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Analyses of measurements made by MERTIS1 (MErcury Radiometer and Thermal Infrared Spectrometer) during the BepiColombo mission's close flyby 2 of Venus (FB2) have already demonstrated the instrument's capacity to explore the planet's mesosphere at near equatorial latitudes. The MERTIS instrument was designed to study the hot surface of Mercury. It performed well beyond its design limits when analyzing the Venusian mesosphere because of the much lower radiances. MERTIS’ measurements are the first spectrally resolved observations of Venus in the thermal spectral range longward of 5 µm since the Venera-15 Fourier spectrometer experiment in 19832. It could be shown that MERTIS FB2 data enable reliable retrievals of mesospheric temperature profiles and cloud parameters between 60 and 75 km altitude. They are in good agreement with the results of the Venera-15 mission. This indicates the stability of the Venusian atmosphere on time scales of decades3,4.In this paper we discuss preliminary results from MERTIS measurements of the first flyby (FB1) in October 2020. During the first flyby the spacecraft approached the planet from the solar direction over the dayside. The closest approach (CA) occurred at about 11,000 km distance above the evening terminator of the planet, and then the spacecraft moved away from the planet to the anti-solar direction. In this time the apparent size of Venus increased from slightly larger than one MERTIS pixel (0.7 mrad) to more than 1 degree. MERTIS performed close-up dayside observations from early morning to late afternoon via noon time on Venus at latitudes between 50°S and 85°N and obtained about 785,000 hyperspectral observations with the spectrometer channel. Thus, FB1 observations permit much larger latitude coverage from 50°S to 85°N compared to FB2. To process the FB1 data in terms of both a reasonable signal-to-noise ratio and comparable observing conditions, individual spectra were averaged over 5° latitude belts and 0.5 h local time intervals. We further excluded extreme observation geometries for latitudes northward of 80°N and southward of 40°S as well as very weak spectra. As a result, we are able to generate a reliable data base for use in radiative transfer analyses for the Venusian mesosphere. We present preliminary results on the temperature fields of the mesosphere as a function of local time, altitude, and latitude. Hiesinger, H. et al. Space Sci. Rev. 216, 6 (2020).Oertel, D. et al. Adv. Space Res. 5, 25-36 (1985).Arnold, G. et al., SPIE Optic+Photonics, San Diego, Proceedings Volume 12233, doi.org/10.1117/12.2632548 (2022).Helbert, J. et al. submitted to Nature Astronomy (2023).

We propose that the observed enrichment of sulfur at the surface of Mercury (up to 4 wt.%) is the product of silicate sulfidation reactions with a S-rich reduced volcanogenic gas phase. Here, we present new experiments on the sulfidation behavior of olivine, diopside, and anorthite. We investigate these reaction products, and those of sulfidized glasses with Mercury compositions previously reported, by mid-IR reflectance spectroscopy. We investigate both the reacted bulk materials as powders, as well as cross-sections of the reaction products by in-situ micro-IR spectroscopy. The mid-IR spectra confirm the presence of predicted reaction products including quartz. The mid-IR reflectance of sulfide reaction products, such as CaS (oldhamite) or MgS (niningerite), is insufficient to be observed in the complex run products. However, the ESA/JAXA BepiColombo mission to Mercury will be able to test our hypothesis by investigating correlated abundances of sulfides with other reaction products such as quartz.

In a study to provide ground truth data for mid infrared observations of the surface of Mercury with the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument onboard the ESA/JAXA BepiColombo mission, we have studied 17 synthetic glasses. These samples have the chemical compositions of characteristic Hermean surface areas based on MESSENGER data. The samples have been characterized using optical microscopy, EMPA and Raman spectroscopy. Mid infrared spectra have been obtained from polished thin sections using Micro FTIR, and of powdered size fractions of bulk material (0-25, 25-63, 93-125 and 125-250 micron) in the 2.5 to 18 micron range. The synthetic glasses display mostly spectra typical for amorphous materials with a dominating, single Reststrahlen Band (RB) at 9.5 micron to 10.7 micron. RB Features of crystalline forsterite are found in some cases at 9.5 to 10.2 micron, 10.4 to 11.2 micron, and at 11.9 micron. Dendritic crystallization starts at a MgO content higher than 23 wt.% MgO. The Reststrahlen Bands, Christiansen Features (CF), and Transparency Features (TF) shift depending on the SiO2 and MgO contents. Also a shift of the Christiansen Feature of the glasses compared with the SCFM (SiO2/(SiO2+CaO+FeO+MgO)) index is observed. This shift could potentially help distinguish crystalline and amorphous material in remote sensing data. A comparison between the degree of polymerization of the glass and the width of the characteristic strong silicate feature shows a weak positive correlation. A comparison with a high-quality mid-IR spectrum of Mercury shows some moderate similarity to the results of this study, but does not explain all features.

We have analyzed 14 impact melt glass samples, covering the compositional range from highly felsic to mafic/basaltic, as part of our effort to provide mid-infrared spectra (7–14 µm) for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer), an instrument onboard of the ESA/JAXA BepiColombo mission. Since Mercury was exposed to many impacts in its history, and impact glasses are also common on other bodies, powders of tektites (Irghizite, Libyan Desert Glass, Moldavite, Muong Nong, Thailandite) and impact glasses (from the Dellen, El'gygytgyn, Lonar, Mien, Mistastin, and Popigai impact structures) were analyzed in four size fractions of (0–25, 25–63, 93–125 and 125–250 µm) from 2.5 to 19 µm in bi-directional reflectance. The characteristic Christiansen Feature (CF) is identified between 7.3 µm (Libyan Desert Glass) and 8.2 µm (Dellen). Most samples show mid-infrared spectra typical of highly amorphous material, dominated by a strong Reststrahlen Band (RB) between 8.9 µm (Libyan Desert Glass) and 10.3 µm (Dellen). Even substantial amounts of mineral fragments hardly affect this general band shape. Comparisons of the SiO2 content representing the felsic/mafic composition of the samples with the CF shows felsic/intermediate glass and tektites forming a big group, and comparatively mafic samples a second one. An additional sign of a highly amorphous state is the lack of features at wavelengths longer than ∼15 µm. The tektites and two impact glasses, Irghizite and El'gygytgyn respectively, have much weaker water features than most of the other impact glasses. For the application in remote sensing, spectral features have to be correlated with compositional characteristics of the materials. The dominating RB in the 7–14 µm range correlates well with the SiO2 content, the Christiansen Feature shows similar dependencies. To distinguish between glass and crystalline phases of the same chemical composition, a comparison between CF the SCFM index (SiO2/(SiO2 + CaO + FeO + MgO)) ( Walter and Salisbury [1989 ] J. Geophys. Res., 94, 9203–9213) is useful, if chemical compositional data are also available.

In order to provide spectral ground truth data for remote sensing applications, we have measured mid-infrared spectra (2–18 µm) of three typical, well-defined lithologies from the Chelyabinsk meteorite that fell on February 15, 2013, near the city of Chelyabinsk, southern Urals, Russia. These lithologies are classified as (a) moderately shocked, light lithology, (b) shock-darkened lithology, and (c) impact melt lithology. Analyses were made from bulk material in four size fractions (0–25 µm, 25–63 µm, 63–125 µm, and 125–250 µm), and from additional thin sections. Characteristic infrared features in the powdered bulk material of the moderately shocked, light lithology, dominated by olivine, pyroxene and feldspathic glass, are a Christiansen feature (CF) between 8.5 and 8.8 µm; a transparency feature (TF) in the finest size fraction at ∼13 µm, and strong reststrahlen bands (RB) at ∼9.1 µm, 9.5 µm, 10.3 µm, 10.8 µm, 11.2–11.3 µm, 12 µm, and between 16 and 17 µm. The ranges of spectral features for the micro-FTIR spots show a wider range than those obtained in diffuse reflectance, but are generally similar. With increasing influence of impact shock from ‘pristine’ LL5 (or LL6) material (which have a low or moderate degree of shock) to the shock-darkened lithology and the impact melt lithology as endmembers, we observe the fading/disappearing of spectral features. Most prominent is the loss of a ‘twin peak’ feature between 10.8 and 11.3 µm, which turns into a single peak. In addition, in the ‘pure’ impact melt “endmember lithology” features at ∼9.6 µm and ∼9.1 µm are also lost. These losses are most likely correlated with decreasing amounts of crystal structure as the degree of shock melting increases. These changes could connect mid-infrared features with stages for shock metamorphism (Stoffler et al., 1991): Changes up to shock stage S4 would be minor, the shock darkened lithology could represent S5 and the impact melt lithology S6 and higher. Similarities of the Chelyabinsk spectra to those of other LL chondrites indicate that the findings of this study could be related to this group of meteorites in general.

In this study we investigated the previously observed young resurfacing absolute model ages at the floor of Occator crater on dwarf planet Ceres on the basis of Dawn data. These young resurfacing absolute model ages have been interpreted to represent the deposition of cryovolcanic material >10 Myr after the formation of Occator crater. In our study we investigated whether these resurfacing events are caused by deposition of cryovolcanic material, or if seismic shaking related to the formation or reactivation of prominent fracture systems at the floor of Occator crater might be responsible for the resurfacing. We chose 22 different count areas with differing distances to the fractures and determined absolute model ages of these areas by performing crater size-frequency distribution measurements. Most of our measurements show the formation age of Occator crater (∼21 Ma) as background age, but also different sets of resurfacing ages, varying from 3.7 Ma to 9.2 Ma. A trend towards younger absolute model ages with decreasing distance to fractures is not supported by our data. Thus, we conclude that seismic shaking might not be responsible for the young resurfacing events spread all over the floor of Occator crater. Moreover, our investigations show that target property effects and differing image resolutions do not affect our measurements significantly. Consequently, deposition of young cryovolcanic material seems to be the most plausible geologic process being responsible for the observed young resurfacing ages.

The lithosphere of the Moon has been deformed by tectonic processes for at least 4 billion years, resulting in a variety of tectonic surface features. Extensional large lunar graben formed during an early phase of net thermal expansion before 3.6 Ga. With the emplacement of mare basalts at ~3.9 – 4.0 Ga, faulting and folding of the mare basalts initiated, and wrinkle ridges formed. Lunar wrinkle ridges exclusively occur within the lunar maria and are thought to be the result of superisostatic loading by dense mare basalts. Since 3.6 Ga, the Moon is in a thermal state of net contraction, which led to the global formation of small lobate thrust faults called lobate scarps. Hence, lunar tectonism recorded changes in the global and regional stress fields and is, therefore, an important archive for the thermal evolution of the Moon. Here, we mapped tectonic features in the non-mascon basin Mare Tranquillitatis and classified these features according to their respective erosional states. This classification aims to give new insights into the timing of lunar tectonism and the associated stress fields. We found a wide time range of tectonic activity, ranging from ancient to recent (3.8 Ga to < 50 Ma). Early wrinkle ridge formation seems to be closely related to subsidence and flexure. For the recent and ongoing growth of wrinkle ridges and lobate scarps, global contraction with a combination of recession stresses, diurnal tidal stresses, as well as with a combination of SPA ejecta loading and true polar wander are likely.

