Ancient Mars May Have Supported Underground Life, Claims New Study

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A new study has found that ancient Mars had an ample supply of key ingredients for microbes to thrive under its surface for millions of years. Lacking energy from sunlight, subterranean microbes on Earth, known as subsurface lithotrophic microbial ecosystems (SliMEs), often get their energy by peeling electrons off molecules in their surrounding environments. Dissolved molecular hydrogen is a great electron donor and is known to fuel SLiMEs on Earth.

If life got a foothold in the Martian subsurface long ago, it could have tapped into a plentiful chemical energy source. That source was hydrogen, generated when radiation split underground water into its constituent parts. And there was probably enough available hydrogen down there to sustain a sizable community of Mars microbes for hundreds of millions of years, starting about 4 billion years ago.

Study lead author Jesse Tarnas, a graduate student at Brown University in Rhode Island, said in a statement that “We showed, based on basic physics and chemistry calculations, that the ancient Martian subsurface likely had enough dissolved hydrogen to power a global subsurface biosphere” and further added, Conditions in this habitable zone would have been similar to places on Earth where underground life exists.”

To find their conclusion, the scientists took data from NASA’s Mars Odyssey spacecraft to map radioactive elements thorium and potassium in the crust of Mars. The findings then allowed the experts to calculate how much uranium would have been in the soil some four billion years ago. As the decay rates of thorium, potassium and uranium are constant on Mars, the scientists were able to calculate how much of these elements were in abundance at the time. They then had to discover how much water there was in the Martian crust, which they did by analyzing rocks on the Red Planet.

The work also has implications for future Mars exploration, suggesting that areas where the ancient subsurface is exposed, might be good places to look for evidence of past life. Since the discovery decades ago of ancient river channels and lake beds on Mars, scientists have been tantalized by the possibility that the red planet may once have hosted life.

Geological evidence suggests there would have been plenty of groundwater bubbling about in the porous rocks of the ancient Martian crust. Researchers conclude that Mars likely had a global subsurface habitable zone several kilometers in thickness. The zone would have persisted for hundreds of millions of years, they said. The study findings were published in the journal Earth and Planetary Science Letters.