Martian deltas record fluvial and sedimentary activity on early Mars. Yet, quantitative understanding of the hydrological and sedimentary processes underlying their formation remains limited. Here we quantitatively analyzed the fluvial and sedimentary processes of seven deltas exhibiting diverse morphologies across Mars. Our analysis is based on deltas and their channel features, from which we estimate paleo-discharge, sediment transport rates, depositional timescales, and the water volume required for delta formation. The deltas are classified into groundwater-sourced, precipitation-fed, and retreating-erosion types based on the geological context of their feeder channels and water sources. We propose that delta formation on Mars may have occurred under multiple scenarios, including retreating erosion, groundwater sapping, ice melting, precipitation-driven runoff, impact events, and variations in Martian obliquity. These scenarios suggest that prolonged warm climates were not a prerequisite for delta formation. Mass-balance calculations indicate that continuous delta formation timescales range from days to thousands of Martian years. However, accounting for likely intermittent water supplies and episodic flows, the overall formation timescales could extend to hundreds of millions of years. These findings provide a quantitative framework for interpreting paleo-sedimentary processes on Mars that may preserve important records of its geological and climatic history.

Dust in the atmosphere of Mars, along with its radiative effects, is the central factor for understanding the Martian climate. Global circulation models and remote sensing observations are used to shed light on the evolution of Martian dust storms. Trajectories of Martian dust storms have been investigated by manual treatment of Mars daily global maps from the MARs Color Imager. However, the tracking of dust storms has neither been automated, nor systematically compared with modeled dust storm trajectories. We therefore developed a simple algorithm to detect regions with an enhanced atmospheric dust content and to attribute these regions to a trajectory. We applied this algorithm to daily global maps of measurements of the column dust optical depth for Mars Years 24-35, and found 20 dust storm trajectories lasting for at least 10 Sols. We compared these observation-based trajectories with the corresponding model-based trajectories from our own simulations using the global circulation model Mars Planetary Climate Model version 6. The obtained distributions of storm speed and direction of propagation show strong similarities between observations and model, demonstrating a reasonably good performance of the model with regard to dust storm trajectories. We find that most dust storms on Mars are traveling east- or westwards, but that dust storms propagating westwards are less well represented in the model. The developed algorithm can be used as a tool for model evaluation, but also for tracking meteorological conditions along dust storms' trajectories, allowing for further development of dust storm understanding.

The first long-distance observations of the Kodiak butte made by the Mars2020 rover "Perseverance" confirmed Gilbert-type delta deposition within a closed-lake system in Jezero crater, Mars. Several outcrops at the actual delta were imaged later during the science campaign but their geology and potential relationship to Kodiak still need to be explored. In this study, we use image data from the Perseverance rover, primarily from the Mastcam-Z and Supercam instruments, to create four digital outcrop models (DOMs) by applying commercial Structure-from-Motion (SfM) photogrammetry software and spatially align the models using SPICE-derived position and orientation data. We analyze the DOMs using the Pro3D software by Joanneum Research, extracting dip and strike as well as size measurements of debris for determining 2D-clast size-frequency distributions. Evidence gathered from the DOMs shows sedimentary facies associated with Gilbert-type delta stratal architectures. Topset, foreset and lower foreset facies were identified at the outcrops Franklin Cliff and Whale Mountain, which additionally displays a prominent mouth bar deposit. Topset-foreset boundaries differ in altitude between outcrops, suggesting different phases of delta progradation and a lake-level rise. Inferred paleo flow directions from Whale Mountain and Franklin Cliff link those to the delta strata found at Kodiak, further indicating that the butte was once part of the delta. Mastcam-Z and Supercam imaged several conglomerates embedded at the delta front, from those six conglomeratic clast samples were taken, prepared and analyzed on image mosaics regarding size-frequency distribution and discharge rates. Three populations of boulder conglomerates can be distinguished, two deltaic (delta slope, delta plain) and one non-deltaic (flood) in origin. The four derived high-resolution, textured and accurately aligned DOMs are made publicly available.

