Effects of Impacts on the Crystalline Structure and IR Spectra of Minerals Found in Comets and Asteroids.

Understanding asteroid and comets is important because their surfaces contain evidence of dynamical evolution of the solar system. The surfaces of these small bodies have undergone many collisions in their lives, leading to shock effects that might be observable in the mineral on their surfaces. Considering this, high velocity experimental impacts into minerals typically found in comets and asteroids were conducted to observe how shocks might affect the crystalline structure of the minerals and determine if these changes could be observed in the minerals infrared (IR) spectra. A Fourier Transform Infrared Spectrometer (FTIR) was used to determine if these changes could be observed in the infrared (IR) spectra of the minerals. The minerals investigated included: diopside , magnesite , fayalite , enstatite , and peridot due to their known presence on these small bodies. Impacts were conducted at NASA’s Johnson Space Center Experimental Impact Laboratory using high velocity vertical gun, varying impact velocities, temperatures and porosities of individual mineral samples. The impacted minerals were then collected, washed, dried and analyzed with the FTIR. These spectra were then compared to spectra of minerals that were not impacted and therefore showed no evidence of shock. This comparison demonstrated that the distinct peaks observed in the spectra were altered in samples that were shocked in the impact experiments. This will allow the use of IR spectra obtained from observations of these small bodies to be compared to laboratory spectra in order to investigate impact history and composition of these objects