The possibility of life surviving after a major impact is crucial for solar system missions with possible sample return, since impact is a dominant process in the solar system – how likely is it that the sample contains life? The related question is that of whether life on one planet can be seeded by life carried on impact ejecta from another planetary body. As a first step to address these questions in the laboratory, we are investigating the effect of the high pressures and shear stresses developed during an impact on simple lifeforms. Using a combination of impact experiments and biological assays, we characterize the survival and response of Deinococcus radiodurans subjected to extreme dynamic stresses. D. radiodurans is commonly studied in astrobiology because it is an extremophile, with exceptional resistance to oxidative stress, desiccation, and ionizing radiation. The pressure-shear plate impact experiment (where interferometry can be used to estimate the stresses experienced by the specimen as well as the loading duration) has been successfully adapted to accommodate microorganism specimens [1]. Their survival was quantified over a range of pressures using microscopy to determine the percent recovery and counting colony forming units (CFUs). Membrane integrity was characterized using TEM imaging, and the quality and yield of RNA following an experiment allowed for additional data analysis on cellular response. We discuss these results and some potential implications.
[1] Zhao, L., et al. 53rd Lunar and Planetary Science Conference. Abstract #2577.
