Our recent work has focused on the properties of ice-rock mixtures, which are likely to occur in the outer solar system’s icy satellites – e.g., Ganymede, Callisto, Titan – and to have played a role in their geological evolution. Rocky particles may pin ice grain boundaries, hindering the flow of the icy matrix, thereby reducing the efficiency of convection. We have carried out tests upon ice-fluorite mixtures (an ‘ice-rock’ proxy) using neutron diffraction on Engin-x to measure the strain partitioning between the phases. We have observed unusual behaviour in that, under certain conditions, increased load leads to reduced stress on the fluorite. We hypothesise that this may be due to pressure melting of ice around points on the fluorite grains. These data show that the ice-rock fabric has a more complex behaviour than hitherto thought, and this may have unexpected consequences for the evolution of icy planetary bodies.
CA Middleton, PM Grindrod, AD Fortes, SA Hunt, J Bowles, IG Wood (University College London), SJ Covey-Crump (Manchester University), S-Y Zhang (ISIS)
Research date: December 2009
Contact: Dr I Wood, firstname.lastname@example.org
Further reading: Durham et al., J Geophys Res 102 (1997) 16293