ESA exposed a total of 664 biological and biochemical samples to open space for 18 months. The best survivor turned out to be Xanthoria elegans, this lichen resisted the solar UV radiation, cosmic rays, vacuum and varying temperatures for 18 months and carried on living as before after giving them some water. You can read the full article at ESA.
“These Xanthoria elegans lichens were flown on Expose-E and they are the best survivors we know,” explains Demets. Lichen is a sort of macroscopic composite organism of a fungus and a photosynthetic partner that is typically alga or cyanobacterium.
“These can be found typically in the most extreme places on Earth. When they are put in an environment they don’t like, they put themselves in off-mode and wait for better conditions. Once you put them back in a suitable environment and give them some water, they just carry on living as before.”
The key issue is water: it is almost immediately vaporised in the vacuum of space. Only anhydrobiotic organisms, which are dry and capable of sustaining long periods in extremely dry conditions, can survive space vacuum. Apart from lichens, only a few animals and plants can resist the vacuum: water-bears, brine shrimp and larvae of the African midge Polypedilum vanderplank are the only animals known to survive open space. Some dried plant seeds are also dry enough.
