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Northwestern Hellas Planitia hosts landforms that are unique on Mars, e.g., the so called honeycomb and banded (aka “taffy pull”) terrains. Recently, robust formation models for the ∼6 km large honeycomb depressions involving salt or ice diapirism have been formulated. However, the nature of the banded terrain, a ∼30,000 km² area characterized by a decameter- to kilometer-scale pattern of curvilinear troughs, has remained elusive. While previous interpretations range from deep-seated, honeycomb-related outcrops to a younger veneer, recent reports of putative periglacial features (e.g., potential thermokarst) strongly indicate it to be a relatively thin, volatile-related surface unit. In order to further constrain the origin and nature of the banded terrain, we investigated the northwestern Hellas basin floor employing various datasets. We mapped the banded terrain's extent at high precision, showing that it partially superposes the honeycomb terrain, but also occurs up to ∼240 km away from it. Via stratigraphic analyses and crater size-frequency measurements, we bracketed the age of the banded terrain between ∼1.9 and ∼3.7 Ga. Furthermore, the banded terrain can be differentiated into two types, ridged and creviced, with the former predominantly occurring among the lowest reaches of the terrain's ∼2 km topographic extent. We also produced a grid map (2 × 2 km box size) of the entire banded terrain and identified no large-scale (> 25 km) band pattern and no correlation between local slope and band orientation. Because of this, we submit that regional tectonics or gravity-driven flow down modern topography are unlikely to have played decisive roles for banded terrain formation. Instead, we observed numerous locations, where band slabs appear to have broken off and subsequently rotated, as well as “cusps” that seem to have resulted from buckling. Based on this, we suggest that the banded terrain experienced both, ductile deformation as well as brittle failure on or near the surface. Despite certain similarities, neither salt (as salt glaciers), lava sheets, or land-based glaciers are in agreement with the extensive curvilinear texture and topographic/geologic setting of the banded terrain. Ice shelf margins, on the other hand, can produce surface textures akin to the banded terrain in both form and scale, even including cusps and broken off, rotated blocks. However, an ice-covered sea between 1.9 and 3.7 Ga ago is not indicated by the geologic inventory of the Hellas basin, which previous investigations found to lack any landforms indicative of a standing body of water. Instead, we identified several sinuous ridges terminating at plains covered by smaller, braiding ridges, which we interpret as eskers and glacial sandurs, respectively. As both are embayed and partially covered by the banded terrain, we tentatively propose an alternative, subglacial model of the banded terrain having formed as wet till that was viscously deformed according to the stress fields created by the ice overburden pressure in conjunction with bed topography. Although this formation model remains inconclusive, it is in agreement with climate models suggesting obliquity excursions and a denser, early Amazonian atmosphere to have caused ice accumulation in the adjacent northwestern Hellas basin rim, thus potentially enabling flow onto the floor entailing subglacial banded terrain formation.

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.

Crater size-frequency distribution (CSFDs) measurements allow the derivation of absolute model ages (AMAs) for geological units across various terrestrial bodies in the Solar System based on body-specific adjustments to the lunar chronology (e.g., Hartmann, 1970; Neukum et al., 1975, 1983, 2001; Stoffler and Ryder, 2001; Stoffler et al., 2006; Hiesinger et al., 2012; Robbins, 2014). Thus, it is important to revisit and test the accuracy of the lunar chronology using data from recent lunar missions (e.g., Hiesinger et al., 2000, 2012, 2015; Rajmon and Spudis, 2004; Stoffler et al., 2006), as well as newer analyses of lunar samples (e.g., Gaffney et al., 2011, Meyer, 2012; Snape et al., 2016; Welsh et al., 2018). We generated a new detailed geological map of the Apollo 11 landing region based on spectral characteristics, topography, and albedo maps, which shows several mare units adjacent to the lunar module. Lunar Reconnaissance Orbiter Camera (LROC) images were used to measure new CSFDs and derive the cumulative number of craters with diameters ≥1 km or N(1) for the Apollo 11 landing site. The newly derived N(1) values are consistent with the presence of only one surficial unit at the landing site: the Group A, High-K (high potassium) “young” mare basalt as described in Meyer (2012). We reviewed the radiometric ages for Apollo 11 samples that have been determined since the calibration of the lunar cratering chronology, used our new geological map to reinterpret their provenance, and correlated them with the new N(1) values. These are plotted and compared with the lunar chronology of Neukum et al. (1983). Our calibration point for the Apollo 11 landing site is consistent with the earlier values, thus, confirming Neukum's 1983 and Neukum and Ivanov's 2001 lunar chronology curves.

We conducted classic dynamic high - pressure experiments on porous San Carlos (SC) olivine powder to examine if and how different shock stages modify corresponding reflectance mid – infrared (MIR) spectra. Microscopic investigation of the thin sections produced of our shocked samples indicates local peak pressures of >60 GPa along with all lower grade shock stages. Spectral analyses of optically identified shock areas were documented and compared in terms of Christiansen Feature (CF) and the position of olivine – diagnostic Reststrahlenbands (RBs). We found that one RB (fundamental vibrations of the orthosilicate - ion) of olivine occurring at 980 cm−1 (corresponding to ≈ 10.2 μm) shows the least energetic shift in the investigated MIR spectra and could therefore serve as a proxy for the presence of olivine in remote sensing application. Furthermore, a peak located at ≈ 1060 cm−1 (≈ 9.4 μm) shows a significant intensity change probably related to the degree of shock exposure or grain orientation effects, as we observe a decline in intensity of this band from our averaged reference olivine spectra of our IRIS database (diffuse reflectance measurement) down to spectra of grains showing mosaicism and recrystallized areas. We also report the presence of a weak band in some of the olivine spectra located at ≈ 1100 cm−1 (9.1 μm) that has an influence on the position of the CF when spectral data of olivine are averaged.

Chang'e-5, China's first lunar sample return mission, is targeted to land in northern Oceanus Procellarum, within a region selected on the basis of 1) its location away from the Apollo-Luna sampling region, 2) the presence of the Procellarum KREEP Terrane (PKT), 3) the occurrence of one of the youngest lunar mare basalts (Em4), and 4) its association with Rima Sharp. In order to provide context for returned sample analyses, we conducted a comprehensive study of the regional and global settings, geomorphology, composition, mineralogy, and chronology of the Em4 mare basalts. Superposed on Imbrian-aged low-Ti basalts, Em4 covers 37,000 km2 and is composed of Eratosthenian-aged (∼1.53 Ga), high-Ti basalts with a mean thickness of ∼51 m and a volume between ∼1450 and 2350 km3. Minor variations in TiO2 and FeO abundance occur within the unit and the thorium content averages ∼6.7 ppm, typical of PKT mare basaltic regolith. No specific source vents (e.g., fissures, cones, domes) were found within the unit. We show that Rima Sharp is actually composed of three major rilles, whose source vents are located outside of, and which flow into, and merge in Em4, suggesting that they may be among the sources for Em4. Regolith thickness averages ∼7 m and there is abundant evidence for vertical and lateral mixing; the most likely sources of distal ejecta are Aristarchus, Harpalus, and Sharp B craters. Returned samples from local and distant materials delivered by impact will thus provide significant new insights into lunar geochronology, inner Solar System impact fluxes, the age of very young mare basalts, the role of the PKT in the generation of mare basalts, the role of sinuous rilles in lava flow emplacement, and the thermal evolution of the Moon.

