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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 <∼5 days in different regions on Mars. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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 ~2km and at least ~100,000–150,000km³ of ice on the southern floor of the Argyre basin during the time those ridges were deposited (>30× the volume of Vatnajökull, 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 3.6Ga 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. [Copyright &y& Elsevier]

Abstract: The Moon is key to understanding both Earth and our Solar System in terms of planetary processes and has been a witness of the Solar System history for more than 4.5Ga. Building on earlier telescopic observations, our knowledge about the Moon was transformed by the wealth of information provided by Apollo and other space missions. These demonstrated the value of the Moon for understanding the fundamental processes that drive planetary formation and evolution. The Moon was understood as an inert body with its geology mainly restricted to impact and volcanism with associated tectonics, and a relative simple composition. Unlike Earth, an absence of plate tectonics has preserved a well-defined accretion and geological evolution record. However recent missions to the Moon show that this traditional view of the lunar surface is certainly an over simplification. For example, although it has long been suspected that ice might be preserved in cold traps at the lunar poles, recent results also indicate the formation and retention of OH− and H2O outside of polar regions. These volatiles are likely to be formed as a result of hydration processes operating at the lunar surface including the production of H2O and OH by solar wind protons interacting with oxygen-rich rock surfaces produced during micrometeorite impact on lunar soil particles. Moreover, on the basis of Lunar Prospector gamma-ray data, the lunar crust and underlying mantle has been found to be divided into distinct terranes that possess unique geochemical, geophysical, and geological characteristics. The concentration of heat producing elements on the nearside hemisphere of the Moon in the Procellarum KREEP Terrane has apparently led to the nearside being more volcanically active than the farside. Recent dating of basalts has shown that lunar volcanism was active for almost 3Ga, starting at about 3.9–4.0Ga and ceasing at ∼1.2Ga. A recent re-processing of the seismic data supports the presence of a partially molten layer at the base of the mantle and shows not only the presence of a 330km liquid core, but also a small solid inner core. Today, the Moon does not have a dynamo-generated magnetic field like that of the Earth. However, remnant magnetization of the lunar crust and the paleomagnetic record of some lunar samples suggest that magnetization was acquired, possibly from an intrinsic magnetic field caused by an early lunar core dynamo. In summary, the Moon is a complex differentiated planetary object and much remains to be explored and discovered, especially regarding the origin of the Moon, the history of the Earth–Moon system, and processes that have operated in the inner Solar System over the last 4.5Ga. Returning to the Moon is therefore the critical next stepping-stone to further exploration and understanding of our planetary neighborhood. [Copyright &y& Elsevier]

Abstract: Scheduled for launch on board the BepiColombo Mercury Planetary Orbiter (MPO) in 2014, the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is an innovative instrument for studying the surface composition and mineralogy of planet Mercury. MERTIS combines an uncooled grating push broom IR-spectrometer (TIS) with a radiometer (TIR), which will operate in the wavelength region of 7–14 and 7–40μm, respectively. The spatial resolution of the MERTIS observations will be about 500m globally and better than 500m for approximately 5–10% of the surface. The thermal infrared range offers unique diagnostic capabilities to study the surface composition of Mercury. In particular, feldspars can easily be detected and characterized, because they show several diagnostic spectral signatures in the 7–14μm range: the Christiansen feature, reststrahlen bands, and the transparency feature. In addition, MERTIS will allow the identification and mapping of elemental sulfur, pyroxenes, olivines, and other complex minerals. The scientific objectives of MERTIS include: (1) characterization of Mercury''s surface composition, (2) identification of rock-forming minerals, (3) mapping of the surface mineralogy, and (4) study of surface temperature variations and the thermal inertia. In preparation for the MERTIS data interpretation, we are performing spectral measurements of appropriate analogue materials in the Planetary Emissivity Laboratory (PEL) and are building a spectral library (Berlin Emissivity Database (BED)) of these materials for a variety of grain sizes. [Copyright &y& Elsevier]

