Life on Mars: Water-Rock Reaction Could Possibly Sustain Microbial Communities

There may be more evidence for life on Mars. Researchers have discovered that a chemical reaction between iron-containing minerals and water may produce enough hydrogen "food" to sustain microbial communities living in pores and cracks within the enormous volume of rock below the ocean floor and parts of continents. This means that when Mars possessed flowing water, these same microbial communities could have existed.

Rock-water reactions can produce hydrogen in places where temperatures are far too hot for living things to survive. For example, this phenomenon occurs on Earth in the rocks that underlie hydrothermal vent systems on the floor of the Atlantic Ocean. The hydrogen gases that are produced eventually feed microbes that are located in small, cooler oases where the vent fluids mix with seawater.

"Water-rock reactions that produce hydrogen gas are thought to have been one of the earliest sources of energy for life on Earth," said Lisa Mayhew, who worked on the study as a doctoral student at CU-Boulder, in a news release.  

In order to investigate whether this same phenomenon could occur in the much more abundant rocks that are infiltrated with water at temperatures cool enough for life to survive, researchers designed an experiment. They submerged rocks in water in the absence of oxygen to determine if a similar reaction would take place at much lower temperatures, between 122 and 212 degrees Fahrenheit. They found that the rocks did create hydrogen--and enough of it to potentially support life.

They weren't done investigating the phenomenon, though. In order to understand the chemical reactions that produced the hydrogen in the experiment, the researchers used "synchrotron radiation," which is created by electrons orbiting in a humanmade storage ring. This allowed the researchers to determine the type and location of iron in the rocks on a microscale.

So what did they find? The scientists discovered newly formed oxidized iron on "spinel" minerals found in the rocks. Spinels are minerals with a cubic structure that are highly conductive. In fact, the findings could mean that, at low temperatures, the conductive spinels could help facilitate the exchange of electrons between reduced iron and water. This process is necessary for the iron to split and the water molecules to create the hydrogen gas.

Although these findings have implications for Earth, they also have implications for Mars. The same type of rocks are prevalent on the Red Planet, which means that the new study may have implications for potential Martian microbial habitats.

The findings are published in the journal Nature Geoscience.