An exceptional deposit covering an area of ∼7700 km 2 , displaying morphology indicative of an originally fluid material, occurs near 42.2°N, 167.4°E on the lunar farside. The material occurs as smooth, flat deposits (here termed “ponds”) on the bottoms of many craters and in other topographic depressions, as well as a veneer across the majority of the region. Within this area, the ponded deposits and widespread-veneer have an estimated volume of ∼8 km 3 ; the veneer constitutes the great majority of this volume. This material appears to have flowed downslope across the surface, collecting in flat-surface accumulations. The surfaces of the ponds and veneer are only lightly cratered, indicating a young (i.e., late Copernican) age. Four possible modes of origin are investigated: basin ejecta, pyroclastic volcanism, effusive volcanism, and ballistically emplaced impact-melt. Volcanism and basin ejecta appear to be inconsistent with the observed morphology: an implausible number of vents are required for volcanism and the morphological properties do not resemble basin ejecta. We suggest that ballistically emplaced impact melt is most consistent with the observations. Possible source craters for impact melt, based on minimum required size (>20 km diameter) and age, are at least 250 km distant and cannot be definitively tied to the pond deposits. This discovery places important new constraints on our knowledge of the distribution of impact melt relative to the parent crater.

Using SELENE/Kaguya Terrain Camera and Lunar Reconnaissance Orbiter Camera (LROC) data, we produced a new, high-resolution (10 m/pixel), geomorphological and impact melt distribution map for the lunar crater Tycho. The distal ejecta blanket and crater rays were investigated using LROC wide-angle camera (WAC) data (100 m/pixel), while the fine-scale morphologies of individual units were documented using high resolution (∼0.5 m/pixel) LROC narrow-angle camera (NAC) frames. In particular, Tycho shows a large coherent melt sheet on the crater floor, melt pools and flows along the terraced walls, and melt pools on the continuous ejecta blanket. The crater floor of Tycho exhibits three distinct units, distinguishable by their elevation and hummocky surface morphology. The distribution of impact melt pools and ejecta, as well as topographic asymmetries, support the formation of Tycho as an oblique impact from the W-SW. The asymmetric ejecta blanket, significantly reduced melt emplacement uprange, and the depressed uprange crater rim at Tycho suggest an impact angle of ∼25–45°.

The Compton–Belkovich Volcanic Complex (CBVC) is a 25 × 35 km feature on the lunar farside marked by elevated topography, high albedo, high thorium concentration, and high silica content. Morphologies indicate that the complex is volcanic in origin and compositions indicate that it represents rare silicic volcanism on the Moon. Constraining the timing of silicic volcanism at the complex is necessary to better understand the development of evolved magmas and when they were active on the lunar surface. We employ image analysis and crater size-frequency distribution (CSFD) measurements on several locations within the complex and at surrounding impact craters, Hayn (87 km diameter), and Compton (160 km diameter), to determine relative and absolute model ages of regional events. Using CSFD measurements, we establish a chronology dating regional resurfacing events and the earliest possible onset of CBVC volcanism at ∼3.8 Ga, the formation of Compton Crater at 3.6 Ga, likely resurfacing by volcanism at the CBVC at ∼3.5 Ga, and the formation of Hayn Crater at ∼1 Ga. For the CBVC, we find the most consistent results are obtained using craters larger than 300 m in diameter; the small crater population is affected by their approach to an equilibrium condition and by the physical properties of regolith at the CBVC.

Lunar surface volcanic processes are dominated by mare-producing basaltic extrusions. However, spectral anomalies, landform morphology, and granitic or rhyolitic components found in the Apollo sample suites indicate limited occurrences of non-mare, geochemically evolved (Si-enriched) volcanic deposits. Recent thermal infrared spectroscopy, high-resolution imagery, and topographic data from the Lunar Reconnaissance Orbiter (LRO) show that most of the historic “red spots” and other, less well-known locations on the Moon, are indeed silica rich (relative to basalt). Here we present a geologic investigation of the Lassell massif (14.65°S, 350.96°E) near the center of Alphonsus A basin in Mare Nubium, where high-silica thermal emission signals correspond with morphological indications of viscous (possibly also explosive) extrusion, and small-scale, low-reflectance deposits occur in a variety of stratigraphic relationships. Multiple layers with stair-step lobate forms suggest different eruption events or pulsing within a single eruption. Absolute model ages derived from crater size-frequency distributions (CSFDs) indicate that the northern parts of the massif were emplaced at ∼4 Ga, before the surrounding mare. However, CSFDs also indicate the possibility of more recent resurfacing events. The complex resurfacing history might be explained by either continuous resurfacing due to mass wasting and/or the emplacement of pyroclastics. Relatively low-reflectance deposits are visible at meter-scale resolutions (below detection limits for compositional analysis) at multiple locations across the massif, suggestive of pyroclastic activity, a quenched flow surface, or late-stage mafic materials. Compositional evidence from 7-band UV/VIS spectral data at the kilometer-scale and morphologic evidence for possible caldera collapse and/or explosive venting support the interpretation of a complex volcanic history for the Lassell massif.

Images of Mars taken by spacecraft in the last few decades indicate that the landscape has changed and that current processes are continuously changing the surface. The modifications of the landscape are caused by exogenic processes including eolian activity, mass movement, the growth and retreat of the polar caps, glacial processes and crater-forming impacts. In particular the High Resolution Stereo Camera (HRSC) on board Mars Express (MEx) and the Context Camera (CTX) on board the Mars Reconnaissance Orbiter (MRO) cover large areas at high resolution and thus are particularly well-suited to detect the extent and origin of surface changes on Mars. Multi-temporal observations of variable features on Mars became possible by the increasing number of repeated image acquisitions of the same surface areas. To support the investigation of surface changes that represents a key element in martian research, we developed MUTED, the “Multi-Temporal Database of Planetary Image Data”, which is a tool for the identification of the spatial and multi-temporal coverage of planetary image data from Mars. Using MUTED, scientists are able to identify the location, number, and time range of acquisitions of overlapping images from, for example, HRSC and CTX. MUTED also includes images from other planetary datasets such as those of the Mars Orbiter Camera (MOC), the Thermal Emission Imaging System (THEMIS), and the High Resolution Imaging Science Experiment (HiRISE). The database supports the identification and analysis of surface changes and short-lived surface processes on Mars based on fast automatic planetary image database queries. From the multi-temporal planetary image database and investigations based on multi-temporal observations we will better understand the interactions between the surface of Mars and external forces, including the atmosphere. MUTED is available for the planetary scientific community via the webpage of the Institut fur Planetologie (IfP) Muenster.

This study is part of an effort to build a mid-infrared database (7-14micron) of spectra for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer), an instrument onboard of the ESA/JAXA BepiColombo space probe to be launched to Mercury in 2017. Mercury was exposed to abundant impacts throughout its history. This study of terrestrial impactites can provide estimates of the effects of shock metamorphism on the mid-infrared spectral properties of planetary materials. In this study, we focus on the Noerdlinger Ries crater in Southern Germany, a well preserved and easily accessible impact crater with abundant suevite impactites. Suevite and melt glass bulk samples from Otting and Aumuehle, as well as red suevite from Polsingen were characterized and their reflectance spectra in mid-infrared range obtained. In addition, in-situ mid-infrared spectra were made from glasses and matrix areas in thin sections. The results show similar, but distinguishable spectra for both bulk suevite and melt glass samples, as well as in-situ measurements. Impact melt glass from Aumuehle and Otting have spectra dominated by a Reststrahlen band at 9.3-9.6 micron. Bulk melt rock from Polsingen and bulk suevite and fine-grained matrix have their strongest band between 9.4 to 9.6 micron. There are also features between 8.5 and 9 micron, and 12.5 - 12.8 micron associated with crystalline phases. There is evidence of weathering products in the fine-grained matrix, such as smectites. Mercury endured many impacts with impactors of all sizes over its history. So spectral characteristics observed for impactites formed only in a single impact like in the Ries impact event can be expected to be very common on planetary bodies exposed to many more impacts in their past. We conclude that in mid-infrared remote sensing data the surface of Mercury can be expected to be dominated by features of amorphous materials.