Abstract: The observation of gullies on Mars raised questions about the presence of liquid water in the recent past. In some regions like Hale and Bond crater, gullies occur in one crater (Hale) but do not in another crater nearby (Bond). These regional differences have been interpreted as an argument for a formation of the gullies related to groundwater. The formation of gullies on Earth depends on rainfall and/or melting of snow as well as on several parameters such as the presence of steep slopes and sufficient amounts of fines and debris. We investigated the Hale/Bond region for differences in crater wall morphology and texture, slopes, and thermal properties to determine whether the gully formation is dependent on factors such as steep slope angles and availability of fine-grained material. Morphologically there exist two kinds of gullies in the Hale crater: Gullies on the south- and east-facing crater slopes have a pristine appearance with deep channels eroded into the talus material and well-preserved aprons. Gully-like features on the north- and west-facing slopes are degraded and superposed by craters, indicating that they are old in comparison to the pristine ones. However, their formation process is unclear and might be due to debris flows, surface runoff or dry mass wasting processes or a combination of these processes. The crater walls of Bond do not show gullies. Their morphology is most likely consistent with a degraded mantle deposit. Slope measurements reveal that the gullies in Hale crater occur on slopes between ∼20° and ∼30° in contrast to the slopes without gullies in Bond that are between ∼10° and ∼20° steep. Mean thermal inertia values on slopes with younger gullies are ∼175Jm−2 K−1 s−1/2 corresponding to higher amounts of fine-grained material. At slopes with older gully-like features mean thermal inertia values are ∼315Jm−2 K−1 s−1/2 corresponding to higher amounts of bedrock or possibly indurated grain sizes. Mean thermal inertia values of the Bond crater walls are ∼230Jm−2 K−1 s−1/2 indicating more consolidated terrain possibly due to the cementation of the dissected mantle material. From our investigation we conclude that the occurrence of gullies in the Hale/Bond region most likely depends on the distribution of unconsolidated material and steep slopes. The regional and local gully distribution on Mars likely varies due to differences in topography and surface material properties. Their proposed clustered distribution on Mars is not an argument for a groundwater formation mechanism of the gullies. [Copyright &y& Elsevier]

Results of NASA's Dawn mission indicate that Ceres, the biggest object in the main asteroid belt, may be geologically active because it shows changes in its morphology that might have happened in geologically recent times. Juling is a ∼2.5 Ma old, 20-km diameter impact crater on this dwarf planet, which has an extensive ejecta blanket of spectrally bright bluish material and water ice exposures on its steep northern inner wall. The crater floor is dominated by a spectrally reddish material, which is distinct from other surface types in this region. No other crater of Juling's size on Ceres, shows such a reddish floor. In addition, the floor has a complex morphology characterized by lobate flows and indications of a north-south directed mass wasting possibly leading to the elongated, ∼16 km long and several hundred-meter-high central structure. Here we describe the characteristics of the material that constitutes the floor, and we present a geological map of the crater, using the Framing Camera (FC) imagery. From the analysis of data acquired by the Visible and Infrared Spectrometer (VIR), we did not find evidence for the presence of organic rich materials in Juling at the available data resolution. The spectrum of the floor material seems to be a combination of mineralogy and physical properties of the regolith. Our findings suggest that the processes leading to the reddish material and the peculiar morphology of the crater floor, must have occurred after the formation of Juling crater. • Juling and its neighbor Kupalo are young craters that share remarkably bright ejecta. • Water ice may have triggered and supported landslides that reshaped the crater. • Material filling Juling's floor is spectrally distinct from the surrounding terrain. • The infrared data does not indicate presence of organic-rich material in Juling. • Physical properties and mineralogy likely cause the red spectral slope of the Juling floor. [ABSTRACT FROM AUTHOR]

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 km 2 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 m 3 ) 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 m 3 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 m 3 /year, which is slightly less than the integrated net deposition rate of 576 to 720 m 3 /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. [ABSTRACT FROM AUTHOR]

