We present the first complete geological map of the Borealis quadrangle (H01), Mercury’s north polar region. H01 spans latitudes 65°N to 90°N and longitudes 0°–360°, covering an area just over 3.5 million km2, approximately 4.7% of the planet’s surface. Map digitisation was conducted at scales between 1:300,000 and 1:700,000, with final presentation at 1:3,000,000, using end-of-mission data products from NASA’s MESSENGER mission. We distinguish three principal photogeologic plains units: intercrater plains, intermediate plains, and smooth plains. All craters ≥20 km in diameter and associated materials were mapped and classified by degradation state. Two versions of the map have been completed, using three-class and five-class respectively. Surficial units and areas of permanent shadow that house radar bright deposits in craters ≥5 km in diameter (poleward of 80°N) have been digitised. This map provides geological context for data to be collected by ESA-JAXA’s BepiColombo mission.

Mercury's Discovery quadrangle (H11) is in the planet's southern hemisphere (0-90 degrees W, 22.5- 65 degrees S), one of fifteen mapping quadrangles covering Mercury. Here we present a 1:3,000,000 (1:3M) scale geological map of H11, constructed using data collected by NASA's MESSENGER spacecraft mission. On top of a similar to 166 m/pixel monochrome basemap, we digitized geological units and their contacts, and additional linear and surface features. We produced two versions of the map, using alternative three and five-class schemes to classify impact crater materials. In addition to crater materials, mapped geological units include intercrater, smooth and intermediate plains, which are common terrains across Mercury. We also mapped units particular to H11, specifically in its notable chaotic terrain. This map is one of a series of quadrangle maps aiming to globally cover Mercury at 1:3M scale, supporting investigations of the planet by the ESA/JAXA BepiColombo space mission.

Introduction: Large scale effusive volcanism, responsible for most of Mercury's 'smooth plains', is accepted to have ended by ca. 3.5 Ga [1]. We present local occurrences of smooth surfaces, often with the evidence for being topographically ponded. These examples are seldom larger than a few 10s of km across and are characterised by extremely smooth surfaces with a paucity of impact craters. Some of these deposits may provide evidence for a protracted phase of waning effusive volcanism post-3.5 Ga. We present a map of the global occurrences of very smooth plains patches and investigate their implications for the effusive volcanic evolution of Mercury. Previously reported occurrences: : During the Mariner 10 era, the partial geological map of H15 was unique in including small very smooth plains (pvs) deposits commonly associated with craters or tectonic features [2]. Similar patches have recently been identified in H10 [3] and an association with tectonic features was discovered (e.g. Calypso, Soya and Enterprise Rupes). Additionally, some patches of very smooth plains have been mapped in the survey of smooth plains deposits < 105 km of Wang et al. [4]. Previous works propose a range of origins which we will explore, namely: · Impact-related origin: Either as impact melt or fluidized impact ejecta · Small-volume effusive volcanic origin: where the age of such deposits are somewhat contested Newly Identified occurrences: The global survey so far has identified approximately 500 potential patches, with varying confidence dependent on the degree of textural difference between the patch and surrounding terrain. These occur in a variety of settings, including low-lying areas of both smooth and intercrater plains, associated with craters or tectonic features, or catenae-hosted. Ongoing work involves mapping each patch, exploring emplacement scenarios and analysis of the association between patches and structural weaknesses. Data and method: We map using NAC (single frame) and WAC (global mosaic) images obtained by MESSENDER’s MDIS. Mapping is carried out on a 116 m/p monochrome primary basemap; high-incidence east and west, and low-incidence angle secondary basemaps; a 665 m/p enhanced color mosaic; and a 665 m/p stereo-derived digital elevation model. Mapping is carried out using ArcGIS Pro. Each image is mapped in the projection most suited to that quadrangle. References: [1] Byrne P. K., et al., (2016). Geophys. Res. Letters. [2] Strom et al., (1990). USGS Astorgeol. Sci. Center [3] Malliband C., et al. (2020). PhD Thesis. [4] Wang et al., (2021). Geophys. Res. Letters.

