Impact resistance of bacteria entrapped in small meteorites

The lunar and Martian origins of some Antarctica meteorites demonstrate clearly the existence of regular exchanges of crust fragments between telluric planets of the solar system. Moreover, putative biological traces found in ejecta from the red planet led to the hypothesis that life was present in rocks of its surface. The distribution of life on at least two bodies of the solar system could easily be explained by transfers of biological know-how: either i) by simple organisms moved by radiation pressure once present in the uppermost level of the atmosphere or ii) by exchange of crust fragments containing entrapped life forms, ejected after a primary hypervelocity impact in solar orbit, and subsequently captured by an other planet. The final steps of the latter kind of interplanetary transfer are analysed with respect to small meteoroids. The comparison between observation of flight and impact parameters of small falling stones and classical microbiological ballistic experiments done between 300 to 600 meters per second lead us to propose for the first time that various kinds of bacteria entrapped in small impactors are able to withstand i) the heat produced by the Earth's aerobraking, reducing preatmo-spheric velocity (usually between 10 and 70 kilometers per second) to that of free fall (125 to 250 meters per second), and ii) the subsequent non-explosive impact. The importance of these biological properties for the origin and the early development of life in the solar system is discussed in this article.