In this paper, we present the results of our detailed study of morphology, topography, and age of the Deuteronilus contact that outlines Vastitas Borealis Formation (VBF) in the northern plains and the Isidis Planitia unit. The Deuteronilus contact represents a sharp and distinct geological boundary that can be traced continuously for many hundreds to thousands of kilometers. In the northern plains, segments of the Deuteronilus contact occur at two distinct topographic levels. In the northern plains, the long-wavelength topography of the Deuteronilus contact occur at two distinct topographic levels. In the Tempe, Chryse, Acidalia, and Cydonia-Deuteronilus regions (the total length is ∼14,000 km), the contact is at the mean elevation of about −3.92 km (the decile range is 180 m, from −4.01 km to −3.83 km). In the Pyramus-Astapus, Utopia, and Western Elysium regions (the total length is ∼7700 km), the mean elevation of the contact is about −3.58 km (the decile range is 270 m, from −3.73 km to −3.46 km). These levels to large extent (but not completely) correspond to the model geoids that may have been characterized the shape of Mars at the time of the VBF emplacement. Largest deviations of the actual topographic position of the contact from the model geoids occur in the Tantalus and Phlegra regions where the deviations are due to the post-VBF changes of the regional topography. The fact that the model geoids satisfactory describe the shape of the largest portion of the contact provides additional evidence for both the emplacement of the VBF edges near an equipotential surface and for relative stability of the shape of Mars during a long time interval of about 3.6 Ga. Within the northern plains in the Tempe Terra, Acidalia Planitia, Cydonia-Deuteronilus, Pyramus-Astapus, and the southern Utopia regions, the absolute model ages of the VBF surface near the Deuteronilus contact are tightly clustered around the age of ∼3.6 Ga, which we interpret as the age of the VBF emplacement. The surface of the VBF-like Isidis Planitia unit is distinctly younger, ∼3.50 ± 0.01 Ga, which suggests that this unit formed independently. Neither volcanic nor glacial modes of emplacement are consistent with the topographic configuration and the shape of the Deuteronilus contact within both the northern plains and in Isidis Planitia. The broad flooding and formation of extensive water/mud reservoirs remains to be the most plausible mode of formation of the VBF in the northern plains and the VBF-like unit on the floor of the Isidis basin. [ABSTRACT FROM AUTHOR]

Kupalo is a ∼4 ​Ma old, 26-km diameter impact crater on dwarf planet Ceres, which exhibits extensive areas of bright bluish material. Here we describe, for the first time, the geology of Kupalo on a regional and local scale in detail, based on Dawn Framing Camera (FC) imagery. We find the crater has a complex geology consistent with a brittle and heterogeneous crust in this area. Through analyses of the FC colour data, we identify a correlation between the geologic units and the spectral variations, which can be explained by a mixture of subsurface materials in response to the impact. The brightest sites of Kupalo, located at the upper west wall and the central ridge, show similar FC colour and spectral IR data, which suggest that the bright material in these locations likely has the same origin. To explain the distribution of the bright bluish material in the crater and its vicinity, we propose two scenarios for the structure of the upper Cerean crust. Both require deep-seated brine or salt reservoirs, possibly connected to a brine ocean at the crust-mantle transition. • Geology of Kupalo suggests that Ceres' crust is rather heterogeneous (69). • Mixture of impacted subsurface materials explains correlation of spectra and geology (84). • Bright material in Kupalo would have originally been deposited at a depth of ∼3 ​km (82). • The brightest exposures are linked to subsurface reservoirs of hydrated carbonates (82). [ABSTRACT FROM AUTHOR]

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 für Planetologie (IfP) Muenster. [ABSTRACT FROM AUTHOR]

Abstract: “Dendritic valley networks” and broad “longitudinal valleys” are widespread within the eastern Libya Montes region. The morphologic characteristics of the studied dendritic valleys, especially their occurrence at local summits, provide evidence for the initial formation by surface runoff due to atmospheric precipitation whereas the longitudinal valley systems are thought to have been formed and modified by groundwater-induced processes. Our crater counts and model ages show, that the dendritic valley networks (average age ∼4.0 Ga) formed earlier than the longitudinal valley systems (average age ∼3.7 Ga). Both fluvial forms indicate a temporal change of the erosive environment at the Noachian/Hesperian transition at ∼3.8 Ga. Our results suggest that the fluvial activity within our investigation area lasted for ∼800 My, from ∼4.1 Ga to ∼3.3 Ga. The dendritic valleys show valley densities between 0.12 km−1 and 0.57 km−1, indicative of highly mature and integrated valley systems that we interpret to be characteristic of warmer and wetter conditions on Mars. [Copyright &y& Elsevier]

