During the European Space agency's 2005 Foton mission lichens were exposed to space for 15 days. They had to endure a wide range of harsh conditions: a vacuum; wide fluctuations of temperature; the complete spectrum of solar UV light; and bombarded with cosmic radiation. If we were living in a comic book then the lichens would have returned with super powers but here in the real world most people were surprised to find the lichens merely survived. They appeared totally dormant whilst in space but soon revived back on earth.
One conclusion of this experiment is that it appears likely that lichens may be able to survive on the surface of Mars. Although the Martian atmosphere is very thin, it is filled with carbon dioxide, which is necessary for photosynthesis. However, long term survival and growth may be prevented by the low oxygen levels in the Martian atmosphere.