Introduction The Context Camera (CTX) on Mars Reconnaissance Orbiter provides near-global coverage of Mars at ~6 m/pixel and underpins countless geomorphological, stratigraphic, and time-series studies. Its absolute pointing, reconstructed from spacecraft trajectory and attitude, is typically uncertain at the level of dozen to hundreds of metres — the limiting factor for change detection, mosaicking, and joint analysis with HiRISE.The HRSC instrument on Mars Express delivers photogrammetrically controlled orthorectified products with metre-to-decametre geodetic accuracy and global-scale internal consistency, making them an ideal reference frame for tying CTX into a homogeneous geodesy. ### Pipeline overview We present a fully automatic two-regime coregistration pipeline, applying similar but extended techniques as reported in [1] and [2].Where HRSC orthomap coverage is available, we derive dense sub-pixel shift fields between CTX and HRSC via phase-correlation using the AROSICS Python library.Where HRSC coverage is absent, we match features between overlapping CTX frames themselves, anchored to neighbouring HRSC-tied images, we start using the KAZE and AKAZE detectors inside ISIS' `findfeatures`, and refine it further using the AROSICS detector.Both regimes feed a single ISIS `jigsaw` bundle adjustment, producing a unified, quality-controlled control network. ### AROSICS regime Each CTX cube is map-projected with `cam2map` using the corresponding HRSC product as map template, preserving projection, pixel resolution and `CenterLongitude` to avoid resampling artefacts.AROSICS searches for tie points on a pre-set regular grid, producing quality factors that can be filtered on; the grid is converted to an ISIS control network for `jigsaw`. ### `findfeatures` / AKAZE regime and scaling On the ISIS side, we replaced `autoseed`+`pointreg` with ISIS `findfeatures` using the KAZE and AKAZE detectors.These coarser scale feature identifications are useful because they are able to shift even strongly offset CTX images without former determination of a search radius.An overlap-aware greedy set-cover algorithm selects reference images for fromlist matching, and the resulting per-reference networks are merged via `cnetmerge`.After successful first alignment, several extra rounds using AROSICS are added to improve the internal coregistration before the merge with the on-ortho CTX coregistered images is performed. ### Validation and metrics We consistently report both σ₀ (a tail-sensitive RMS) and median residuals: aggressive `pointreg` settings on smooth Martian dust plains can fabricate correlation peaks that inflate σ₀ by an order of magnitude while leaving the median sub-pixel.Per-pair versus all-at-once bundle adjustments converge currently to comparable σ₀ (0.448 vs 0.438 px) under conservative parameters, which supports pre-coregistration work with final merges, because all-at-once tie-point generations can run into memory issues using the findfeatures tool. ### Outlook Work in progress includes (i) anchoring the gap bundle to background MOLA/THEMIS basemaps to improve coregistration from the beginning towards absolute geodetic control, (ii) closing the loop across full HRSC tiles, and (iii) extending the pipeline application to HiRISE data for precise change monitoring analyses. ### References[1] Robbins, S. J., Kirchoff, M. R., & Hoover, R. H. (2020). Fully Controlled 6 Meters per Pixel Mosaic of Mars's South Polar Region. Earth and Space Science, 7, e2019EA001054. doi:10.1029/2019EA001054[2] Robbins, S. J., Kirchoff, M. R., & Hoover, R. H. (2023). Fully Controlled 6 Meters per Pixel Equatorial Mosaic of Mars From MRO CTX Images, Version 1. Earth and Space Science, 10, e2022EA002443. doi:10.1029/2022EA002443

The JPL rover Perseverance's investigations of Jezero crater's floor reveal that the ultramafic S & eacute;& iacute;tah formation and the overlying mafic M & aacute;az formation are deformed into a broad, low-amplitude structural dome. Mastcam-Z stereo images processed into digital outcrop models, together with RIMFAX ground-penetrating radar profiles, were used to reconstruct the three-dimensional stratal geometry of both units along a SW-NE transect across a southern domain of the dome called south S & eacute;& iacute;tah. Measurements from 3-D reconstructions show a progression from sub-horizontal layers in the central parts of the dome to dips <20 degrees away from the dome on its flanks, with M & aacute;az and underlying S & eacute;& iacute;tah layers dipping concordantly. RIMFAX profiles and imaging around the dome confirm that limb dips are continuous into the subsurface and form a flat-crested composite quaquaversal fold structure. S & eacute;& iacute;tah rocks in the fold core are up to 17 m higher than adjacent M & aacute;az lava flows, despite stratigraphically underlying them, a relationship attributed to structural uplift. Fold geometry, wavelength (similar to 1 km), and amplitude (similar to 30-50 m), match models of forced folding produced by inflation of shallow igneous intrusions. The most likely cause is the emplacement of a sill or laccolith beneath the crater floor, generating elastic bending of the overlying layers. This intrusion-driven uplift explains S & eacute;& iacute;tah's elevated position, constrains the deformation history of Jezero's crater floor units post-emplacement of the S & eacute;& iacute;tah and M & aacute;az formations, and supports a significant role for shallow magmatic intrusion in shaping intracrustal structures on Mars.

In our study we examined water-related processes and events in the Jezero crater on Mars using flow discharge and sediment transport models of: 1) the western inlet valley carving, 2) the northern inlet valley carving, 3) crater flooding by only northern inlet and 4) by both northern and western inlets, 5) erosion of the western rim by the western inlet, 6) erosion of the eastern rim due to the outlet, 7) water outflow from the crater, 8) outlet valley carving, 9) western delta deposition, 10) northern delta deposition. Detailed geomorphological analyses, delta and valley mapping and measurements served as a base for our investigations. As our knowledge is limited mostly to remote sensing data and only few in situ data from the Perseverance rover, a range of scenarios for each event was modeled by varying, where necessary, the values of input parameters - grain size, channel depth, channel width, channel slope, median grain size, 90th percentile grain size. We calculated the minimum timescales and the minimum volume of available water for each event. The obtained results were interpreted, taking into account the limitations of the model. We found that: 1) the northern inlet participated in the first crater flooding and the eastern rim breaching and it alone could have flooded the crater; 2) the northern and western deltas were deposited during the last incisions of the corresponding inlets; 3) Jezero crater was flooded multiple times, implying open-basin lake conditions during or after the eastern rim breaching. Our findings complement results and interpretations of previous studies and also reveal new insights into the fluvial history in Jezero crater.