Abstract: It is widely accepted that lunar volcanism started before the emplacement of the mare fills ( b.p.) and lasted for probably more than 3.0Ga. While the early volcanic activity is relatively easy to understand from a thermal point of view, the late stages of volcanism are harder to explain, because a relatively small body like the Earth''s Moon is expected to cool rapidly and any molten layer in the interior should solidify rather quickly. We present several thermal evolution models, in which we varied the boundary conditions at the model surface in order to evaluate the influence on the extent and lifetime of a molten layer in the lunar interior. To investigate the influence of a top insulating layer we used a fully three-dimensional spherical shell convection code for the modelling of the lunar thermal history. In all our models, a partial melt zone formed nearly immediately after the simulation started (early in lunar history), consistent with the identification of lunar cryptomare and early mare basalt volcanism on the Moon. Due to the characteristic thickening of the Moon''s lithosphere the melt zone solidified from above. This suggests that the source regions of volcanic rock material proceeded to increasing depth with time. The rapid growth of a massive lithosphere kept the Moon''s interior warm and prevented the melt zone from fast freezing. The lifetimes of the melt zones derived from our models are consistent with basalt ages obtained from crater chronology. We conclude that an insulating megaregolith layer is sufficient to prevent the interior from fast cooling, allowing for the thermal regime necessary for the production and eruption of young lava flows in Oceanus Procellarum. [Copyright &y& Elsevier]

To detect the mineral diversity of a planet's surface, it is essential to study the spectral variations over a broad wavelength range at relevant simulated laboratory conditions. The MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) mission to Mercury discovered that irrespective of its formation closest to the Sun, Mercury is richer in volatiles than previously expected. This is especially true for sulfur (S), with an average abundance of 4 wt%. It has been proposed that sulfur in the interior of Mercury can be brought to the surface through volcanic activity in the form of sulfides as slag deposits in Mercury hollows and pyroclastic deposits. However, comprehensive spectral library of sulfide minerals measured under vacuum conditions in a wide spectral range (0.2–100 μm) was lacking. This affects the detectability and understanding of the distribution, abundance, and type of sulfides on Mercury using remote-sensing spectral observations. In the case of Mercury, the effect of thermal weathering affecting the spectral behavior of these sulfides must be studied carefully for their effective detection. In this study, we present a spectral library of synthetic sulfides including MgS, FeS, CaS, CrS, TiS, NaS, and MnS. For each sample, we performed emissivity measurements in the thermal infrared range (TIR: ∼7–14 μm) for sample temperatures from 100 °C–500 °C, covering the daytime temperature cycle on Mercury's surface. In addition, for each sample we measured the spectral reflectance of fresh and thermally processed sulfides over a wide spectral range (0.2–100 μm) and at four different phase angles, 26°, 40°, 60°, 80°. This spectral library facilitates the detection of sulfides by past and future missions to Mercury by any optical spectrometer of any spectral range. Specifically, the emissivity measurements in this study will support the Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS) instrument on the ESA/JAXA BepiColombo mission, which will study the surface mineralogy over a wavelength range of 7–14 μm at a spatial resolution of 500 m/pixel. The measured reflectance of these sulfides in 0.2–100 μm at various phase angles will support the interpretation of measurements from past (MDIS, MASCS on MESSENGER) and future missions (SIMBIO-SYS on BepiColombo). • Emissivity of sulfides under simulated Mercury Daytime conditions is studied. • Reflectance of fresh and thermally processed sulfides at wide spectral range (0.2–100 μm) is measured. • Sulfides show strong and distinct spectral features in thermal IR (7–14 μm) spectral region. • UVVIS (0.3–0.6 μm) spectral region is immune to thermal weathering for sulfides. [ABSTRACT FROM AUTHOR]