The observed geochemical heterogeneity on the surface of Mercury is key to understanding the planet's volcanic activity and mantle conditions. The Caloris basin shows a diversity in elemental composition, spectral properties, and geomorphology, both within and around it. However, the relationship among these characteristics has not been well understood due to the mismatch in spatial resolutions of the available observation data. This study investigates the geochemical end-members around the Caloris basin, overcoming the limitation of the low spatial resolution of MESSENGER's X-Ray Spectrometer (XRS) data. End-member units are defined using spectral and geomorphological units from MESSENGER's VIS-NIR spectral data and high-resolution images, with the assumption of homogeneous elemental compositions within each unit. A mixing model is constructed to reproduce the XRS data by mixing the end-members, and we solve the inverse problem to calculate the respective end-member compositions. Five end-member compositions were determined, including those corresponding to the post-Caloris volcanic smooth plains interior and exterior to the basin and surrounding pre-Caloris crust. Two smooth plains units, which are geomorphologically indistinguishable but spectrally distinct, showed a compositional variation consistent with magma evolution through fractional crystallization. This suggests that they originated from parent magmas with a common composition. The pre-Caloris crust units showed a large compositional variation, ranging from low- to high-Mg content, implying the potential existence of high-Mg crusts comparable to the HMR. The observed crustal diversity could be explained by relatively minor heterogeneity in source mantle compositions and/or conditions of partial melting within the mantle.

We present six newly identified examples of lobate ejecta in Mercury's south polar quadrangle (H15), providing the first evidence of syn‐impact formation through our observation of perched impact melt at Nairne and Magritte craters. This finding challenges the idea that lobate forms could have developed post‐impact via mass wasting or landslide processes, suggesting instead that many, if not all, lobate ejecta deposits formed contemporaneously with the impact event. We present detailed morphostratigraphic maps of two exemplary case studies: Nairne and Magritte, for which we used shadow measurements to better constrain the morphology of their lobes. Many examples globally, including Nairne, have been formed by deposition of the lobe material into a topographically lower antecedent crater. While we confirm that topography plays a significant role in the formation of lobate ejecta, it cannot be the sole factor, as similar impacts onto pre‐existing craters do not always produce these features and not all lobate ejecta exhibit evidence for a topographic control. Our study also highlights the frequent association between lobate ejecta and characteristics of oblique impacts. Considering analogous features at Mars and the Moon in particular, lobate ejecta on Mercury is likely the result of either fluidized or dry granular flows, with minimal delay between impact and emplacement. Our findings suggest that lobate ejecta are more widespread on Mercury than previously recognized, and future studies and missions, such as a comprehensive global survey with higher resolution data from BepiColombo, will continue to constrain their formation mechanisms and prevalence.

