Planetary Defense and the High Temperture Physical Properties of Meteorites.

Abstract:

The Ames Meteorite Characterization Laboratory is examining the physical proprerties of a diverse selection of meteorites. Each meteorite will be processed by the full suite of observations and measurements: petrographic/microscopic studies, density, porosity, albedo, shock effects, thermal conductivity, heat capacity, emissivity, and acoustic velocity. Of these measurments, density and porosity are the most studied to date (Macke, 2010; Britt and Consolmagno, 2003). The thermal properties of meteorites are less well understood. Thermal conductivity, heat capacity, and thermal emissivity are important data for a number of applications but especially to understanding the behavior of a meteor as it passes through the atmosphere. Opeil et al. (2010) have shown that meteorites have a thermal conductivities lower than the pure minerals they are composed of by a factor of 3 to 10, with the values coming to a roughly constant number from 150 to 300 K. Calculated conductivity numbers from Yomogida and Matsui (1983) show the H chondrites have the higest conductivity in the range of 3.8 W/m*K at 200 K and then slowly decreases to 3.2 W/m*K at 400 K. Whereas they show the LL chondrites do not reach 1 W/m*K over the temperature range 100 to 400 K. While there have been several high temperature spectroscopic studies of meteorites, to date all experimental data for the physical properties of meteorites were obtained at temperatures below 400 K, since previous studies were made in attempts to understand the formation and evolution of asteroids. Our laboratory will focus on understanding the thermal properties of materials at temperatures above 300 K and, where possible, up to atmospheric entry temperatures. Work on pure minerals has shown that thermal conductivity decreases as temperatures exceed 300 K but it is unknown whether this holds true for meteorites. We will describe our laboratory and procedures, and present some preliminary data, at the meeting.