Abstract Twelve landing ellipses (15 × 30 km each) were previously selected during the preliminary science and safety assessment of details of the Russian Luna-Glob mission. In our work, we have conducted a photogeological and topographical study of the top three most desirable landing ellipses (ellipses 1, 4, and 6) and modelled the thickness of the lunar basin ejecta at these locations in order to characterize their safety conditions and possible sources of materials. For all three potential landing sites large (>0.3–0.5 m) boulders do not represent a significant threat to the mission. The major safety concerns are small but abundant craters whose walls are steeper than the technical constraint of 7°. We have collected the data on density, areal fraction, and the mean distance between the neighboring steep-wall craters, which allow us to rank the safety of terrains within each landing ellipse. A set of morphologically and topographically distinctive units make up the surface of the landing ellipses. The units form two groups, the hilly units and the flat plains. The hilly units within the ellipses 1 and 6 are among the safest terrains. The flat plains of ellipses 1 and 4 represent the most unsafe surfaces. The ejecta of the South Pole-Aitken basin (SPA) strongly dominate the Luna-Glob landing zone and constitute ∼95% (by volume) of materials than can be encountered and analyzed within the landing ellipses. For example, the hilly units in the ellipses 1 and 6 likely represent materials of the SPA ejecta. In the ellipse 4, the hilly unit corresponds to the ejecta of Moretus crater and may represent materials excavated from below the SPA ejecta blanket. However, the small area and configuration of the hilly unit in ellipse 1 and abundant small steep-wall craters on the hilly unit in ellipse 4 make them either a difficult or an unsafe target to land. The flat plains in ellipses 1 and 4 are the most unsafe terrains to land because of the abundant steep-wall craters on their surfaces. Materials ejected by the large craters Boguslawsky and Boussingault from the lower portions of the SPA ejecta blanket make up the majority of the hilly unit in the landing ellipse 6. This unit is among the safest terrains in all top three landing ellipses of the Luna-Glob mission. Highlights • The sources of materials in the top-three (1, 4, 6) Luna-Glob landing sites were analyzed. • The ejecta of the SPA basin dominate the entire Luna Glob landing area. • Flat plains in ellipses 1 and 4 may represent materials ejected from below the SPA ejecta. • Flat plains in ellipses 1 and 4 are the most unsafe units to land. • Units in ellipse 6 may represent materials from the lower portions of the SPA ejecta. [ABSTRACT FROM AUTHOR]

Impact crater size-frequency measurements are key to date and investigate surface processes on terrestrial planetary bodies. Using high-resolution images of numerous space missions, various regional and global crater datasets of the Moon and other planetary bodies have been created in recent years. In addition, machine-learning techniques are increasingly being used to automatically detect craters and to create extensive crater catalogs. Accurate map projection-independent measurement of crater sizes is essential for an accurate dating of the investigated surface. Thus, based on the work of Kneissl et al. (2011) on CraterTools for the geographic information system ArcGIS, we developed the OpenCraterTool as an open source QGIS extension. Our tool allows a map projection-independent measurement and comparison of craters. Results can be visualized within the tool or exported for further external analysis. With our new tool, we compared five global lunar crater datasets; three datasets based on manual crater measurements and two machine-learning products. The comparison revealed substantial differences in both the number of craters and crater diameters. In particular, two catalogs have about three times as many craters as the two smaller catalogs in the analyzed crater diameter range (>5 ​km). The compared craters revealed mean relative differences of 0.4 and 2.3% between the respective catalogs. As expected, the best agreements were found between the manual and automatically generated crater catalogs, where the manual counts were used as training datasets. However, the comparison of the machine-learning products revealed the lowest agreements between themselves. Although the mean relative differences between all the catalogs are small, the number of outliers, as well as the number of under- and overcounted craters over the entire diameter range, are high between all compared catalogs. The differences in crater diameter, as well as the number of over- and undercounted craters have noticeable effects on the age determination of the surfaces. • The OpenCraterTool is an open source extension for QGIS to measure and compare craters. • Our tool enables a map projection-independent measurement of crater sizes as basis for accurate dating of planetary surfaces. • We compared five global crater catalogs of the Moon that result from both manual and machine-learning based methods. • The comparison revealed substantial differences in both the number of craters and crater diameters. [ABSTRACT FROM AUTHOR]

