Earth-like Habitable Environments in the Subsurface of Mars.

Area of Science:

• Astrobiology
• Geochemistry
• Microbiology

Background:

• Deep subsurface groundwaters on Earth, isolated for millions of years, host microbial life fueled by radiolysis.
• Radiolysis of water and rock minerals produces oxidants and reductants, driving microbial metabolism.
• Similar processes on Mars could support past or present life in its subsurface.

Purpose of the Study:

• To assess if radiolysis alone can provide sufficient energy for life in Mars' subsurface.
• To determine potential habitability for Earth-like microorganisms on Mars.
• To identify specific Martian regions suitable for high microbial cell densities.

Main Methods:

• Modeling radiolysis of water and rock minerals.
• Calculating redox energy production.
• Estimating supportable microbial cell densities (sulfate-reducing bacteria).
• Analyzing Martian meteorite source regions.

Main Results:

• Radiolysis can generate enough redox energy to sustain a habitable environment in the Martian subsurface.
• Martian meteorite source regions can support millions of sulfate-reducing microbial cells per kilogram of rock.
• Variability in habitable cell densities exists across different Martian regions.

Conclusions:

• Martian subsurface groundwaters are likely habitable for sulfate-reducing bacteria due to radiolysis.
• Regions rich in sulfides may support particularly high microbial cell densities.
• These findings guide future Martian subsurface exploration missions.