Lichens, which are a mix of fungi and algae, can survive in extreme temperatures. Some, like this Buellila fridgida, can be found just 250 miles from the South Pole in Antarctica. Stephenson notes that in May 2005, Spanish researcher Leopold Sancho placed two species of lichens aboard a Russian rocket; once in orbit, the capsule holding the lichens opened and they were exposed to the extreme temperature fluctuations of space. The lichens, Stephenson writes, suffered no apparent problems from their cosmic adventure.

Lichens can also be used as an emergency food, Stephenson says. Pilots who have crashed high in the mountains have consumed them, and some Biblical scholars suggest that the Bible's "manna from heaven" could have been a form of lichen found in the deserts of the Middle East. "Lichens have a pretty earthy taste," Stephenson says. "They're pretty tough and hard to digest but they do provide some nutrition."