Abstract 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 ∼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 ∼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.
We observed Europa (A event) and Io (H and Q events) with a high speed photometer at the 0.6m telescope at Castel Gandolfo, Italy, to search for impact light echoes. Although several fluctuations in light level from these moons were detected, most can be attributed to terrestrial effects. However, some signals during all three events cannot be easily diagnosed as spurious, and may represent real flashes. In particular, we see possible light echoes (at roughly the 2‐sigma level) for the A, Q2 and Q1 events; an increase in signal from Io during the brightest part of the H event as seen from Earth; and a three‐sigma event four minutes after the Q2 event that matches a similar event observed in Kiev.
Abstract Lunar meteorites are the most diverse and readily available specimens for the direct laboratory study of lunar surface materials. In addition to informing us about the composition and heterogeneity of lunar material, measurements of their thermo‐physical properties provide data necessary to inform the models of the thermal evolution of the lunar surface and provide data on fundamental physical properties of the surface material for the design of exploration and resource extraction hardware. Low‐temperature data are particularly important for the exploration of low‐temperature environments of the lunar poles and permanently shadowed regions. We report low‐temperature‐specific heat capacity, thermal conductivity, and linear thermal expansion for six lunar meteorites: Northwest Africa [NWA] 5000, NWA 6950, NWA 8687, NWA 10678, NWA 11421, and NWA 11474, over the range 5 ≤ T ≤ 300 K. From these, we calculate thermal inertia and thermal diffusivity as functions of temperature. Additionally, heat capacities were measured for 15 other lunar meteorites, from which we calculate their Debye temperature and effective molar mass.
The physical properties of the stone meteorites provide important clues to understanding the formation and physical evolution of material in the Solar protoplanetary disk as well providing indications of the properties of their asteroidal parent bodies. Knowledge of these properties is essential for modeling a number of Solar System processes, such as bolides in planetary atmospheres, the thermal inertia of atmosphereless solid body surfaces, and the internal physical and thermal evolution of asteroids and rock-rich icy bodies. In addition, insight into the physical properties of the asteroids is important for the design of robotic and crewed reconnaissance, lander, and sample return spacecraft missions to the asteroids. One key property is meteorite porosity, which ranges from 0% to more than 40%, similar to the range of porosities seen in asteroids. Porosity affects many of the other physical properties including thermal conductivity, speed of sound, deformation under stress, strength, and response to impact. As a result of the porosity, the properties of most stone meteorites differ significantly from those of compact terrestrial rocks, whose physical properties have been used in many models of asteroid behavior. A few physical properties, such as grain density, magnetic susceptibility, and heat capacity are not functions of porosity. Taken together, the grain density and the magnetic susceptibility can be used to classify unweathered or minimally weathered ordinary chondrites. This provides a rapid screening technique to identify heterogeneous samples, classify new samples, and identify misclassified meteorites or interlopers in strewn fields.
