Search

We present the first highly detailed morphological analysis of three craters located in Mercury's north pole, characterized by permanently shadowed regions (PSRs). This study, which began with an initial sample of 14 craters, highlighted three morphological classes, based on the craters' features: Complete complex morphology, Flat-floor morphology, and Immature complex morphology, presented here as maps of three representative craters, one for each class. As demonstrated by decades of studies, areas of PSRs within these craters could host water ice deposits, making them among the most interesting targets for future studies by the ESA/JAXA's BepiColombo mission. Our mapping work aims to give a cartographic context to subsequent chronological, thermal, and compositional analyses, as well as to provide a support to the acquisition strategy of the BepiColombo mission upon its arrival on Mercury in late 2025. The mapping highlights landforms which might be related to volcanic, gravitational, and maybe periglacial events. [ABSTRACT FROM AUTHOR]

In computer vision, stereoscopy allows the three-dimensional reconstruction of a scene using two 2D images taken from two slightly different points of view, to extract spatial information on the depth of the scene in the form of a map of disparities. In stereophotogrammetry, the disparity map is essential in extracting the digital terrain model (DTM) and thus obtaining a 3D spatial mapping, which is necessary for a better analysis of planetary surfaces. However, the entire reconstruction process performed with the stereo-matching algorithm can be time consuming and can generate many artifacts. Coupled with the lack of adequate stereo coverage, it can pose a significant obstacle to 3D planetary mapping. Recently, many deep learning architectures have been proposed for monocular depth estimation, which aspires to predict the third dimension given a single 2D image, with considerable advantages thanks to the simplification of the reconstruction problem, leading to a significant increase in interest in deep models for the generation of super-resolution images and DTM estimation. In this paper, we combine these last two concepts into a single end-to-end model and introduce a new generative adversarial network solution that estimates the DTM at 4× resolution from a single monocular image, called SRDiNet (super-resolution depth image network). Furthermore, we introduce a sub-network able to apply a refinement using interpolated input images to better enhance the fine details of the final product, and we demonstrate the effectiveness of its benefits through three different versions of the proposal: SRDiNet with GAN approach, SRDiNet without adversarial network, and SRDiNet without the refinement learned network plus GAN approach. The results of Oxia Planum (the landing site of the European Space Agency's Rosalind Franklin ExoMars rover 2023) are reported, applying the best model along all Oxia Planum tiles and releasing a 3D product enhanced by 4 × . [ABSTRACT FROM AUTHOR]

The South Polar Layered Deposits (SPLD) are the largest water ice reservoirs on Mars. Their accumulation is believed to result from climate oscillations that drive the movement of ice and dust on the surface. The High‐Resolution Imaging Science Experiment and the Colour and Stereo Surface Imaging System have imaged exposures of its internal structure in troughs and marginal scarps. Here we use the stereo imaging products of these instruments to extract stratigraphic profiles representative of various locations throughout the SPLD. Through wavelet and series‐matching analyses of these profiles, we reveal periodicities in the stratigraphy that correlate to the orbital oscillations that drive climate change on Mars and that have been observed to force the accumulation of the north polar cap. We infer that the water ice and dust of the SPLD were deposited at variable rates of 0.13–0.39 mm/year, taking a minimum of 10–30 Myr to accumulate. Plain Language Summary: The single location on Mars with the most water ice is in the southern polar ice cap, in the so‐called South Polar Layered Deposits (SPLD). Changes in Martian climate through time affect the locations on Mars where ice is stable, and it is believed that these changes drove the accumulation of layers upon layers of ice and dust in the SPLD. The High‐Resolution Imaging Science Experiment and the Colour and Stereo Surface Imaging System are satellite cameras that have photographed troughs and scarps within the SPLD to produce 3‐D views of this layered internal structure. We analyzed this structure and found patterns in the layering related to variations of Mars' orbit and spin axis. These variations drive climate change on Mars, so our analysis confirms the connection between the SPLD and Mars' astronomical parameters. From this relationship, we inferred that the ice and dust of the SPLD took at least 10–30 Myr to accumulate. Key Points: Patterns in the stratigraphy of Mars' south polar ice sheet are consistent with orbital climate forcingMars' south polar ice sheet accumulated nonuniformly at rates of 0.11–0.39 mm/yearSimilar orbital oscillations forced the accumulation of the northern and southern ice sheets [ABSTRACT FROM AUTHOR]

