Analysis and Comparison of Physical Properties and Morphology of Impact Melt Flows on Venus and the Moon

Abstract:

The cratering process sometimes produces melt that flows out of and away from the impact crater. These impact melt flows have been studied in the past using remote sensing on both Venus and the Moon. The purpose of this study is use radar to compare the reflectivity, morphology, and roughness of impact melt flows on Venus and the Moon. For the Venus portion of the study, we used reflectivity data from the Magellan mission to examine flow reflectivity and morphology, and circular polarization ratio (CPR) data from the Arecibo Observatory to examine flow roughness. For the Moon portion of the study, we used Mini-RF (on Lunar Reconnaissance Orbiter) data to examine flow reflectivity, morphology, and CPR. Reflectivity values were averaged and morphology was recorded for a sample of 25 Venus craters, and CPR values were averaged for five of these craters that were in range of the Arecibo data and had large enough flows that were resolvable in the ground based polarimetry data. The CPR values of the five crater sample ranged from ~-0.032 to ~0.287 over a range of incidence angles from 17.5° to 61.8°. The Venus impact melt flows are brighter and generally have higher CPR values than their surroundings, have both crisp and diffuse edges, and both reflectivity and CPR often vary along the length of the flow. The impact melt flows have similar CPR values to those measured for volcanic flows on Venus, indicating similar surface roughness.  The Venus impact melt flows appear to be smoother than those on the Moon based on a comparison of CPR values at similar incidence angles. The Venus and lunar impact melt flows have different trends in crater diameter versus flow length relative to crater diameter, although smaller (<30 km diameter) craters on both objects have the longest flows relative to crater diameter. We will present a comparison of the results from Venus to those of impact melt flows on the Moon to investigate the effect that the presence of a thick, hot atmosphere has on impact melt emplacement process.