Some bacteria are able to survive at least three years in space, Wired reports.
It adds that as part of the Tanpopo mission, Japanese astronauts exposed dried colonies of different Deinococcus species to the vacuum of space. As researchers led by Tokyo University of Pharmacy and Life Sciences' Akihiko Yamagishi now report in Frontiers in Microbiology, cell pellets that were at least 500 millimeters thick survived their time in space. The outer cells of the pellets mostly died from UV exposure, but protected the inner ones. Additionally, the surviving cells could then repair the UV-induced DNA damage.
"Ultraviolet light in space is so strong and was expected to kill bacteria. We were surprised to see the surviving bacteria within the cell pellet for up to three years," Yamagishi tells New Scientist.
The researchers add that the findings support the controversial panspermia hypothesis, which supposes that life on Earth may have originated elsewhere in the universe.
Wired notes the results also have implications for planetary protection efforts that aim to keep both Earth-origin microbes off of Mars or other places people visit, and vice versa, if microbes are found beyond Earth.
"Any millimeter-thick aggregates would appear as dirt to the eye and would be wiped off the surface of a clean room in preparation of a related mission to Mars," Harvard University's Avi Loeb tells Wired. "But these results remind us of the importance of sterilizing all spacecraft sent to other planets in search of life."