Bacterial spores survive simulated meteorite impact

A hypothetical interplanetary transfer of viable microorganisms requires that the microbes survive the following steps: (i) escape process, (ii) transient journey in space, and (iii) entry process. Step 1 involves hypervelocity impact under strong shock metamorphism of the ejected microbe-bearing rock fragment. This paper reports experimental studies on the survival of microbes after a simulated meteorite impact. In shock recovery experiments with an explosive setup, spores of Bacillus subtilis HA 101, immobilized between two quartz plates, were subjected to a peak shock pressure of 32 GPa, Although the spore layer showed an intense darkening after the shock treatment, 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 martian meteorites have experienced according to well-calibrated shock effects of their mineral constituents. The data support the hypothesis that bacterial spores may survive an impact-induced escape process in a scenario of interplanetary transfer of life, (C) 2000 Academic Press.