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 ( Petit et al. 2001; Minton and Malhotra, 2009 ). 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 and 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 (~Ø 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. [ABSTRACT FROM AUTHOR]

Sieved size fractions (0–25 ​μm, 25–63 ​μm, 63–125 ​μm, and 125–250 ​μm) and bulk (unsieved) material from lunar soils from Apollo 14 (14163,135 and14259,672), Apollo 15 (15101,319 and 15401,147), and 16 (61220,41, 62231,55 and 67481,96) were analyzed in diffuse reflectance in the mid-infrared (3–18 ​μm). These soils reflect formation in a range of geological settings including basalt protoliths (Apollo 15), and feldspathic impact ejecta protoliths (Apollo 14 and Apollo 16). Mid-IR spectra analyses were made with the same samples using broad spot analyses using a diffuse reflectance set up, and by micro-FTIR under low vacuum and ambient laboratory conditions. Comparison of the data generated by the Broad Spot and micro-FTIR Techniques shows only minor differences in terms of both band positions and relative intensities. Aims were to investigate the mid-infrared reflectance features of the Apollo soils, extract and compare spectral parameters with varying sample composition. Results show a general similarity of the mid-IR spectra with spectral bands indicating the presence of the mineral anorthite, a glassy/amorphous component and a weak contribution from pyroxene. Furthermore, we have investigated the effects of space weathering to the soils, all of which have different maturity indices (from immature, to submature, and mature). This indicator could, thus, provide an easy, non-destructive technique for future laboratory studies of space weathering of airless planetary body soils. • Mid-infrared reflectance spectra of Apollo soils were obtained. • Samples from Apollo 14, 15 and 16 were studied. • Comparison of broad spot and micro-FTIR techniques show similar results. • An indicator for soil maturity was investigated. [ABSTRACT FROM AUTHOR]

The surface of Mercury is enriched in sulfur, with up to 4 wt.% detected by the NASA MESSENGER mission, and has been challenging to understand in the context of other terrestrial planets. We posit, that magmatic S was mobilized as a gas phase in volcanic and impact processes near the surface, exposing silicates to a hot S-rich gas at reducing conditions and allowing conditions for rapid gas-solid reactions. Here, we present novel experiments on the reaction of Mercury composition glasses with reduced S-rich gas, forming Ca- and Mg-sulfides. The reaction products provide porous and fragile materials that create previously enigmatic hollows on Mercury. Our model predicts that the gas-solid reaction forms Ca-Mg-Fe-Ti-sulfide assemblages with SiO 2 and aluminosilicates, distinct from formation as magmatic minerals. The ESA/JAXA BepiColombo mission to Mercury will allow this hypothesis to be tested. • Reduced S-rich gas reacts rapidly to form sulfides at the surface of Mercury. • Sulfidation of forsterite and diopside forms MgS, CaS, and quartz. • Volume changes in the regolith due to sulfidation affect hollow formation. [ABSTRACT FROM AUTHOR]