Mobile robotic surface platforms are critical for the exploration of the solar system. In the past, robotic ex-plorers were limited by their abilities to navigate and traverse challenging terrain, such as boulder fields andslopes steeper than 15°. The ESA topical team ’LEAP’ studies the feasibility of using an innovative loco-motion system - a dynamically walking quadrupedal robot - to address challenging terrain and unlock hard-to-reach, but high-reward scientific targets. Here, we present preliminary results of this assessment, includ-ing 1) the selection of several promising science targets that are inaccessible by traditional means, 2) ourrobotic platform, 3) a provisional payload suite that can address relevant science questions, and 4) sugges-tions for future hard- and software developments. Plain Language SummaryGeologically interesting sites, such as outcrops, slopes, and caves, are often difficult to access. TheESA Topical team ’LEAP’ studies the feasibility of using an innovative locomotion platform - a leggedrobot - to access such sites, potentially enabling unprecedented sampling and science opportunities. Inthis work, we present our preliminary findings. 1. Mission scenarioTriggered by ESA’s call for ideas(https://tinyurl.com/mrxn8f5u) on exploring the Moon with a large European lander (L3), we haveformed a topical team to assess the potential of an innovative robotic platform to provide access tohigh-risk & high-reward targets on the moon(Fig. 1). ’LEAP’ (Legged Exploration of theAristarchus Plateau) is considering science targets on the Aristarchus plateau (AP). AP is a geologically uniquely diverse region that hosts one of the highestconcentrations of volcanic features - including an irregular mare patch (IMP) and widespread evidencefor multiphased volcanism (Glotch et al., 2020). While our analysis of the plateau and the literature iscurrently ongoing, we identified four geologic targets that appear to be inaccessible by traditional surfaceassets, but could potentially enable transformational science: #1 the flank and peak of Herodotus Mons, #2pits in Aristarchus’ IMP, #3 skylights and fractured terrain around Aristarchus crater’s central peak, and#4 the bright outcrops at Cobra Head (Fig. 2a). The identified targets enable the study of a largenumber of highly relevant science objectives, including many of ESA’s priority goals, such as: A) theanalysis of new and diverse (silicic, basaltic, and other) samples, B) the detection & characterizationof volatiles, C) deployment of geophysical instruments, D) the characterization of the lunar dust envi-ronment, while E) demonstrating unprecedented surface mobility (ESA, 2019). Sites could be traversedby one or multiple quadruped robots within one lunar day, starting from, for example, ESA’s L3(https://tinyurl.com/2p8vfd9n). 2 Legged robots for explorationLegged locomotion systems are ideal to navigate difficult terrain on Mars or the Moon. They are lesslikely to get stuck in loose regolith and can traverse slopes up to 25° or steeper, including large rocksand other obstacles. LEAP uses the quadrupedal robot ANYmal (Hutter et al., 2017). ANYmal canadapt its walking mode to different environmental conditions. These modes range from energy-efficient,over traversing, to stabilized walking. The latter allows to satisfy measurement requirements of theinstruments. The traversing mode allows for 0.5 m/s to cross low-risk & low-interest areas efficiently.ANYmal can use its limbs to manipulate the environment, including trenching and scraping. ANYmal’slocomotion system proved its reliability in dusty environments as the joints need to only allow rotations ofup to 270° and are sealed against dust. The robot can recover and get back on its feet from any position andis able to fall back to three- or even two-legged walking if one or two legs fail.3. InstrumentationThe initial design has a payload mass budget of 15 kg and provides between 15 W to 100 W ofpower, depending on the current thermal loads. For the (autonomous) operation of the robot, two baselineinstruments are used: lidars and cameras, which provide 3D information for navigation. Depending on the mission profile, a variety of additional science payloads can be attached to therobot, such as a ground-penetrating radar, a gravimeter, neutron or mass spectrometers or asampling arm, & VIS/NIR/UV imager, and a Raman spectrometer. The current list of pay-loads allows the robot to address a wide range of science questions related to geomorphology, mineralogy,and petrography. We are currently refining the selection of payloads. Acknowledgements This topical team is supported by ESA under grantagreement 4000135310/21/NL/PA/pt.

Introduction: The dating of geological surfaces on the Moon is crucial for understanding its geological history and evolution. The measurement of Crater Size-Frequency Distributions (CSFDs) can be used for determining relative and absolute ages of surfaces. Older surfaces reflect more and larger craters than younger geological units [1-4]. To determine the relative surface ages, a production function (PF) is constructed to which the CSFD is fitted. One frequently used PF was empirically-derived by measuring craters on reference surfaces using Apollo era data (Neukum, 1983 [1]), which was revised in 2001 [5], and is valid for crater diameters of 10 m - 300 km and 10 m - 100 km, respectively. With increased image resolution of more recent missions [e.g., 6], it has been possible to measure CSFDs for crater diameters down to a few meters. Therefore, it would be beneficial to be able to extend the PF to smaller crater diameters, which would allow the determination of relative and absolute ages for young/small geological units. A crucial influence on small craters formed in the strength regime are target properties, which has been investigated in several studies [e.g., 7, 8, 9]. Therefore, we aim to perform the crater counts exclusively on continuous ejecta blankets. Secondary craters [e.g., 10-12] influence the CSFD as well and can contaminate the count area, causing a steeper CSFD-slope [e.g., 10, 13, 14]. To avoid this effect and obtain the cleanest PF possible, we selected ejecta areas derived from young Copernican-aged craters. This minimizes the number of field secondary craters on the ejecta and also avoides major degradation of the small craters [15, 16]. However, the identification of self-secondary craters remains problematic, since they occur irregularly distributed on the ejecta blankets and often have morphologies similar to primary craters [e.g., 12, 13]. Method: We used Lunar Reconnaissance Orbiter Narrow Angle Camera (NAC) images [6] including M180509194LE, M1122929850LE and M103831840LE/RE at Giordano Bruno (GB), M1107052575RE and M1112971104RE at Moore F, M129187331LE/RE at North Ray (NR), M119754107RE at South Ray (SR) and M114064206LE at Cone. The resolutions vary between 1.6 m/px and 0.5 m/px, the incidence angles are from 54° to 78°. The CSFDs were measured in ArcGIS with the CraterTools add-in of [18] and displayed in CraterStats with pseudo-log binning [19]. Two areas were investigated at Cone, three at GB, Moore F and SR, respectively. Four areas were investigated by [17] at NR. The selected counting areas are all on the ejecta blakets of the named craters. Results: Similar to [17] we combined the statistics from the separate count areas into one file and display these CSFDs in a cumulative plot in Figure 1. Figure 1: Display of the combined CSFDs at GB (green), Moore F (blue), NR (violet), SR (red) and Cone (orange), respectively. The vertical lines of individual data points represent the error bars. The comparison between the individual CSFD-slopes at GB, Moore F, NR, SR and Cone generally show slightly steeper slopes than the nominal -3 slope of [1] for crater diameters between 10 m and 23 m (in our case 20 m, see Table 1). Table 1: Display of the considered crater diameter range and the respective CSFD-slopes. Discussion: We found that the CSFD-slopes on the ejecta blakets of the investigated craters show a tendency regarding the crater diameter. Considering only diameters ≤10 m the slope is marginally shallower than Neukum’s [1] -3 slope, except at GB, which might be explained through secondary cratering. This trend was also observed by [15] (and references therein) and [20] who investigated NR, Cone, Copernicus and Tycho. This might suggest that CSFDs of young Copernican craters have actually a slightly shallower slope at smaller crater diameters. Another possible explanation is the faster degradation of smaller craters [e.g., 21]. Further effects might be the coverage of ejecta material of nearby craters; NR (52.3 Ma [20]), might be influenced by the ejecta of SR (2 Ma [22]), SR by Baby Ray. Moreover, larger craters in two areas at NR and Cone probably penetrated through the ejecta blanket, which can lead to mixed target propertie effects. Further investigations are required to quantify the effects of secondary cratering, target properties, crater degradation or impactor flux on the determination of our CSFDs. Additional investigation is necessary to determine at which crater diameter the slope becomes shallower or if a transition zone is present. Acknowledgments: This Project is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 263649064 – TRR 170. References: [1] Neukum (1983), NASA TM-77558. [2] Öpik (1960), RAS 120(5), 404-41. [3] Shoemaker et al. (1970), Science, 167 (3918), 452-455. [4] Baldwin (1971), Icarus, 14, 36-52. [5] Neukum et al. (2001), Space Sci. Rev., 96, 55. [6] Robinson et al. (2010), Space Sci. Rev. 150, 81-124. [7] van der Bogert et al. (2010), LPSC 41, #2165. [8] Wünnemann et al. (2011), Proceedings of the 11th hypervelocity impact symposium., Vol. 20. [9] van der Bogert et al. (2017), Icarus, 298, 49-63. [10] McEwen and Bierhaus (2006), Annu. Rev. Earth Planet. Sci. 34, 535-567. [11] Xiao and Strom (2012), Icarus 220, 254. [12] Zanetti et al. (2017), Icarus 298, 64-77. [13] Plescia et al. (2010), LPSC 41, #2038. [14] Plescia and Robinson (2011), LPSC 42, #1839. [15] Moore et al. (1980), Moon and Planets, 23, 231-252. [16] Fassett and Thomson. Journal of Geophysical Research: Planets 119.10, 2255-2271. [17] Hiesinger et al. (2012), JGR 117, E00H10. [18] Kneissl et al. (2011), PSS 59, 1243-1254. [19] Michael et al. (2016), Icarus 277, 279-285. [20] Williams et al. (2014), Icarus 235, 23-36. [21] Mahanti et al. (2018), Icarus, 299, 475-501. [22] Stöffler and Ryder (2001), Space Sci. Rev., 96, 9-54.

