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Microbial rock inhabitants survive hypervelocity impacts on Mars-like host planets

First phase of lithopanspermia experimentally tested
: Horneck, G.; Stoffler, D.; Ott, S.; Hornemann, U.; Cockell, C.S.; Möller, R.; Meyer, C.; Vera, J.P. de; Fritz, J.; Schade, S.; Artemieva, N.A.


Astrobiology 8 (2008), Nr.1, S.17-44
ISSN: 1531-1074
ISSN: 1557-8070
Fraunhofer EMI ()

The scenario of lithopanspermia describes the viable transport of microorganisms via meteorites. To test the first step of lithopanspermia, i. e., the impact ejection from a planet, systematic shock recovery experiments within a pressure range observed in martian meteorites (5-50 GPa) were performed with dry layers of microorganisms ( spores of Bacillus subtilis, cells of the endolithic cyanobacterium Chroococcidiopsis, and thalli and ascocarps of the lichen Xanthoria elegans) sandwiched between gabbro discs ( martian analogue rock). Actual shock pressures were determined by refractive index measurements and Raman spectroscopy, and shock temperature profiles were calculated. Pressure- effect curves were constructed for survival of B. subtilis spores and Chroococcidiopsis cells from the number of colony-forming units, and for vitality of the photobiont and mycobiont of Xanthoria elegans from confocal laser scanning microscopy after live/dead staining (FUN-I). A vital launch window for the transport of rock-colonizing microorganisms from a Mars-like planet was inferred, which encompasses shock pressures in the range of 5 to about 40 GPa for the bacterial endospores and the lichens, and a more limited shock pressure range for the cyanobacterium ( from 5-10 GPa). The results support concepts of viable impact ejections from Mars-like planets and the possibility of reseeding early Earth after asteroid cataclysms.