2003 Annual Science Report
NASA Jet Propulsion Laboratory Reporting | JUL 2002 – JUN 2003
Martian Biogenic Gases
If life exists beneath the Martian surface similar to terrestrial bacteria that obtain their energy by chemical reactions utilizing H2 and CO, then it may be possible to infer the presence of subsurface life by observing metabolic by-products as trace gases in the Martian atmosphere. In this study we use a chemical model of the Martian atmosphere to study the fate of several organic trace gases. Although most of these gases have short chemical lifetimes, CH4 has a chemical lifetime of about 300 yrs, and thus it will tend to be uniformly distributed in the Martian atmosphere. Using this model and the current observational upper limit on atmospheric CH4, we deduce that global flux, from all sources, of CH4 into the Martian atmosphere must be at least 1.2 × 105 times less than terrestrial value. If there are abiotic sources of CH4 on Mars, then the biological component of the CH4 must be even less. Furthermore, using current detection techniques, we estimate that it is possible to detect a Martian CH4 source that is about 7 × 107 times less than the terrestrial source. This will provide the strictest test that we are aware of for a hypothetical subsurface biosphere on Mars.