Over the course of NASA’s Dawn Discovery mission, the onboard framing camera mapped Ceres across a wide wavelength spectrum at varying polar science orbits and altitudes. With increasing resolution, the uniqueness of the 92 km wide, young Occator crater became evident. Its central cryovolcanic dome, Cerealia Tholus, and especially the associated bright carbonate and ammonium chloride deposits—named Cerealia Facula and the thinner, more dispersed Vinalia Faculae—are the surface expressions of a deep brine reservoir beneath Occator. Understandably, this made this crater the target for future sample return mission studies. The planning and preparation for this kind of mission require the characterization of potential landing sites based on the most accurate topography and orthorectified image data. In this work, we demonstrate the capabilities of the freely available and open-source USGS Integrated Software for Imagers and Spectrometers (ISIS 3) and Ames Stereo Pipeline (ASP 2.7) in creating high-quality image data products as well as stereophotogrammetric (SPG) and multi-view shape-from-shading (SfS) digital terrain models (DTMs) of the aforementioned spectroscopically challenging features. The main data products of our work are four new DTMs, including one SPG and one SfS DTM based on High-Altitude Mapping Orbit (HAMO) (CSH/CXJ) and one SPG and one SfS DTM based on Low-Altitude Mapping Orbit (LAMO) (CSL/CXL), along with selected Extended Mission Orbit 7 (XMO7) framing camera (FC) data. The SPG and SfS DTMs were calculated to a GSD of 1 and 0.5 px, corresponding to 136 m (HAMO SPG), 68 m (HAMO SfS), 34 m (LAMO SPG), and 17 m (LAMO SfS). Finally, we show that the SPG and SfS approaches we used yield consistent results even in the presence of high albedo differences and highlight how our new DTMs differ from those previously created and published by the German Aerospace Center (DLR) and the Jet Propulsion Laboratory (JPL).

Patterned ground, especially polygonal surface structures, are of particular importance for planetary sciences, as they are known from the Earth as well as from other celestial bodies such as Mars, Mercury, Venus and Pluto. They are therefore ideally suited as a basis for analogue studies. However, the classification of these structures is often based on individually and intuitively perceived parameters, which are difficult to determine, especially with remote sensing data. In our work, we therefore propose a new classification of polygonal surface structures. Based on a variety of conventional and established geometric parameters, in combination with the innovative approach of fractal geometry, we suggest a classification based on objective mathematical parameters. Based on remote sensing data from more than 100 sites, we show that polygons of different depositional environments can be distinguished and assigned to specific environmental conditions based on purely geometric data. Polygons formed in periglacial depositional environments can be clearly distinguished from structures formed in arid to hyper-arid environments. Furthermore, the structures can be correlated with the known subsurface conditions. The polygon classes resulting from the geometric investigations show a strong correlation with the ground ice content of the depositional areas. Polygons can thus serve as proxies, for example, to identify suitable landing sites for future Mars missions.

Jezero crater, which once contained a paleolake, is the investigation site of the current NASA's Mars 2020 mission. We modelled 9 water related processes in Jezero: 1) western inlet valley carving, 2) northern inlet valley carving, 3) crater flooding by only northern inlet and 4) by both northern and western inlets, 5) erosion of the eastern rim for the outlet, 6) water outflow from the crater, 7) outlet valley carving, 8) western delta deposition, 9) northern delta deposition. We claim that the northern inlet had participated in the crater flooding because it has terraces at the same height level as the breaching terraces in the outlet (breaching happened in 3 phases, as shown in [1]).Measurements of channel sizes, valleys, deltas, eroded rim and outflowed water volumes were conducted in ArcGIS 10.8 using Mars 2020 Science Investigation CTX DEM Mosaic and HRSC Mars Chart DTM and corresponding ortho-mosaics.We used flow discharge and sediment transport models by [2] to calculate minimum water and sediment transport timescales under constant bank-full discharge. For northern and western inlet-related processes we took 0.005 m as median grain size D50 (it is the biggest grain size reported for samples from the western delta front in [3] so far; considering that the delta front is characterized by fine-grained deposition, it is reasonable to assume that for the whole delta D50 could be equal and even exceed 0.005 m). For outlet and breaching-related processes we used 0.1 m as D50 (which is used to model breaching events, e.g. in [1] and [4]).Various scenarios have been modelled; the most probable (according to our current knowledge) were analyzed.Deposition of the deltas could happen simultaneously with the last incision of corresponding valleys; the amount of carved material from last incised valleys is approximately the same as deposited in deltas.According to the modelled scenario, the eastern rim erosion lasts five times longer than the water outflow after breaching. This indicates that water discharged from the breach could not alone erode the rim and thus more water supply from inlets would be needed. However, the uncertainty of grain size calls this result into question.Another conclusion is that the northern valley alone could provide enough water (~1000 km3) during its last incision to fill the crater before breaching (446 km3). Moreover, the last incised valleys were mostly carved after the breach; if not, they would have already provided enough water to fill the crater and the breaching would have already happened.Comparison of water discharged after the breach (238 km3) with water needed to carve at least the last incision outlet valley (~4000 km3) shows that Jezero had to be an open-basin lake after breaching. References:[1] Salese, F. et al. (2020). Astrobiology, 20(8), 977–993.[2] Kleinhans, M. G. (2005). Journal of Geophysical Research: Planets, 110(12), 1–23.[3] Farley K., and Stack K. (February 15, 2023). Mars 2020 reports, Volume 2 - https://mars.nasa.gov/internal_resources/1656/[4] Roda, M. et al. (2014). Icarus, 236, 104–121.

