Microbial life and shock compression - Life or death?

The role of shock compression in killing microbial life is discussed. As well as the extreme pressures involved, the duration of the shock is also important (i.e. static vs. dynamic). For shock pressures and durations typical of impacts on planetary surfaces, there is experimental data now available from a variety of sources illustrating that microbial survival rates are small but finite (typically order 10(4) to 10(-7)). Thus any viable biological material on a rock arriving from space at high speed may survive intact after impacting the Earth. Similarly, it is possible to define a zone of lethality around an impact site, and predict survival rates of indigenous microbial life in the target material as a function of shock pressure. Finally, it is noted that post-impact the altered crater environment may be more suitable for sustaining life than the surrounding region was before the impact event.