Survival of bacteria and spores under extreme shock pressures

Some rocky objects on Earth originated on other planets (e.g. Martian meteorites). Modelling of interplanetary transfer times (Mars-Earth) and calculations of the survival of cells and spores in the radiation environment of space show that this is not an insurmountable obstacle to the successful delivery of life from one planetary surface to another via these rocks. However, the initial launch into space and the subsequent arrival at a new planet involve short-duration extreme accelerations, and shock pressures in the 1-100 GPa range. Recently it has been shown that survival of such accelerations and at such shock pressures is possible. Here we show that in hypervelocity impacts (which involve extreme short-duration accelerations), as shock pressures vary from 1 to 78 GPa, the survival rate (N/N-0) for Rhodococcus erythropolis cells falls from 10(-4) to 10(-7). Whilst survival rates are low at 78 GPa, they are still finite. For a different organism, Bacillis subtilis, the survival rate at 78 GPa was found to be of the order of 10(-5), i.e. significantly greater than for the R. erythropolis, indicating that survival rates may vary greatly with different organisms. By contrast, the variation between the survival rate in impacts on agar at 78 GPa for B. subtilis spores versus active B. subtilis was found only to be a factor of 2, well within the experimental uncertainties and not significant. Overall, whilst extreme shock pressures clearly have a deleterious effect on survival rates, it is shown that, even at extreme shock pressures of near to 100 GPa, there is still a finite and sufficient survival rate for this not to be an insurmountable obstacle to successful natural transfer of life through space.