The ever-changing transparency of the Martian atmosphere hinders the determination of absolute surface colour from spacecraft images. While individual high-resolution images from low orbit reveal numerous colour details of the geology, the colour variation between images caused by scattering off atmospheric dust can easily be of greater magnitude. The construction of contiguous large-scale mosaics has thus required a strategy to suppress the influence of scattering, often a form of high-pass filtering, which limits their ability to convey colour variation information over distances greater than the dimensions of single images. Here we use a dedicated high altitude observation campaign with the Mars Express High Resolution Stereo Camera (HRSC) (Neukum and Jaumann, 2004; Jaumann et al., 2007), applying a novel iterative method to construct a globally self-consistent colour model. We apply the model to colour-reference a high-altitude mosaic incorporating long-range colour variation information. Using only the relative colour information internal to individual images, the influence of absolute image to image colour changes caused by scattering is minimised, while the model enables colour variations across image boundaries to be self-consistently reconstructed. The resulting mosaic shows a level of colour detail comparable to single images, while maintaining continuity of colour features over much greater distances, thereby increasing the utility of HRSC colour images in the tracing and analysis of martian surface structures.

Introduction: The current NASA's Mars 2020 mission is exploring the Jezero crater that was once filled with water. Since it is widely acknowledged that access to liquid water is essential for life, studying the fluvial activity in Jezero can aid in the crater’s habitability assessment. We examined ten water-related processes using water and sediment transport models by [3]: 1) the western inlet valley carving, 2) the northern inlet valley carving, 3) crater flooding by only northern inlet, 4) by both northern and western inlets, 5) erosion of the western rim by the western inlet, 6) erosion of the eastern rim due to the outlet, 7) water outflow from the crater, 8) outlet valley carving, 9) western delta deposition, 10) northern delta deposition. The goal of our study was to calculate the minimum timescales for each event and estimate the minimum volume of water provided/released during each event. Relative comparison of timescales and of water amount which we calculated based on new geomorphological observations introduces a deeper understanding of the water history in Jezero.Data: Measurements of channel sizes, valleys, deltas, eroded rims, and outflowed water volumes were based on Mars 2020 Science Investigation CTX DEM Mosaic [5] and HRSC Mars Chart (HMC) DTM and corresponding orthomosaics [2].Geomorphological observations: The northern inlet was most likely involved in the crater flooding because it has terraces at the same height as the breaching terraces in the eastern rim (breaching happened in 3 phases, as shown in [7]). The western inlet, in contrast, has no terraces at the breaching heights. This implies that either it was not involved in crater flooding, or its terraces were eroded.Mapping: Both deltas were mapped using three potential extents: minimum, medium, and maximum. Valleys were mapped based on two morphological features: 1) initial valley, borders of which are not visible on HMC ortho-mosaics and could only be recognized on slope and profile curvature rasters, calculated from HMC DTM; 2) last incision valley, which was mapped on HMC ortho-rectified image mosaic.Measurements: Dimensions of the channels were derived from longitudinal and cross-sectional profiles on CTX DTM. Water volume to fill the crater before breaching and the amount of sediments, transported from valleys and deposited in deltas were estimated using ArcGIS Tools „Surface Volume“ and „CutFill“.Methodology: Flow discharge and sediment transport models [3] are used to calculate water and sediment transport timescales under constant bank-full discharge when most of erosion occurs. The models do not include the climate and non-bank-full conditions to constrain minimum timescales. Main input parameters include: Median Grain Size, Channel depth, width and slope, Sediment porosity, Shields criterion for incipient motion, Sediment density, Martian gravity, and Water density. Data from the Perseverance rover [1] were taken for the Median Grain Size estimation. Sediment porosity, Sediment density, and Shields criterion for incipient motion were taken based on previous research [3], [4], [6]. Several scenarios were modeled with varying values of input parameters in the most expectable ranges. Eastern and western rim breechings were modelled both in a catastrophic scenario and in a long-term erosion under constant flow scenario.Results: A comparison of the timescales of the last incised valleys carving and delta depositions showed that deltas were deposited during the last incision of the corresponding valleys. For the northern delta, the medium extent is the most probable; for the western delta, the maximum extent is the most probable.Most modelled cases, in both long-term and catastrophic scenarios of the rim breaching, showed that the outlet valley carving lasted longer than the eastern rim erosion. Therefore, Jezero was an open-basin lake after breaching.The eastern rim erosion and water outflow during breaching showed different results depending on the scenario. In the long-term scenario, the eastern rim erosion lasted longer than the outflow of water which was stored in the crater before breaching. That means, that this amount of water (236 km3) was not enough to carve the breach. In the catastrophic scenario there are overlapping timescales, therefore, the eastern rim breaching, and water outflow could happen simultaneously.Multiplying the timescales by corresponding discharges allows us to calculate the minimum water volume provided/released during each event. Dividing the minimum water volume by the volume of the crater before breaching (446 km3) shows that the northern inlet as well as the western inlet could alone flood the crater (last column in Table 1).A comparison of the minimum amount of water discharged after the breach (236 km3) with the amount of water needed to carve the whole outlet valley (1000 – 14800 km3, Table 1) confirms that Jezero must have been an open-basin lake after the breaching.Table 1. Minimum water volume provided/released during the carving of the valleys. Timescales presented for the total valley carving (initial valley and last incised valley together). Timescale, Earth years Discharge, km3/day Minimum volume of provided/released water, km3 How many times Jezero could be filled before breaching (basin volume = 446 km3) Northern Valley Total 70 – 632 ~0.2 4600 – 42000 10 – 94 Western Valley Total 505 – 3792 ~0.2 33500 – 253000 75 – 567 Outlet Valley Total 1.4 – 21.2 ~1.9 1000 – 14800 – References: [1] Farley K., and Stack K. (February 15, 2023). Mars 2020 reports, Volume 2. https://mars.nasa.gov/internal_resources/1656/[2] Gwinner, K. et al. (2016). The High Resolution Stereo Camera (HRSC) of Mars Express and its approach to science analysis and mapping for Mars and its satellites. Planetary and Space Science, 126, 93–138. https://doi.org/10.1016/j.pss.2016.02.014[3] Kleinhans, M. G. (2005). Flow discharge and sediment transport models for estimating a minimum timescale of hydrological activity and channel and delta formation on Mars. Journal of Geophysical Research: Planets, 110(12), 1–23. https://doi.org/10.1029/2005JE002521[4] Kleinhans, M. G., van de Kasteele, H. E., & Hauber, E. (2010). Palaeoflow reconstruction from fan delta morphology on Mars. Earth and Planetary Science Letters, 294(3–4), 378–392. https://doi.org/10.1016/j.epsl.2009.11.025[5] Malin, M. C. et al. (2007). Context Camera Investigation on board the Mars Reconnaissance Orbiter. Journal of Geophysical Research: Planets, 112(5). https://doi.org/10.1029/2006JE002808[6] Roda, M. et al. (2014). Catastrophic ice lake collapse in Aram Chaos, Mars. Icarus, 236, 104–121. https://doi.org/10.1016/j.icarus.2014.03.023[7] Salese, F. et al. (2020). Estimated Minimum Life Span of the Jezero Fluvial Delta (Mars). Astrobiology, 20(8), 977–993. https://doi.org/10.1089/ast.2020.2228