Introduction The MErcury Radiometer and Thermal Infrared Spectrometer (MERTIS) onboard BepiColombo is designed to study and map Mercury surface mineralogy and temperatures. It combines an imaging push-broom infrared spectrometer (TIS, 7-14 µm) with a radiometer (TIR, 7-40 µm) that share the same in-flight optics, electronics, and calibration unit [1]. During the two Venus flybys of BepiColombo spacecraft in October 2020 and August 2021, MERTIS-TIS acquired several hundred thousand spectra in the mid-infrared range with spectral resolution down to 90 nm [2, 3, 4]. The MERTIS measurements were the first spectrally resolved observations of Venus in the mid-IR range since the Venera 15 mission in 1983 [8]. We report on the results of MERTIS mid IR measurements and show average brightness temperature spectra. Basing on a multi-channel radiative transfer simulation and retrieval algorithm we extract atmospheric temperature profiles and cloud parameters of Venus’ upper troposphere and mesosphere. Method A multi-channel radiative transfer simulation and retrieval algorithm has been adapted to investigate MERTIS-TIS data and to extract atmospheric temperature altitude profiles and cloud mode factors MF1/2 of Venus’ atmosphere. The Radiative Transfer Model (RTM) includes the discrete ordinate package DISORT [5]. It considers absorption, emission, and multiple scattering by gaseous and particulate atmospheric constituents and makes simultaneous use of information from different spectral ranges of an individual spectrum [6,7]. Mesospheric temperature profiles are retrieved using Smith’s relaxation method [8]. It employs initial and measured brightness temperatures in the 15 µm CO2 band. The results of the MERTIS measurements were compared with mid-infrared data recorded by the FS-1/4 spectrometer (PMV) aboard the Venera-15 mission in 1983 [8]. Results We show that Venusian mesospheric parameters like temperature profiles and cloud properties can reliable determined from MERTIS flyby data (Fig. A). The short-wave edge of the 15-µm CO2 band was used to determine atmospheric temperature profiles in an altitude range of about 58-77 km (Fig. B). The retrieved temperature profiles well agree both with VIRA [9] and corresponding profiles obtained from Venera 15 PMV data. Atmospheric cloud factors were investigated from MERTIS spectral data around 10 µm. They are also well coinciding with earlier analyses. Still ongoing refinements of calibration will allow the use of data between 7 and 10 μm for the analysis of further atmospheric properties. Fig. MERTIS-TIS FB2, A: Comparison of measured and simulated MERTIS brightness temperature spectra, B: Comparison of initial and retrieved temperature profiles. References [1] Hiesinger, H. and Helbert, J., Planet. Space Sci. 58, (2010). [2] Maturilli, A., et al., 52nd LPSC, 1435, (2021). [3] Helbert, H., et al., 52nd LPSC, 1521, (2021). [4] Arnold, G., et al., SPIE Optics+Photonics, IR Remote Sensing and Instrumentation XXIX, 1183009, (2021). [5] Stamnes, K. et al., Appl.Opt. (12), 2502-2509, (1988). [6] Haus, R., Kappel, D., Arnold, G., Icarus 232C, 232-248, (2014) [7] Haus, R., Kappel, D., Arnold, G., Planet. Space Sci. 89, 77-101, (2013). [8] Smith, W.L., Appl. Opt.9(9), 1993-1999, (1970). [8] Oertel, R. et al., Adv. Space Res. 5(9), 25-36, (1985). [9] Zasova, L.V. et al., Cosmic Res. 44(4), 364-383, (2006).

Introduction: The Multi-Temporal Database of Planetary Image Data (MUTED) is a comprehensive web-tool to identify and to access orbital images of Mars, Moon, and Mercury. The database is available at https:\\muted.wwu.de and provides various tools for the identification of multi-temporal images of the major space missions as a basis for diverse surface change analyses [1, 2]. Multi-temporal images, i.e., images covering the same surface at different times, are essential for the analysis and understanding of short-term, long-term, and seasonal processes on the surface of Mars, Moon, and Mercury. Tools and services: The multi-temporal database combines several tools for the selection, visualization, and processing of planetary data. Users can explore the planetary bodies using diverse global base maps (spectral, topographic, geologic information). The planetary bodies are visualized as spheres or in Mercator map projection. On top of the global base maps, planetary data of various missions can be visualized globally or for a user-defined region of interest. The data can be filtered by various attributes (e.g., acquisition date or solar longitude). Additional information, e.g., data acquisition time, the temporal and spatial context, as well as preview images and raw data download links are available for each image. Figure 1: User interface of the multi-temporal database showing the intersections of CTX images with a temporal distance of 7 days (white polygons). Areas with a high temporal coverage, e.g., the pole regions as well as selected observation sites are ideal to study short-term surface changes, e.g., expansion and retreat of the seasonal surface ice and frost. A key feature of the multi-temporal database is the intersection tool, that visualizes the intersection areas of overlapping images (Fig. 1). Based on user-defined parameters, such as datasets and the time interval between overlapping images, users are able to identify the spatial intersections on top of the global base maps. High-resolution previews as well as metadata, including e.g., download links of multi-temporal images provide the basis for diverse analyses of short- or long-term surface changes and processes. The timeline tool is another key feature to explore the multi-temporal coverage of planetary surfaces. Images within an area of interest can be displayed in chronological order, allowing a quick overview of data availability and temporal context. Amongst others, it can be used to identify an overlapping dataset with the smallest or the longest time-interval (Fig. 2). In addition to data identification tools the multi-temporal database offers a data processing service in order to facilitate the access to planetary image data. The processing service helps to reduce the amount of data as well as processing time by providing image data on demand, fitting to the user-defined research area and settings. After processing of the images which ​includes the calibration, georeferencing, and clipping of the images to the user-defined AOI, the processed images are available in a standard image file format (GeoTIFF). Figure 2: User interface of the multi-temporal database showing the temporal coverage of HiRISE images for a research area at Green Crater in the Noachis Terra region in the southern hemisphere of Mars. The timeline tool at the bottom reveals a good temporal coverage to analyze dune migration over several martian years. Scientific applications: The multi-temporal database enabled several studies on past and present-day changes of the surface of Mars [2-6]. In particular, the database has been used in recent projects on the contemporary activity of dark slope streaks [2-4] and martian gullies [5, 6]. Furthermore, the database has been used for data selection as a basis for geological mapping in several projects [e.g., 7, 8]. Acknowledgments: This research has been funded and supported by the German Aerospace Agency (DLR) (Grant # 50 OO 2102). References: [1] Erkeling et al. (2016) PSS, 125, 43-61. [2] Heyer et al. (2018) PSS, 159, 56-65. [3] Heyer et al. (2019) Icarus, 323, 76-86. [4] Heyer et al. (2020) Icarus, 351, 113951. [5] Raack et al. (2020) Icarus, 350, 113899. [6] Sinha et al. (2020) Icarus, 352, 113979. [7] Bernhardt et al. (2019) PSS, 321, 171-188. [8] Cairns et al. (2020) LPSC 51, #1929.

Context – The Bepi-Colombo mission (ESA-JAXA) will reach Mercury in December 2025 (Benkhoff et al. 2021). Onboard, the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS; Hiesinger et al. 2010) will study the surface composition and map the surface temperature. The interpretation of the MERTIS data requires a dedicated thermal model, able to predict accurately the surface temperature at any location and any time on Mercury. Previous works on this topic have been performed by, e.g., Wohlfarth et al. (2021, 2022). The scientific objectives are to produce thermal inertia maps, to look for thermal anomalies (cold or hot spots), to look at the icy environment (polar cups craters), and to determine the thermal continuum for compositional studies.Thermal model – We developed a thermal model that considers solar heating, thermal emission, heat conductivity, projected shadows, and self-heating (i.e. mutual heating of facets seeing each other’s). This thermal model is inherited and adapted from our previous works on small bodies (e.g. Groussin et al. 2004). Our thermal model is applied to the USGS Digital Elevation Model of Mercury with 20 million facets, and run for six revolutions of Mercury, i.e. three complete thermal cycles, until convergence. The geometry is computed by the OASIS software (Jorda et al. 2016). The thermal model is parallelized, and for a given set of parameters (typically for a given thermal inertia), it runs in two hours for a polar cup (1.4 million facets) on a 24 cores CPU PC. The output of the model is the surface temperature map, for any position (time) of Mercury on its orbit, and for various thermal inertia. The surface temperature can then be used to compute the spectral energy distribution, to be compared with the MERTIS data.Preliminary results – We applied our thermal model to the Northern polar cup of Mercury. Figure 1 shows the maximum surface temperature over one complete thermal cycle, i.e. two revolutions of Mercury, for a thermal inertia of 50 J/K/m2/m1/2. The maximum temperature varies strongly across the surface, and many surface morphologies like craters are still visible in the thermal infrared, with the side facing the pole being colder than the side facing the equator. Many blue patches are also visible, inside craters, and correspond to areas of permanent shadows, where the temperature is constantly below 150 K, allowing the presence of exposed water ice. Those results are similar to those obtained by Paige et al. (2013), also discussed by Chabot et al. (2019).Perspectives – The current shape model, with 20 million facets, provides a spatial resolution of 3.7 km2 per facet on average, while the MERTIS instrument will have a spatial resolution up to 0.1 km2 per pixel (at 400 km altitude). Even though the topography is crucial for thermal models, unresolved surface roughness further influences the thermal behavior, but occurs on much smaller scales of approximately 0.5 – 1 cm (Bandfield et al. 2015). The current standard is therefore to include a model that addresses surface roughness to mitigate directional effects, which are due to shadowing and self-heating. We will do this by adding fractal roughness, as we already did in the past for small bodies in particular (Davidsson et al. 2015), as illustrated in Figure 2.ReferencesBandfield et al. 2015, Icarus 248, 357Benkhoff et al. 2021, Space Science Review 217, 90Chabot et al. 2019, Mercury – The view after MESSENGER, Cambridge Univ. Press, 13Davidsson et al. 2015, Icarus 252, 1Groussin et al. 2004, Astronomy & Astrophysics 419, 375Hiesinger et al. 2010, Planetary and Space Science 58, 144Jorda et al. 2016, Icarus 277, 257Paige et al. 2013, Science 339, 300Wohlfarth et al. 2021, LPSC conference 52, 2548Wohlfarth et al. 2022, LPSC conference 53, 2431Figure 1 – Maximum surface temperature on the Northern polar cup of Mercury, for a thermal inertia of 50 J/K/m2/m1/2. The blue areas are in permanent shadows, inside craters, with a temperature constantly below 150 K, allowing the presence of exposed water ice. Figure 2 – Example of a terrain with 32000 facets, on which we added fractal roughness, with a fractal dimension of 2.2.