The STereo imaging Channel (STC) is the first push-frame stereo camera on board an European Space Agency (ESA) satellite, i.e., the ESA-Japan Aerospace eXploration Agency mission BepiColombo. It was launched in October 2018, and it will reach its target, Mercury, in 2025. The STC main aim is to provide the global three-dimensional reconstruction of the Mercury surface. STC, the stereo channel of spectrometer and imagers for Mercury Planetary Orbiter BepiColombo-Integrated Observatory System, is based on an original optical design that incorporates the advantages of a compact unique detector instrument and the convenience of a double direction acquisition system. In fact, STC operates in a push-frame imaging mode and its two optical sub-channels will converge the incoming light on a single focal plane assembly allowing to minimize mass and volume. The focal plane of the instrument is housing six different filters: two panchromatic filters in the range 600-800 nm and four broadband filters with central wavelengths in the range 420-920 nm. In this paper, the geometrical calibration of the instrument, including the optical setups used, will be described. The methods used to derive the focal lengths, the boresights, and the reference systems of the different filter models are presented, and the related distortion results are discussed. The STC off-axis configuration forced to develop a distortion map model based on the RFM (rational function model). In contrast to other existing models, which allow linear estimates, the RFM is not referred to specific lens geometry, but it is sufficiently general to model a variety of distortion types, as it will be demonstrated in this particular case. [ABSTRACT FROM AUTHOR]

The factors shaping cometary nuclei are still largely unknown, but could be the result of concurrent effects of evolutionary and primordial processes. The peculiar bilobed shape of comet 67P/Churyumov-Gerasimenko may be the result of the fusion of two objects that were once separate or the result of a localized excavation by outgassing at the interface between the two lobes. Here we report that the comet's major lobe is enveloped by a nearly continuous set of strata, up to 650 metres thick, which are independent of an analogous stratified envelope on the minor lobe. Gravity vectors computed for the two lobes separately are closer to perpendicular to the strata than those calculated for the entire nucleus and adjacent to the neck separating the two lobes. Therefore comet 67P/Churyumov-Gerasimenko is an accreted body of two distinct objects with 'onion-like' stratification, which formed before they merged. We conclude that gentle, low-velocity collisions occurred between two fully formed kilometre-sized cometesimals in the early stages of the Solar System. The notable structural similarities between the two lobes of comet 67P/Churyumov-Gerasimenko indicate that the early-forming cometesimals experienced similar primordial stratified accretion, even though they formed independently. [ABSTRACT FROM AUTHOR]

As part of the ongoing activities for the European space mission BepiColombo to Mercury, a new stereo-matching algorithm is here proposed: this algorithm uses deformable surfaces, or snakes, to find a dense disparity map. Subject to both external and internal forces, respectively represented by the similarity function and by smoothness constraints on the disparity map, a "deformable" disparity map evolves from an initial approximate state to an optimal one in which the algorithm has reached convergence. This algorithm is expected to provide one of the image matching tools for the Digital Terrain Model generation procedure that will be used by the BepiColombo stereo camera. To check the algorithm, tests have been performed on synthetic images derived from 3D models of geological features relevant to planetary science. The results show that it is possible to obtain an image measurement accuracy comparable to the one attainable with the Least Squares Matching algorithm. In addition, less object smoothing can be obtained since the object points are not derived by a large scale averaging over a terrain patch, as for example, in area-based methods; this means that more details of the terrain can be captured. Finally, because of the continuity constraint, this method is also expected to be robust in case of blunders in the reconstruction of the parallax field. [ABSTRACT FROM AUTHOR]