Introduction:Current efforts for image mosaics from the High Resolution Stereo Camera (HRSC, Jaumann, 2007) on board Mars Express are ongoing (Michael et al. 2016, Michael et al., 2019). Usually, illumination effects between adjacent single images related to the planetary curvature are reduced by using a Lambert correction and subsequent normalization to a common brightness reference. Here we present an extended correction of topography-induced shading effects by using the illumination angles with reference to the local topography represented by the digital terrain model (DTM) associated to every single HRSC scene, resulting in top-of-the-atmosphere albedo images of the surface.Scattering models:When used for illumination corrections taking the local topography into account, the Lambertian model and its associated cosine correction tends to over-correct on large incidence angles (under-illuminated pixels), as observed on crater slopes at low Sun angles. Therefore we do not consider it for our work but use it as a reference for comparison reasons (see Fig. 1 top -- the saturation level of one is reached at around 70° effective incidence angle).The one-parameter model by Minnaert (Minnaert, 1941) is known for its good reproduction of the Martian surface. Depending on its power-law parameter k, the saturation effect of the correction appears at very high incidence angles only and is therefore better suited for topographic corrections. Still, in the case of HRSC, the Sun incidence angle on the ellipsoid is often higher than 60° and adding the slope angles results in incidence angles higher than 80°. This leads to very bright over-corrected pixels in highly inclined areas facing away from the Sun (see Fig. 1 middle -- depending on the k parameter, the saturation level is reached at around 80° incidence).The correction used by Teillet et al. (1982) is well suited for topographic corrections due to its minimal amount of overcorrection (cf. Fig. 1 bottom for plots of varying parameter settings and Fig. 2 for the result). The single parameter is derived by a relation of the incidence on the ellipsoid to the mean incidince with regards to the topography. Figure 1: Correction curves using different photometric functions; top: Lambert model; middle: Minnaert model, emission angle=0°; bottom: Teillet model, incidence on ellipsoid=60°. A reflectance of 0.3 is assumed for all plots.Results:We corrected a common set of HRSC images using the three mentioned scattering models and assembled a respective mosaic for each by correcting the single images for the illumination effects and then normalizing the images to TES albedo data (see Fig. 2). The parameters for the models are estimated using non-linear least square minimization for every single HRSC scene assuming constant parameters over the full image. The results for the Minnaert and the Teillet model appear very consistent by visual inspection. Due to the very high slope angles often appearing in HRSC scenes, the Minnaert model sometimes results in saturated pixels, while the Teillet model achieves the most modest levels of correction. We have not observed any advantage of the Minnaert model over the Teillet model, although it additionally includes emission angle values in the model. This lets us assume that the emission angles have a minor effect on the topography-induced illumination effects. Figure 2: Subsets of the image mosaics; top: uncorrected image mosaic as shown in Michael et al., 2016; middle: Image mosaic with removed shading using the Minnaert scattering model, bottom: Image mosaic with removed shading using the Teillet scattering model.Outlook:The albedo mosaics here serve for a broad range of applications: Image classification using computer vision algorithms, geologic interpretation without influences of the topography and therefore better differentiation between albedo and shading, data fusion with uniform illumination characteristics, as well as the ability to add homogeneous shading from a uniform illumination direction for the application in Virtual Reality scenarios.