Introduction: Mercury’s surface is exposed to a multitude of surface altering effects that have a significant influence on its optical properties. Impact events – small or large, are one of the major surface-altering agents. Inferred from hypothetical modal abundances[1] graphite can comprise up to 4wt% on Mercury’s surface. Graphite as a possible stable phase on Mercury can explain the relatively low albedo of the planet[2]. Our experimental setup probes the hypothetical impact into a graphite- and olivine–bearing, pyroxene-rich (Px(En87)=68wt%;Ol(Fo91)=29wt%,C=3wt%) surface. The effect of post-shock heating and pressure on a powder comprised of silicates with grain sizes ≤125 µm and graphite(hexagonal) was simulated in a classic shock recovery experiment[3]. The experiments were performed in the framework of the BepiColombo mission to Mercury. The onboard Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) will send thermal emissivity data once it reaches the Hermean orbit in 2025. A spectral database for mid infrared data is currently set up at the Institut für Planetologie in Münster. Published mid infrared data will soon be available and sample related spectral information of interest can be traced via assigned IDs (e.g., IDxxx). Experimental set-up and µ-FTIR: One aliquot of the prepared powder mixture served as a blank(ID467) and was not shocked, the second (ID464) aliquot was filled into an ARMCO-Fe container. The cavity (ø=16mm;depth=2mm) that held the powder was lined with tantalum foil (thickness=50 µm) in order to avoid Fe0-metal contamination from the container. Graphite foil particles vary in size (mean=500µm). The foil was cut with a razor to avoid smearing. The calculated peak pressure at the steel/sample interface reached ca. 60 GPa. Pore space was crushed upon impact and contributed to increase the post-shock temperature significantly[4]. Preliminary spectral results were obtained with a Bruker Hyperion 3000. Spectra were measured in reflectance between 3950cm-1-700cm-1. Reflectivity was calculated by measuring a gold standard equaling the sample’s surface roughness. We used a 100x100 µm2 knife edge aperture to limit obtained spectral data from defined regions of interest (ROIs) and integrated over 256 scans to improve the signal/noise ratio. Preliminary spectral results were obtained from both aliquots, ID467 and ID464. ID464 material was extracted from the steel container, from which spectral information were obtained (Fig.1bottom) and are compared to spectral data of the unshocked aliquot (Fig.1top). Figure 1 top&bottom: ID467 spectra(top). Graphite (bright material) embedded in light grey silicate matrix. Areas with indices in micrograph correlate with spectra of same numbering. Yellow highlighted rectangles are magnified for clarity, RBs are labelled and discussed in text. ID464 spectra are plotted below. Pyroxene is dominant in both aliquots. The CF is located at 1187cm-1 in ID464. Both aliquots show comparable reflectance intensities. Yellow arrows denote CO2-related adsorption in ID467. Results and discussion: We observed a dark pumice-like mass protruding perpendicular to the shockwave propagation direction. The center part of the sample shows a glassy luster (e.g.,Fig.2) which is indicative of melt formation. Figure 2: Light microscope image of graphite (dark) embedded in “fluffy”glassy matrix (arrow). Scale bar is 100 µm. ID464 compacted entirely during impact and shows a clearly distinguishable Christiansen feature (CF; a material characteristic reflectance minimum) at 1187cm-1 (similar to CF(En87)=1193cm-1. The CF of ID467 is difficult to determine. The shallowing of the adsorbed CO2-related absorption band[5] at 3677cm-1 steepens the slope towards shorter wavenumbers. Glassy material was identified in many areas. However, crystalline pyroxene surviving the impact is easily distinguished in the electromagnetic range between 1187cm-1-700cm-1, where vibrational normalmodes/or Reststrahlenbands (RBs) of silicates typically occur. RB1 of ID464 (see Fig. 1 bottom) has a shoulder at 1131cm-1, a double peak at 1103cm-1 and 1074cm-1, and another shoulder at 1043cm-1. RBs of both silicate starting materials occur in this range (En87 at 1131cm-1,1107cm-1,and 1056cm-1, and Fo91 at 1063cm-1and 1056cm-1). The envelope of the RB1 region is identical in ID464 and 467, however, a shoulder peak at 1043cm-1 missing in the unshocked, appears in the shocked aliquot and broadens the base of RB1. Pure En87 has a remarkably invariant(energy-wise) RB at 1010cm-1 (ID467) that shifted to 1006cm-1 in ID464. RB3 of the Mg-pyroxene typical “triplet-RBs” (RB3, RB4, RB5 in Fig. 1 top) at 979cm-1 is similarly invariant, however, olivine has a stable RB nearby, at 981cm-1[6]. This band is shifted to a weak shoulder at 973cm-1, either indicating the absence of olivine due to melt formation, or a shock related shift of the En87-associated RB3. Augmenting chemical analyses will help to disambiguate this. Silicate material in direct contact with graphite displays a foam like texture (Fig. 2). Graphite is an excellent thermal conductor. Silicates and graphite have a large density gradient, when shock waves traverse the individual phases, graphite-grains experience significantly higher post-shock temperatures, and thus help in melting the silicate fraction[7]. Shock-related “pumice” pressed toward the outer cylinder margins is dark and has large, entrained cavities. Future chemical and µ-FTIR analyses of the entire ID464 will improve our understanding of how graphite though chemically inert “catalyzes” processes that either not/or insufficiently take place in its absence. This work was funded by the DLR grants 50 QW 1701 and 50 QW 2201A. MERTIS group are A.N.S,A.M,H.H.,I.W.,M.P.R,K.E.B.,J.H.P.,J.H. The authors thank U.Heitmann, F.Spaleck, P.Pelka and M.Artmeier for careful sample and cylinder preparation References: [1] Vander Kaaden & McCubbin (2015), JGR: Planets, 120(2), 195-209 [2] Klima et al. (2018). Geophysical Research Letters, 45(7), 2945-2953. [3] Langenhorst & Deutsch (1994) EPSL, 125(1-4), 407-420. [4] Güldemeister et al. (2013) Meteoritics & Planetary Science, 48(1), 115-133 [5] Bianchi et al. (1994) Applied Catalysis A: General, 112(2), 219-235. [6] Stojic et al. (2021) Icarus, 357, 114162. [7] Moreau & Schwinger (2021) Physics of the Earth and Planetary Interiors, 310, 106630.

The mid-latitudes of Mars host a large amount of buried ice deposits [1], which bear a record on the very Late Amazonian climate evolution (~107 to 108 yr.) [2] and are a possible resource for future exploration [3]. The reconstruction of the history of these ice reservoirs and the characterization of their current state is critical to enable putting constraints on the interplay between climate change, volatile migration and landform evolution. Examination of terrestrial analogs can help to identify similarities and – equally important – differences between the response of buried ice on Mars and Earth to changing environmental parameters. Here we report on our long-term investigations of an ice-cored moraine on Svalbard, a proxy for mid-latitude debris-covered glacier on Mars [4]. Our study area is an ice-cored lateral moraine of Kongsvegen glacier on the southern shore of Kongsforden in NW Spitsbergen (Svalbard). This site is subject to rapid degradation by melting and redistribution of surficial sediment, e.g., by thaw slumps and debris flows [5]. We couple multi-year fieldwork with repeat remote-sensing observations. Fieldwork includes DGPS-supported monitoring of surface changes by several imaging methods comparisons to environmental data (e.g., [6]). In 2008, a flight campaign with HRSC-AX (an airborne version of DLR’s High Resolution Stereo Camera on Mars Express) provided orthoimages (20 cm/px) and a Digital Elevation Model (DEM; 50 cm ground sampling distance, GSD) [7]. In 2020 a repeat campaign with DLR’s MACS (Modular Airborne Camera System) achieved ground pixel sizes between 5 cm and 10 cm for RGB images, and 10 cm to 15 cm for NIR images. The associated DEM has the same resolution [8]. MACS also acquires TIR data,which we use to identify regions with anomalous temperatures (e.g., exposed ice). We use for detailed mapping of ice-rich viscous flow features on Mars [9]. This study focuses on the Nereidum Montes area in the northern part of the Argyre basin. Image analysis, mapping of landforms and documentation of results were carried out using the QGIS software. A difference DEM was generated to determine the elevation differences (i.e. volume changes) on the ice-cored moraine between 2008 and 2020. Hillshade layers were created for each dataset to facilitate quick visual identification of morphological changes. Slump scars were digitized in 2008 and 2020 on orthoimages and hillshade views, and prominent slumps of 2020 (most recent, visible and best preserved) have been geomorphologically mapped with a focus on buried dead ice, collapsed sediment, and the relative activity of mud flows. Image analysis and mapping of Martian landforms is currently ongoing. There are 4 areas of major activity within the ice-cored moraine (Fig.1.a) highlighted by the four red boxes b, c, d and e, with more than 10m of elevation losses. There are many areas showing a neutral balance in terms of topographic evolution (white pixels). Hillshade layers from 2008 (Fig.1.f) and 2020 (Fig.1.g) correspond to the area of box d and show that significant changes have occurred in 12 years, indicating a massive degradation of ice-cored moraine in the last decade. This also demonstrates that the general trend is towards a heterogenous loss of material. The slump scars appear to be concentrated in the same areas described above. In 2008, 85 scars were counted against 157 scars in 2020, i.e. almost twice as many. It also appears that the 2020 scars are following the outlines of high activity areas while the 2008 scars are within these areas. Regarding the detailed mapping of slumps, the area corresponding to the buried dead ice, mapped with the TIR channel, can vary in shape and size depending on the shape of headscarp and the other units, i.e. the collapsed sediments and the mudflows (Fig.2.b,d). The collapsed sediments are washed away by the mudflows. The mudflow seems more active near the previously exposed dead ice. Therefore, the degradation of ice-cored moraines takes place mainly through the melting of the ice, which leads to mass wasting and rapid degradation. As Mars does not have the same climatic conditions, it is interesting to see whether the same landforms can be found on it at a very local scale. The Mars case study displays gullies, arcuate ridges with small gullies superposed on their slopes, flow features and also possible sublimation features such as pitted terrain, broad pits, and lineated patterned ground (Fig.3.b). The area is also filled with washboard terrain which is only found at steep slopes, above the lobate flow feature. It is marked by a close alternation of closely-spaced scarps which are parallel to the contour lines (possible evidence for paraglacial sacking [10]). Tension cracks are also found at the ridges and parallel to gully headscarps indicating recent activity. These tension cracks may be similar to headscarp retreats on backwasting processes on ice-cored moraines (Fig.3.d). The ice-cored ridge or arcuate ridge may still undergo degradation. The first results show that the degradation processes are rather related to potential ice sublimation and that signs of melting ice, if they exist on Mars, are not strongly encountered, which is consistent with the studies on very Late Amazonian climate evolution. References [1] Levy, J. S. et al. (2014), J. Geophys. Res. Planets, 119, 2188– 2196. [2] Bramson, A. et al. (2021), Bull. Amer. Astron. Soc., 53(4), e-id. 115. [3] Putzig, N. et al. (2022) LPSC 53, #2443. [4] Petersen,E. et al. (2017) LPSC 48, #2966. [5] Bennett, M. et al. (2000) Geomorphology, 35, 21-40. [6] Boike, J. et al. (2018), Earth Syst. Sci. Data, 10, 355–390. [7] Hauber, E. et al. (2011), Geological Society of America, 483, 177–201. [8] DLR - Institut für Optische - Sensorsysteme, (2020). [9] Souness, C. and Hubbard, B. (2012), Progress in Phys. Geog. 36(2), 238-261. [10] Jawin, E. R. et al. (2018), Icarus, 309, 187-206.

