Lawrence Berkeley National Laboratory

Successful location of icy deposits on the moon and other planets requires detailed knowledge of the physical properties of both icy and ice-free potential reservoir materials in order to design geophysical equipment, implement surveys, and interpret data. In support of this goal, we have conducted acoustic characterization experiments to measure the physical properties of dry and icy regolith simulant using synchrotron x-ray transmission microtomography and ultrasonic acoustic sensing as a function of temperature. Measurements were performed on a porphyritic basaltic glass from a cinder cone. Synchrotron x-ray microtomography was performed at beamline 8.3.2 at the Advanced Light Source (ALS). Ultrasonic measurements were made on an ultrasonic pulse-transmission system consisting of an upright cylindrical acrylic column outfitted with ultrasonic and temperature sensors. Samples were cooled to -35°C and allowed to equilibrate. Ultrasonic measurements were then taken as the samples were slowly warmed. Waveforms from experiments were then analyzed to calculate changes in acoustic velocity and attenuation as a function of temperature. Oven dried samples show only slight variations in velocity with temperature, while slightly wet samples show significant variations, suggesting water on grain surfaces plays a significant role in the physical behavior of the samples. Further work is needed to address the temperature dependence of truly dry materials versus those with adsorbed volatiles; however, these initial results suggest that temperature-dependent acoustic measurements may be useful in the location of volatiles in regolith.