Origins of Life and Evolution of the Biosphere 31: 527–547, 2001.

PROTECTION OF BACTERIAL SPORES IN SPACE, A CONTRIBUTION
TO THE DISCUSSION ON PANSPERMIA

GERDA HORNECK1∗, PETRA RETTBERG1, GÜNTHER REITZ1, JÖRG WEHNER1, UTE ESCHWEILER1, KARSTEN STRAUCH1, CORINNA PANITZ1,
VERENA STARKE1 and CHRISTA BAUMSTARK-KHAN2

Abstract. Spores of Bacillus subtilis were exposed to space in the BIOPAN facility of the European
Space Agency onboard of the Russian Earth-orbiting FOTON satellite. The spores were exposed
either in dry layers without any protecting agent, or mixed with clay, red sandstone, Martian analogue
soil or meteorite powder, in dry layers as well as in so-called ‘artificial meteorites’, i.e. cubes
filled with clay and spores in naturally occurring concentrations. After about 2 weeks in space, their
survival was tested from the number of colony formers. Unprotected spores in layers open to space
or behind a quartz window were completely or nearly completely inactivated (survival rates in most
cases ≤10−6). The same low survival was obtained behind a thin layer of clay acting as an optical
filter. The survival rate was increased by 5 orders of magnitude and more, if the spores in the dry
layer were directly mixed with powder of clay, rock or meteorites, and up to 100% survival was
reached in soil mixtures with spores comparable to the natural soil to spore ratio."

BD