Introduction: The IRIS (Infrared and Raman for Interplanetary Spectroscopy) laboratory generates mid-infrared spectra for the ESA/JAXA BepiColombo mission to Mercury. Onboard is a mid-infrared spectrometer (MERTIS-Mercury Radiometer and Thermal Infrared Spectrometer), which will allow to map the mineralogy in the 7-14 µm range [1, 2]. In order to interpret the future data, a database of laboratory spectra is assembled at the Institut für Planetologie in Münster (IRIS) and the DLR in Berlin. So far, we have studied for this purpose natural mineral and rock samples (e.g. 3, 4), impact melt rocks (e.g. 5, 6, 7) and meteorites (e.g. 8, 9, 10, 11). Furthermore, surface processes like regolith formations and space weathering were of interest (e.g. 12, 13, 14). Synthetic analogue materials have become one of the foci of our work, since they allow to produce ‘tailor-made’ materials based on remote sensing data and/or modelling and experiments. These are closer than natural terrestrial materials, which formed usually under different conditions as expected on Mercury [e.g. 1]. We synthesized analogs for surface regions of Mercury and other planetary bodies (15, 16, 17). In this part of our study, we present mixtures based on phase equilibria of peridotite and partial melt compositions which were studied under hermean mantle conditions - temperature, pressure, oxygen fugacity (18,19,20). These experiments suggested that the crustal mineralogy should be dominated by variable abundances of plagioclase, olivine, clino- and orthopyroxene, with unconstrained proportions of silicate glass. Based on the model mineralogy of representative results, we produced mineral/glass mixtures based on the Low-Mg Northern Volcanic Plains (NVP)(Y121, Y131, Y172), High-Mg NVP (Y143, Y144), Smooth Plains (Y140, Y143, Y144), Inter crater Plain and Heavily Cratered Terrains (IcP-HCT) (Y126, Y131, Y132, Y146), and High-Mg Province (Y126, Y131, Y146) [20]. Samples and Techniques: We conducted diffuse reflectance studies of sieved size fractions (0-25 µm, 25-63 µm, 63-125 µm and 125-250 µm) under vacuum conditions, ambient heat, and variable geometries. We used a Bruker Vertex 70v with A513 variable geometry stage. The results will be made available in the IRIS Database [1]. Results: First results show the Christiansen Feature (CF), a characteristic, easy to identify reflectance low (or emission high) ranging from 7.9 µm to 8.2 µm (always average of all size fractions). The Transparency Feature (TF), typical for the finest size fraction (0-25 µm) is in many mineral mixtures less pronounced than for pure mineral phases. Here the individual TF of the components result in a broad feature. The resulting spectra can be divided into three groups – such as dominated by a single glass feature at 9.6 – 9.9 µm, a second groups with forsterite bands 9.4 µm- 9.5 µm, 10.2 µm, 10.6 µm, 11.9 µm and 15.9 µm-16 µm, and a third dominated by pyroxene bands at 8.9-9.1 µm, 9.4-9.5 µm, 9.9 µm, 10.2 µm, 10.4-10.5 µm, 10.6 µm, 10.8-11 µm 11.1-11.3 µm and 11.4-11.6 µm. Plagioclase features, even when the phase is dominating the composition, are usually ‘overprinted’ by forsterite and pyroxene bands. Discussion: A classic way to connect an easy to identify spectral feature in the mid-infrared to the chemical bulk composition is using the CF and the SiO2 content. Both show a strong correlation for both terrestrial rocks [21] and a variety of synthetic analogue samples from earlier studies in this project [15, 16, 17] (Fig.1). Summary & Conclusion: In a next step, we will study these mixtures under more realistic conditions, i.e., high vacuum and high temperature, in order to better simulate the hermean surface. Also, these mixtures will be used to test spectral unmixing routines, which allow to identify abundances of single minerals in a complex mixture of phases. References: [1] Hiesinger et al. (2020) Space Sci. rev. 216, 110 [2] Benkhoff et al. (2022) Space Sci. Rev. 217, 90 [3] Reitze et al.(2020) Min. Pet. 114, 453-463 [4] Reitze et al.(2021) EPSL 554, 116697 [5] Morlok et al.(2016) Icarus 264, 352-368 [6] Morlok et al.(2016) Icarus 278, 162-179 [7] Reitze et al.(2021) JGR (Planets) 126, e06832 [8] Weber et al. (2016) MAPS 51, 3-30 [9] Morlok et al. (2017) Icarus 284, 431-442 [10] Morlok et al. (2020) MAPS 55, 2080-2096 [11] Martin et al. (2017) MAPS 52, 1103-1124 [12] Weber et al. (2020) EPSL 530, 115884 [13] Weber et al. (2021) EPSL 569, 117072 [14] Stojic et al. (2021) Icarus 357, 114162 [15] Morlok et al. (2017) Icarus 296, 123-138 [16] Morlok et al. (2019) Icarus 324, 86-103 [17] Morlok et al. (2021) Icarus 361, 114363 [18] Charlier et al. (2013) EPSL 363, 50-60 [19] Namur et al. (2016) EPSL 439, 117-128 [20] Namur and Charlier (2017) Nature Geosci. 10, 9-13 [21] Cooper at al. (2002) JGR 107, 5017-5034 [22] Morlok et al. (2020) Icarus 335, 113410 Figure 1: Comparison of the Christiansen Feature (CF), a characteristic reflectance low, to the SiO2 bulk composition. The results from this study (red circles) fall along the regression line for terrestrial intermediate rocks.

In December 2020, Chang’e-5 returned samples from mare basalt unit Em4/P58 in northern Oceanus Procellarum. With an absolute model age of 1.21-1.53 Ga (Hiesinger et al. 2003; Qian et al., 2018, 202...

The MErcury Radiometer and Thermal Infrared Spectrometer (MERTIS) is an instrument to study the mineralogy and temperature distribution of Mercury’s surface in unprecedented detail. MERTIS was proposed in 2003 as payload of the Mercury Planetary Orbiter spacecraft of ESA-JAXA BepiColombo mission and will reach Mercury in 2025. MERTIS will map the whole surface at 500 m scale, combining a push-broom IR grating spectrometer (TIS) with a radiometer (TIR) sharing the same optics, instrument electronics and in-flight calibration components for the whole wavelength range of 7- 14μm (TIS) and 7-40μm (TIR). MERTIS successfully completed its planned tests of the Near-Earth Commissioning Phase (NECP) between 13 and 14 November, collecting thousands of measurements of its internal calibration bodies and deep space. The data collected during NECP, are being used to verify the operational performances of onboard sub-modules, in particular the spectrometer and radiometer sensor sensitivity. A preliminary look at calibrated data shows a performance comparable with ground-based measurements and no appreciable performance loss or misalignment. The next important dates for MERTIS are the Earth/Moon flyby on 6 April 2020 and the first Venus flyby on 12 October 2020. Both those encounters will be important both for further instrument calibration refinement and for possible unprecedented measurement in the thermal infrared of the Moon and Venus.

The ESA-JAXA BepiColombo Mercury mission was launched in October 2018. It performed successful flybys of the Earth-Moon system on April 10, 2020 and of Venus on October 15, 2020 during which the MERTIS instrument operated. MERTIS obtained a total of 1.2 million spectra during the Moon flyby from a distance of more than 700000km. Venus observations started at a distance of more than 1.3 Mio km recording more than 3 million spectra. For reference at Mercury MERTIS will observe the planet from a distance of less than 1500km. These data and the Near-Earth commissioning show that MERTIS performance exceeds requirements.

Glassy materials have been recognized over Mars, Moon and many different meteorites (Farrand et al. 2016; Delano 1986; Varela & Kurat 2004). Planetary glasses result from impact events but they are also found as volcanic products (Farrand et al 2016). Morlock et al. (2017) and Morlok et al. (2021) investigated by means of different experimental techniques (bi-directional diffuse reflectance FTIR, in situ FTIR microscopy, Raman, EPMA and optical microscopy) a suite of synthetic samples with composition similar to those inferred for different Hermean terrains. Here we extended the study of the same materials to the VNIR region (bidirectional reflectance spectroscopy: 350 to 2500 nm). We analyzed 8 different samples with different chemical compositions, produced under different oxygen fugacity conditions We prepared eight granulometric classes between 0 and 250 μm, namely: 0-25; 25-63; 63-100; 100-125; 125-150; 150-180; 180-200 and 200-250 μm. The dominant feature in the VNIR region is due to the Fe absorption band at about 1 μm accompanied, in the more oxidized samples, by a smaller feature at 480 nm likely due to ferric oxide development. Iron free samples (FeO < 0.1 wt%) show characteristic spectral shapes with a distinctive feature at about 640 nm attributable to TiO2. Even for very low FeO content, it is possible to observe a weak yet clear band at about 900-1000 nm due to Fe absorption which explain the dominance of the spectral features due to Fe absorption at higher FeO content. Additional small bands at higher wavelengths (1300-1400 and 1900 nm) suggest a low content of water and/or –OH species in the samples. We investigated the spectral features as a function of composition, grain size and oxidation in order to gain as much information as possible on the nature of the spectra and compare them with remote sensing data or meteorites VNIR comparison. Our data on synthetic and realistic Hermean compositions will allow a better understanding of remotely acquired VisNIR spectra, which will be particularly helpful in view of the upcoming beginning of the BepiColombo ESA/JAXA mission. Acknowledgments: The authors acknowledge financial contribution from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0 (Simbio-SYS). CC, EB are also supported by agreement ASI-INAF n.2018-16-HH.0.

