In two of the studies, scientists tested the ability of the spore-forming bacterium Bacillus pumilus SAFR-032 - which has a high resistance to the ultraviolet (UV) radiation and peroxide used to clean spacecraft - to survive in space. (One study also looked at another spore-forming bacterium, B. subtilis 168).
Using the European Technology Exposure Facility (EuTEF) mounted on the International Space Station, scientists exposed the bacteria to a simulated Mars atmosphere. They also subjected the bacteria to various space parameters, including space vacuum, solar radiation and intense temperature fluctuations.
"To our surprise, some of the spores survived for 18 months," Kasthuri Venkateswaran, a researcher with NASA's Jet Propulsion Laboratory in Pasadena, Calif., and a co-author on all three papers, said in a statement. A mission to Mars would take less than half that time, spaceflight experts have said.
Surviving B. pumilus SAFR-032 spores also demonstrated elevated levels of proteins associated with UV resistance, the researchers said. Given that UV radiation is a big threat to space-living bacteria, the researchers believe that spores sheltered from solar radiation, such as those living under spacecraft structures, or mutant subpopulations with heightened UV protection, could possibly survive a trip to Mars.