We investigated six bright swirls associated with magnetic anomalies of variable strength using Chandrayaan-1 Moon Mineralogy Mapper (M3) hyperspectral image data. We examined the 3 μm absorption band generally ascribed to solar wind-induced OH/H2O and spectral trends in the near-infrared wavelength range at on-swirl and off-swirl locations. We found that the 3 μm absorption band is weaker at on-swirl than at off-swirl locations and shows only weak variations with time-of-day. This result is consistent with magnetic anomaly shielding that reduces solar wind interaction with the surface. For a small swirl structure in Mare Moscoviense, we found the 3 μm absorption band to be similar to that of its surroundings due to the absence of strong magnetic shielding. Our spectral analysis results at on-swirl and off-swirl locations suggest that the spectral trends at on-swirl and off-swirl locations cannot always be explained by reduced space-weathering alone. We propose that a combination of soil compaction possibly resulting from the interaction between the surface and cometary gas and subsequent magnetic shielding is able to explain all observed on-swirl vs. off-swirl spectral trends including the absorption band depth near 3 μm. Our results suggest that an external mechanism of interaction between a comet and the uppermost regolith layer might play a significant role in lunar swirl formation.

<p><strong>Abstract.</strong> We have expanded our existing Shape and Albedo from Shading framework which has primarily been used to generate Digital Terrain Models (DTMs) of the Lunar Surface. The extension consists of an atmospheric model such that the approach can be applied to Mars which is covered by a thin atmosphere. The atmospheric model includes attenuation by the atmosphere, diffuse illumination of the surface and scattering from the atmosphere into the direction of the sensor with physically motivated parameters. To estimate the newly introduced atmospheric parameters without additional CRISM measurements, the radiance image and an initializing surface are used. The initial surface is derived from stereo images and serves two purposes. On the one hand, it is the height constraint of the SfS algorithm and on the other hand, it is used for estimating the atmospheric parameters. Relying on this estimation, the aforementioned Shape and Albedo from Shading method is carried out. The results show a considerable improvement compared to DTMs derived with stereo algorithms. The omnipresent stereo artifacts such as pixel locking and mismatches are smoothed out and small details are reconstructed convincingly. The procedure is then compared to the reconstruction without atmospheric compensation. Images in which shadows are present benefit from this method because shadows can now be described by the diffuse illumination of the surface. The reconstruction results indicate the viability of the approach since it can produce convincing DTMs compared to HiRISE ground truth.</p>

The depth and intensity of postdepositional subaerial weathering were examined in several Coastal Plain formations from New Jersey to Virginia. This region was divided into three study areas: (1) west of Chesapeake Bay, (2) between Chesapeake and Delaware Bays (Delmarva Peninsula), and (3) northeast of Delaware Bay. The mineralogy of well-drained sandy beds from 12 sites in these three areas was com pared to ascertain compositional maturity (defined, for example, for clay-sized material as the presence of iron and aluminum oxides or hydrated silicates) in relation to the age of the formation containing the sand. Three categories of weathering profiles were recognized. In the first, the clay-mineral type and the degree of intrastratal solution of sand minerals seemed reasonable relative to the age of the formation on which the weathering profile was developed. In the second, the mineralogy appeared too young relative to the age of the formation on which the weathering profile had developed. This type of unit is most common west of Chesapeake Bay. The relationship is interpreted as resulting from local tectonics. In the third, the weathering mineralogy appeared too old relative to the age of the unit. The overmature minerals in these units were either reworked into these units during a marine transgression or introduced into a sandy unit as loess and subsequently distributed throughout the dominantly sandy units by illuviation. In summary, most of the weathering-age relationships followed a predictable pattern. The use of this technique to determine relative ages and uplift patterns in this region is in its initial stage but holds much promise. The existence of some anomalies, however, points to the need to obtain a detailed geologic history of a given deposit before this weathering-age technique can be applied.

Context. Lunar swirls are bright albedo features only found on the Moon that are still not entirely understood. It is commonly accepted that reduced space weathering plays a role in explaining the origins of lunar swirls because the local magnetic fields that are typically associated with these albedo anomalies are effective in reducing the solar wind influx. However, additional processes are required to fully explain the spectral, photometric, and polarimetric properties of the swirls. Aims. In this study, we compare the photometric properties of the Chang’e-5 landing site to those of the Reiner Gamma swirl. Because the physical effects of a landing rocket jet on the lunar regolith are relatively well known, these observations can provide important insights into the physical properties of lunar swirls. Methods. We determined the single scattering albedo, opposition effect strength, and surface roughness of the Reiner Gamma swirl and the Chang’e-5 landing site with their respective statistical uncertainties based on the Hapke model and Bayesian inference sampling. Results. The Chang’e-5 landing site and the Reiner Gamma swirl exhibit similar photometric properties, in particular: an increased albedo and a reduced opposition effect strength. Additionally, the landing site is about 20% less rough compared to the surrounding area. Conclusions. These findings suggest that the swirl surface is less porous compared to the surrounding surface, similarly to a landing site where the top layer of the regolith has been blown away effectively so that the compactness was increased. We conclude that external mechanisms that are able to compress the uppermost regolith layer are involved in lunar swirl formation, such as interactions with the gaseous hull of a passing comet.

Lunar surface disturbances by spacecraft engine jets are of particular concern in the current new phase of lunar exploration, when dozens of landing missions and permanent bases are being planned. Some of these exploration efforts will involve multiple landings and liftoffs around the same lunar site; thus, it is essential to evaluate their effect on astronauts and assets on the lunar surface. Here, we assess the surface disturbances during the Chang'e‐5 landing and liftoff procedures through the photometric analysis of high‐resolution multi‐temporal surface and orbital images. Centimeter‐scale surface images reveal a four‐stage evolution of the landing plume impingement over a period of ∼50 s, which involves phenomena such as dust devils and streaks, and displacement of cobbles. Temporal‐ratio calculation of orbital images (including one acquired between landing and liftoff) enables the first direct observation of ascent plume effects. The ascent blast zone consists of two separated sub‐areas (∼3,400 km2 in total), which is nearly twice larger than that of the landing blast zone. The final disturbed surface is characterized by a central main zone (∼2,300 m2) surrounded by a marginal diffuse zone (∼15,300 m2). Phase‐ratio analyses suggest that plume impingement destroys the micro‐porous structure of the uppermost regolith. We estimate that future lunar landers (e.g., SpaceX's Starship) may cause significant lunar surface disturbances over an area of square kilometers. Our results provide unique insights into Chang'e‐5 mission activities, and instructive references for the planning of future lunar endeavors, including the design and construction of surface experiment packages and permanent lunar bases.