Introduction The data collected during the Apollo missions played a decisive role in shaping our knowledge of the Moon and its geological features. Up until today this data collection helps us to understand the ongoing processes occurring on the Moon and throughout the Solar system. The method of gaining absolute model ages (AMAs) of unsampled surfaces through crater size-frequency distribution (CSFD) measurements using the lunar cratering chronology was one of the many innovations of these missions. Recent improvements in the remote sensing data have helped to establish more accurate methods to further comprehend the processes on the Moon, as well as to test previously used methodology. We conducted a series of studies [1-4] to test the validity of the commonly used lunar cratering chronology function [5]. The studies used recent available data to create detailed geological maps and CSFD measurements, which later were correlated with most recently measured sample ages. Methodology Lunar Reconnaissance Orbiter Cameras (LROC) Wide Angle (WAC, ~100m/px) and Narrow Angle (NAC, ~0.5m/px) data with incidence angles between 55-80° [6], and SELENE (Kaguya) morning, evening, ortho-image (~10 m/px) data were used to identify albedo variations. Merged LOLA/SELENE (~60 m/px) [7] and NAC-derived digital terrain models (DEMs) (~2.5 m/px) [8] were used to define morphological differences, whereas Clementine [9], Chandrayann-1 Moon Mineralogy Mapper (M3) [10] and Kaguya Multiband Imager (MI) [11] defined spectral variations. CraterTools [12] was used in ArcGIS for the CSFD measurements, and CraterStats [13] was used to plot the CSFDs. Randomness Analysis [14] was used to avoid secondary crater chains and clusters. For geological mapping we relied on Federal Geographic Data Committee (2006) [15] standards for the symbology, and Gazetteer of Planetary Nomenclature (1999) [16] regarding the nomenclature. Meanwhile, stratigraphic units were identified using the stratigraphic scheme of Wilhelms (1987) [17]. Testing the Lunar Chronology Function In our series of studies [1-4] we produced several detailed geological maps (e.g., Figure 1) of the Apollo landing sites, which were eventually used to measure CSFDs (e.g., Figure 2) on the defined geologically homogeneous areas. The gained N(1) (cumulative number of the craters ≥1 km in diameter) values were linked with the recently measured isotopic ages of the Apollo samples. The gained calibration points were used to test the calibration of the lunar cratering chronology [5] (Figure 3). The extrapolation of the tested lunar cratering chronology function is used to derive absolute model ages (AMAs) of the unsampled surfaces, which enables us to understand the evolution and ongoing processes of other terrestrial bodies in the solar system. Other Implications Our detailed geological maps provide advanced perspectives on the relationship of the samples and the remotely sensed compositional and morphological differences. Therefore, our studies are being used to investigate the exact origin of the collected samples [18]. Furthermore, our studies provide a comprehensive view on the scientific goals behind the landing site selection. Therefore, these studies can be used to assess future landing sites for the demonstration of in situ resource utilization (ISRU) missions [19]. Newly prepared comprehensive geological maps and carefully measured CSFDs will provide key domain knowledge for the development of tools to perform automatic detection of various features (e.g., craters). Such a tool will be integrated into the multi temporal data base (MUTED) [20], which will be able to show temporal differences on the planetary bodies instantaneously. In future, this tool will aid the interpretation of geological processes and help determining AMAs of planetary surfaces, while reducing cognitive bias and systematic errors. Acknowledgements WI, TH and NS were funded by German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt) Grant #50OO2102. HH was funded by the German Research Foundation (Deutsche Forschungsgemeinschaft SFB-TRR170, subproject A2) and CvdB was supported by EU H2020 project #776276, PLANMAP. References [1] Iqbal et al. (2019) Icarus 333, 528-547. [2] Iqbal et al. (2020) Icarus 3352, 113991. [3] Iqbal et al. (2019) LPSC 50, 1005. [4] Iqbal et al (2020) LPSC 49, 1073. [5] Neukum (1983) NASA TM-77558 [6] Robinson et al (2010) Space Sci. Rev. 150, 81-124. [7] Barker et al. (2016) Icarus 273, 346-355. [8] Henriksen, et al. (2017) Icarus 283, 122-137. [9] Pieters et al. (1994) Science 266, 1844-1848. [10] Isaacsom, et al. (2013). JGR Planets. 118, 369-381. [11] Ohtake et al (2013) Icarus 226, 364-374. [12] Kneissl et al. (2011). PSS 59, 1243-1254. [13] Michael et al. (2016) Icarus 277, 279-285. [14] Michael et al. (2012) Icarus 218, 169-177. [15] FGDC (2006). FGDC-STD- 013-2016. [16] Blue, J. (1999) Gazette. of Planet. Nomen. USGS. [17] Wilhelms, (1987) USGS Prof paper: 1348.[18] Haber, et al (2018) AGU, P31G- 3785. [19] van der Bogert, et al. (2020) LPSC 51, 1876. [20] Heyer et al. (2021) LPSC 52, 1124.

Introduction: The IRIS (Infrared and Raman for Interplanetary Spectroscopy) laboratory at the Institut für Planetologie in Münster produces a database of mid-infrared spectra for the ESA/JAXA BepiColombo mission to Mercury. The MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument onboard the BepiColombo Mercury Planetary Orbiter allows mapping spectral features in the 7-14 µm range, with a spatial resolution of about 500 meters [1,2]. In addition to a variety of natural terrestrial and meteoritic materials for the comparison of the expected results, we started using synthetic analogues based on the chemical composition of Mercury measured by MESSENGER. This allows to produce infrared spectra of bodies from which no material as returned samples or meteorites is available so far [3-5]. Advanced modelling based on the chemistry of Mercurian lavas and high-temperature experiments to simulate the mantle formation and the crystallization of lavas at the surface resulted in prediction for modal mineral compositions for distinct surface regions [6-8]. This allows to produce synthetic mixtures of minerals and glass representative for these hermean regions. Samples & Techniques: For the first round of mixing studies of powdered samples, sample compositions were selected from modal compositions based on experiments covering the dominant mineralogically diverse, 3.6–3.5 Gyr old volcanic smooth plains regions on Mercury [6,7]. The experimental conditions (for details see [7,8]) were temperatures between 1170-1360°C and highly reducing conditions (ΔIW of -4.9 to -6.2). Of the run products described in [7], we picked modal compositions covering a wide range of phase compositions, ranging from pure glass to the most crystalline composition modelled (crystalline content from 9-58 wt%). The analogues were prepared using mixtures of synthetic glass material based on hermean compositions [7-9] and natural crystalline forsterite, enstatite, diopside and plagioclase, with compositions in the range that was observed in the petrological experiments [7]. All materials were sieved into 4 size fractions before (0-25 µm, 25-63 µm, 63-125 µm, 125-250 µm), and the analogue mixtures composed directly from the size fractions. Diffuse reflectance mid-infrared spectra were made with a Bruker Vertex 70 infrared system using a Cooled MCT detector. Analyses of the powders were made at low pressure (10-3bar) to reduce atmospheric bands from 2-20 µm. For calibration, a diffuse gold standard was used for ratioing, to guarantee low noise, we integrated 512 scans for each spectrum. Spectral features of interest are the Christiansen Feature (CF), a characteristic reflectance low that also serves as proxy for the bulk composition; the Transparency Feature (TF), typical and indicator for the finest grain size fraction (0-25 µm); and the Reststrahlen Bands (RBs), the molecular vibration modes. Results: In the range of interest for MERTIS (7-14 µm), the entirely glassy end member shows a simple spectrum with a strong RB at 9.6 µm, a CF at 7.9 µm and the TF at 11.77 µm [4]. Increased crystalline content (9 wt% forsterite, 91 wt% glass) in sample ID 345 Smooth Plains has two RB appearing at 9.6 µm and 10.5-10.6 µm, and a weaker RB at 10.2 µm. The CF is at 7.9-8 µm, the TF at ~11.7 µm. Sample ID 344 Smooth Plains contains several crystalline species (5 wt% forsterite, 2 wt% diopside, 28 wt% plagioclase and 11 wt% enstatite). This results in a feature-rich spectrum, with RBs at 9.5 µm, 9.9 µm, 10.2 µm, 10.5 µm, 10.8 µm, 11.1 µm and 11.3-114 µm. The CF is found at 7.8-7.9 µm, the TF is at 11.7 µm. The crystalline-rich end member ID 343 Smooth Plains has only 42 wt% glass components with 6 wt% forsterite, 11 wt% diopside, 34 wt% plagioclase and 7 wt% enstatite. RBs are seen at 9.4 – 9.6 µm, 9.9 µm, 10.2 µm, 10.5 µm, 10.8 µm and 11.3 µm. The TF is at 11.6 µm, the CF at 7.9 - 8 µm. Discussion: Spectra show increasing RB features with decreasing content of glass (Fig.1). However, a comparison of the finest size fractions (0-25 µm) (Fig.2) of the 4 samples shows astonishingly similar spectra, basically the smooth glass spectra of with relatively weak RB on top, with the spectrum dominated by the TF. This could make distinguishing of such spectra of a continuum of similar composition difficult. Contrasts between the spectra are stronger at the larger grain size fractions (>25µm), where the RB features are stronger. Variations in band intensities between the different samples – particular the high intensity of the ID 344 Smooth Plains spectrum – could be results of a highly reflective component (Enstatite?) or indicator of insufficient mixing of the phases. Summary & Conclusions: We will continue by mixing further samples based on the hermean surface models and experiments [7], with the aim to have series of samples representative for each of the terranes. Future spectral unmixing models will test if the individual mineral components can be extracted by modelling form the spectra. References: [1] Benkhoff J. et al. (2020) Planetary and Space Science 58, 2-20 [2] Hiesinger H. et al. (2020) Planetary and Space Science 58, 144–165 [3] Morlok et al. (2020) Icarus 335, 113410 [4] Morlok et al. (2019) Icarus 324, 86-103 [5] Weber et al. (2020) Earth and Planetary Science Letters 530, 115884 [6] Weider S.Z. et al. (2015) Earth and Planetary Science Letters 416, 109-120 [7] Namur and Charlier (2017) Nature Geoscience 10, 9-15 [8] Namur O. et al. (2016) Earth and Planetary Science Letters 448, 102-114 [9] Nittler L.R. et al. (2018) Mercury: The View after MESSENGER. Cambridge University Press, Cambridge, pp. 30-51. Figure 1. Mid-infrared diffuse reflectance spectra of 4 size fractions. CF: Christiansen Feature, TF: Transparency Feature. Figure 2. Mid-infrared diffuse reflectance spectra of the 0-25 µm size fractions.

