Mosses are thought to have evolved from plant ancestors that began emerging from the water and colonizing land around 450 million years ago.
These organisms are known to be extremely hardy and capable of growing everywhere from the Antarctic tundra to the peaks of the Himalayas, volcanic lava fields and all manner of aquatic habitats.
Fujita said he was inspired by this impressive resilience.
“I began to wonder: Could this small but amazingly tough plant survive in space?” – he said.
His team started by studying a species of moss known as Open Fiscomitrium under simulated space conditions in a laboratory on Earth, including extreme high and low temperatures, vacuum conditions and high levels of UV radiation.
They determined that moss sporophytes—encapsulated spores that function as reproductive structures—are the parts of moss most likely to survive in space, as they appear to be able to withstand high levels of UV radiation. The spores were also able to germinate after exposure to scorching temperatures: 131 degrees Fahrenheit for a month and minus 320 degrees Fahrenheit for more than a week.
So in March 2022, researchers sent hundreds of moss sporophytes to the International Space Station aboard aerospace company Northrop Grumman's cargo spacecraft. Astronauts on the orbiting outpost attached the sporophyte samples to the outside of the space station, where they remained for 283 days.
The moss samples were then returned to Earth by a SpaceX cargo mission in January 2023.
The researchers found that more than 80% of the spores survived the nine-month stay outside the space station. Of these, almost 90% were able to germinate again in a laboratory on Earth.