IntroductionSurface reconstruction of planetary bodies such as the Moon and Mercury is crucial for geomorphological analysis, reflectance normalization, thermal modeling, rover landing site planning, and outreach activities. Stereo algorithms and Shape-and-Albedo-from-Shading (SAfS) are well-established methods for planetary 3D reconstruction. The current state-of-the-art combines both methods. SAfS refines the surface slopes of a stereo digital elevation model (DEM) and typically yields 3D models at image resolution [1,2,3,4,5,6]. This approach is generally well-validated for scientifically calibrated instruments that observe the planetary body under favorable conditions. However, the limits of SAfS still need to be explored. This work applied the SAfS algorithm to planetary flyby images acquired with uncalibrated off-the-shelf cameras. We qualitatively and quantitatively assessed the algorithm's performance and found the method robust even under these challenging conditions.MethodsWe considered two images: First, a flyby image of Mercury (Figure 1, left), which was obtained with a monitoring camera during BepiColombo’s third flyby, and second, a flyby image of the Moon captured by a GoPro during the Artemis I mission (Figure 1, right). In both cases, off-the-shelf cameras without a proper radiometric calibration routine were used instead of scientific instruments. Therefore, it was necessary to calibrate the images before applying the SAfS algorithm. For calibration, we estimated a reflectance image of the region of interest with Hapke parameters from [7] to establish a relationship between the digital number output of the camera and the physical radiances. The resulting Mercury flyby DEM was evaluated qualitatively, compared to MDIS WAC images [8]. The lunar flyby DEM was compared to the SLDEM2015 (60-100 m/pixel) [9], which serves as a ground truth. Figure 1. Left: Flyby image from the BepiColombo mission [10]. Right: Flyby image from the Artemis I mission [11]. ResultsFigure 2 shows the color-coded SAfS DEM for the BepiColombo image. We found that the algorithm successfully reconstructed the surface in the center of the image but struggled with the more extremely illuminated sections at the edges. It is obvious that the algorithm reconstructed some details that are not visible in the input DEM and hence improved the resolution. Figure 3 compares a grey-scale representation of the SAfS DEM with MDIS WAC image EW0251718878F. Small craters in Izquierdo (the crater in the right half of the marked section), a few kilometers in diameter, become especially visible. Figure 4 shows the marked section in more detail. Due to the lack of high-resolution ground truth, a detailed algorithm evaluation was not possible for this image.Figure 2. Color-coded presentation of the reconstructed SAfS DEM from the BepiColombo image. Figure 3. Left: grey scale reconstructed SAfS DEM from the BepiColombo image. Right: wide-angle camera (WAC) image from MDIS [8]. The marked image section was evaluated in more detail (Fig. 4). Figure 4. Comparison of WAC image, input DEM, BepiColombo (BC) image and SAfS DEM. Below the images are the height and slope of the profile (red dashed line). However, the ground truth evaluation with the Artemis I image gives a quantitative measure under comparable conditions. Figure 5 shows the color-coded SAfS DEM of a region of interest (ROI) reconstructed from the flyby image. The results for the Artemis I image for all ROIs were of high quality. Figure 6 shows the elevation profile indicated by the dashed line in Figure 5. The algorithm refines the low-frequency initial DEM (dashed line), yielding a SAfS DEM (red line), which closely resembles the ground truth DEM (black line). The vertical RMSE between the reconstructed DEM and the ground truth is 523 m, lower than the pixel size of approximately 1500 m. However, there were inaccuracies near the ROIs’ edges, and a preferred direction aligned with the illumination direction became visible.Figure 5. Color-coded presentation of the reconstructed SAfS DEM from the Artemis image. The black dashed line marks the profile that was analyzed in detail (see Fig. 6). Figure 6. Height profile of a selected terrain profile (see black dashed line in Fig. 5). Red line: DEM generated with the SAfS algorithm. Black line: Ground truth DEM. Dashed line: Initial DEM (input for the SAfS algorithm). ConclusionIn conclusion, it is possible to obtain sharp results by applying our SAfS framework to flyby images. Both results show that, despite the challenging conditions, the SAfS algorithm could reconstruct the surface up to image resolution and increase the level of detail of the input DEM. The quality differences between the two images can mainly be attributed to the (spatial) resolution of the original images and the oblique illumination direction. Usually, the image center is distortion-free, and the illumination geometry is best suited for SAfS. We found that the surface reconstruction at the edge of the image is also possible, but the quality decreases significantly. All in all, our flyby-derived DEMs are accurate, and a previous version has been used for ESA outreach activities, similar to [12]:https://www.esa.int/Science_Exploration/Space_Science/BepiColombo/BepiColombo_s_third_Mercury_flyby_the_movie References[1] A. Grumpe, F. Belkhir, C. Wöhler. Advances in Space Research, 53(12):1735–1767, 2014.[2] C. Jiang, S. Douté, B. Luo, L. Zhang, P&RS,130, 2017 [3] O. Alexandrov, R. Beyer. Earth and Space Science, 5, 2018[4] B. Wu, W. C. Liu, A. Grumpe, C. Wöhler. P&RS, 140, 2018[5] M. Tenthoff, K. Wohlfarth, C. Wöhler. Remote Sensing, 12(23), 2020.[6] M. Hess, M. Tenthoff, K. Wohlfarth, and C. Wöhler. Journal of Imaging, 8(6), 2022.[7] J. Warell, Icarus, 167, 2,2004[8] Hawkins, S. Edward, et al. Space Science Reviews 131 (2007): 247-338.[9] M.K. Barker, E. Mazarico, G.A. Neumann, M.T. Zuber, J. Haruyama, D.E. Smith, Icarus, 273, 2016.[10] ESA. Planetary science archive.2023.https://archives.esac.esa.int/psa/#!Image%20View/MCAM=instrument, accessed 10th May 2024[11] NASA. flickr, 2022, https://www.flickr.com/photos/nasa2explore/52547180935/in/album-72177720303788800/, accessed 10th May 2024[12] K. Wohlfarth, M. Tenthoff, J. Wright, V. Galluzzi, C. Wöhler, H. Hiesinger, J. Helbert, J. Zender, J. Beckhoff. MExAG Annual Meeting, 02.2023

Mercury has a large core, but paradoxically the surface is also volatile rich. Most core-enlarging scenarios envisaged for Mercury would have heated the silicates and preferentially driven-off these volatiles. Mercury’s hollows, flat floored, rimless depressions tens of metres deep and up to tens of kilometres across, appear to have formed by the loss of some volatile material to space upon its exposure at the surface, often by impact craters. Hollows lack superposing craters, indicating that they may be undergoing active formation today. The subsurface distribution of Mercury’s hollow-forming material is not known. If confined to the upper few kilometres of Mercury’s crust, sampled by the craters up to a few hundred kilometres in diameter in which most hollows are found, then perhaps it was accreted as a late veneer after the core-enlarging event. Alternatively, if the hollow-forming material is present throughout a greater thickness of Mercury’s silicate portion then the timing of any high-temperature core-enlarging event must have taken place very early in the planet’s history to allow time for a volatile-rich silicate fraction to reaccrete. Here, we study the Caloris basin: Mercury’s largest, well-preserved impact structure. We employed a combination of geological mapping, reflectance spectroscopy, and numerical impact simulations to map the present-day distribution of the hollow-forming material in Caloris ejecta, preserved as hummocky plains hosting km-scale knobs, back to its pre-Caloris, subsurface distribution. Our results suggest that Mercury’s hollow forming material comes from the whole thickness of the crust, a deeper constraint than previous studies.

