Lichens are strange organisms, a partnership between a fungus that provides shelter, water and minerals, and an alga or cyanobacterium that provides food from their photosynthesis. And even though lichens tend to be unassuming to look at, they are so incredibly tough that some can even survive the harsh environment of space.
When lichens were attached to the outside of the International Space Stationed for 18 months, they survived the vacuum of space, no water, extreme temperatures and the full onslaught of radiation and ultraviolet rays from the sun, continuing photosynthesis.
Lichens kept in a simulated Martian environment on Earth survived and were active, raising the prospect that life could exist on Mars, where the environment is intensely dry and cold, with low atmospheric pressure and radiation bombing. In fact, lichens can handle radiation that is 12,000 times the lethal dose for humans and still continue to photosynthesize, although their reproduction may be impaired. However, bacteria given the same treatment died. There is even a thought that life on Earth, or any other planet, could possibly have been spread through space by lichens that ride on meteoritescomets or asteroids.
