When the first humans go to Mars, they may want to bring lichens with them. Because lichens are mini-ecosystems made of both fungi and algae or bacteria, they are particularly good at surviving the extreme conditions on Mars, and could even be used to produce rocket fuel in space. Kiriakos Kotzabasis at the University of Crete in Greece and his colleagues subjected lichen to brutal conditions similar to those seen on Mars with no water, temperatures as low as -196°C, and low oxygen levels to see how they would survive. They found that, as long as the lichen were deprived of water before they experienced extremely low temperatures which the team achieved by dipping the lichen in liquid nitrogen they were able to recover almost completely. While we dont know exactly why lichens are so good at coping, Kotzabasis says that it likely has something to do with the symbiosis between the fungi and the algae. Each of the two partners is sensitive to different stressors, so they can shore one another up. Despite their exposure to an unfavourable environment or to repeated extreme conditions, lichens remain alive, Kotzabasis says. The researchers say that surviving these tough conditions may make lichens particularly good candidates for lithopanspermia, the idea that life can spread through space by hitching a ride on an interstellar rock. Not only were the lichens able to survive Mars-like conditions, after they were revived and placed in a friendlier environment, they went right back to producing lots of hydrogen, just like lichens normally do. That might be a boon to explorers on long space journeys, because hydrogen is a key ingredient in some types of rocket fuel. Explorers could bring lichens with them and produce their own fuel by reviving the lichens when they need more hydrogen. They could even leave the lichens behind on Mars for the next group of astronauts to revive and reuse, Kotzabasis says. He says that the next steps are testing how well lichens survive through other extreme conditions in space, like high radiation levels.
New Scientist, 9 November 2018 ; http://www.newscientist.com/