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin's exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to similar to 1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context.

Geological maps of Earth typically incorporate field observations of rock lithology, structure, composition, and more. In contrast, conventional planetary geological maps are often made using primarily qualitative morphostratigraphic remote sensing observations of planetary surfaces. However, it is possible to define independent quantitative spectral units (SUs) of planetary surfaces, which potentially contain information about surface composition, grain size, and space weathering exposure. Here, we demonstrate a generic method to combine independently derived geomorphic and SUs, using the Rachmaninoff basin, Mercury, as an example to create a new geostratigraphic map. From this geostratigraphic map, we can infer some compositional differences within geomorphic units, which clarifies and elaborates on the geological evolution of the region.

Introduction: Mercury is divided into 15 quadrangles, and the one yet to be mapped using NASA’s MESSENGER mission data is the Bach quadrangle (H-15) at Mercury’s south pole. This region encompasses everything from 65 ° poleward. Prior to this project, the only published map of this quadrangle is at 1:4.3M scale, based on Mariner-10 imaging at 0.5 km per pixel or worse resolution, and covers less than half of H15 (Fig 1). It includes patches of a ‘very smooth plains’ unit that was not mapped elsewhere on Mercury at the time. Our inspection of MESSENGER image data suggests that some of these patches are additional examples of topographically/tectonically confined late-stage lavas recently tentatively identified further north, consistent with a drawn-out waning phase of effusive volcanism. We aim to produce a detailed 1:3M resolution geological map and interpret the geology of H-15, tying it in to the ongoing mapping of quadrangles H-11 and H-14 bordering it. This is essential preparation for planning more detailed studies using BepiColombo. Alongside the geological mapping, this project aims to analyse polar tectonic features that are largely invisible in the north polar region (possibly because of flooding by the smooth plains of Borealis Planitia). This will involve comprehensive investigation of the nature, distribution and cause of the abundant south polar tectonic features and will use multiple illumination angles so as to limit illumination bias.Our initial reconnaissance of the quadrangle has led to the identification of lobate ejecta forms extending from impact craters. Such craters with ejecta flows are rare on Mercury and in H-15 exclusively originate from the rims of fresh craters, propagating into interiors of older craters. The example with the most distinct lobes exhibits two discrete lobes with steep fronts, spectrally bright material around the crater rim and bluer impact melt on the larger of the two lobes (Fig 3). Comparisons can be drawn between the morphology of these lobate ejecta and ejecta deposits of the Hokusai crater (Barnouin et al., 2015)[1] and the Tsiolkovskiy crater on the Moon (Boyce et al., 2020)[2]. We find that formation of these ejecta flows is topographically controlled, and favour the conclusions of Barnouin et al. (2015) and Xiao and Komatsu (2013)[3] that these are fluidized ejecta deposits, although the nature and role of crustal volatiles is currently unclear.References: [1] Barnouin et al. (2015) LPSC 46, 2672. [2] Boyce et al. (2020) Icarus 337, 113464. [3] Xiao, Z. and Komatsu, G. (2013) Planet. Space Sci. 82, 62–78.

