Impact pressures generated by spherical particle hypervelocity impact on Yorkshire sandstone

We characterise the pressures achieved in spherical particle impact, as a precursor to investigating the possibility of shock-driven DNA modification in sandstone targets, which could occur at lower pressures than those previously established to cause extinction e.g. for \textit{B. subtilis} [1, 2]. Hypervelocity impact experiments at 5 km/s using spherical chrome stainless steel projectiles onto Yorkshire sandstone were carried out using the Open University's Hypervelocity Impact Facility [3]. Noting that the impact tests cannot be carried out in a completely sterile environment, we also establish the degree of background microbial contamination present by examining post-impacted targets. Hydrocode simulations (2-D and 3-D) are used to estimate the peak loading time and pressures as a function of target geometry, supported by 1-D hydrocode simulations using the CAV{\_}KO software and published flyer plate data from the Cambridge Plate Impact Facility [4, 5]. 1) D. St\"{o}ffler et al, Icarus, 186 (2), 585-588, 2007; 2) M. J. Burchell et al, Mon. Not R. Astron. Soc., 352, 1273-1278, 2004; 3) E. A. Taylor et al, 37$^{th}$ ARA Conf, Sept 2006; 4) E. A. Taylor et al., APS 2005; 5) E. A. Taylor et al., ESTEC Impact Conf., May 2005