Introduction The Chang’e-5 (CE-5) mission is China’s first lunar sample return mission. CE-5 landed at Northern Oceanus Procellarum (43.06°N, 51.92°W) on December 1, 2020, collected 1731 g of lunar samples, and returned to the Earth on December 17, 2020. The CE-5 landing site is ~170 km ENE of Mons Rümker, on one of the youngest mare basalts (Em4/P58) of the Moon [1,2], which are never sampled by the Apollo or Luna missions. The CE-5 returned samples are currently being analyzed by the Chinese scientists, and the first batch of data have been released by the Lunar Sample Information Database (https://moon.bao.ac.cn/moonSampleMode/index.html). This study describes the provenance of lunar regolith at the CE-5 landing site in order to provide context for the ongoing sample analysis. Exotic Material Source Craters Because Em4/P58, where CE-5 landed, has a late-Eratosthenian age [1], all pre-Eratosthenian craters and most Eratosthenian craters nearby are not ejecta source craters. Calling on the initial selection of ejecta source craters by [3] and the local geological backgrounds [4], we proposed Aristarchus, Copernicus, Harding, Harpalus, Kepler, Lichtenberg, Pythagoras, and Sharp B are potential main ejecta source craters. Rümker E is also taken into account because its ray/ejecta is easily distinguished from the mare basalts to the southeast of Mons Rümker. To determine post-Em4/P58 craters, we conducted a comprehensive literature study of these nine craters to collect their AMAs or relative ages (Table1 in [5]). Aristarchus (280 Ma), Copernicus (779-796 Ma), Harding (881 Ma), and Kepler (625-950 Ma) are Copernican-aged and dramatically younger than ∼1.53Ga, and their ejecta inevitably overlies the Em4/P58. Lichtenberg (>1.68G) and Pythagoras (2.68 Ga) are older than 1.53 Ga, therefore, they are unlikely to be ejecta source craters. To the east of Em4/P58, albedo and compositional data show abundant ejecta with a NE-SW direction; thus, we inferred that the NE-SW orientated ejecta should dominate the ejecta composition because of their extensive areal distribution. Ejecta tracing back to the parent craters indicate an origin either from Harpalus or Sharp B or both. More detailed morphological and compositional investigations of Harpalus and Sharp B craters show that Harpalus has a much younger appearance, with distinct high albedo radial ray/ejecta and boulders. Sharp B crater has a more subdued morphology, without clear radial ejecta and boulders. Based on their morphology and degradation state, Harpalus is likely to be Copernican-aged and Sharp B should be Eratosthenian-aged or even older, while crater counting directly on their rims are NOT reliable [5], which may be contaminated by secondary craters, self-secondary craters, partially buried craters, and the extra slopes. After we examined the main source craters of ejecta in the mapped region, we conducted a thorough investigation of ejecta in Em4/P58 using their long axis directions (Fig. 1); the ejecta was traced back to one of the nine listed craters. According to the mapping, the eastern part of Em4/P58 is covered by extensive ejecta from Harpalus crater, which can be traced continuously back to its source. Three large Copernican craters to the southeast of Em4/P58 (Aristarchus, Copernicus, and Kepler) also provide a significant amount of ejecta, especially Copernicus crater. Quantitative Assessment of Exotic Materials To quantitatively analyze the contribution from different distant ejecta sources, we calculated their thicknesses in the study region using the power-law model modified by [6]. According to this calculation, Harpalus contributes the most ejecta to Em4/P58 (∼10 cm), followed by two Copernican-aged craters Copernicus (∼8 cm) and Aristarchus (∼3 cm). Contributions from Kepler and Rümker E are negligible. The ejecta thickness calculation agrees well with the ejecta distribution tracing, suggesting Harpalus is the main ejecta source, dominating the overall ejecta thickness for Em4/P58. Sharp B crater is OLDER than Em4/P58 based on its morphological characteristics, thus its ejecta does NOT overlie Em4/P58. The percentage of contributions from each ejecta source crater was calculated to first-order by employing [7]’s regolith gardening model. Considering the CE-5 mare basalts have an age of between 1.6-1.7 Ga, the top ∼74 cm regolith is mixed up. Because the total ejecta thickness from studied source craters is ∼22 cm, we can assume all ejecta layers are mixed into the first ∼74 cm of lunar regolith. This yields the overall exotic components at the CE-5 landing site of ∼9%. Harpalus (∼6%), Copernicus (∼2%), and Aristarchus (∼1%) are the three most important source craters, agreeing with the map results (Fig. 1). Figure 1. Ejecta distribution of major source craters in the Northern Oceanus Procellarum Discussion & Conclusion In addition to exotic materials delivered by the distal impacts (e.g., Harpalus, Copernicus, and Aristarchus), three other types of exotic materials have high scientific significance. The first one is exotic components from subjacent and adjacent highlands by lateral mixing [8], the second type of exotic components may originate from silica-rich domes, and the third one from the meteorites. However, the overall composition of the lunar regolith are from the local (~91%) mare basalts erupted by Rima Sharp (Qian et al., 2021b) with foreign materials from mainly Harpalus, Copernicus, and Aristarchus craters (Qian et al., 2021c). All of the local and exotic materials can be used to answer at least some of the scientific questions listed by Qian et al. (2021c) to deepen our understanding of the Moon. References [1] Hiesinger, et al. (2011) Spec. Pap. Geol. Soc. Am., 477, 1–51.[2] Qian, et al. (2021) EPSL, 555, 116702.[3] Xie, et al. (2020) JGR-P, 125, e2019JE006112.[4] Qian, et al. (2018) JGR-P, 123, 1407–1430.[5] Qian, et al. (2021) EPSL, 561, 116855.[6] Huang, et al. (2018) JGR-P, 123, 1684–1700.[7] Costello, et al. (2018) Icarus, 314, 327–344.[8] Liu, et al. (2021) GRL, 48, e2021GL092434.[9] Qian, et al. (2021) GRL, 48, e2021GL092663.

The Dawn Framing Camera repeatedly imaged Ceres’ North Pole quadrangle (Ac-1 Asari, latitudes >66°N) at a resolution of ∼35 m/pixel through a panchromatic filter, enabling the derivation of a digital terrain model (DTM) and an ortho-rectified mosaic. Using this dataset, a photo-geologic map and stratigraphy, complemented with absolute model ages of impact craters, were produced. We identified the following key surface features: an ancient 4.5 km high isolated dome with a non-impact origin; recent lobate materials on crater interiors possibly formed as high-speed flows of collapsed rim material; and recent bright areas in permanently shadowed regions (PSRs), which we interpret as ice accumulation mostly by infall of exogenic material. Crater morphologies and dimensions do not differ from those in other quadrangles, suggesting the widespread influence of a rheologically weak target during the crater formation process. There is a paucity of lobate materials associated with impact cratering, in contrast to previous identifications with lower spatial resolution imagery.

We conducted a geologic mapping investigation of Dawn spacecraft data to determine the geologic history of the Kerwan impact basin region of dwarf planet Ceres, which is mostly located in the Ac-7 Kerwan Quadrangle. Geological mapping was applied to Dawn Framing Camera images from the Low Altitude Mapping Orbit (LAMO, 35 m/pixel) and supplemented by digital terrain models and color images from the High Altitude Mapping Orbit (HAMO, 135 m/pixel), as well as preliminary Visible and Infrared Spectrometer (VIR) and gravity data. The 284-km diameter Kerwan impact basin is the oldest unequivocal impact crater on Ceres, and has a highly discontinuous, polygonal, degraded rim and contains a ‘smooth’ unit that both fills the basin floor and surrounds the degraded rim to the west, south, and east. Although there are some subtle topographic features in the Kerwan basin that could be interpreted as flow boundaries, there is no indisputable evidence of cryovolcanic features in or around the basin (however if such features existed they could be buried). Nevertheless, all data point to impact-induced melting of a cerean crust enriched in a volatile, likely water ice, to produce the Kerwan smooth material. Subsequent geologic activity in this region includes emplacement of impact craters such as Dantu, which produced a variety of colorful deposits, and rayed craters such as Rao and Cacaguat. Based on the crater size-frequency distribution absolute model ages of the Kerwan smooth material in and around the basin, marking a minimum age for the Kerwan basin, our mapping defines this as the oldest boundary within the cerean geologic timescale, separating the Pre-Kerwanan and Kerwanan Periods at > 1.3 Ga (Lunar-derived chronology model) or > 230–850 Ma (Asteroid-derived chronology model, depending on strength of target material).

Since its arrival at Ceres, DAWNs Framing Camera has been imaging the dwarf planet at different altitudes, using 8 different filters. Based on these images, global clear filter mosaics, digital terrain models, and global color mosaics were produced. These datasets are basis for the derived photogeologic map of the Ac2 Coniraya quadrangle, located between 0° and 90° eastern longitude and between 20° and 40° northern latitude. Crater size frequency distribution (CSFD) measurements have been applied to derive the stratigraphic history of the identified geologic units in the Ac2 Coniraya quadrangle. Based on these investigations, we found that the Ac2 Coniraya quadrangle shows evidence for a long geologic history lasting over 3.5 Ga. Most of the identified geologic units are related to impact cratering at different periods of time. While the oldest unit identified in the Ac2 Coniraya quadrangle, the cratered terrain, shows an absolute model age (AMA) of 3.3 to 3.5 Ga, the youngest units, including fresh impact craters and lobate flows, show AMAs of < 100 Ma. The large number of different sized impact craters excavated a variety of materials with different colors and albedo, indicative of a heterogeneous crustal composition, including water or volatiles. Pits identified at Ikapati craters smooth deposits might further indicate the presence of volatiles in the subsurface. Furthermore, our mapping of the Ac2 Coniraya quadrangle shows that possible H 2 O ice in the crust is heterogeneously distributed, as lobate flows, bright spots, and pits are only found at certain locations, related to relatively fresh impact craters.

Within the European Space Agency’s “Commercial In Situ Resource Utilization (ISRU) Demonstration Mission Preparation Phase,” we examined two types of lunar sites in preparation for an ISRU demonstration mission. First, we considered poorly characterized potential resource sites. For these so-called characterization sites, precursor missions would investigate the material properties and address strategic knowledge gaps for their use as ISRU feedstock. Regions of interest for characterization missions include the Aristarchus plateau, Montes Harbinger/Rimae Prinz, Sulpicius Gallus, and Rima Bode. Regional pyroclastic deposits at the Aristarchus plateau and adjacent Montes Harbinger/Rimae Prinz exhibit remotely sensed low-Ti, high-Fe2+ compositions. They differ from the high-Ti pyroclastics at Rima Bode and Sulpicius Gallus, which are similar to the pyroclastics northwest of the Taurus Littrow valley (Apollo 17 site). Thus, exploration of the Aristarchus plateau would allow investigation of previously uncharacterized materials, whereas Rima Bode or Sulpicius Gallus would allow comparison to Apollo 17 pyroclastics. Any of these sites would enable evaluation of reported H2O/OH in these deposits. Second, we examined a possible site for a direct ISRU demonstrator mission. For a stand-alone end-to-end (E2E) ISRU demonstrator, a fuller understanding of the physical and compositional characteristics of potential feedstock is required for mission risk reduction. In this case, locations near preexisting sites would allow extrapolation of ground truth to nearby deposits. Because a Ti-rich pyroclastic deposit appears advantageous from beneficiation and compositional perspectives, we examine an example E2E demo site northwest of the Taurus Littrow valley. Hydrogen and methane reduction, as well as the Fray–Farthing–Chen Cambridge process, could be tested there.