Virtual Reality (VR, with headsets) and Augmented Reality (AR, using a smartphone or tablet) coupled with 3D photogrammetric reconstructions are increasingly used for science, education and outreach applications. These techniques are not new [e. g. 1, 2], but they are becoming progressively more widespread thanks to the release in 2016 of technologically mature and cost-effective hardware solutions accessible to the general public. In the field of planetology, VR and AR theoretically allow the possibility to simulate field trips to remote places that are otherwise inaccessible to humans. Using high-resolution imaging, coupled with spectral or morphological data gathered by robotic explorers (orbiters, landers, rovers), we can create integrated virtual environments that accurately represent the surface of planetary bodies and allow the cross-comparison of different datasets. These virtual environments provide the possibility to navigate on a global scale using orbital data, and move down to the surface when in situ data are available to visualize and analyze local outcrops. This is particularly the case of the Moon and Mars, where both extensive remote and groundtruth data are available [3, 4, 5].We are investigating how the information from various sources can be combined in a comprehensive way to display, manipulate, analyze and share both analytical data and results. We have for example integrated visible high-resolution imagery, digital elevation and outcrop models, geomorphological maps and compositional maps derived from spectroscopic measurements on several test sites such as the Copernicus crater and Apollo 17 landing site on the Moon, the Crommelin crater and Kimberley area (Gale crater) on Mars, and the Hokusai quadrangle area on Mercury. The VR and/or AR rendering of simple orbital and/or ground-based 3D models can be performed using a web-based solution such as Sketchfab (e.g. https://sketchfab.com/LPG-3D or https://sketchfab.com/planmap.eu), offering the possibility to visualize, interact, and share medium-resolution 3D versions of these multi-scale data (Fig. 1a and 1b). The use of a more powerful and versatile solution based on a game engine [6] allows the development of more complex solutions, for example dedicated measurement tools (Fig. 1c) or multi-layering capabilities (Fig. 1d). These approaches offer new possibilities in terms of data exploration, analysis, and applications for research and education during “virtual planetary field-trips”.Acknowledgments: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 776276 (PLANMAP). References : [1] McGreevy (1993), M.W. Virtual reality and planetary exploration. In Virtual Reality; Elsevier: Amsterdam, The Netherlands,; pp. 163–197, ISBN 0-12-745045-9.[2] Favalli, M. et al. (2012), Multiview 3D reconstruction in geosciences. Comput. Geosci. 2012, 44, 168–176.[3] Ostwald, A.; Hurtado, J. 3D models from structure-from-motion photogrammetry using MSL images: Methods and implications. In Proc. of the 48th LPSC, The Woodlands, TX, USA, 2017. LPI Contribution No. 1964, id.1787.[4] Caravaca, G. et al. (2020) Planet Space Sci, 182, 104808, DOI: 10.1016/j.pss.2019.104808[5] Le Mouélic, S. et al. (2020) Remote Sensing, 12 (11), DOI: 10.3390/rs12111900[6] Nesbit, P.R et al. (2020), GSA Today, vol. 30, 4–10. DOI: 10.1130/GSATG425A.

Abstract:Our tectonic mapping as part of a larger morphostratigraphic mapping effort of the H13, Neruda Quadrangle (1) has led us to recognise the “Neruda-Paramour” thrust system. The system appears to extend from the southern limits of H13 north through H09 and H08 and simplifies at its northern end into Paramour Rupes (Figure 1). Mercury’s tectonic evolution is dominated by global scale contractional structures of which the Neruda-Paramour system is part of (2). These structures are believed to have formed either by secular cooling of the planet (3), tidal despinning (4), mantle overturn (5), true polar wander (6) or a combination of these processes. Regardless of the process, Mercury’s surface exhibits abundant evidence of global contraction in the form of shortening structures such as lobate scarps, high relief ridges and wrinkles ridges (7,8). These features are widely accepted as the surface expressions of thrust faulting and folding, produced by lithospheric horizontal compression. Often, these contractional features comprise major thrust systems as linked segments with a consistent trend (8). In order to understand the development of the Neruda-Paramour system and to ascertain if there is any sequence of movements, we are first mapping the system in its entirety followed by age dating of each thrust segment’s last movement using the buffered crater counting (BCC) technique.Methods:Tectonic lineament mappingPrimary basemap: Global ~166 mpp v1.0 BDR tiles with moderate (~74°) solar incidence angles.Secondary basemaps: low (~45°) and high (~78°) incidence angle basemaps, ~665mpp enhanced colour mosaic; MLA- and stereo-derived DEMs.Scale: 1:3M scale with digitisation at 1:300k.Software: Esri ArcGIS 10.5.1 GIS software. Buffered crater countingSoftware: Esri ArcGIS 10.5.1 GIS software with CraterTools extension (9). CraterStats 2.0 (10).We use the BCC technique by (8,11) which counts craters that are unfaulted and undeformed by the structures under investigation to derive absolute model ages of linear landforms. The BCC technique uses a buffer zone around the linear feature to include more craters to be taken into consideration for the crater size frequency distribution (CSFD) count. This addition of included craters produces a more robust measurement, which is important due to the restricted surface area that the structures occupy (12). We have chosen to consider all craters that directly intersect the structures ≥2 km. A fault buffer width of 2R (R=radius of the crater) for buffer generation is used. CSFD data is exported to CraterStats 2.0 where it is plotted in a log Ncum (cumulative crater frequency) vs log D (diameter) and using the production function (PF) a best fit of the CSFD data is made, giving an absolute model age value. The Neukum Production Function and Le Feuvre and Wieczorek Production Function are used and the results from each are compared. Method after (8).Results:We will present our analysis of the mutual age relationships between elements of the Neruda-Paramour thrust system and discuss the implications for the tectonics of this part of the globe.Acknowledgements:Mapping is in association with Planmap, funded through the EU Horizon 2020 research and innovation programme under grant agreement No. 776276. Ben Man is supported by STFC and the Open University’s Space Strategic Research Area.References:

