Bacterial spores survive simulated meteorite impact

A hypothetical interplanetary transfer of viable microorganisms requires th at the microbes survive the following steps: (i) escape process, (ii) trans ient journey in space, and (iii) entry process. Step 1 involves hyperveloci ty impact under strong shock metamorphism of the ejected microbe-bearing ro ck fragment. This paper reports experimental studies on the survival of mic robes after a simulated meteorite impact. In shock recovery experiments wit h an explosive setup, spores of Bacillus subtilis HA 101, immobilized betwe en two quartz plates, were subjected to a peak shock pressure of 32 GPa, Al though the spore layer showed an intense darkening after the shock treatmen t, up to 500 spores per sample survived, resulting in a survival rate up to 10(-4). This experimental pressure is in the pressure range which some mar tian meteorites have experienced according to well-calibrated shock effects of their mineral constituents. The data support the hypothesis that bacter ial spores may survive an impact-induced escape process in a scenario of in terplanetary transfer of life, (C) 2000 Academic Press.