Low-temperature thermal properties of iron meteorites

We have measured the thermal conductivity and specific heat capacity of subsamples from four iron meteorites with nickel concentrations between 5% and 8% (Agoudal, Canyon Diablo, Muonionalusta, and Sikhote-Alin) at temperatures between 5 and 300 K. From these, we have calculated their thermal diffusivity and thermal inertia values across this temperature range. For comparison, we also measured subsamples from two L chondrites (NWA 11038 and NWA 11344) at the same time, using the same methods. The thermal diffusivity results of the irons show a relatively constant value for T > 100 K with a characteristic low-temperature maxima at similar to 5 K for the iron meteorites; by contrast, the diffusivities of the L chondrites fell by a factor of two over this range and reached low-temperature maxima at similar to 20 K. Thermal inertia values show a crossover behavior, with a strong increase in thermal inertia as temperatures drop below 55 K and a less dramatic change at higher temperatures. Our new diffusivity and inertia values cover a wider range of temperatures than previous literature data for iron meteorites. They also provide a useful ground truth in understanding remotely sensed thermal inertias of potentially metal-rich asteroids, including 16 Psyche, target of the NASA Psyche mission.