This Microbe ‘Plays Dead’ in NASA Clean Rooms, and We May Have Sent It to Mars

The tiniest life forms are sometimes the strongest of them all—that is, they’ll survive anywhere and do everything they can to stay alive. Apparently, this even includes faking their own death.

In 2007, NASA found an entirely new bacterium, named Tersicoccus phoenicis, hiding inside two separate clean rooms—spacecraft manufacturing rooms disinfected to the extreme—each located 2,500 miles (4,000 kilometers) apart. After years of not understanding how exactly it got there, a recent paper published in Environmental Microbiology finally offers an answer: it hibernates, leading scientists to believe it was dead.

“It is not dead. It was playing dead,†Madhan Tirumalai, study lead author and a microbiologist at the University of Houston, told National Geographic back in October. “It is only dormant.â€

The clean room is not clean

The reason spacecraft are built in specialized clean rooms is to prevent unexpected contamination during space missions—both to astronauts and extraterrestrial locations. For the latter case, a rover searching for alien microbes wouldn’t want to be carrying Earthly microbes.

To that end, scientists take some extreme measures, including, but not limited to, repeated heating, drying, chemical cleaning with microbe-killing gases, ultraviolet treatment, and radiation attacks. Then microbiologists do another sterilization check to confirm nothing is alive.

So it’s impressive—scary, even—to think that T. phoenicis not only survived this treatment but also managed to evade sterilization checks. When NASA publicly announced the discovery of the bacterium in 2013, the agency clarified that the microbe did not pose any health risks. NASA scientists did note that they would continue to study similar species, and that was that.

Now you see them, now you don’t

Not content to leave it at that, the team behind the new paper sought to learn more about the tiny germ and its apparent superpowers. For their experiment, the team deprived T. phoenicis of all nutrients and placed them on sterile glass Petri plates to dehydrate them to the maximum. What they found was that, within 48 hours of this “killing†process, the bacteria went dormant—silent and seemingly dead based on their vital signs.

The bacteria also remained that way for the next seven days, even after the researchers tried to wake them from dormancy by reintroducing food. But they were definitely not dead, the paper explained, as exposing them to a certain protein “revived†their biological activities.

“The fact that this bacterium can intentionally suspend its metabolism makes survival on spacecraft surfaces or during deep-space cruise more plausible than previously assumed,†Nils Averesch, a microbiologist at the University of Florida uninvolved in the study, explained in a university statement.

Did we accidentally contaminate Mars?

One of the clean rooms where scientists discovered T. phoenicis for the first time was during preparations for NASA’s Phoenix Mars lander, which successfully traveled to our neighboring planet. If these bacteria—and potentially others like them—are so good at hiding, is there any chance that they ended up on Mars undetected?

The idea is a scary one to entertain, but experts believe chances are slim, as “[a]nything directly exposed on the Martian surface is unlikely to survive,†according to Averesch. There is also the possibility that T. phoenicis evolved specifically to adapt to spacecraft clean rooms, given how it hasn’t been found anywhere else in the world, the paper pointed out.

That said, the results also serve as alternative “cleaning†tips for cleanrooms. Now that scientists have an idea of how to coax elusive bacteria out of dormancy, it could help enhance cleaning strategies for these spaces.

But above all else, this strange metabolic shutdown further proves the incredible survival mechanisms of the tiniest living forms known to us.