The rotation axis of the Moon is tilted by only 1.5° relative to the normal of the ecliptic plane and some craters in the lunar polar regions are therefore permanently shadowed. A portion of these PSRs are cold enough (<∼110 K) to trap water ice (Paige, Siegler, et al., 2010;Watson et al., 1961). Volatiles are delivered to the lunar surface by comets and (carbonaceous) meteoroids (Arnold, 1979;Berezhnoy et al., 2012). Among those common volatiles, the strongly polar H 2 O molecule has the lowest vapor pressure and sublimation rate (Watson et al., 1961). Other ices ("super-volatiles" or "hypervolatiles") are trapped at lower temperatures, and are therefore expected to be exceedingly rare. The sublimation rate of solid CO 2 becomes negligible at around 50 K (Zhang & Paige, 2009). Carbon dioxide cold traps, if they exist at all, would lie within the water ice cold traps. Carbon is found, at low concentration ∼100 ppm, in Apollo samples and likely of solar wind origin (Gibson, 1977;Haskin & Warren, 1991). If trapped in unusually cold areas near the lunar poles, carbon may exist at far higher concentration as dry ice, and would be valuable for the production of fuel and biological materials (Cannon, 2021).Diviner, on the Lunar Reconnaissance Orbiter (LRO), provides surface temperature measurements at hundreds of meters resolution and has extensive time coverage (

We present new high-resolution topographic, illumination, and thermal models of Mercury’s 112 km diameter north polar crater, Prokofiev. The new models confirm previous results that water ice is stable at the surface within the permanently shadowed regions (PSRs) of Prokofiev for geologic timescales. The largest radar-bright region in Prokofiev is confirmed to extend up to several kilometers past the boundary of its PSR, making it unique on Mercury for hosting a significant radar-bright area outside a PSR. The near-infrared normal albedo distribution of Prokofiev’s PSR suggests the presence of a darkening agent rather than pure surface ice. Linear mixture models predict at least roughly half of the surface area to be covered with this dark material. Using improved altimetry in this crater, we place an upper limit of 26 m on its ice deposit thickness. The 1 km baseline topographic slope and roughness of the radar-bright deposit are lower than the non-radar-bright floor, although the difference is not statistically significant when compared to the non-radar-bright floor’s natural topographic variations. These results place new constraints on the nature of Prokofiev’s volatile deposit that will inform future missions, such as BepiColombo.

Observations made by Earth-based radar telescopes and the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft provided compelling evidence for water ice in Mercury's polar craters. In our investigation, we constructed higher-resolution (125 m pixel−1) digital elevation models (DEMs) for four of the largest northernmost craters, Kandinsky, Tolkien, Chesterton, and Tryggvadóttir. The DEMs were leveraged to model solar illumination and the thermal environment, products that were used to identify permanently shadowed regions and simulate surface temperatures. From these models, we predicted the regions of surface stability for ice and volatile organic compounds. These predictions were then compared against the Arecibo radar, Mercury Laser Altimeter (MLA), and Mercury Dual Imaging System (MDIS) data. Our radar analysis shows that areas of high radar backscatter are correlated with areas predicted to host surface ice. Additionally, we identify radar backscatter heterogeneities within the deposits that could be associated with variations in ice purity, mantling of the ice, or ice abundances. The MDIS analysis did not reveal conclusive evidence for ice or volatiles at the surface, while MLA results support the presence of water ice at the surface in these craters. However, evidence for boundaries between the surface ice and low-reflectance volatile organic compounds, as suggested could be present by our models, was inconclusive owing to the limited MESSENGER data in these regions. BepiColombo’s upcoming orbital mission at Mercury has the opportunity to obtain new measurements of these high-latitude craters and test our predictions for the distribution of surface volatiles in these environments.

Mercury’s south polar region is of particular interest since Arecibo radar measurements show many high-reflectance regions consistent with ice deposits. However, current elevation information in Mercury’s southern hemisphere is not sufficient to perform detailed modeling of the illumination and thermal conditions at these radar-bright locations and to constrain properties of the volatiles potentially residing there. In this work, we leverage previously existing elevation maps of Mercury’s surface from stereo-photogrammetry at 665 m pix−1, Mercury Dual Imaging System Narrow Angle Camera images, and Shape-from-Shading tools from the Ames Stereo Pipeline, to provide the first high-resolution topographic maps of the south pole with a resolution of 250 m pix−1 poleward of 75°S. We show that the increased resolution and level of detail provided by our new elevation model allow for a more realistic recovery of illumination conditions in Mercury’s south polar region, thus opening the way to future thermal analyses and for the characterization of potential ice and volatile deposits. We compare both the old and new topographic models to the Mercury Dual Imaging System Narrow Angle Camera images to show the higher level of fidelity with our products, and we assess the improved consistency of derived permanently shadowed regions with reflectance measurements by Arecibo’s antennas.