High atop a platform inside a clean room at the European Space Agency’s (ESA) launch site in South America, scientists painstakingly searched for microbes near the Ariane 5 rocket due to launch the Herschel space telescope in May 2009. Only very unusual organisms can survive the repeated sterilization procedures in clean rooms, not to mention the severe lack of nutrients available. But the scientists’ careful inspection was fruitful, turning up a type of bacteria that had been seen only once before. Two years earlier this same bug had surfaced 4,000 kilometers away in the clean room at NASA’s Kennedy Space Center in Florida where engineers were preparing the Mars lander Phoenix for launch.*

After the two discoveries, the teams joined forces to analyze the bacterium, and found it was so different from known organisms that it constituted not just a new species, but a new genus, which they described in a paper published in July in the International Journal of Systematic and Evolutionary Microbiology. “This is the first report of bugs isolated in two different clean rooms, and nowhere else,” says Parag Vaishampayan, a microbiologist at the NASA Jet Propulsion Laboratory who led the team behind the Kennedy Space Center detection.

The researchers named the bacterium Tersicoccus phoenicis. “Tersi” is Latin for clean, as in clean room, and “coccus” comes from Greek and describes the bacterium in this genus’s berrylike shape. “Phoenicis” as the species name pays homage to the Phoenix lander. The scientists determined that T. phoenicis shares less than 95 percent of its genetic sequence with its closest bacterial relative. That fact, combined with the unique molecular composition of its cell wall and other properties, was enough to classify Tersicoccus phoenicis as part of a new genus—the next taxonomic level up from species in the system used to classify biological organisms. The researchers are not sure yet if the bug lives only in clean rooms or survives elsewhere but has simply escaped detection so far, says Christine Moissl-Eichinger of the University of Regensburg in Germany, who identified the species at the ESA’s Guiana Space Center in Kourou, French Guiana. Some experts doubt that Tersicoccus phoenicis would fare well anywhere other than a clean room. “I think these bugs are less competitive, and they just don't do so well in normal conditions,” says Cornell University astrobiologist Alberto Fairén, who was not involved in the analysis of the new genus. “But when you systematically eliminate almost all competition in the clean rooms, then this genus starts to be prevalent.”

Only the hardiest of microbes can survive inside a spacecraft clean room, where the air is stringently filtered, the floors are cleansed with certified cleaning agents, and surfaces are wiped with alcohol and hydrogen peroxide, then heated to temperatures high enough to kill almost any living thing. Any human who enters the room must be clad head to foot in a “bunny suit” with gloves, booties, a hat and a mask, so that the only exposed surface is the area around a person’s eyes. Even then, the technician can enter only after stomping on sticky tape on the floor to remove debris from the soles of her booties, and passing through an “air shower” to blow dust away from the rest of her. “It’s the cleanest place on Earth,” Vaishampayan says.

Scientists go to all this trouble for the purpose of “planetary protection”—which usually means protecting other planets from contamination by microbes originating on Earth. Most spacefaring countries have agreed to follow guidelines from the International Council for Science’s Committee on Space Research to reduce the chances of their vehicles carrying Earth organisms to other planets. The clean room procedures also safeguard against scientists mistaking Earthly microbes as extraterrestrial in origin if they are discovered on another planet, having caught a ride with a man-made spacecraft. “The whole idea of collecting information about what kind of bugs we have in the spacecraft assembly facility is to have baseline information so that in the future, if you find it on Mars, you have some grounds to rule out the possibility that it came from Mars,” Vaishampayan says.

The fact that bugs like T. phoenicis have proved hardy enough to survive in clean rooms doesn’t necessarily mean they’re likely to contaminate another planet. And the chances of a spacecraft like Phoenix mistaking this species as Martian life are very low, experts say. “This is a minimal risk considering that the portions of the spacecraft that are actually part of the experimental or sample collecting apparatus are kept exceptionally clean, if not sterile,” says Peter Smith, Phoenix’s principal investigator. “The surface environment on Mars is superlow pressure, no water, high [in] ultraviolet flux and high [in] cosmic radiation. In other words, a terrible place for life, even microbes that like clean rooms.”

Still, researchers would like to know whether such organisms could survive the trip from Earth to Mars, and survive on the Red Planet once they get there. To answer this question, scientists launched spores of the bacteria Bacillus subtilis and B. pumilus to the International Space Station in February 2008 and mounted them outside the orbiting laboratory for a year and a half. The experiment, called PROTECT, subjected the organisms to the vacuum of space, extreme temperature fluctuations and a barrage of radiation. Although many spores died, some survived, proving that certain bugs could successfully hitchhike to Mars. The most damaging effects came from the ultraviolet radiation the spores experienced outside Earth’s protective atmosphere. To survive, “either they have to hide or come up with an ingenious mechanism of repairing the DNA damage,” says Vaishampayan, who worked on the PROTECT experiment.

There is no proof that T. phoenicis actually accompanied Phoenix to Mars, but it is possible. “This genus has surely traveled to Mars already, recently in one or more of our spacecraft—they live comfortably in the clean rooms where we build the craft, right?—and maybe even onboard meteorites millions or billions of years ago,” Fairén says. “Therefore, if these bugs can actually survive on Mars, they must be there already.” Ultimately, the discovery of bacteria as resilient as T. phoenicis just goes to show how robust life is. The finding suggests that “once life originates on a planet, it has great adaptive power and can survive a great variety of environmental stresses,” says Dirk Schulze-Makuch of Washington State University, who wasn’t involved in the study of the new genus. “The $1-million question, of course, is: Under which conditions life can originate in the first place?”

*Correction (11/20/13): The last two sentences in this paragraph were edited after posting. The earlier version stated that the new bacterium genus was collected at Kennedy Space Center in 2011. It was actually found in 2007, before the launch of the Phoenix Mars lander, which lifted off August 4, 2007.