Atmospheric energy for subsurface life on Mars?

Area of Science:

• Astrobiology
• Planetary Science
• Geochemistry

Background:

• Biomass, distribution, and size of Martian life are constrained by energy sources.
• Subsurface life could utilize atmospheric hydrogen (H2) and carbon monoxide (CO) diffusing into the Martian regolith.

Purpose of the Study:

• To investigate the limiting factors for potential life on Mars, focusing on energy availability versus water.
• To assess the potential of atmospheric gases as an energy source for Martian life.

Main Methods:

• Analysis of atmospheric gas abundance measurements on Mars.
• Estimation of photochemical energy flux and its penetration depth in the Martian subsurface.
• Comparison of available energy with estimates of water availability.

Main Results:

• Actual consumption of atmospheric H2 and CO by potential Martian life is less than a few percent of the available flux.
• The unused photochemical energy flux is substantial, exceeding previous estimates from hydrothermal and chemical weathering.
• Liquid water availability, not energy, is likely the primary limitation for life, as water is probably frozen at depths accessible to photochemical energy.

Conclusions:

• The apparent scarcity of life on Mars is not due to a lack of energy.
• Liquid water availability is a more critical factor for limiting biological activity on Mars.
• Detection of short-lived trace gases may serve as a more effective indicator of extant Martian life than atmospheric gas consumption.