Using MESSENGER Mercury Dual Imaging System data, we produced three new maps of Sibelius Crater, Mercury. Geomorphological and spectral maps were combined into a single hybrid map containing units associated with ejecta deposits, crater floor landforms and impact melt ponding. Spatial measurement of these units shows that similar to 50% of the mapped melt pond area lies within a large, degraded impact crater (crater B), beyond the significantly lower northern Sibelius rim, with a potential melt flow to a smaller, degraded impact structure further north (crater C). Freshly processed spectral data from the eight-colour Map Projected Multispectral Reduced Data Record data highlight the emplacement of multiple uplifted ejecta units with distinct spectral properties. A new, high-resolution digital elevation model was created to help define and analyse crater floor uplift features and disrupted crater rims and to create detailed cross-sections. These illustrate a proposed location of B's central uplift structure exposed in the northern wall slopes of Sibelius. Small features at the limit of visibility, such as a groove possibly associated with a rolling or sliding mega-boulder and lobate melt flow on the crater floor with accompanying channel opening, are highlighted for future investigations by BepiColombo's instruments once it reaches orbit.

Introduction: The lunar South Pole-Aitken basin (SPA) is of special interest for human and robotic missions for the near future [e.g. 1–4]. This makes detailed studies of the geological background and setting of the region a high priority. Located on the lunar farside, centered at ~53° S, 191° E, SPA basin is the largest and likely the oldest lunar basin [5-7]. The region is widely influenced by rays of the ~3.85 Ga old Orientale basin [8].In this study, we constructed a geologic map of the full extent of the SPA basin, covering the South Pole, and extending eastward to include part of the Orientale basin (Fig. 1). Altogether, this provides a comprehensive overview of the geology of the region.Methods: This map, which is an extension of an Apollo basin map [9], was done as part of the PLANetary MAPping (PLANMAP - H2020 n°776276) project (https://planmap.eu/). For large scale mapping, we used the Lunar Reconnaissance Orbiter (LRO) Wide-Angle Camera (WAC) basemap (100 m/pixel). For more detailed, smaller areas, and for identifying specific features, we used LRO Narrow-Angle Camera (NAC; 0.5 m/pixel) [10] and Kaguya (10 m/pixel) data with different incidence angles. We also used a hybrid spectral mapping technique using Clementine [11], M3 [12] and Kaguya MI [13] data. The topographic features were mostly mapped using Lunar Orbiter Laser Altimeter (LOLA) digital elevation models (DEMs) and a LOLA/Kaguya merged DEM with a resolution of 59 m/pixel [14]. To reduce shadows, particularly in the southernmost latitudes, we produced hillshade maps with various illumination conditions. We used PLANMAP mapping standards [15], which are based on USGS standards [16].We identified units using morphological appearance and albedo contrasts. The mapping scale is 1:500,000. For the purpose of determining the stratigraphic relationships, we first established the relative ages of units using morphological evidence. For an absolute stratigraphy, we then performed crater size-frequency distribution (CSFD) measurements for fitting of absolute model ages (AMAs) using the production and chronology functions of [17]. CSFD measurements were made using CraterTools [18] in ArcGIS, and we fit the AMAs with Craterstats [19]. Detailed descriptions of the CSFD measurement technique are given by [17, 20]. The Apollo basin map is currently available on the PLANMAP website (https://data.planmap.eu/pub/moon/PM-MOO-MS-SPAApollo/) and the map of SPA will be available shortly.Geology: In our study area, we defined three classes of geologic features: Basin materials, crater materials, and plains-forming materials. Basin materials are related to the formation of the large basins in the area with the oldest and most dominant being the SPA. We also specifically identified materials related to Apollo, Schrödinger, and Orientale Basins. Crater materials are divided into different classes according to the state of degradation and shape of the craters. For achieving a framework for the absolute chronology, we determined AMAs for several key craters. Plains-forming materials are characterized by their relatively flat, smooth surfaces and can be further divided into dark and light plains based on their albedo. Furthermore, we observed dark mantle material, which might be originate from pyroclastic volcanic events. These mantle materials occur most prominently in Schrödinger and Oppenheimer craters.The SPA basin rim is obscured by various later impacts and is degraded due to its old age. The most distinctive appearance of the SPA basin rim is in the NW quadrant, close to the Apollo basin. Here, we identified two topographic rings of SPA basin rim massifs. Around the South Pole, image quality is lower and features become obscured by the low sun angle. We were able to find traces of the outer massif, but most of the inner massif is hidden below younger craters. The whole region is large influenced by the Orientale basin-forming impact, resulting in large quantities of ejecta-covered terrain and secondary cratering across the entire SPA basin.Acknowledgments: This paper is part of a project that has received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement Nº776276 (PLANMAP). References: [1] Flahaut et al. (2019) PSS., in press. [2] Steenstraet al. (2016) Adv. Space Res. 58, 1050–1065. [3] Allender et al. (2018) Adv. Space Res. 63, 692–727. [4] Hiesinger et al. (2019) LPSC 50, 1327. [5] Garrick-Bethell and Zuber (2009) Icarus, 204, 399–408. [6] Hiesinger et al. (2012), LPSC 43, 1659. [7] Fortezzo et al. (2020), LPSC 51, 2760. [8] Stuart-Alexander (1978) USGS Map I-1047. [9] Ivanov et al. (2018) JGR Planets, 123, 2585–2612. [10] Robinson et al. (2010) Space Sci. Rev., 150, 81–124. [11] Pieters et al. (1994). Science, 266, 1844–1848. [12] Isaacsom et al. (2013). JGR, 118, 369–381. [13] Ohtake et al (2013) Icarus, 226, 364–374. [14] Barker et al. (2016) Icarus, 273,346-355. [15] wiki.planmap.eu/display/public/D2.1-public. [16] FGDC (2006). FGDC-STD-013-2016. [17] Neukum et al. (2001) Space Sci. Rev. 96, 55–86. [18] Kneissl et al. (2011) PSS, 59, 1243–1254. [19] Michael and Neukum (2010) EPSL, 294, 223–229. [20] Hiesinger et al. (2000) JGR, 105, 29239–29276.

