“C’mon Martian microbe, do you live under a rock?” Actually, yes.
Researchers have discovered, using precise computer modeling, that the chemical composition of Mars’s subsurface during the Noachian period was conducive for potential microbial life. The concentrations of water, hydrogen, and various radioactive elements allowed for the area underneath the red planet’s sand to be the perfect home for microorganisms. If the model is accurate, then we should be able to find traces of Martian life from over 4 billion years ago.
The paper, scheduled to be published in Earth and Planetary Science Letters in the November issue, details how the team, led by Astronomers at Brown University in Rhode Island, synthesized calculations of radioactivity amount with models of Mars’ geophysical structure. From this, they were able to posit an explanation for the habitability of Mars. Chris Glein, an unaffiliated Astronomer at the Southwest Research Institute in San Antonio, noted how “this is consistent with the picture that’s emerging within our solar system–most of the most habitable environments are underground.”
The methodology involved taking gamma ray measurements from NASA’s Odyssey Rover, launched in 2001. With these measurements, the researchers can quantify the concentrations of radioactive elements like potassium and uranium on Mars. Using a half-life decay model (a process of calculating the decay of radioactive elements over time), they are able to calculate the concentrations of these elements during Mars’s Noachian period. Jesse Tarnas, lead researcher, explains that “we integrate the results of these [radioactive] elemental concentrations with the latest geophysical models.” With knowledge of the geophysical structure, Tarnas and the team can more accurately understand how radioactive elements fit into the larger picture of the Martian subsurface.
During this period, Mars was rich in liquid water–both above and below the surface. Knowing how much water was something the researchers needed to find out. They looked at models of the Martian subsurface to find cracks and crevasses where water would have been most likely to flow. Also beneath the surface were the aforementioned radioactive elements. Radioactivity has a destructive effect on water, causing it to split into Hydrogen and Oxygen. When you split a compound in this manner, energy is released. In this case, “you have the energy required for redox reactions,” says Glein, which are key for sustaining life.
The team can get even more precise with their modeling. Tarnas explains that the team performs “thermodynamic calculations for the amount of dissolved hydrogen that the groundwater can hold at different temperatures and pressures.” From there, the team can pinpoint a smaller-scale subsurface region and calculate its habitability levels. The search for Martian life could be optimized by using this method by targeting the most habitable areas.
If there was abundant life below Mars’s surface, how could we find out? Tarnas and Glein both note that a potential way to find evidence of Martian life would be to analyze mega-breccia–pieces of the subsurface that were kicked up by meteor impacts. These are usually located in the centers of craters and could be easily probed by rovers. From mega-breccia, future researchers could search for hard evidence of subsurface life.
Extraterrestrial life may seem an alien idea, but soon scientists may prove that it’s right below the surface.