Credit: NASA

Much of the subsurface of Mars may well be a nice niche for microbial life.

That’s a finding from a new study published in the journal Astrobiology that looked at the chemical composition of Martian meteorites tossed off the Red Planet that eventually landed here on Earth.

New research determined that those Mars-spawned rocks — if in consistent contact with water — would generate the chemical energy needed to support microbial communities on the faraway world, similar to those that endure in the unlit depths of the Earth. Because these meteorites may be representative of vast swaths of the Martian crust, the findings suggest that much of the Mars subsurface could be habitable.

NASA’s Mars Perseverance rover image from Right Mastcam-Z Camera. Photo acquired on April 15, 2021 (Sol 54).
Credit: NASA/JPL-Caltech/ASU

Ample energy

“We don’t know whether life ever got started beneath the surface of Mars, but if it did, we think there would be ample energy there to sustain it right up to today,” says Jesse Tarnas, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory who led the study while completing his Ph.D. at Brown University.

“The big implication here for subsurface exploration science is that wherever you have groundwater on Mars, there’s a good chance that you have enough chemical energy to support subsurface microbial life,” Tarnas adds in a Brown University press statement.

Underground systems

In places like Canada’s Kidd Creek Mine, “sulfate-reducing” microbes have been found living more than a mile underground, in water that hasn’t seen the light of day in more than a billion years.

Jesse Tarnas, a Brown University graduate and postdoctoral research at NASA’s Jet Propulsion Laboratory, work in Canada’s Kidd Creek Mine. Mars has right ingredients for present-day microbial life beneath its surface a new study finds.
Credit: Jesse Tarnas/ University of Toronto Stable Isotope Laboratory

According to the study paper, “radiolysis” by itself could produce sufficient redox energy to sustain a habitable environment in the subsurface of present-day Mars, one in which Earth-like microorganisms could survive wherever groundwater exists.

The ingredients for radiolysis: radioactive elements like thorium, uranium and potassium; sulfide minerals that could be converted to sulfate; and rock units with adequate pore space to trap water.

Tarnas has been working with a team co-led by Brown University professor Jack Mustard and Professor Barbara Sherwood Lollar of the University of Toronto to better understand these underground systems with an eye toward looking for similar habitats on Mars and elsewhere in the solar system. The project, called Earth 4-D: Subsurface Science and Exploration, is supported by the Canadian Institute for Advances Research.

NASA’s Mars Perseverance rover acquired this image at Jezero Crater using its Left Mastcam-Z camera on April 23, 2021 (Sol 62).
Credit: NASA/JPL-Caltech/ASU

Concentration zones

The surface of Mars is an extremely unfriendly environment, the study paper explains, a topside characterized by freezing temperatures, desiccating conditions, high levels of ionizing radiation, oxidizing chemicals, low pressures, “and a lack of liquid water that preclude any Earth-like organisms from surviving without adaptation that is unprecedented on Earth.”

“Our results demonstrate that martian subsurface groundwaters, where present, would largely be habitable for sulfate-reducing bacteria from a redox energy perspective via radiolysis alone,” Tarnas and colleagues explain in the study paper. “We present evidence for crustal regions that could support especially high cell densities, including zones with high sulfide concentrations, which could be targeted by future subsurface exploration missions.”

Digging in…on Mars.
Credit: NASA Langley Advanced Concepts Lab/Analytical Mechanics Associates

Drilling to depth

Tarnas and Mustard say in the Brown University press release, that while there are surely technical challenges involved in subsurface exploration, those challenges are not show-stoppers.

A drilling operation on Mars wouldn’t require “a Texas-sized oil rig,” Mustard says, and recent advances in small drill probes could soon put the Martian depths within reach.

“The subsurface is one of the frontiers in Mars exploration,” Mustard said. And about the prospect of finding present-day life on the Red Planet, “the subsurface is absolutely going to be where the action is.”

To access the Astrobiology journal paper – “Earth-like Habitable Environments in the Subsurface of Mars” – go to:

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