[Introduction] Mawrth Vallis (Figure 1) is generally understood to be one of Mars’ catastrophic out-flow channels. It is incised into Noachian (> 3.7 Ga) terrain and is associated with thick (> 150 m) clay deposits [1]. These clays are well-documented [e.g. 1–3], and have made Mawrth Vallis a candidate landing site for multiple rover missions. However, the atypical geomorphology of the channel is less well-studied. In the PLANMAP project, we will produce a geological map of Mawrth Vallis to establish its his-tory of erosion and deposition and relationship with the clays.

In the last months of its mission, MESSENGER was able to obtain measurements at low altitude (< 120 km). This has made it possible to measure small magnetic field signals, probably of crustal origin (Johnson et al, 2015). Maps of the crust signatures at 40 km altitude were produced by Hood (2016) and Hood et al. (2018), showing that the strongest anomalies are about 9 nT in the Caloris basin. Some of the anomalies are associated with impact craters, and it has been demonstrated that this is not a coincidence (Hood et al., 2018). It is believed that these anomalies are the result of impactor materials rich in magnetic carriers (e.g., metallic iron) that were incorporated on the surface acquiring remanent magnetic fields during the cooling of the material. We analyzed whether the anomalies of the crustal field are related to geological characteristics by examining two Hermean craters in order to test this impactor hypothesis. Anomalies associated with Rustaveli and Stieglitz craters are slightly or totally asymmetric with respect to the crater center. The morphology and geological setting of these two fresh impact craters that still maintain a well-preserved ejecta blanket and visible secondary crater chains are investigated to constrain the overall impact dynamics. In both cases, slight asymmetries in the morphology and ejecta distribution show that the magnetic anomalies correlate well with the location of impact melt. Rustaveli is associated with a ~5 nT crustal magnetic anomaly centered close to the crater’s midpoint, although offset ~20 km east-southeast. This offset is somewhat consistent with the downrange direction implied by Rustaveli’s impact melt and crater chains distribution. For Stieglitz, an anomaly larger than 3 nT includes most of the ejecta melt locations towards southwest. The ejecta melt cluster to the north of the crater corresponds to an anomaly of ~5 nT, while the largest anomaly of ~7 nT is found further north and closely corresponds to the crater’s deepest chain. For both craters, the melt likely recorded the prevailing magnetic field of Mercury after quenching. Hence, both impactors brought magnetic carriers to the surface that could record the past magnetic field of Mercury. Acknowledgments: The authors gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0 and the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 776276. Hood, J. Geophys. Res. Planets 121, 2016; Hood et al., J. Geophys. Res. Planets 123, 2018; Johnson et al., Science 348, 2015.