The Hellas basin on Mars is the second-largest topographically well-defined impact structure in the Solar System and has repeatedly been interpreted as a major sink of volcanic, glacio-fluvial and eolian materials. Based on established guidelines for planetary mapping, we compiled a comprehensive photogeological map of Hellas Planitia, i.e., the Hellas basin floor (1:2,000,000; ∼1.8 × 106 km2; see Supplementary online material ), using the Thermal Emission Imaging System (THEMIS-IR) day-time mosaic as basemap (supplemented by several other datasets). We identified 33 units, which were categorized into a “Rim Assemblage”, containing “Dissected units”, a “Layered rim sequence”, and “Other basin rim units”, as well as a “Floor Assemblage”, containing the “Honeycomb formation”, an “Interior formation”, and a “Plains sequence”. Relative dating of units was performed wherever contacts revealed stratigraphic relationships and was complemented by absolute model ages (AMAs) of all units that lend themselves to reliable crater-size frequency distribution (CSFDs) measurements. On the basis of our results, as well as AMAs of circum-Hellas volcanic provinces by previous authors, we compiled a chronostratigraphic model of the Hellas basin floor. The northern basin rim shows evidence (vast layered, hydrous mineral-bearing deposits containing meandering, channel-like valleys), that the early history of the basin until ∼3.8 Ga ago experienced extended periods of low-energy fluvial, and possibly lacustrine, activity. Superposing the layered rim sequence, the majority of the Hellas basin infill (∼1.5–1.7 × 106 km3) consists of volcanic material (a lower and an upper wrinkle-ridged plains unit), which was shortened by a compressive stress field relatively soon after its emplacement. Based on their ages and stratigraphic considerations, we identified Malea Patera (and possibly also Tyrrhena Patera) as a suitable source for the older, lower plains (∼3.8 Ga), and Hadriaca and/or Amphitrites Paterae for the younger, upper plains (∼3.7 Ga). Shortly after these volcanic episodes, the entire basin floor was covered by large amounts of deposits (>106 km3) containing aqueously altered mafic materials. We interpret the deposits to have originated from Hesperia Planum and the Hesperia-Hellas trough, where they might have been removed by glacio-fluvial processes, which also sculpted the Hellas rim sections along northern Promethei Terra and Malea Planum around the same time. Such an apparent correlation between nearby volcanic activity and increased erosion/deposition is in agreement with previous models, which suggest outgassing by a maximum in global volcanism at that time caused warmer episodes enabling repeated subaerial water run-off. After the emplacement of these deposits, intense erosion, likely deflation along a rim-parallel annulus, began to exhume the outer parts of the wrinkle-ridged plains again, forming an interior formation of more elevated erosional remnants including the Alpheus Colles. Since ∼3.7 Ga ago, fluvial activity of Dao/Niger and Harmakhis Valles dissected the eastern plains and emplaced pancake-shaped deposits in the basin center. Later, deflation and abrasion by katabatic winds moving through the Hellas basin in a clock-wise direction parallel to the basin floor outline carved out the northwestern Hellas Planitia trough (called Peneus Palus), possibly within a time span of few hundreds of Ma or less within the Amazonian. Being consistent with erosional patterns we observed within the basin, circulation models predict such winds to be ongoing today and might, thus, have recently exhumed the so called “honeycomb” formation on parts of Peneus Palus. This enigmatic, unique terrain was possibly formed by ductile deformation of pre-3.8 Ga material and appears to be partially covered by another unique landform, the “banded terrain”. Although we cannot rule out that it is the surface expression of a thicker unit, the banded terrain might represent flows of volatile-rich airfall deposits emplaced along the edges of the Hellas wind alley by turbulent, marginal wind currents, which currently/recently prevail on both sides of the Hellas Planitia trough. In summary, our investigations enabled us to draw an updated, comprehensive and self-consistent picture of the geologic evolution of the Hellas basin floor, including volcanic, (peri-)glacial, fluvial and eolian processes, their possible interactions, and the implications on the climatic and geologic development of the circum-Hellas region and the entire planet.

We have performed a combined geological and spectral analysis of two impact craters on Mercury: the 15 km diameter Waters crater (106°W; 9°S) and the 62.3 km diameter Kuiper crater (30°W; 11°S). Using the Mercury Dual Imaging System (MDIS) Narrow Angle Camera (NAC) dataset we defined and mapped several units for each crater and for an external reference area far from any impact related deposits. For each of these units we extracted all spectra from the MESSENGER Atmosphere and Surface Composition Spectrometer (MASCS) Visible-InfraRed Spectrograph (VIRS) applying a first order photometric correction. For all the mapped units, we analyzed the spectral slope in two wavelength ranges, 350–450 nm and 450–650 nm, and the absolute reflectance in the 700–750 nm range. Normalized spectra of Waters crater display a generally bluer spectral slope than the external reference area over both wavelength windows. Normalized spectra of Kuiper crater generally display a redder slope than the external reference area in the 350–450 nm window, while they display a bluer slope than the external reference area in the 450–650 nm wavelength range. The combined use of geological and spectral analyses enables reconstruction of the local scale stratigraphy beneath the two craters, providing insight into the properties of the shallower crust of Mercury. Kuiper crater, being ~4 times larger than Waters crater, exposes deeper layers with distinctive composition, while the result for Waters crater might indicate substantial compositional homogeneity with the surrounding intercrater plains, though we cannot exclude the occurrence of horizontal compositional heterogeneities in the shallow sub-surface.

Lunar samples returned by the Apollo program have provided insights into numerous solar system processes. However, no samples were returned from the lunar farside, where one of the Moon's most geologically important features resides: the 2500-km-diameter South Pole-Aitken basin (SPA). Here, we explore the hypothesis that lunar troctolite 76535 was excavated by SPA. This hypothesis is motivated by the sample's low peak shock pressure ( Neukum (1983) chronology.

The MErcury Radiometer and Thermal infrared Imaging Spectrometer (MERTIS) is a highly integrated instrument to study mineralogy and temperature distribution of Mercury’s surface in unprecedented quality. MERTIS was proposed in 2003 as payload of the Mercury Planetary Orbiter spacecraft of the joint ESA-JAXA BepiColombo mission. With the planned launch on top of an Ariane 5 in October of 2018, the mission will soon start its 7 years journey to Mercury. On its way to Mercury, BepiColombo will have 2 flybys of Venus and one of the Earth-Moon system. MERTIS will obtain data during each of these flybys – for Venus the first mid-infrared spectral data since Venera 15 in 1983. After arrival at Mercury in 2025 MERTIS will globally map the surface composition with a resolution of 500m, and study surface temperature variations providing an insight into the thermo-physical properties of the surface. To achieve this, MERTIS combines 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 7-14 µm (TIS) and 7-40 µm (TIR), respectively. Instrument operations in the challenging environment at Mercury with power and data constraints require a sophisticated mapping scheme for the TIS observations, which also has to account for the MERTIS calibration needs. Execution of this scheme creates challenges for the operation of the instruments, data processing, and the creation of map products. Extensive onground testing and rehearsals during the Venus and Earth flybys will ensure flawless performance at Mercury.

