By Layal Liverpool
MICHAEL J DALY/Science Photo Library
Microbes strapped to the outside of the International Space Station can survive for at least three years, suggesting that life has the potential to survive a journey through space from Earth to Mars.
“If bacteria can survive in space, [they] may be transferred from one planet to another,” says Akihiko Yamagishi at Tokyo University of Pharmacy and Life Sciences in Japan.
“We don’t know where life emerged. If life emerged on Earth, it may [have been] transferred to Mars. Alternatively, if life emerged on Mars, it may [have been] transferred to Earth … meaning that we are the offspring of Martian life,” says Yamagishi. If the journey is possible, then the probability of finding life on planets outside our solar system increases, he says.
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Deinococcus radiodurans bacteria are naturally very resistant to radiation, because of their extraordinary capacity to repair their DNA when it gets damaged, says Yamagishi. He and his colleagues wanted to investigate whether this might enable them to survive in the harsh environment of space, where levels of radiation – particularly in the ultraviolet range – are extremely high.
Yamagishi and his team sent Deinococcal cell clumps of various thicknesses to the International Space Station, where they were placed on aluminium plates and attached to the outside of the spacecraft for three years. Samples were taken each year and sent back to Earth for analysis.
Within the clumps that were at least half a millimetre thick, the researchers found surviving bacteria – even in the samples that were left outside the space station for three years. “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,” says Yamagishi.
Although the bacteria in the outer layer of the clumps were destroyed by the UV, these dead cells seem to have shielded the bacteria in the innermost layers, which survived. These surviving bacteria were then able to repair their DNA from damage and could be grown in the laboratory.
Jean-Pierre de Vera at the German Aerospace Center (DLR) says the results add to growing evidence for panspermia – the idea that life could be transferred between planets on rocks thrown up into space in the aftermath of a large asteroid impact, such as the one 66 million years ago that is thought to have led to the extinction of the dinosaurs. He says it will be important to investigate whether and how the bacteria can shield themselves against other types of radiation in space, such as cosmic radiation.
Journal reference: Frontiers in Microbiology, DOI: 10.3389/fmicb.2020.02050
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