On Twitter, @Massimo posted this

Did you know? Lichen survived 18 months attached to outside of International Space Station. When lichens were attached to the outside of the International Space Station 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, and carried on photosynthesising. In fact, lichens can cope with radiation 12,000 times the lethal dose for humans and still carry on photosynthesising, although their reproduction can be harmed. However, bacteria given the same treatment died. There is even a thought that life on Earth, or any other planet, could conceivably have been spread through space by lichens hitching a ride on meteorites, comets or asteroids.

A lichen is a composite organism – a symbiotic relationship between algae or cyanobacteria and fungi. The fungi provide a protective environment for the algae, and in return, the algae produce food for the fungi through photosynthesis.

Here is the Linnean Society, on Beatrix Potter and her work on lichen.