For a better spectral characterization of planetary bodies with enstatite-rich surfaces like Mercury or E-type asteroids, we synthesized two different enstatite (Mg2Si2O6) polymorphs: Orthoenstatite and clinoenstatite. Both enstatite polymorphs are known from the meteorite record and are commonly observed in aubrites and enstatite chondrites. The synthesized enstatites are particulate samples suitable for laboratory reflectance measurements and can be used for compositional modelling by preparing mixtures of samples in the laboratory or by using the sample's spectra in mathematical models. We report on the synthesis process, chemical composition, grain size distribution, and reflectance spectra of these synthetic enstatites covering the wavelength range from 0.25 to 17 μm, compare them to other pyroxenes (meteoritic enstatite and other synthetic enstatites and diopside), and discuss the implications of retrieving surface compositions of planetary bodies like E-type asteroids, comets, or Mercury. Both enstatite spectra are very bright in the VIS and NIR and show almost neutral to slightly bluish spectral slopes with a steep absorption in the UV. Very low iron in the enstatites (below ∼0.04 wt% FeO) already results in weak albeit noticeable absorptions in the VNIR between 0.4 and 0.9 μm. Orthoenstatite and clinoenstatite are not distinguishable based only on their spectra in the VIS and NIR. At the Reststrahlen bands in the MIR a systematic difference in the number and exact position of local minima at ∼10 μm between clinoenstatite and orthoenstatite is evident. This can be used to discern between the polymorphs in this wavelength range. Additionally, we can distinguish between Fe-free low- and high-Ca pyroxenes in the MIR.

In this paper, we investigate how well an automatic crater detection algorithm is suitable to determine the surface age of different lunar regions. A template-based crater detection algorithm is used to analyze image data under known illumination conditions. For this purpose, artificially illuminated crater templates are used to detect and count craters and their diameters in the areas under investigation. The automatic detection results are used to obtain the crater size-frequency distribution (CSFD) for the examined areas, which is then used for estimating the absolute model age (AMA) of the surface. The main focus of this work is to find out whether there exists an ideal sensitivity value for automatic crater detection to obtain smallest possible errors between the automatically derived AMA and a reference AMA derived from manually detected craters. The detection sensitivity threshold of our crater detection algorithm (CDA) is calibrated based on five different regions in Mare Cognitum on the Moon such that the age inferred from the manual crater counts corresponds to the age inferred from the CDA results. The obtained best detection threshold value is used to apply the CDA algorithm to another five regions in the lunar Oceanus Procellarum region. The accuracy of the method is examined by comparing the calculated AMAs with the manually determined ones from the literature. It is shown that the automatic age estimation yields AMA values that are generally consistent with the reference values with respect to the one standard deviation errors.

Multi-temporal spacecraft observations are key to detect and understand surface changes and time-critical processes on Mars. Since the 1970s, the number of orbital observations of Mars has increased to over one million images. The observations have revealed that the surface of Mars is changing due to exogenic processes, including eolian activity, mass movement, seasonal ice and frost cover, and crater-forming impacts. The increasing number of observations highlights the importance of efficient and convenient tools for planetary image data management and change detection analyses. To support the identification of surface changes we developed the Multi-Temporal Database of Planetary Image Data (MUTED), which is accessible at “http://muted.wwu.de”. The database enables scientists to quickly identify the spatial and multi-temporal coverage of planetary image data from Mars. As a basis for various change detection analyses, the location, number, and time range of acquisitions of overlapping images taken by the Viking Orbiter (VO), the Mars Orbiter Camera (MOC), the High Resolution Stereo Camera (HRSC), the Thermal Emission Imaging Instrument (THEMIS), the High Resolution Imaging Science Experiment (HiRISE), the Compact Reconnaissance Imaging Spectrometer of Mars (CRISM) and the Context Camera (CTX) as well as future instruments (e.g., Colour and Stereo Surface Imaging System (CaSSIS)) can be identified. The database will assist and optimize image data searches to support the analysis and understanding of short-term, seasonal, and long-term processes at the surface and in the atmosphere of Mars. To demonstrate the capability and scientific potential of the database, we analyzed the occurrence of dark slope streaks and observed their formation within a time interval of

Hillslope lobate landforms on Earth, formed by slow creep in periglacial terrain, always involve the action of liquid water. This chapter reviews previous observations of small-scale lobate forms from the northern hemisphere of Mars and adds new observations from the southern mid- and high latitudes that have a similar morphology, scale, and geological setting to those on Earth. We suggest that these features represent some of the best evidence for the action of liquid water at or near the surface in the Late Amazonian Epoch. We searched all available 25 cm/pix High-Resolution Imaging Science Experiment images (2007–13) from 40°S to 80°S. These newly reported small-scale lobes are extremely similar in morphology, morphometry, and setting to their northern counterparts and to their (possible) terrestrial counterparts. All martian lobes form at latitudes where near-surface ground ice is hypothesized and in close proximity to other landforms that might also indicate ground ice, such as small-scale polygonally patterned ground and gullies. We propose that a thaw-based hypothesis provides the best explanation for the assemblage of landforms and their geographical distribution. In this scenario gullies, patterned ground, and small-scale lobes may form a hydrologic continuum on slopes where available water content governs the type of landform produced.

Boguslawsky crater (72.9°S, 43.3°E, ~100 km in diameter) is a primary target for the Luna-Glob mission. The crater has a morphologically smooth (at the resolution of WAC images), flat, and horizontal floor, which is about 55–60 km in diameter. Two ellipses were selected as specific candidate landing areas on the floor: the western ellipse is centered at 72.9°S, 41.3°E and the eastern ellipse is centered at 73.9°S, 43.9°E. Both ellipses represent areas from which Earth is visible during the entire year of 2016 and lack permanently shadowed areas. Boguslawsky crater is located on or near the rim of the South Pole–Aitken basin, which provides the unique possibility to sample some of the most ancient rocks on the Moon that probably pre-date the SPA impact event. The low depth/diameter ratio of Boguslawsky suggests that the crater has been partly filled after its formation. Although volcanic flooding of the crater cannot be ruled out, the more likely process of filling of Boguslawsky is the emplacement of ejecta from nearby and remote large craters/basins. Three morphologically distinctive units are the most abundant within the selected landing ellipses: rolling plains (rpc), flat plains (fp), and ejecta from crater Boguslawsky-D (ejf), which occurs on the eastern wall of Boguslawsky. The possible contribution of materials from unknown sources makes the flat and rolling plains less desirable targets for landing. In contrast, ejecta from Boguslawsky-D represents local materials re-distributed by the Boguslawsky-D impact from the wall onto the floor of Boguslawsky. Thus, this unit, which constitutes about 50% of the eastern landing ellipse, represents a target of clearer provenance and a higher scientific priority.

The howardite, eucrite and diogenite (HED) meteorites are genetically related and represent the most voluminous group of achondrites. They are the closest analog materials to Vesta and V-type asteroids. Many of these meteorites were the focus of intense petrologic and visible to near infrared spectral studies. As ground-based and orbital observations of basaltic asteroids have increased, an improved understanding of HEDs is needed. For this study, we investigated 24 HED samples, mainly new finds from Northwest Africa (NWA). Visible to near infrared (up to 2.5 μm) spectral measurements under varying illumination and observation geometries were acquired for 4 samples. Phase reddening and bluing (i.e., increase and decrease in spectral slope) is observed for the visible slope as phase angle increase. Monotonic phase reddening can occur for the near infrared slope as phase angle increase. Non-systematic changes with phase angle are found for the Band Area Ratio parameter. At phase angles higher than ∼60°, the decrease of reflectance and decrease of pyroxene bands depth are undistinguishable from admixture of low albedo material to HED samples. To assess the precision of empirical equations relating spectral properties and composition, the pyroxenes, feldspar, and olivine chemistry of the samples was determined. Using previous calibrations, systematic overestimations of the ferrosilite (Fs) and wollastonite (Wo) contents are found, especially in the 15–40 Fs range. To overcome such discrepancies, a new set of empirical equations is proposed. For an application of the new calibration, we selected two compositional end-member areas on Vesta on the basis of their iron content. For the iron-poor terrain we found an average pyroxene composition of Fs30Wo5 and for the iron-rich terrain an average of Fs47Wo14.

