On 4 March 2022, astronauts locked 20,000 moss spores outside the International Space Station and left them exposed to the rigours of space for 283 days. They then rescued the spores and returned them to Earth on a SpaceX capsule so that scientists could attempt to germinate them. Surprisingly, these attempts were successful.
Mosses were among the earliest land plants and are well known for colonising some of the harshest environments on Earth – Antarctica, volcanic fields and deserts, says Tomomichi Fujita at Hokkaido University in Japan, who was on the team that ran the experiment.
“We wondered whether their spores might also survive exposure to outer space – one of the most extreme environments imaginable,” he says.
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A control group of spores that had stayed on Earth had a germination rate of 97 per cent, as did another set of spores that were exposed to space but shielded from the damaging ultraviolet radiation found there.
Most astonishingly, over 80 per cent of the spores that were exposed to the full brunt of space – a vacuum, extreme temperatures, microgravity, UV and cosmic radiation – remained viable and germinated into normal plants. The team predicted it is possible that, based on the results of these experiments, some of the spores could remain viable in space for 15 years.
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Fujita says the multiple layers of spore walls that encase the reproductive tissue appear to offer “passive shielding against space stresses”.
He says it is as if the spores are inside their own spacecraft. This might have been an adaptive feature they developed to cope with the harsh environmental conditions that existed on land when life first moved out of the oceans hundreds of millions of years ago.
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David Eldridge at the University of New South Wales in Sydney says the true test isn’t whether the spores will germinate once back on Earth, but whether they can also germinate in space.
“The trick will be to check the growth rates of these taxa in space and see whether they can reproduce,” he says.
Source: Moss spores survive and germinate after 283-day ‘space walk’ | New Scientist
Robin Edgar
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