Lichens can survive unprotected in the harsh conditions of space, a European Space Agency experiment discovers.
The organisms are a composite of algae and fungi. They are commonly found on the surface of rocks on Earth and can survive in extreme conditions such as high mountains latitudes. Lichens are the most complex form of life now known to have survived prolonged exposure to space.
In an experiment led by Leopoldo Sancho from the Complutense University of Madrid, two species of lichen – Rhizocarpon geographicum and Xanthoria elegans – were sealed in a capsule and launched on a Russian Soyuz rocket on 31 May 2005.
Once in Earth orbit, the lid of the container opened and the samples were exposed to the space environment for nearly 15 days before the lid resealed and the capsule returned to Earth.
The lichens were subjected to the vacuum of space and to temperatures ranging from -20°C on the night side of the Earth, to 20°C on the sunlit side. They were also exposed to glaring ultraviolet radiation of the Sun.
“To our big surprise, everything went fine after the flight,” says Rene Demets, ESA’s project scientist for the Foton project. “The lichens were in exactly the same shape as before flight.”
In space, the lichens turned dormant and did not metabolize, but once returned to Earth, they returned to their normal activity and their DNA appeared not to have been damaged, Demets told New Scientist. All of the lichen appeared to endure the ultraviolet radiation, even those receiving the most exposure.
Lichens have a tough mineral coating that could shield them from UV rays. They are also made from individual organisms layered on top of one another, so outer layers may provide protection for underlying cells. The organisms have already been shown to be capable of withstand high levels of UV radiation on Earth.
The experiment adds weight to the theory of panspermia – that life could somehow be transported between planets, perhaps by hitching a ride on an asteroid. It also indicates that organisms similar to lichens might be able to survive on the surface of Mars – at least during the planet's summer.
Although the Martian atmosphere is very thin, it is filled with carbon dioxide, which is necessary for lichens’ photosynthesis. The lichens might not survive on Mars for long, however, because of low oxygen levels in the atmosphere.
In the 1980s, experiments carried out on NASA’s Long Duration Exposure Facility satellite showed that certain bacteria are hardy enough to endure space. Rocco Mancinelli, a microbial ecologist with the SETI Institute in California, who has also done experiments with micro-organisms in space, says he is not surprised to see lichens survive outside the Earth's atmosphere.
The algae and fungi that make up lichens exist in a symbiotic relationship. The algae provide the fungi with food while the fungi offer the algae a cozy living environment.
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10:45 10 October 2008
19:00 09 October 2008
