When spores from a humble moss were sent into space, it was one small step for moss, one giant leap for moss-kind. Over 80% of the spores survived nine months attached to the outside of the International Space Station (ISS) and made it back to Earth still able to reproduce.
The feat, described in iScience, demonstrates the ability of early land plants to survive long-term exposure to the extremes of space.
From the peaks of the Himalayas to the sands of Death Valley, mosses are well known for their ability to withstand harsh environments. Space, however, is a different kettle of fish, with high levels of UV radiation, extreme high and low temperatures and vacuum conditions.
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To find out if moss could survive in space, researchers from Japan’s Hokkaido University first simulated the conditions in a lab on Earth. Three structures from the spreading earthmoss (Physcomitrium patens) were tested - juvenile moss, stem cells and spore-containing structures called sporophytes.
Sporophytes were the hardiest. Encased spores were a thousand times more tolerant to UV radiation than stem cells. They were also able to survive and germinate after being exposed to -196oC for over a week, as well as after living in 55oC heat for a month.
After that, it was time for blast off. In early 2022, hundreds of sporophytes were loaded onto the Cygnus NG-17 supply spacecraft and then transferred to an exterior platform on the ISS. They stayed there, orbiting the Earth approximately once every 90 minutes, for 283 days, before hitching a lift back to terra firma on SpaceX CRS-16.
“We expected almost zero survival,” says lead author Tomomichi Fujita, “but the result was the opposite: most of the spores survived. We were genuinely astonished.”
Of the 80% of spores that survived, 89% were subsequently able to germinate. In addition, mathematical modelling suggested that the spores could have survived for up to 15 years in space.
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It’s thought that the sporophyte’s protective outer coating helped to shield the spores from damage, and that this could explain how bryophytes – the group that includes mosses – were able to transition from aquatic to land-based plants 500 million years ago, and then survive several mass extinction events.
The research will help those trying to develop agricultural systems for use in space. “Ultimately, we hope this work opens a new frontier toward constructing ecosystems in extraterrestrial environments such as the Moon and Mars,” says Fujita. “I hope that our moss research will serve as a starting point.”
Top image: Earth from space. Credit: Getty
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