Simulating Cometary Delivery of Lunar Water

by Parvathy Prem

Abstract: Several missions have recorded observations that could indicate the presence of water ice on our moon- but the origin and amount of water present remain uncertain. We investigate comet impacts as a mechanism for delivery of water to permanently shadowed craters at the lunar poles, so cold that they can trap water over geological time scales. This problem requires a 3D, unsteady, long time simulation. Comet impact and vaporization are modeled using the SOVA hydrocode. Subsequently, we use a Direct Simulation Monte Carlo (DSMC) code, designed to handle rarefied planetary flows, to simulate the transient water vapor atmosphere that develops, the migration of water molecules to cold traps and resultant deposition patterns. We are particularly interested in the influence of parameters such as impact angle, speed and location on the amount of water ultimately retained.

DSMC Simulations of Io's Pele Plume

by William McDoniel

Abstract: Io's Pele plume rises over 300km in altitude and leaves a deposition ring 1200 km across on the surface of the moon. Material emerges from an irregularly-shaped vent, and this geometry gives rise to complex 3D flow features. Direct Simulation Monte Carlo is used to model the gas flow in the rarefied plume, demonstrating how the geometry of the source region is responsible for the asymmetric structure of the deposition ring and illustrating the importance of very small-scale surface features in explaining large observed features of interest. Simulations of small particles in the plume and comparisons to the black "butterfly wings" seen at Pele are used to constrain particle sizes and entrainment mechanisms.