We identified and mapped 28 mare basalt occurrences, between the Australe and South Pole-Aitken basins on the southern lunar farside, and determined their absolute model ages (AMAs) by performing crater size–frequency distribution (CSFD) measurements. Our study area can be subdivided into seven major mare basalt occurrences in and around Bolyai, Roche V, Rosseland, Pauli, and Roche craters, south of both Rosseland and Coblentz craters, as well as mare patches between Eotvos and Roche craters. The AMAs of the mare basalts in and around Bolyai crater range from 2.1 Ga to 3.5 Ga (two units), varying drastically within short distances. The mare patches south of Coblentz crater contain nine units that have AMAs ranging from 2.1 Ga to 3.8 Ga. The mare basalts in Roche V crater show an AMA of 2.2 Ga. We mapped seven volcanic units in Rosseland crater and derived AMAs for five of these units. The mare basalts in Rosseland crater show the youngest AMAs found in our study area, ranging from 1.5 Ga to 2.9 Ga. The mare basalt occurrence south of Rosseland crater shows significantly older ages with an AMA of 3.3 Ga. The mare basalts in Pauli and Roche craters show AMAs from 1.7 Ga to 3.1 Ga. The mare patches between Eotvos and Roche craters show a similar range of AMAs from 1.9 Ga to 3.1 Ga. The AMAs of the mare basalts in our study show that the lunar farside was volcanically active for nearly as long as the lunar nearside (1.2 Ga ago), or at least longer than previously thought (2.5 Ga ago) and predicted by models of the ascent and eruption of lunar basalts. In addition, we calculated thicknesses and volumes of the investigated mare basalts. With thicknesses between ∼21 m and ∼172 m and volumes from ∼0.1 km3 to ∼379 km3, the mare basalts in our study area show a wide range of dimensions, similar to other mare basalts of the lunar near- and farsides.

The observations of the surface of 4 Vesta by the Visible and Infrared Mapping Spectrometer (VIR) onboard the Dawn spacecraft reveals that its composition is dominated by pyroxenes with olivine in very localized spots. To derive new constraints on the surface composition of the asteroid, we apply a scattering model to VIR reflectance spectra. The model is first calibrated by performing a non-linear deconvolution of laboratory spectra of mineral mixtures and howardite, eucrite, diogenite (HED) meteorites. Abundance estimates of minerals are accurate to within 15–25% for the analyzed samples, while the estimated particle sizes are within the intervals of actual sizes. Grain size effects complicate spectral deconvolution and estimation of modal abundances of samples (both HED and mineral mixtures) that contain olivine. The magnesium-rich olivine detection threshold is 10–20% for large grain sizes (100s μm) and several 10s% for small grain sizes (

The large amount of multi-temporal high-resolution images acquired in the last few years offers the opportunity to identify morphological changes associated with recent geologic activity on the surface of Mars. In this study we focus on a single gully in Sisyphi Cavi, located in the south polar region at 1.44°E and 68.54°S. The gully incises the gullied equator-facing slope of an isolated polar pit within an infilled impact crater. It is important to notice that the following investigations describe the activity and modifications of an existing gully and not the formation of the gully itself. High-resolution image data analyses show new deposits at the terminus of the gully channel and on the gully apron within spring (after solar longitudes of 236°) of martian years (MY) 29 and 31. Our morphological investigations show that the identified new deposits were formed by dark flows through the entire gully deposited on top of the apron between solar longitudes ( L S ) ∼218° and ∼226°. Thermal data show a temperature increase between L S ∼218° and ∼226°. Near-infrared spectral data show relatively constant band strengths of CO 2 ice and H 2 O ice in this time range. After the formation of the dark flows (after L S ∼226°), temperatures increase rapidly from ∼180 K to >∼270 K at L S ∼250°. At this time, spectral data indicate that all volatiles on the surface sublimated. However, an earlier beginning of sublimation when the dark flows were observed (between L S ∼218° and ∼226°) is likely, due to the fact that the instruments can only show the last phase of sublimation (decrease of volatile band strengths). Spectral modeling shows that from winter to mid-spring, the surface of the studied area is covered by translucent CO 2 slab-ice contaminated by minor amounts of H 2 O ice and dust. Furthermore, our spectral modeling indicates that the dark material most likely flows on top of the CO 2 slab-ice cover. Three different scenarios were proposed to explain the identified dark flows, including (1) flows supported by liquid H 2 O, (2) flows supported by CO 2 gas, and (3) dry flows. On the basis of our study we find that scenario (1) is unlikely because of the very low temperatures. While scenario (2) is consistent with the observed beginning of CO 2 ice sublimation in the study area, it is unlikely because of the limitation of the activity to only one gully compared to surrounding gullies that share the same morphologies, slope angles, and volatile contents. Also with scenario (3), dry flows, the activity of only one gully is difficult to explain. Thus, we propose a mixture of scenario (2 and 3), dry flows supported by the ongoing sublimation of CO 2 ice within the gully, to be the most plausible scenario, when the observed active gully comprises different source material than the surrounding gullies, i.e., a higher content of probably sand-sized material from outcrops located in the alcove.

Utopia and Acidalia Planitiae show a set of similar morphologic features indicative of the presence of large reservoirs of water/mud in these regional topographic lows. The most important of these features are: (1) impact crater ejecta morphology that progressively changes from ballistic/rampart at the basins periphery to strongly degraded pancake-like in the central portions of the basins, and (2) etched flows (interpreted as mudflows) that are concentrated in those regions of the central portions of both basins where the pancake-like ejecta prevail. The Vastitas Borealis Formation (VBF) in Utopia and Acidalia Planitiae represents the uppermost stratigraphic limit of possible reservoirs in both basins and has practically the same age in these regions; ∼3.57 (±0.02) Ga in Utopia Planitia and ∼3.61 (+0.05/−0.08) Ga in Acidalia Planitia. The southern contact of the VBF closely follows specific contour lines in Utopia Planitia (∼−3.6 km ± 54 m, over a distance of ∼1500 km) and Acidalia Planitia (∼−3.9 km ± 70 m, over the distance of ∼6000 km). The presence of the large water/mud reservoirs and the age and topographic configuration of the VBF in Utopia and Acidalia Planitiae are consistent with the existence of an extensive single body of water (an ocean) in the northern plains of Mars.

The Ries crater is a well-preserved, complex impact crater that has been extensively used in the study of impact crater formation processes across the solar system. However, its geologic structure, especially the megablock zone, still poses questions regarding crater formation mechanics. The megablock zone, located between the inner crystalline ring and outer, morphologic crater rim, consists of allochthonous crystalline and sedimentary blocks, Bunte Breccia deposits, patches of suevite, and parautochthonous sedimentary blocks that slumped into the crater during crater modification. Our remote sensing detection method in combination with a shallow drilling campaign and geoelectric measurements at two selected megablocks proved successful in finding new megablock structures (>25 m mean diameter) within the upper approximately 1.5 m of the subsurface in the megablock zone. We analyzed 1777 megablocks of the megablock zone, 81 of which are new discoveries. In our statistical analysis, we also included 2318 ejecta blocks >25 m beyond the crater rim. Parautochthonous megablocks show an increase in total area and size toward the final crater rim. The sizes of allochthonous megablocks generally decrease with increasing radial range, but inside the megablock zone, the coverage with postimpact sediments obscures this trend. The size-frequency distribution of all megablocks obeys a power-law distribution with an exponent between approximately −1.7 and −2.3. We estimated a total volume of 95 km3 of Bunte Breccia and 47 km3 of megablocks. Ejecta volume calculations and a palinspastic restoration of the extension within the megablock zone indicate that the transient cavity diameter was probably 14–15 km.