This review paper summarizes the observations and results of the Mars Express Mission and its application in the analysis of geological processes and landforms on Mars during the last 20 years. The Mars Express observations provided an extended data base allowing a comparative evaluation of different geological surface landforms and their time-based delimitation. High-resolution imagery and digital elevations models on a local to regional scale and spectral measurements are the basis for geological analyses of water-related surface processes on Mars. This includes the nature and discharges of valley networks, formation timescale of deltas, volumina of sedimentary deposits as well as estimating the age of geological units by crater size–frequency distribution measurements. Both the quantifying of geological processes and the determination of absolute model ages allows to constraint the evolution of Martian water-related activity in space and time. Comparative age estimation of fluvial, glacial, and lacustrine deposits, as well as their timing and episodicity, has revealed the nature and evolution of the Martian surface hydrological cycle. Fluvial and lacustrine activity phases are spread over a time span from Noachian until Amazonian periods, but detailed studies show that they have been interrupted by multiple and long-lasting phases of cessation and quiescent. In addition, evidence of glacial activity shows discrete phases of enhanced intensity correlating with increased spin-axis obliquity amplitude. The episodicity of geological processes, erosion, deposition, and glaciation on Mars demonstrate a close correlation between individual surface processes and endogenic activity as well as spin-axis/orbital variations and changing climate condition.

The South Pole–Aitken (SPA) basin is the oldest and largest visible impact structure on the Moon, making it a high priority science site for exploration missions. The 492 km diameter Apollo peak-ring basin is one of the youngest and largest basins within the SPA basin. We selected three regions of interest (ROIs) in the Apollo basin for which the landing and operational hazards are minimized and evaluated their science and in situ resource utilization (ISRU) potential. We examined topography, slope, crater density, rock abundance, geologic mapping, mineralogy, and inferred subsurface stratigraphy within each ROI. The results show that the terrain is safe for landing without precision landing (within a few hundred meters). The mare materials have high ISRU potential with relatively high FeO (∼16–20 wt%) and TiO _2 (∼3–10 wt%) contents. Two robotic exploration mission architectures were examined for their scientific potential: (1) lander and rover with a dedicated payload suite and (2) the same architecture with sample return capability. In situ observations can address six of seven National Research Council concepts (1–3, 5–7) and Campaigns 1 and 5 of the European Space Agency’s Strategy for Science at the Moon.

Abstract The image data of the Context Camera (CTX) of the Mars Reconnaissance Orbiter require a flat‐field correction that is currently available as a plain text file in the Planetary Data System “Calib” folders for all CTX Enhanced Data Record releases or automatically implemented as part of the ctxcal application of the Integrated Software for Images and Spectrometers (ISIS). We noticed (a) differences between these two flat‐fields and (b) residual edge darkening (vignetting) after applying ctxcal. This work examines in detail the edge‐darkening effect over time and creates a new improved flat‐field calibration file to be implemented into the ISIS ctxcal application as a new default. We introduce a method to quantify the vignetting effect and its residuals after regular ISIS calibration. With the old calibration, the amount of residual edge‐darkening is about eight percent. We prove that the new calibration does remove the effect completely, does not introduce any artifacts and qualitatively and quantitatively validate newly calibrated images. Mosaics produced with images that have been calibrated with our new flatfield show immediately less striping issues, without the application of any standard mosaicking‐related tone‐matching techniques.

