Investigation of Changes in Sample Density During Impact Processes Using X-Ray Analysis

English Abstract:

Meteorites have been used as analogs for asteroids in experiments to study the results of catastrophic disruption. Samples with a variety of sizes, projectile velocities and material compositions have been shot and the resulting debris used to compare outcomes [1]. Currently there is interest in looking at changes in the physical properties of these same materials as a result of impact. To date we have investigated density, but are also looking at compression strength and speed of sound. The densities of 32 pieces of pumice from 8 shots were compared to the density of an unimpacted sample of pumice. There was a decrease from 0.90 g/cm³ to an average of 0.77 + 0.09 g/cm³. The range of densities for the individual pieces was 0.56 to 0.93 g/cm³. The %RSD varied from 2 to 16% when measuring 3 to 6 pieces from the same shot. There does not appear to be a correlation between the density and the original sample size, the projectile velocity or extent of disruption (measured by the largest remaining fragment size). The X-Ray information can also be useful in studying changes in the texture of samples and in the porosity when exposed to processes such as impact disruption. We have previously shown there is no change in the layering texture of a highly porous pumice sample when exposed to impact disruption [2] and are investigating the effects of impact on the porosity of an ordinary chondrite.

References: [1] Flynn G. J. et al. (2009) Planet. and Space Sci., 57, 119-126; [2] Flynn G. J. et al. (2014) Planet. and Space Sci., in review.