As part of systematic global mapping of Vesta using data returned by the Dawn spacecraft, we have produced a geologic map of the north pole quadrangle, Av-1 Albana. Extensive seasonal shadows were present in the north polar region at the time of the Dawn observations, limiting the ability to map morphological features and employ color or spectral data for determination of composition. The major recognizable units present include ancient cratered highlands and younger crater-related units (undivided ejecta, and mass-wasting material on crater floors). The antipode of Vesta’s large southern impact basins, Rheasilvia and Veneneia, lie within or near the Av-1 quadrangle. Therefore it is of particular interest to search for evidence of features of the kind that are found at basin antipodes on other planetary bodies. Albedo markings known as lunar swirls are correlated with basin antipodes and the presence of crustal magnetic anomalies on the Moon, but lighting conditions preclude recognition of such albedo features in images of the antipode of Vesta’s Rheasilvia basin. ‘‘Hilly and lineated terrain,’’ found at the antipodes of large basins on the Moon and Mercury, is not present at the Rheasilvia or Veneneia antipodes. We have identified small-scale linear depressions that may be related to increased fracturing in the Rheasilvia and Veneneia antipodal areas, consistent with impact-induced stresses (Buczkowski, D. et al. [2012b]. Analysis of the large scale troughs on Vesta and correlation to a model of giant impact into

The Dawn Framing Camera (FC) has imaged the northern hemisphere of the Asteroid (4) Vesta at high spatial resolution and coverage. This study represents the first investigation of the overall geology of the northern hemisphere (22–90°N, quadrangles Av-1, 2, 3, 4 and 5) using these unique Dawn mission observations. We have compiled a morphologic map and performed crater size–frequency distribution (CSFD) measurements to date the geologic units. The hemisphere is characterized by a heavily cratered surface with a few highly subdued basins up to ∼200 km in diameter. The most widespread unit is a plateau (cratered highland unit), similar to, although of lower elevation than the equatorial Vestalia Terra plateau. Large-scale troughs and ridges have regionally affected the surface. Between ∼180°E and ∼270°E, these tectonic features are well developed and related to the south pole Veneneia impact (Saturnalia Fossae trough unit), elsewhere on the hemisphere they are rare and subdued (Saturnalia Fossae cratered unit). In these pre-Rheasilvia units we observed an unexpectedly high frequency of impact craters up to ∼10 km in diameter, whose formation could in part be related to the Rheasilvia basin-forming event. The Rheasilvia impact has potentially affected the northern hemisphere also with S–N small-scale lineations, but without covering it with an ejecta blanket. Post-Rheasilvia impact craters are small (

Vesta is a unique, intermediate class of rocky body in the Solar System, between terrestrial planets and small asteroids, because of its size (average radius of ∼263 km) and differentiation, with a crust, mantle and core. Vesta’s low surface gravity (0.25 m/s2) has led to the continual absence of a protective atmosphere and consequently impact cratering and impact-related processes are prevalent. Previous work has shown that the formation of the Rheasilvia impact basin induced the equatorial Divalia Fossae, whereas the formation of the Veneneia impact basin induced the northern Saturnalia Fossae. Expanding upon this earlier work, we conducted photogeologic mapping of the Saturnalia Fossae, adjacent structures and geomorphic units in two of Vesta’s northern quadrangles: Caparronia and Domitia. Our work indicates that impact processes created and/or modified all mapped structures and geomorphic units. The mapped units, ordered from oldest to youngest age based mainly on cross-cutting relationships, are: (1) Vestalia Terra unit, (2) cratered highlands unit, (3) Saturnalia Fossae trough unit, (4) Saturnalia Fossae cratered unit, (5) undifferentiated ejecta unit, (6) dark lobate unit, (7) dark crater ray unit and (8) lobate crater unit. The Saturnalia Fossae consist of five separate structures: Saturnalia Fossa A is the largest (maximum width of ∼43 km) and is interpreted as a graben, whereas Saturnalia Fossa B-E are smaller (maximum width of ∼15 km) and are interpreted as half grabens formed by synthetic faults. Smaller, second-order structures (maximum width of

On 6 March 2015, Dawn arrived at Ceres to find a dark, desiccated surface punctuated by small, bright areas. Parts of Ceres’ surface are heavily cratered, but the largest expected craters are absent. Ceres appears gravitationally relaxed at only the longest wavelengths, implying a mechanically strong lithosphere with a weaker deep interior. Ceres’ dry exterior displays hydroxylated silicates, including ammoniated clays of endogenous origin. The possibility of abundant volatiles at depth is supported by geomorphologic features such as flat crater floors with pits, lobate flows of materials, and a singular mountain that appears to be an extrusive cryovolcanic dome. On one occasion, Ceres temporarily interacted with the solar wind, producing a bow shock accelerating electrons to energies of tens of kilovolts.

The MERTIS instrument is a thermal infrared imaging spectrometer onboard of ESA's cornerstone mission BepiColombo to Mercury. MERTIS will provide detailed information about the mineralogical composition of Mercury's surface layer by measuring the spectral emittance in the spectral range from 7-14 μm with a high spatial and spectral resolution. Furthermore MERTIS will obtain radiometric measurements in the spectral range from 7-40 μm to study the thermo-physical properties of the surface material. Under the lead of the German Aerospace Center DLR (Dep. Optical Information Systems, Berlin) a development model (DM) is in development which integrates all MERTIS sub-units of later flight models. With the DM the general design and performance goals of the system shall be investigated and verified. Besides a general overview about the instrument principles the following topics are addressed: Optics setup with a Three Mirror Anastigmatic (TMA) telescope and Offner Spectrometer, Manufacturing techniques for the robust and high precision optics and Radiometer Concept and Design

For the structure of this chapter we chose to discuss the terrestrial planets and their satellites in terms of their geological evolution with time. We start with ancient times and end with modern times. Orthogonal to this time line, we describe the processes and their effects acting on each planetary body. Our home planet, Earth, serves as a reference framework and important anchor point for our comparative planetology studies because it is the best studied object for which we have knowledge gained from hundreds of years of sample analyses, mapping efforts, drilling, mining, and remote sensing, to name only a few sources of information. Comparing the entire suite of terrestrial planets requires to individually characterize each of them and the processes acting on them through time. However, there are several limitations involved in such a reconstruction, partially due to the discontinuous and fragmentary nature of the accessible geologic records and the lack of enough well-contextualised field data.

On March 6, 2016 at 21:36:51 UT, extended areas of Upper Austria, Bavaria (Germany) and the southwestern part of the Czech Republic were illuminated by a very bright bolide. This bolide was recorded by instruments in the Czech part of the European Fireball Network and it enabled complex and precise description of this event including prediction of the impact area. So far six meteorites totaling 1473 g have been found in the predicted area. The first pieces were recovered on March 12, 2016 on a field close to the village of Stubenberg (Bavaria). Stubenberg is a weakly shocked (S3) fragmental breccia consisting of abundant highly recrystallized rock fragments embedded in a clastic matrix. The texture, the large grain size of plagioclase, and the homogeneous compositions of olivine (Fa31.4) and pyroxene (Fs25.4) clearly indicate that Stubenberg is an LL6 chondrite breccia. This is consistent with the data on O, Ti, and Cr isotopes. Stubenberg does not contain solar wind-implanted noble gases. Data on the bulk chemistry, IR spectroscopy, cosmogenic nuclides, and organic components also indicate similarities to other metamorphosed LL chondrites. Noble gas studies reveal that the meteorite has a cosmic ray exposure (CRE) age of 36 ± 3 Ma and that most of the cosmogenic gases were produced in a meteoroid with a radius of at least 35 cm. This is larger than the size of the meteoroid which entered the Earth's atmosphere, which is constrained to