Introduction: The Context Camera (CTX) has so far delivered more than 145,000 images [1]. The images are one of the most popular datasets for planetary geologists, providing extensive coverage, excellent radiometric resolution, and a unique resource for interpreting surface features. The Integrated Software for Imagers and Spectrometers (ISIS) is a software to support the ingestion, processing and analysis of planetary image data [2] and is the standard processing framework for CTX. Since the beginning of its mission, calibrated images from CTX have shown a subtle darkening effect from the centre of the image towards the edges. Due to its typical shape when plotted as a profile, this effect has been called the "frown" effect (see Figure 1).Figure 1: Subset of CTX image G09_­021566­_1800 after nominal ISIS calibration together with a plot of the reflectance values averaged over all lines [3]. Some authors assume a varying darkening effect over the mission time, and workarounds to correct for this have been described [4,5]. Here we present an up­dated flat-field calibration for ISIS that removes the edge darkening effect. We ensure that it does not introduce any artefacts and perform quantitative validation of calibrated images to show the validity of the improvements.Methods: The overall shape of the CTX flat-field is a curve, where the difference between the centre and the edges of the detector represents a quantifiable amount of darkening caused by lens vignetting. To quantify the amount of this edge darkening correction by a flat-field, we use the concept of the frown factor. Similar to the quantification of the band depth feature in spectral analysis, the amount of darkening correction by a flat-field can be expressed as the ratio of the mean values of the central area of the flat field to the mean values of its edges (see Figure 2).Figure 2: Elements for the composition of the frown factor of a flat-field [3].Before building a flat-field from a pool of input images, we correct the input data from bias and dark-current effects without any initial flat-field correction. As the ISIS ctxcal command combines these two corrections, we turn off the flat-field correction in ctxcal by providing a custom flat-field file where all values are set to one. We use the resulting pre-processed bias/dark-current corrected files for calculating the new flat-field.Figure 3: Top: Scatter plot of the frown factor over time. Bottom: mean monthly frown factor over time [3].Results: Figure 3 shows the temporal evolution and distribution of the frown factor, i.e. the amount of darkening towards the detector edges. We exclude images exhibiting overexposure or the ones with negative reflectance values after calibration. The frown factor remains relatively consistent around its mean of 1.55 until the end of 2018, followed by a subsequent rise until early 2020. Throughout this interval, the average frown factor for all images rises to approximately 1.6, and throughout 2020, it reverts to the value observed before the mentioned change.Investigating the distribution of the frown factor excluding images from the problematic year 2019, we observe a skewed data distribution (Figure 4 right). As the frown factor outside the irregular time interval from 2019 until early 2020 appears very stable, we can safely assume that the edge-darkening effect is stable over time. The deviation from its mean during the period in question is not representative, as the central limit theorem is not fulfilled, which we observe in its non-symmetrical distribution.Figure 4: Kernel density plot of the frown factor of all images except the ones from the year 2019 (left) compared with the ones from year 2019 (right) [3].Evaluation: One of the main advantages of the improved calibration is better in-image stability for image mosaicking, which leads to homogeneous mosaics. An example of this is provided in Figure 5. The seams between adjacent images are strongly visible in the "before" mosaic (case a), processed with the nominal flat-field in ISIS. Using our new flat-field calibration file, most seams are no longer visible (case b).Figure 5: Example CTX mosaic of the Oxia Planum region. Images were chosen from Martian Year 33. a) calibrated with the nominal ISIS internal flat-field calibration – b) calibrated with the new global flat-field calibration [3].For a quantitative evaluation, we randomly chose 10.000 images over the full timespan and calibrated them with our new flat-field file when using ctxcal. The arithmetic mean of the frown factor of these images is then 1.00, proving a very good result and confirming the frown factor as a good quantification. We randomly reduced the subset to 1.000 images and performed a systematic visual inspection for qualitative evaluation. We could not find any signs of a remaining edge-darkening effect during the visual investigation. The residual edge-darkening effect is 1.079, calculated as the arithmetic mean over the individual factors of all images from the validation dataset calibrated with the previous flat-field file. This means, a surface recflectance measurement taken at the edge of a CTX image appears 8% darker than in the center, when calibrated with the previously available flat-field file.The new flat-field calibration file is available from this data repository: http://dx.doi.org/10.17169/refubium-41645. It has also been provided to the ISIS development team in order to publish it in their default data directory, beginning with ISIS version 9.0.Acknowledgements: This work is supported by the German Space Agency (DLR Bonn), grant 50 OO 2204, on behalf of the German Federal Ministry for Economic Affairs and Energy.References: [1] M. C. Malin et al., JGR Planets (2007). [2] Jason Laura et al., 2023, DOI: 10.5281/zenodo.2563341. [3] Walter, et al., ESS 11 (2024), DOI: 10.1029/2023EA003491. [4] J. L. Dickson et al., LPSC 49 (2018), #2480. [5] Stuart J. Robbins et al., ESS 10 (2020).

The current approach for ortho-rectifying images taken by the Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO) uses MOLA data as a global reference ([1]), but this approach is imprecise, specifically at the equator, due to the large difference in spatial resolution between the two datasets (6 vs 463 m/pix). Automatic point matching of image pixels to DTM pixels are not reliable, therefore usually the CTX pixels are matched to imagery datasets which are themselves controlled to MOLA, such as the THEMIS IR dataset ([2]).The HRSC team is working on creating global mosaics of bundle-block-adjusted digital terrain models (DTMs) and corresponding image mosaics with better internal photogrammetric precision than the 50 m used as the grid size, and less deviation from MOLA profile heights, aimed to be finished by the end of 2023. This abstract presents our progress in using a new approach, by using HRSC DTMs as the global reference for CTX image rectification instead of MOLA, which involves using the HRSC ortho-image for co-registration of CTX images and applying brightness correction before combining all images of a quadrangle together to form a seamless mosaic which is then exported as a single image file. The workflow and processing is performed using modern pixel registration techniques, the USGS’ ISIS system, a database management system, and high-performance computing, and results in significantly less pixel offsets compared to the previous approach.References[1] J. L. Dickson et al., LPSC 49, #2480. [2] S. J. Robbins et al., LPSC 52, #2066. Acknowledgements: This work is supported by the German Space Agency (DLR Bonn), grant 50OO2204, on behalf of the German Federal Ministry for Economic Affairs and Climate Action. We thank the HPC Service of FU for computing time.

