We explored the geological history of the Taurus-Littrow Valley at the Apollo 17 landing site through the induced thermoluminescence (TL) properties of regolith samples collected from the foothills of the Northern and Southern Massifs, near the landing site, and the deep drill core taken in proximity to the landing site. The samples were recently made available by NASA through the Apollo Next Generation Sample Analysis program, in anticipation of the forthcoming Artemis missions. We found that the two samples from the foothills of the massifs exhibit induced TL values approximately four times higher than those of the valley samples. This observation is consistent with their elevated plagioclase content, indicating their predominantly highland material composition. Conversely, the valley samples display induced TL values characteristic of lunar mare material. The samples from the deep drill core demonstrate uniform induced TL properties, despite originating from depths of up to 3 meters. Notably, one of the samples from the lower section of the deep drill core presents anomalous induced TL readings. This anomaly coincides with elevated levels of low-potassium KREEP, along with reduced quantities of anorthositic gabbro and orange glass, and could be due to the traces of phosphate minerals. Alternatively, this observation raises the possibility that this sample contains Tycho impact material. The induced TL data is consistent with the regolith, extending to a depth of at least 3 meters, having been deposited by a singular event approximately 100 million years ago. This timing aligns with the hypothesized formation of the Tycho crater.

By placing Apollo 17 regolith samples in a freezer, and storing an equivalent set at room temperature, NASA effectively performed a fifty-year experiment in the kinetics of natural thermoluminescence (TL) of the lunar regolith. We have performed a detailed analysis of the TL characteristics of a sunlit sample near the landing site (70180), a sample 3 m deep near the landing site (70001), a sample partially shaded by a boulder (72320), and a sample completely shaded by a boulder (76240). We find eight discrete TL peaks, five apparent in curves for samples in the natural state, seven in samples irradiated in the laboratory at room temperature. For each peak we suggest values for peak temperatures and the kinetic parameters E (activation energy, i.e. “trap depth”, eV) and s (Arrhenius factor, s-1). The lowest natural TL peak in the continuously shaded sample 76240 dropped in intensity by 60±10% (1976 vs. present room temperature samples) and 43±8% (freezer vs room temperature samples) over the 50-year storage period, while the other samples showed no change. These results are consistent with our E and s parameters. The large number of peaks, and the appearance of additional peaks after irradiation , and literature data, suggest that glow curve peaks are present in lunar regolith at ~100 K and their intensity can be used to determine storage times at these temperatures. Thus a TL instrument on the Moon could be used to prospect for a micro-cold traps capable of deposition, build-up and storage of volatiles.

Heat transport plays a crucial role in igneous processes, and the thermal evolution of the interiors of terrestrial bodies. Thermal conductivity is a product of density (ρ), thermal diffusivity (D) and heat capacity (CP). We measured Dand CPas a function of temperature for a suite of planetary analog lavas relevant to the Moon, Mars, Mercury, Io and Vesta. Heat capacity measurements were conducted by differential scanning calorimetry (DSC) on glasses and liquids covering temperatures from 400 to 1750 K, Dmeasurements were conducted by laser-flash analyses (LFA) on glasses from room temperature up to their melting point slightly above the glass transition (Tg), and densities were already known. Our results demonstrate that the variability of Dand CPis very composition-specific, making thermal conductivity (k= DρCP) strongly composition-dependent. We present an empirical model to estimate Dof glasses as a function of temperature and composition, with 2σ uncertainty of 0.040 mm2s-1. Thermal diffusivity of the corresponding melt can be calculated with an uncertainty of 0.044 mm2s-1, but only independent of temperature. The model for Dpresented here, in combination with already available models to calculateCPand ρ, allows to predict thermal conductivity for a wide range of compositions for glasses and melts relevant to major planetary objects in the solar system. We show that basaltic liquids have thermal conductivities between 1.0 and 1.7 Wm-1K-1, about half that of the mantle from which they are generated, and therefore partial melting of ascending mantle leads to a positive feedback that promotes high melt fractions. The chemical dependence of ksuggests that this effect may have been more or less effective on different planetary bodies and at different times in their evolution.