There are currently three different Mars rovers (two from NASA and one from China) puttering around the surface of the Red Planet with the express purpose of trying to find signs of past or present alien life. However, they might not find anything—not because extraterrestrial life on Mars doesn’t exist, but because it has simply found its way underground.
A new study run by Northwestern University scientists and published in the journal Astrobiology has found that ancient bacteria would have the ability to survive under the surface of Mars for much longer than we previously thought. Those buried microorganisms would be guarded from solar radiation that penetrates through the Martian atmosphere, while still living relatively close to the surface.
The new results suggest that our best bet for finding any evidence of current life on Mars would be to advance missions that can drill and extract samples at least two meters below the surface.
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That’s great news for missions like ExoMars run by the European Space Agency, which will include the Rosalind Franklin rover; and the Mars Life Explorer concept pitched by NASA. Both missions would include the ability to drill down into the surface to extract materials.
The findings of the study hinge on new experiments that test out how much radiation bacteria might be able to withstand. Mars is a cold, dry hellscape, and any organisms that can withstand freezing temperatures of up to -81 degrees Fahrenheit must also contend with the fact that the surface is being pummeled by cosmic and solar radiation.
So the researchers decided to find out whether life could actually survive these conditions. They grew six types of Earthbound bacteria and fungi in Mars-like conditions emulating the frozen temperatures and intense dryness—and blasted them with radiation.
Some of these microorganisms proved they could outlive the torture, perhaps for hundreds of millions of years. One in particular, Deinococcus radiodurans (also called “Conan the Bacterium”), proved to be especially robust. The new study found that when this microbe is dried, frozen, and buried under the surface, it would withstand radiation 28,000 times greater than what would kill a human. It would only be able to live for a few hours at the surface, but even just 10 centimeters underground, it could potentially thrive for 1.5 million years. When buried 10 meters down, it might be able to survive for 280 million years.
The researchers found that the ability of these organisms to survive seems to correlate with increased amounts of manganese antioxidants in the cells or spores. If a microbe like Conan managed to evolve billions of years ago when water was teeming on Mars, and managed to absorb enough manganese antioxidants, it could still be alive in a dormant state just below the surface.
Mars lost its surface water a very long time ago—earlier than 280 million years ago. But the researchers suggest that periodic melting of ice reserves on Mars, caused by meteorite impacts, could have allowed these microbe populations to repopulate and disperse over time.
If there’s alien life waiting to be found on Mars, we’ll need to launch a mission that can drill, baby, drill. And unfortunately, it’s unclear when that might happen. Rosalind Franklin’s status is up in the air after Russia pulled out of the mission in the wake of its war on Ukraine. It will eventually launch, but ESA needs to figure out a new timetable. And if it’s greenlighted, Mars Life Explorer isn’t something that would launch until next decade at the earliest.
For now, the intrigue of life on Mars continues to swell, and we’ll just have to hope any living microbes on the Red Planet can hang on just a bit longer.
