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Turns out that P. cryohalolentis finds precious little shelter from UV radiation, even under global dust storm conditions or sitting inside a salt mineral matrix.

"We found that the UV radiation was readily and easily able to penetrate the salt-organic matrix that the bacterial cells were embedded in," Schuerger said.

Such findings suggest that this type of extremophile poses little risk of spreading across the surface of Mars — at least not on its current-day hostile surface environment. P. cryohalolentis even fared poorly under the dry conditions on the lab bench, let alone inside the Mars simulator.

The study points to a need for future investigations on how much UV protection a microbe can find in salt mineral layers within the Martian regolith.

"The research emphasizes the point that you're not going to automatically get protection from UV when embedded within salt deposits," Schuerger noted. "Some salt encrustations might protect with just a few millimeters of salt, while others might need 5 to10 centimeters."

UV is not the only challenge facing hitchhiking microbes. Schuerger's past research found at least 13 separate factors on Mars that can kill Earth microbes, not counting perchlorate salts uncovered by NASA's Phoenix Mars Lander in the polar region of Mars.