text: After 1.5 years in space, samples were retrieved, rehydrated and spread on different culture media. The only two organisms able to grow were isolated from a sample exposed to simulated Mars conditions beneath a 0.1% T Suprasil neutral density filter and from a sample exposed to space vacuum without solar radiation exposure, respectively. The two surviving organisms were identified as Stichococcus sp. (green algae) and Acarospora sp. (lichenized fungal genus). Among other fungal spores tested were Cryomyces antarcticus and Cryomyces minteri, and although 60% of the cells' DNA studied remained intact after the Mars-like conditions, less than 10% of the fungi were able to proliferate and form colonies after their return to Earth. According to the researchers, the studies provide experimental information on the possibility of eukaryotic life transfer from one planet to another by means of rocks and of survival in Mars environment.
  Cryptoendolithic microbial communities and epilithic lichens have been considered as appropriate candidates for the scenario of lithopanspermia, which proposes a natural interplanetary exchange of organisms by means of rocks that have been impact ejected from their planet of origin. A 1.5 years exposure experiment in space was performed with a variety of rock-colonizing eukaryotic organisms. Selected organisms are known to cope with the environmental extremes of their natural habitats. It was found that some — but not all — of those most robust microbial communities from extremely hostile regions on Earth are also partially resistant to the even more hostile environment of outer space, including high vacuum, temperature fluctuation, the full spectrum of extraterrestrial solar electromagnetic radiation, and cosmic ionizing radiation. Although the reported experimental period of 1.5 years in space is not comparable with the time spans of thousands or millions of years believed to be required for lithopanspermia, the data provide first evidence of the differential hardiness of cryptoendolithic communities in space.