Seminars

Revealing the Complex Dynamics of Two-Phase Flow in the Near-Vent Region of Io’s Tvashtar Eruption with DSMC Simulations
A. O. Adeloye

Io’s Tvashtar volcanic plume, reaching heights of ~350 km, exhibited an unusual increase in brightness by an order of magnitude during the 2007 New Horizons (NH) flyby as Io’s solar phase angle relative to NH increased. High-resolution NH/LORRI images captured this evolving brightness throughout the flyby. This phenomenon cannot be explained without understanding how the plume material flows and how different factors within the plume influence that flow. Using axisymmetric Direct Simulation Monte Carlo (DSMC) simulations, we model both gas and grain radiation across the entire plume. Since the plume material is ejected at supersonic speeds into a vacuum, the flow dynamics near the vent critically influence downstream properties at higher altitudes. This presentation will demonstrate how DSMC simulations, using our in-house code PLANET, capture the complex physics governing gas and grain behavior in the near-vent region. These simulations account for competing processes, such as gas rarefaction, convection, ro-vibrational radiative cooling, gas-grain collisional coupling, and grain-lava radiative transport, each operating on distinct timescales.

Impact of The LCROSS Centaur Upper Stage and Lunar Subsurface Layering Assessment through Isale-2D Simulations
William Jo

We simulate impacts of a high-fidelity, 2D axisymmetric Lunar Crater Observation Sensing Satellite (LCROSS) Centaur Upper Stage model body in iSALE-2D to better understand the ejecta physics of the actual mission on the Moon. Our current goal is to identify the lunar subsurface layering conditions on Cabeus Crater that closely match water-ice observations made by the Near Infrared Spectrometer 2 (NSP2) instrument on Shepherding Spacecraft (S-S/C). We simulate various two- and three-layer impact targets using various combinations of porous regolith, non-porous regolith, and water- ice, and we present the layered depths, thicknesses, and weight percent content of water-ice that could fit NSP-2 observations. We show that a low-porosity target (likely saturated with water ice) can possibly explain NSP2 column density observations. We also show that upright impact simulations of the LCROSS impactor will yield a transient crater that can achieve a diameter of ~20 m, supporting ShadowCam and Mini-RF observations of the impact location.