There are currently three different Mars rovers (two from NASA and one from China) circulating on the surface of the Red Planet with the express purpose of trying to find signs of past or present alien life. However, they may find nothing, not because extraterrestrial life on Mars doesn’t exist, but because it has simply found its way underground.
A new study by Northwestern University scientists and published in the journal Astrobiology found that ancient bacteria would have the ability to survive beneath the surface of Mars much longer than previously thought. Those buried microorganisms would be protected from solar radiation penetrating through the Martian atmosphere, while living relatively close to the surface.
The new findings suggest that our best bet for finding any evidence of current life on Mars would be to advance missions capable of drilling and extracting samples at least two meters below the surface.
This is great news for missions like ExoMars operated by the European Space Agency, which will include the Rosalind Franklin rover; and the Mars Life Explorer concept pioneered by NASA. Both missions would include the ability to pierce the surface to extract materials.
The results of the study depend on new experiments testing how much radiation the bacteria might be able to withstand. Mars is a cold, dry hellish landscape, and any organism that can withstand freezing temperatures as low as -81 degrees Fahrenheit also has to contend with the fact that the surface is affected by cosmic and solar radiation.
So the researchers set out to find out if life could actually survive these conditions. They cultivated six types of Earth-related bacteria and fungi in conditions similar to those of Mars, emulating freezing temperatures and intense dryness, and detonated them with radiation.
Some of these microorganisms have been shown to survive torture, perhaps for hundreds of millions of years. One in particular, Deinococcus radiodurans (also called “Conan the Bacterium”), proved to be particularly robust. The new study found that when this microbe is dried, frozen and buried beneath the surface, it resists radiation 28,000 times greater than what would kill a human. It would only be able to live for a few hours on the surface, but even as low as 10 centimeters underground, it could potentially thrive for 1.5 million years. If buried 10 meters deep, it may be able to survive for 280 million years.
The researchers found that the ability of these organisms to survive appears to be related to a greater amount of manganese antioxidants in the cells or spores. If a microbe like Conan managed to evolve billions of years ago when water swarmed 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 water surface a long time ago, before 280 million years ago. But the researchers suggest that the periodic melting of ice reserves on Mars, caused by meteorite impacts, may have allowed these populations of microbes to repopulate and disperse over time.
If there’s alien life waiting to be found on Mars, we’ll have to launch a mission that can drill, honey, drill. And unfortunately, it’s not clear when that might happen. Rosalind Franklin’s status is in the air after Russia withdrew from the mission following its war against Ukraine. It will eventually be launched, but ESA has to find a new timetable. And if it has the green light, Mars Life Explorer isn’t something that will launch until at least the next decade.
For now, the intrigue of life on Mars continues to grow and we will just have to hope that the microbes living on the Red Planet can hold out a little longer.
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