Hydrothermal Geology at Meridiani Planum, Mars, and the Possibility of a Marker for Microbial Life in the Iron Oxyhydroxide, Schwertmannite

Microbial life on Earth seems to have begun almost as soon as the planet cooled enough to allow solid rock to form and liquid water to exist, ~ 4 billion years ago. These first microbes would have performed a catalyzed version of the reactions already occurring between the igneous rocks and liquid water, reactions which released energetic elements like H⁺, and oxidized compounds like CO₂. Chemical traces in rock from this time show that microbes were performing redox reactions, reducing and oxidizing carbon, iron and sulfur. Evidence of ancient microbial activity was also left in the physical forms of minerals left through biomineralization. Several sites on Mars have been found from orbital data to have deposits of water-weathered basalts. One of these sites, Meridiani Planum, which lies near the equator, has been explored by robotic rover and found to have deep deposits of sulfate salts, silicates, and iron oxides. The ancient environment that formed these deposits could possibly have nurtured a microbial community, and evidence of this could have been left in certain forms of minerals likely to be at this site, like the iron oxyhydroxide sulfate, schwertmannite