Organic and inorganic interpretations of the martian UV–IR reflectance spectrum

Abstract

Although some data from the Viking Lander biology experiments can be interpreted as indicative of biological activity, the existence of organisms in the martian soil samples is considered unlikely because of the non-detection of organic compounds in the sample¹. Viking gas chromatography–mass spectrometer analysis detected no organic molecules above a concentration of parts per 10⁹ (ref. 2). We consider here why no organic molecules were detected at the landing sites, whether the sterility of the two sites is representative of the entire planet and if there are locations on Mars more conducive to the formation and preservation of organics. We first simulate the destruction of organic compounds in Mars-like laboratory conditions, and then examine whether the destructive mechanism would operate planetwide; and second re-examine UV and IR reflectance spectra of Mars for any evidence of organic molecules, and in doing so set an upper limit on the organic carbon content of average martian soil. The results reveal that the average martian soil is organic-poor and makes an unfavourable habitat for life forms based on carbon chemistry. There is no reason to believe that organic molecules are preferentially preserved anywhere on the planet.