Fan-shaped accumulations of debris flow deposits are common landforms in polar regions such as Svalbard. Although depositional processes in these environments are of high interest to climate as well as Mars-analog research, several parameters, e.g., debris flow recurrence periods, remain poorly constrained. Here, we present an investigation based on remote sensing as well as in situ data of a ~ 0.4 km2 large colluvial fan in Hanaskogdalen, central Spitsbergen. We analyzed high resolution satellite and aerial images covering five decades from 1961 to 2014 and correlated them with lichenometric dating as well as meteorological data. Image analyses and lichenometry deliver consistent results and show that the recurrence period of large debris flows (≥ 400 m3) is about 5 to 10 years, with smaller flows averaging at two per year in the period from 2008 to 2013. While this is up to two orders of magnitude shorter than previous estimates for Svalbard (80 to 500 years), we found the average volume of ~ 220 m3 per individual flow to be similar to previous estimates for the region. Image data also reveal that an avulsion took place between 1961 and 1976, when the active part of the fan moved from its eastern to its western portion. A case study of the effects of a light rain event (~ 5 mm/day) in the rainy summer of 2013, which triggered a large debris flow, further shows that even light precipitation can trigger major flows. This is made possible by multiple light rain events or gradual snow melt pre-saturating the permafrost ground and has to be taken into account when predicting the likelihood of potentially hazardous mass wasting in polar regions. Furthermore, our findings imply a current net deposition rate on the colluvial fan of ~ 480 m3/year, which is slightly less than the integrated net deposition rate of 576 to 720 m3/year resulting from the current fan volume divided by the 12,500 to 10,000 years since the onset of fan build-up after the area's deglaciation. However, the actual deposition rate, which should increase in a warmer climate including more rain, cannot be constrained due to effects like ongoing toe-cutting of the debris fan and some flows only causing internal redistributions.

Five decades of observations of Ceres suggest that the dwarf planet has a composition similar to carbonaceous meteorites and may have an ice-rich outer shell protected by a silicate layer. NASA’s Dawn spacecraft has detected ubiquitous clays, carbonates and other products of aqueous alteration across the surface of Ceres, but surprisingly it has directly observed water ice in only a few areas. Here we use Dawn Framing Camera observations to analyse lobate morphologies on Ceres’ surface and we infer the presence of ice in the upper few kilometres of Ceres. We identify three distinct lobate morphologies that we interpret as surface flows: thick tongue-shaped, furrowed flows on steep slopes; thin, spatulate flows on shallow slopes; and cuspate sheeted flows that appear fluidized. The shapes and aspect ratios of these flows are different from those of dry landslides—including those on ice-poor Vesta—but are morphologically similar to ice-rich flows on other bodies, indicating the involvement of ice. Based on the geomorphology and poleward increase in prevalence of these flows, we suggest that the shallow subsurface of Ceres is comprised of mixtures of silicates and ice, and that ice is most abundant near the poles. Despite evidence for an ice-rich outer shell, little water ice has been observed on the surface of Ceres. Lobate morphologies observed on Ceres that are increasingly prevalent towards the dwarf planet’s poles are consistent with ice-rich flows.

Radar provides a unique means to analyze the surface and subsurface physical properties of geologic deposits, including their wavelength-scale roughness, the relative depth of the deposits, and some limited compositional information. The NASA Lunar Reconnaissance Orbiter's (LRO) Miniature Radio Frequency (Mini-RF) instrument has enabled these analyses on the Moon at a global scale. Mini-RF has accumulated 67% coverage of the lunar surface in S-band (12.6 cm) radar with a resolution of 30 m/pixel. Here we present new Mini-RF global orthorectified uncontrolled S-band maps of the Moon and use them for analysis of lunar surface physical properties. Reported here are readily apparent global- and regional-scale differences in lunar surface physical properties that suggest three distinct terranes, namely: a (1) Nearside Radar Dark Region; (2) Orientale basin and continuous ejecta; and the (3) Highlands Radar Bright Region. Integrating these observations with new data from LRO's Diviner Radiometer rock abundance maps, as well Clementine and Lunar Prospector derived compositional values show multiple distinct lunar surface terranes and sub-terranes based upon both physical and compositional surface properties. Previous geochemical investigations of the Moon suggested its crust is best divided into three to four basic crustal provinces or terranes (Feldspathic Highlands Terrane (-An and -Outer), Procellarum KREEP Terrane, and South Pole Aitken Terrane) that are distinct from one another. However, integration of these geochemical data sets with new geophysical data sets allows us to refine these terranes. The result shows a more complex view of these same crustal provinces and provides valuable scientific and hazard perspectives for future targeted human and robotic exploration.

We derived model functions for the crater production size-frequency distribution and chronology of the asteroids 951 Gaspra, 243 Ida, 21 Lutetia and 4 Vesta, based on a lunar-like crater production function and a lunar-like chronology with a smooth exponential decay in impact rate for the first ~1 Ga of Solar System history. For Gaspra, Ida and Lutetia we find surface ages roughly in agreement with published data. Using the same approach for Vesta leads to results with high correlation to Ar–Ar reset ages of HED meteorites, for which a strong dynamical and spectroscopic connection to Vesta has been found. In contrast to recently published young formation ages of the Rheasilvia and Veneneia basins of about 1 and 2 Ga, respectively, we find for Rheasilvia a formation age of 3.5±0.1 Ga and for the Veneneia formation a lower limit of 3.7±0.1 Ga. For comparison we also give surface model ages for a preliminary version of a chronology (pers. comm. D.P. O׳Brien) based on the Late Heavy Bombardment theory. Error bars presented in our work stem only from statistical analysis of measured crater distributions and do not include the uncertainty of the used chronology model.

The magmatism characterizing the early history of the asteroid Vesta has long been investigated with the mafic and ultramafic meteorites howardite, eucrite, and diogenite (HED). The lack of geologic context for the meteorites, however, has limited its understanding. Here we use the visible to near-IR (VIR) orbital observations of Vesta's surface to detect relative enrichments in olivine and to study the associated geologic features. Because the near-IR signature of olivine on Vesta's surface is subtle relative to the widespread pyroxene absorption bands, a method was developed to distinguish olivine enrichments from admixture of pyroxenes with high Fe2+/M1, dark material, and potential Fe-bearing glass. Relative enrichment of olivine (~

A study in context with the Helmholtz Alliance ‘Planetary Evolution and Life’ focused on the (temporary) existence of liquid water, and the likelihood that Mars has been or even is a habitable planet. Both geomorphological and mineralogical evidence point to the episodic availability of liquid water at the surface of Mars, and physical modeling and small-scale observations suggest that this is also true for more recent periods. Habitable conditions, however, were not uniform over space and time. Several key properties, such as the availability of standing bodies of water, surface runoff and the transportation of nutrients, were not constant, resulting in an inhomogeneous nature of the parameter space that needs to be considered in any habitability assessment. The planetary evolution of Mars led to environmental changes, which in turn affected its habitability potential. Similarly, considerable variations in climate due to latitudinal or elevation effects combined with a diverse surface geology caused distinctively different local conditions that influenced the planet׳s habitable potential.