Summary: The volcanic history of Mercury is slowly being revealed as the Mercury aficionado community is analysing data returned by the MESSENGER mission. Although the presence of products of effusive and explosive volcanism is not disputable anymore (Byrne et al., 2018), their origin, evolution, and age is still a matter of debate. The description of Hermean volcanism is often the result of analysing orbital observations while their connection to the interior properties is still largely unanswered. Using MESSENGER/MASCS spectral scientific observations, we show that a heterogeneous mantle is not needed to explain the lateral variability of volcanic products seen in Mercury’s basins. Similarly, the support of deep learning techniques in analysing spectra from explosive volcanism highlights that this volcanic activity may have been long-lived on Mercury, likely younger than 1 Gy.Do we need an heterogeneous mantle? The study of geological processes such as impact cratering and volcanism provides information on Mercury’s evolution. Volcanism has shaped Mercury's surface and considerably modified impact basins after their formation by the emplacement of younger volcanic infills. Caminiti et al. (2023) clarified the volcanic history of the Caloris basin by classifying MESSENGER MASCS footprints according to spectral units (Murchie et al., 2015). We applied this same spectral classification to the Rembrandt basin, improved the classification and characterized a new younger volcanic spectral unit (Helbert et al., 2013; Semenzato et al., 2020). These improvements allow us to distinguish low-reflectance material, high-reflectance red plains, low-reflectance blue plains and intermediate plains as well as to define the younger high-reflectance red plains. We investigated and compared major impact basins on Mercury: Caloris, Rembrandt, Tolstoj, Beethoven and Rachmaninoff. A detailed analysis of each basin allows us to clarify their geological histories including the number of volcanic infillings as well as to confirm that volcanic smooth plains are spectrally heterogeneous (Helbert et al., 2013). Similarities between spatially distributed basins highlight that spectral units associated with basin infills have no spatial and compositional dependence suggesting no lateral heterogeneity in the mantle. However, it depends on the size of the basin. This could be linked to vertical heterogeneities or different intensities of deep perturbations by impacts leading to different melt production and evolution through time. BepiColombo data are eagerly awaited to investigate the compositional variability of volcanic smooth plains and refine the definition of spectral and morphological units.Is explosive volcanism extremely young? Explosive volcanic activity on Mercury extended after the end of the widespread effusive volcanism era. While prior research has recognized a prolonged period of explosive volcanic activity, the specific eruption timing for individual pyroclastic deposits remains unknown. We explored the evolution of explosive volcanism by examining the relationship between the morphological degradation of the vents and spectral changes in the associated deposits. We found a diverse range of spectral properties in pyroclastic deposits, which are typically characterized by increased brightness, a red spectral slope, and a higher curvature compared to the average surface. We observed a trend between the deposit spectra and the vent degradation characterized by a rapid initial darkening and flattening over time followed by stabilization. The oldest deposits reach a steady state with no further spectral changes. To explain these temporal variations in spectral properties, we propose three potential processes: space weathering, mixing with the background and changes in pyroclast size over time. We examine the implications of space weathering on spectral properties and discuss the eruption timeline for each scenario. This research aims to gain insight into Mercury’s volcanic history and the processes that have shaped its surface over time.

Abstract Since Mariner 10 first imaged Mercury in 1974, tectonic landforms, of which shortening structures dominate, have been well documented. Most tectonic structures on Mercury are thought to have formed, and been most active, early in the planet’s history but here we report the discovery of widespread young extensional grabens. These landforms occur as secondary tectonic features on larger, compressional tectonic structures and indicate continued activity of the parent structure. Extensional grabens are 10s to 100s of metres deep, tens of km in length and generally less than one kilometre wide. We calculate that they are ~300 million years old or younger, otherwise impact gardening would mask their signature. Together, the global distribution of extensional grabens and their young age provide compelling evidence that many of Mercury’s shortening structures have continued to move until geologically recent times.

We present the results of geological mapping of Mercury’s Derain (H10) quadrangle (0°-72°E and 22.5°N-22.5°S) using data from the MESSENGER spacecraft. The map is presented on a scale of 1:3,000,000, for which linework was drawn at 1:300,000. We distinguish three major morphological plains units: Smooth, Intermediate, and Intercrater Plains. We produced two versions of the map, with craters classified according to a 3- and 5-class degradation system. This allows compatibility with other MESSENGER-era maps and Mariner 10-era maps. This map will help provide science context for the ESA-JAXA BepiColombo mission to Mercury.