Shock Compression of Seeds in Impacts at 1 -- 5 km s$^{-1}$

Panspermia (``seeds everywhere'') is an old idea, suggesting that life can naturally migrate through space. The survival of microbial life under the shock compression involved with transfer of a body through space between planets has been much studied; e.g. Burchell et al., \textit{Origin of Life and Evol. of the Biosphere}, \textbf{33}, 53 -- 74, 2003 showed that micro-organisms could survive in high speed ejecta from a hypervelocity impact (the favoured launch mechanism to spray life into space from its home planet) and Burchell et al., \textit{Icarus} \textbf{154}, 545-547 2001; \textit{MNRAS} \textbf{352}, 1273 -- 1278, 2004 showed that micro-organisms carried on projectiles in hypervelocity impacts can successfully transfer to a target (with survival rates that fall with a power law for GPa shock pressures). Here we address survival of more complex biological materials under shock compression, namely seeds. We report on experiments firing seeds at speeds of 1 -- 5 km s$^{-1}$ into water targets ($\sim $0.5 to 5 GPa for short durations). The method is described in a preliminary report (Jerling et al., \textit{Int. J. Astrobiology} \textbf{7}, 217 -- 222, 2008). In new data presented here we are finding intact capture of seeds at 1 km s$^{-1}$, but above this speed increasing fragmentation occurs. Tests are underway to try to germinate the seeds captured at 1 km s$^{-1}$ and the results will be described.