A new experiment placing bacteria on the outside of the International Space Station (ISS) has found that micro-organisms can survive in space for years, or even decades. The study lends weight to the idea that life could travel between planets.
Bacteria are hardy little creatures. They thrive in practically every environment on Earth, from deep polar ice to the driest deserts, from miles underground to high in the atmosphere. But space is the final frontier, so they say, and whether microbes could survive out there has important implications for life on Earth – and other planets.
A new study has now put that to the test. Researchers at Tokyo University placed dry pellets of a tough bacteria called Deinococcus radiodurans in panels on the outside of the ISS, where they were exposed to the freezing cold, high radiation vacuum of space. These pellets contained “aggregates” – large colonies of the bacteria of different thicknesses, with no protective shielding.
These aggregates were analyzed after one, two and three years of exposure. By the end, all pellets thicker than 0.5 mm showed at least partial survival, faring better the thicker they were. On closer inspection, the researchers found that the colonies survived because the individual bacteria on the outside died of exposure, forming a protective shell for the rest.
Using the data gathered each year, the team was able to extrapolate how long colonies of different thicknesses might last in space. Those thicker than 0.5 mm could have lived between 15 and 45 years on the ISS, while a 1-mm thick colony floating loose in space could potentially survive for up to eight years.
The team says that this finding supports the hypothesis of panspermia, where life jumps between planets. The type of panspermia thought most plausible is lithopanspermia – where microbes hitch a ride on asteroids or comets, protected by a rocky shield. But the new study suggests it’s possible that unshielded bacterial colonies could also survive, in a new form of the phenomenon dubbed massapanspermia.
“The results suggest that radioresistant Deinococcus could survive during the travel from Earth to Mars and vice versa, which is several months or years in the shortest orbit,” says Akihiko Yamagishi, corresponding author of the study.
A previous study had similar results a few years earlier. A Russian team placed an array of bacteria, fungi and other organisms in ISS capsules exposed to space, and found that many survived, raising hopes for microbial life on Mars.
Although it does add evidence to support the panspermia hypothesis, the team says there are still a few major holes to plug in the story. Further work will need to be done to assess whether bacteria can survive the intense pressures and heat of being ejected from a planet or crash-landing on a new one.
The study was published in the journal Frontiers in Microbiology.
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