Introduction: The South Pole-Aitken (SPA) basin is located on the lunar farside. Centered at ~53° S, 191° E the SPA is the largest observable basin on the Moon [1-5]. The SPA Region in general and the South Pole in particular are high priority targets for ongoing and future robotic and human missions [e.g., 6–10]. The area potentially includes exposed mantle material [14, 15], sources of volatiles (e.g., pyroclastic deposits [11]), and permanently shadowed regions around the South Pole that may harbor ice or other volatiles [12]. As the oldest lunar basin, the timing of SPA formation gives valuable information on the formation and evolution of the lunar crust [11,13]. These missions make detailed studies of the geological history and setting of the region necessary. Here, we provide a geologic map at a scale of 1:500,000 of the SPA basin region, including the South Pole region which is an extension of a map of the Apollo basin region [13]. Our map provides a comprehensive overview of the geology in the region. Methods: We used the Lunar Reconnaissance Orbiter (LRO) Wide-Angle Camera (WAC) basemap (100 m/pixel) for the majority of the mapping. To look at smaller areas and to identify specific features, we then also used Narrow Angle Camera (NAC; 0.5 m/pixel) [14] and Kaguya (10 m/pixel) data. Spectral information was taken from Clementine [15], M3 [16], and Kaguya MI [17] data. We determined the topographic features using Lunar Orbiter Laser Altimeter (LOLA)/Kaguya merged digital elevation models with a resolution of 59 m/pixel [18] where available. For higher latitudes we used LOLA digital elevation products [19, 20]. At the poles we mitigate the effect of low solar illumination angles, which cause significant shadows, by producing hillshade maps with various illumination conditions. We worked according to PLANMAP mapping standards [21], an extension of USGS standards [22]. With the available data we identified different units and features based on their morphological appearance, albedo contrasts and, if applicable, spectral signal. We then established a relative stratigraphy for these units using morphological and stratigraphic evidence. Next, we performed crater size-frequency distribution (CSFD) measurements and determined absolute model ages (AMAs) using the production and chronology functions of [23] to put constraints on the chronology. CSFD measurements were made using CraterTools [24] in ArcGIS, and fit with Craterstats [25]. The technique is described in detail by [23, 26]. Geology: In this map, we cover the full extent of the SPA basin. We were able to identify the rim of SPA basin, which presents itself best in the elevation data. Due to its old age, however it remains difficult to identify original rim units. Best preserved in the NE part of SPA basin the rim makes up a two ring structure. While in most of the other segments of the rim, the rim itself is covered by younger geologic units. We extended our map to the East from the central SPA basin to include a large part of Orientale basin. Due to the size and proximity to the SPA basin, Orientale basin has had a modifying influence on large parts of SPA basin. The whole area is covered in small, sharp-rim craters some of which form crater chains and clusters. A plausible origin for most of these small sharp-rim craters could be the Orientale basin. The area also exposes extensive light plains of which some might also coincide with the formation of Orientale basin. Acknowledgments: This paper is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement Nº776276 (PLANMAP) and N°871149 (GMAP). References: [1] Stuart-Alexander (1978) USGS Map I-1047. [2] Spudis et al. (1994) Science 266, 1835-1839. [3] Hiesinger and Head (2004) PLPSC 35, 1164. [4] Shevchenko et al. (2007) Solar Sys Res 41, 447-462. [5] Garrick-Bethell and Zuber (2009) Icarus 204, 399-408. [6] Flahaut et al. (2020) PSS 180, 104750. [7] Steenstra et al. (2016) Adv Space Res 58, 1050–1065. [8] Allender et al. (2018) Adv Space Res 63, 692–727. [9] Hiesinger et al. (2019) LPSC 50, 1327. [10] Huang et al. (2018) JGR 123, 1684 – 1700. [11] Wilhelms (1987) USGS SP-1348, 302. [12] Nozette et al. (2001) JGR 106, 23253– 23266. [12] Hiesinger et al. (2012) LPSC 43, 2863. [13] Ivanov et al. (2018) JGR 123, 2585–2612. [14] Robinson et al. (2010) Space Sci Rev 150, 81–124. [15] Pieters et al. (1994) Science 266, 1844–1848. [16] Isaacson et al. (2013) JGR 118, 369–381. [17] Ohtake et al (2013) Icarus 226, 364–374. [18] Barker et al. (2016) Icarus 273, 346-355. [19] Smith et al. (2010) Icarus 283, 70-91. [20] Smith et al. (2010) GRL 37, L18204. [21] wiki.planmap.eu/display/public/D2.1-public. [22] FGDC (2006) FGDC-STD-013-2016. [23] Neukum et al. (2001) Space Sci Rev 96, 55–86. [24] Kneissl et al. (2011) PSS 59, 1243–1254. [25] Michael and Neukum (2010) EPSL 294, 223–229. [26] Hiesinger et al. (2000) JGR 105, 29239–29276.

The spectral analysis of a planetary surface is fundamental for a deeper understanding of the mineralogy and composition. In particular, the determination of spectral units is a reliable method to infer the physical and compositional properties of a surface by processing several spectral parameters simultaneously, instead of the more traditional approach of interpreting each single parameter separately. To define the spectal units, we first compute the most relevant spectral parameters, based on a preliminary detailed analysis of the spectral properties of a surface. This method could be used for different bodies and is described in [1].For this work, we selected the Apollo Basin area within South Polar Aitken [2,3], the largest and deepest impact basin on the Moon. We analyzed the M3/Chandrayaan-1 data [4] after performing the most up-to-date calibration, thermal removal and photometric correction [5,6]. Lunar spectra are characterized by two strong pyroxenes absorption bands at 1 and 2 µm. In this regard, we decided to define the Apollo Basin spectral units by using the two pyroxenes band depths, the reflectance at 540 nm (standard visible wavelength), and the spectral slope of the 1 µm (see [7]). In Apollo Basin, we found 12 different spectral units. Among these units, the most peculiar is the one linked to the basaltic smooth plains within the floor of the crater. This unit is characterized by low reflectance, deep band depths and a strongly positive spectral slopes (more red surfaces). Subsequently, an analysis of absorption band center at 1 and 2 µm and a comparison with RELAB synthetic pyroxenes [8] revealed a composition compatible with material dominated by strong pyroxene absorptions, e.g. clinopiroxenes, such as pigeonite or augite, with Low Ca and Mg, and relatively high Fe (Fs: 34-75; En: 6-23; Wo: 10-27). The rest of the units show a similar mineralogy to the orthopyroxenes, with intermediate amount of Fe and Mg.This work allows for a detailed understanding of the mineralogy of Apollo Basin, but also lays the groundwork to search for a link between spectral, and morpho-stratigraphic units [9] to reach out highly informative geological maps of the Moon. This innovative approach is one of the main goals of the H2020 no. 776276-PLANMAP project [10].Acknowledgments: This work is funded by the European Union’s Horizon 2020 research grant agreement No 776276- PLANMAP.References: [1] Zambon et al., 2020 LPSC. [2] Ohtake, M. et al., 2014, GRL. [3] Moriarty, D.P. et al., 2018, JGR. [4] Pieters et al., 2009, Current Science. [5] PLANMAP D4.3- Spectral Indices and RGB maps. [6] Besse, S. et al., 2012, Icarus. [7] PLANMAP D4.3- Spectral Indices and RGB maps. [8] http://planetary.brown.edu/relabdocs/synth_pyx/pyroxenes.html. [9] Ivanov, M.A., 2018, JGR. [10] https://www.planmap.eu/.

We analyzed plagioclase feldspar samples that were well-characterized in terms of chemical composition as well as degree of Al,Si order in mid-infrared reflection spectra between 7 μm and 14 μm (1429 cm−1 and 714 cm−1). The chemical compositions were derived with an electron microprobe analyzer. To determine the degree of Al,Si order, powder X-ray diffraction methods were applied. For the interpretation of the infrared spectra, we used the wavelength of the Christiansen feature (CF) and the autocorrelation function for a specific wavelength region. The CF shifts from around 7.72 μm (1296 cm−1) in Na-richest samples to 8.10 μm (1234 cm−1) in the Ca-richest sample. Combining the CF position and the autocorrelation-derived value allowed to determine the degree of Al,Si order of the samples based on reflection spectra. The wavelength of the Transparency feature (TF) in the finest analyzed grain size fraction also depends on the chemical composition and the degree of Al,Si order. Our results are helpful for the interpretation of data returned by the MERTIS experiment onboard BepiColombo. The data help to distinguish between space weathering, shock effects, and ordering effects in plagioclase samples.

The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is part of the payload on the joint ESA-JAXA BepiColombo Mission, launched in October 2018. The spectrometer is designed to map surface composition, identify rock-forming minerals, map surface mineralogy, and study surface temperature variations. The surface of Mercury undergoes large temperature variations depending on solar irradiation. Mineral spectra show significant changes in spectral features with changing temperature. In preparation of the experiment, we developed a thermal model that calculates surface temperatures based on appropriate insolation conditions and thermo-physical properties. This model has been validated with lunar parameters and hence been applied to the conditions of Mercury. Here we present surface temperature maps based on MESSENGER albedo and topography data. The results have been compared to previous models and measurements of Mercury's surface temperatures. The surface of Mercury undergoes large temperature variations each diurnal period. At the equator temperatures vary between less than 100 K during the night up to 700 K at local noon at longitudes 0° W and 180° W, and up to 570 K at longitudes 90° W and 270° W. Due to the 3:2 spin orbit resonance local noon at longitudes 0° W and 180° W coincide with perihelion, while longitudes 90° W and 270° W experience local noon at aphelion, which results in “hot” and “warm” poles around the equator. At 45° N surface temperatures at local noon reach 645 K (0° W and 180° W) and 510 K (90° W and 270° W).