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Survival of lichens and bacteria exposed to outer space conditions - Results of the Lithopanspermia experiments |
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| Authors: | Rosa de la Torre Leopoldo G Sancho Asunción de los Ríos Karen Olsson-Francis Petra Rettberg Jean-Pierre P de Vera Jesus Martinez Frías Maria Mercedes Lucas Ana Pintado |
| Institution: | a INTA, Instituto Nacional de Técnica Aeroespacial, Crta. Ajalvir, km. 4, 28850-Torrejón de Ardoz, Madrid, Spain b Universidad Complutense de Madrid, Departamento de Biología Vegetal II, Pza. Ramón y Cajal s/n, 28040 Madrid, Spain c Deutsches Zentrum für Luft- und Raumfahrt, Institut für Luft- und Raumfahrtmedizin, Linder Höhe, 51170 Köln, Germany d CSIC, Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, Serrano 115dpdo, 28006 Madrid, Spain e The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom f Heinrich-Heine-Universität, Institut für Botanik, Universitätsstr. 1, 40225 Düsseldorf, Germany g INTA-CSIC, Centro de Astrobiología, Crta. Ajalvir, km. 4, 28850-Torrejón de Ardoz, Madrid, Spain h ESA-ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands i Deutsches Zentrum für Luft- und Raumfahrt, Institut für Planetenforschung, Rutherfordstr. 2, 12489 Berlin, Germany j Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Campus de Montegancedo, Autopista M-38, Pozuelo de Alarcón, 28223 Madrid, Spain |
| Abstract: | In the space experiments Lithopanspermia, experimental support was provided to the likelihood of the lithopanspermia concept that considers a viable transport of microorganisms between the terrestrial planets by means of meteorites. The rock colonising lichens Rhizocarpon geographicum and Xanthoria elegans, the vagrant lichen Aspicilia fruticulosa, and endolithic and endoevaporitic communities of cyanobacteria and bacteria with their natural rock substrate were exposed to space for 10 days onboard the Biopan facility of the European Space Agency (ESA). Biopan was closed during launch and re-entry. In addition, in the Stone facility, one sample of R. geographicum on its natural granitic substrate was attached at the outer surface of the re-entry capsule close to the stagnation point, only protected by a thin cover of glass textolite. Post-flight analysis, which included determination of the photosynthetic activity, LIVE/DEAD staining, and germination capacity of the ascospores, demonstrated that all three lichen were quite resistant to outer space conditions, which include the full spectrum of solar extraterrestrial electromagnetic radiation or selected wavelength ranges. This high resistance of the lichens to space appears to be due to their symbiotic nature and protection by their upper pigmented layer, the cortex. In contrast, the rock- or halite-inhabiting bacteria were severely damaged by the same exposure. After atmospheric re-entry, the granite of the Stone sample was transformed into a glassy, nearly homogenous material, with several friction striae. None of the lichen cells survived this re-entry process. The data suggest that lichens are suitable candidates for testing the concept of lithopanspermia, because they are extremely resistant to the harsh environment of outer space. The more critical event is the atmospheric re-entry after being captured by a planet. Experiments simulating the re-entry process of a microbe-carrying meteoroid did not show any survivors. |
| Keywords: | Astrobiology Exobiology Meteorites Solar radiation |
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