In 2005, scientists stated that moss can grow inside spaceships. The small plants that scientists have sent back on NASA spacecraft missions have grown in a stunningly strange shape, a sort of fuzzy spiral, an apparent response to a low-gravity environment.
It wasn't as fancy an experiment as you might think. While researchers ponder how humans might someday feed themselves beyond Earth, it's anyone's guess how plants that evolved on Earth, with Earth's gravity and atmosphere, and protection from the radiation of outer space, will cope with such strange habitats.
Since this space moss set off on its journey, many research groups have sent seeds and spores to the International Space Station (ISS) and plant cultivation is organized there. Now, following in the footsteps of those researchers, the team published Nov. 20 in the journal iScience shows that more than 80% of moss spores left outside the ISS for nine months and brought back to Earth germinated normally. The results confirm that moss spores, already known to be hardy, can easily withstand the stresses of low-Earth orbit.
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This particular type of moss, called spreading ground moss, is often used by scientists in the lab, says Tomomichi Fujita, a professor at Hokkaido University and author of the new paper. Its spores, each containing everything needed to create a new moss plant, traveled into space because Fujita and his colleagues were curious how they could cope with long-term exposure to these harsh conditions, hoping to one day grow such mosses on other planets. On Earth, “moss is a pioneering land plant,” he says. When plant life on this planet first moved from the seas to land, it was believed that mosses one of the first to accept a new life situation.
Before the spores flew away, the researchers first tested how they cope with stress on Earth. They recorded how many spores sprouted after exposure to extreme heat and cold, ultraviolet light and very low pressure, confirming that compared to other life stages of the moss, the spores were more resilient. The spores were then stored outside the ISS for nine months, where they were subjected to multiple tests simultaneously.
Fujita and his colleagues weren't sure any spores would end up there; each of the problems on Earth seemed to significantly reduce their viability. But in the end: “[more than] 80% of the spores survived. It was very surprising,” he says, and hopes the results will help advance research into how plants from Earth might one day grow on Mars or the Moon.
One factor the spores may face once they leave low-Earth orbit that this study couldn't address is how they cope with cosmic ionizing radiation, said Agata Zupanska, a research fellow at the SETI Institute, a nonprofit that studies the origins of life in the universe. The Earth's magnetic field largely deflects these rays before they can penetrate genetic material and cause mutations, and the ISS is located low enough to be reasonably shielded. But such protection is not available in deep space, and it is a major concern that crop seeds en route to another planet could become so damaged that they become unusable upon arrival, Zupanska says.
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To solve this problem in her work, Zupanska bombards the hardy Antarctic mosses with radiation in a particle accelerator. “The most radiation-resistant plant is moss. That’s why I became interested in moss,” she says. (She also adds with a laugh, “Moss is cute.” He has amazing charisma for a little green creature.) Her group includes sent these buried plants to the ISS see how low gravity conditions affect their ability to recover from radiation; The results of this experiment have not yet been published.
If mosses—either their spores or entire plants—can survive the challenges of space travel, perhaps their strategies could be adapted to help other plants. And the mosses themselves, Fujita and Zupanska believe, could play a role in making other planets hospitable to terrestrial life. After all, it is believed that mosses have helped pump large amounts of oxygen into the Earth's atmosphere more than 400 million years ago.
“This is a pioneering plant. Here on Earth, even if a forest is devastated by forest fires, the first plants to invade the ecosystem and restore it will be moss,” Zupanska says. Perhaps someday green cushions will appear on the red Martian dust, which will adapt to the new environment and, in turn, modify it.
