence of life in a sample [3]. Any reduced carbon detected in samples from Mars should also have features that provide the ability to discriminate between non-life and life sources and, preferably, between an origin on Earth and Mars. For detecting life, the usefulness of organic carbon to biochemistry is in its ability to form complex and specific organic structures. Recognizing the organic signatures of life is therefore an achievable goal. For discriminating provenance on Earth and Mars, detailed environmental adaptions must be sought. Although based on carbon and water the biochemical similarities between organisms on Earth and Mars would not be expected to be exact. Our terrestrial examples of environmental adaptations reveal substantial biochemical variations that reflect the challenges and opportunities presented by the host environment 3. This is a provisional report from the iMOST subteam on the objective of Seeking the Signs of Life, identifying key samples and measurements needed to understand Martian Organic Carbon.