The Context Camera (CTX) on board NASA's Mars Reconnaissance Orbiter (MRO) has been in orbit since 2006 and has so far delivered more than 130,000 images. The images are one of the most popular data sets for planetary geologists because the data cover almost the entire planet and have good radiometric resolution, allowing very detailed interpretation of surface features. Since the beginning of the mission, the images have exhibited a darkening effect from the centre of the images towards the edges, creating visible seam lines when multiple images are stitched together. Due to the symmetric decrease in reflectance plots averaged over all lines, this problem is often referred to as "frowning" (see Figure 1 left). Since the standard calibration routines of the Integrated Software for Imagers and Spectrometers (ISIS) only include flatfield files for the first year of the mission, there are no quick and easy standard methods to correct for these artefacts. In this work, we provide an extended in-flight radiometric calibration and the resulting flatfield files that can be used directly in the ISIS environment (see correction example in Figure 1 right). The files are updated regularly and are permanently available in this repository: https://dx.doi.org/10.17169/refubium-37236 .Figure 1: left: CTX image N05_064260_1638 with standard ISIS calibration applied (top) and curve plot of all averaged lines (bottom); right: after additional in-flight calibration the image (top) shows less darkening to the borders and the downward trent in the plot has been removed.In addition, we are in the process of updating our "integrated Mars analysis and research system" (iMars) to include the full set of CTX images, which will be readily processed and made available for download in GIS-compatible formats. As with the previous system, users can select the footprints and visualise the data directly in the map view. Special tools for switching between images with multiple coverage provide an excellent infrastructure for analysing surface changes and seasonal or interannual variations. We have made a complete overhaul of the graphical interface, which is accessible under https://maps.planet.fu-berlin.de/ctx . This work is supported by the German Space Agency (DLR Bonn), grant 50 OO 2204, on behalf of the German Federal Ministry for Economic Affairs and Energy. We thank the HPC Service of Freie Universität Berlin for computing time.

Abstract We demonstrate the capabilities of a published MADNet monocular height estimation network in producing a refined digital terrain model (DTM) mosaic at 50 cm/pixel resolution for the Mars 2020 Perseverance rover landing site in Jezero crater on Mars. Our approach utilizes the publicly available Mars 2020 Terrain Relative Navigation (TRN) High‐Resolution Imaging Science Experiment (HiRISE) Digital Terrain Model (DTM) mosaic, which was originally created by the United States Geological Survey (USGS) Astrogeology Science Centre. Our resultant HiRISE MADNet DTM mosaic is strictly matched with the original HiRISE TRN DTM and orthoimage mosaics. These mosaics are themselves co‐aligned with the USGS TRN Context Camera (CTX) based DTM and orthoimage mosaics, as well as the ESA/DLR/FUB (European Space Agency/German Aerospace Center/Free University Berlin) High Resolution Stereo Camera (HRSC) level 5 DTM and orthoimage mosaics. In this paper, we provide a brief description of the technical details, and present both visual and quantitative assessments of the refined MADNet HiRISE Jezero DTM mosaic product. This DTM product is now publicly available at http://dx.doi.org/10.17169/refubium-38359.

We demonstrate the creation of a large area of high-resolution (260 × 209 km2 at 1 m/pixel) DTM mosaic from the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images over the Chang’E-4 landing site at Von Kármán crater using an in-house deep learning-based 3D modelling system developed at University College London, called MADNet, trained with lunar orthorectified images and digital terrain models (DTMs). The resultant 1 m DTM mosaic is co-aligned with the Chang’E-2 (CE-2) and the Lunar Orbiter Laser Altimeter (LOLA)—SELenological and Engineering Explorer (SELENE) blended DTM product (SLDEM), providing high spatial and vertical congruence. In this paper, technical details are briefly discussed, along with visual and quantitative assessments of the resultant DTM mosaic product. The LROC NAC MADNet DTM mosaic was compared with three independent DTM datasets, and the mean differences and standard deviations are as follows: PDS photogrammetric DTM at 5 m grid-spacing had a mean difference of −0.019 ± 1.09 m, CE-2 DTM at 20 m had a mean difference of −0.048 ± 1.791 m, and SLDEM at 69 m had a mean difference of 0.577 ± 94.940 m. The resultant LROC NAC MADNet DTM mosaic, alongside a blended LROC NAC and CE-2 MADNet DTM mosaic and a separate LROC NAC, orthorectified image mosaic, are made publicly available via the ESA planetary science archive’s guest storage facility.