Results of our detailed geological mapping and interpretation of the nature and relative and absolute model ages of units and structures in the SW portion of Utopia Planitia (20–45°N, 100–120°E) suggest the following. (1) The size–frequency distribution (SFD) of craters that both are buried by materials of the Vastitas Borealis units (VB) and superpose its surface indicate that the absolute model ages of terrain predating the emplacement of the VB is ∼3.7 Ga. (2) Lack of craters that are partly embayed by materials of the VB in the SW portion of Utopia Planitia implies that the emplacement of the VB was faster than the rate of accumulation of impact craters and is consistent with the geologically short time of emplacement of the VB due to catastrophic release of water from outflow channels (e.g., Carr, M.H. [1996]. Water on Mars. Oxford University Press, New York, p. 229). (3) The SFD of craters that superpose the surface of the VB indicates an absolute model age of ∼3.6–3.5 Ga. The absolute model ages of etched flows, which represent the upper stratigraphic limit of the VB, are estimated to be ∼3.5 Ga. (4) The majority of the larger (i.e., >1 km) impact craters show ejecta morphologies (rampart and pancake-like ejecta) that are indicative of the presence of ice/water in the target materials. The distal portions of the pancake-like ejecta are heavily degraded (not due to embayment). This suggests that these craters formed in targets that contained higher abundances of volatiles. (5) The diameter ranges of the craters with either rampart- or pancake-like ejecta are overlapping (from ∼2 to ∼60 km). Craters with pancake-like ejecta are concentrated within the central portion of the Utopia basin (less than ∼1000 km from the basin center) and rampart craters occur at the periphery of the basin. This pattern of the crater spatial distribution suggests that materials within the center of Utopia Planitia contained more ice/water. (6) Etched flows around the central portion of Utopia Planitia were erupted from beneath of the surface of the VB. Their morphology and pattern of degradation, however, are inconsistent with lava and, instead, indicate formation of the flows due to mud volcanism. (7) Etched flows are spatially associated with giant polygons and there is evidence that these features populated the center portion of Utopia Planitia before it was covered by the Elysium-derived units. The outer (southern) edge of the zone of polygonal troughs and etched flows approximately corresponds to the transition from pancake-like ejecta to rampart ejecta. This suggest that the outer edge of the zone of the polygons and flows may outline the deeper portions of the large body (∼2000 km across) of water/ice that likely existed in the center of Utopia Planitia in late Hesperian.

The dwarf planet Ceres (equatorial diameter 963km) is the largest object that has remained in the main asteroid belt ( Russell and Raymond, 2012 ), while most large bodies have been destroyed or removed by dynamical processes ( Minton and Malhotra, 2009 , Petit et al., 2001 ). Pre-Dawn investigations ( McCord and Sotin, 2005 , Castillo-Rogez and McCord, 2010 ; Castillo-Rogez et al., 2011 ) suggest that Ceres is a thermally evolved, but still volatile-rich body with potential geological activity, that was never completely molten, but possibly differentiated into a rocky core, an ice-rich mantle, and may contain remnant internal liquid water. Thermal alteration should contribute to producing a (dark) carbonaceous chondritic-like surface ( McCord and Sotin, 2005 , Castillo-Rogez and McCord, 2010 ; Castillo-Rogez et al., 2011 ; Nathues et al., 2015 ) containing ammoniated phyllosilicates ( King et al., 1992 ; De Sanctis et al., 2015 , De Sanctis et al., 2016 ). Here we show and analyse global contrast-rich colour mosaics, derived from a camera on-board Dawn at Ceres ( Russell et al., 2016 ). Colours are unexpectedly more diverse on global scale than anticipated by Hubble Space Telescope ( Li et al., 2006 ) and ground-based observations ( Reddy et al. 2015 ). Dawn data led to the identification of five major colour units. The youngest units identified by crater counting, termed bright and bluish units, are exclusively found at equatorial and intermediate latitudes. We identified correlations between the distribution of the colour units, crater size, and formation age, inferring a crustal stratigraphy. Surface brightness and spectral properties are not correlated. The youngest surface features are the bright spots at crater Occator (~O 92km). Their colour spectra are highly consistent with the presence of carbonates while most of the remaining surface resembles modifications of various types of ordinary carbonaceous chondrites.

Although olivine was expected to occur within the deep, south-pole basins of asteroid Vesta, which are thought to be excavated mantle rocks, spectral data from NASA’s Dawn spacecraft show that it instead occurs as near-surface materials in Vesta’s northern hemisphere. Between July 2011 and September 2012, NASA's Dawn spacecraft was in orbit around the asteroid Vesta. In this paper, Dawn's Visible and Infrared Mapping Spectrometer (VIR) team presents a surprising finding — the signature of olivine on the asteroid's surface. Olivine is a major component of the mantle of differentiated bodies, including Earth. Vesta is a large asteroid, large enough to have differentiated into an Earth-like layered structure and the expectation was that olivine would be found within Vesta's deep, south-pole basins, thought to be excavated mantle rocks. Yet the spectroscopic data reveal olivine-rich material close to the surface in the northern hemisphere. An understanding of the differentiation processes that have occurred on Vesta will be invaluable as a window on the primordial Solar System, but these latest findings show that Vesta's evolutionary history is more complicated than was thought. Olivine is a major component of the mantle of differentiated bodies, including Earth. Howardite, eucrite and diogenite (HED) meteorites represent regolith, basaltic-crust, lower-crust and possibly ultramafic-mantle samples of asteroid Vesta, which is the lone surviving, large, differentiated, basaltic rocky protoplanet in the Solar System1. Only a few of these meteorites, the orthopyroxene-rich diogenites, contain olivine, typically with a concentration of less than 25 per cent by volume2. Olivine was tentatively identified on Vesta3,4, on the basis of spectral and colour data, but other observations did not confirm its presence5. Here we report that olivine is indeed present locally on Vesta’s surface but that, unexpectedly, it has not been found within the deep, south-pole basins, which are thought to be excavated mantle rocks6,7,8. Instead, it occurs as near-surface materials in the northern hemisphere. Unlike the meteorites, the olivine-rich (more than 50 per cent by volume) material is not associated with diogenite but seems to be mixed with howardite, the most common7,9 surface material. Olivine is exposed in crater walls and in ejecta scattered diffusely over a broad area. The size of the olivine exposures and the absence of associated diogenite favour a mantle source, but the exposures are located far from the deep impact basins. The amount and distribution of observed olivine-rich material suggest a complex evolutionary history for Vesta.

We present new insights into possible formation mechanisms and implications for previously identified landforms of putative glacio-fluvial origin along the southern rim of the Argyre basin on Mars. We compiled a detailed geomorphologic map of the study area and conducted morphometric and stratigraphic analyses of specific features, e.g., esker-like sinuous ridges on layered terrain. Based on their morphology and orientations, we subdivided the sinuous ridges on the southern Argyre basin floor into two populations, which could reflect changing conditions of glacial retreat. With the transition and oblique path methods we quantified the ice thickness of the glacier under which the first, lesser degraded, population of ridges probably formed. Our results imply an ice sheet thickness of ~2 km and at least ~100,000–150,000 km³ of ice on the southern floor of the Argyre basin during the time those ridges were deposited (>30× the volume of Vatnajokull, Iceland). The second population of ridges is more degraded and shows layers occasionally extending into the surrounding layered terrain. Comparisons with the morphology surrounding the Piedmont-style Malaspina Glacier in Alaska show similarities, suggesting population II formed during a glacial retreat involving back- and downwasting of stagnant ice lying beneath fresh outwash sediments, creating degraded and layered lag deposits around the emerging eskers. If outwash sediments were fed by the same drainage source as the eskers, sections of layers can extend from a given ridge into the surrounding deposits. The differences between the two ridge populations are probably a result of the subglacial drainage direction changing from northward to north-eastward around 3.6 Ga ago. This was likely coupled with the deposition of less or no outwash sediments resulting in a decrease of lag deposits. A subsequent phase of stagnant glacial retreat left no terminal moraines and largely preserved the population I ridges, thus implying sufficient glacial thinning in order for the ice flow to stop. This, in turn, may have been caused either by sublimation in a cold but increasingly dry climate, or by melting and increased glacier surface runoff due to rising temperatures.