The High Resolution Stereo Camera (HRSC) of ESA׳s Mars Express is designed to map and investigate the topography of Mars. The camera, in particular its Super Resolution Channel (SRC), also obtains images of Phobos and Deimos on a regular basis. As HRSC is a push broom scanning instrument with nine CCD line detectors mounted in parallel, its unique feature is the ability to obtain along-track stereo images and four colors during a single orbital pass. The sub-pixel accuracy of 3D points derived from stereo analysis allows producing DTMs with grid size of up to 50 m and height accuracy on the order of one image ground pixel and better, as well as corresponding orthoimages. Such data products have been produced systematically for approximately 40% of the surface of Mars so far, while global shape models and a near-global orthoimage mosaic could be produced for Phobos. HRSC is also unique because it bridges between laser altimetry and topography data derived from other stereo imaging instruments, and provides geodetic reference data and geological context to a variety of non-stereo datasets. This paper, in addition to an overview of the status and evolution of the experiment, provides a review of relevant methods applied for 3D reconstruction and mapping, and respective achievements. We will also review the methodology of specific approaches to science analysis based on joint analysis of DTM and orthoimage information, or benefitting from high accuracy of co-registration between multiple datasets, such as studies using multi-temporal or multi-angular observations, from the fields of geomorphology, structural geology, compositional mapping, and atmospheric science. Related exemplary results from analysis of HRSC data will be discussed. After 10 years of operation, HRSC covered about 70% of the surface by panchromatic images at 10–20 m/pixel, and about 97% at better than 100 m/pixel. As the areas with contiguous coverage by stereo data are increasingly abundant, we also present original data related to the analysis of image blocks and address methodology aspects of newly established procedures for the generation of multi-orbit DTMs and image mosaics. The current results suggest that multi-orbit DTMs with grid spacing of 50 m can be feasible for large parts of the surface, as well as brightness-adjusted image mosaics with co-registration accuracy of adjacent strips on the order of one pixel, and at the highest image resolution available. These characteristics are demonstrated by regional multi-orbit data products covering the MC-11 (East) quadrangle of Mars, representing the first prototype of a new HRSC data product level. [ABSTRACT FROM AUTHOR]

We examine compositional variations of volcanic units in the Imbrium basin using spectral observations from the Moon Mineralogy Mapper (M³) instrument on board the Chandrayaan-1 spacecraft. The spectral range of M³ reflectance measurements from 400 to 3000 nm is well-suited to study distinctive absorption bands near 1000 and 2000 nm resulting from mafic minerals in lunar basaltic flows. Eighty-three units with various mineralogical compositions were identified, and spectroscopic analyses were used to map variations in olivine and pyroxene content within basalts emplaced in the Imbrium basin. The results exhibit a more precise mapping of basaltic flow units with M³ data based on their better spatial and spectral range in comparison to previous available datasets. Nevertheless, there is a general correlation between units mapped in this work and previous studies. Moreover, the results tend to indicate an increase in olivine abundances in the stratigraphically younger high-Ti basalts compared to the older low-Ti basalts. Therefore, on the basis of M³ data, we refine previous spectral maps that have been used, for example, to determine first order homogenous units for crater size-frequency distribution measurements. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Monitoring the lunar surface for impacts is a highly rewarding approach to study small asteroids and large meteoroids encountering the Earth–Moon System. The various effects of meteoroids impacting the Moon are described and results from different detection and study techniques are compared. While the traditional statistics of impact craters allow us to determine the cumulative meteoroid flux on the lunar surface, the recent successful identification of fresh craters in orbital imagery has the potential to directly measure the cratering rate of today. Time-resolved recordings, e.g., seismic data of impacts and impact flash detections clearly demonstrate variations of the impact flux during the lunar day. From the temporal/spatial distribution of impact events, constraints can be obtained on the meteoroid approach trajectories and velocities. The current monitoring allows us to identify temporal clustering of impacts and to study the different meteoroid showers encountering the Earth–Moon system. Though observational biases and deficiencies in our knowledge of the scaling laws are severe, there appears to be an order-of-magnitude agreement in the observed flux within the error limits. Selenographic asymmetries in the impact flux (e.g., for equatorial vs. polar areas) have been predicted. An excess of impacts on the lunar leading hemisphere can be demonstrated in current data. We expect that future missions will allow simultaneous detections of seismic events and impact flashes. The known locations and times of the flashes will allow us to constrain the seismic solutions. While the numbers of flash detections are still limited, coordinated world-wide observations hold great potential for exploiting this observation technique. The potential for identification of fresh craters in high-resolution orbital image data has just barely been tapped, but should improve significantly with the LRO extended mission. [Copyright &y& Elsevier]

Abstract: Typical flow thicknesses of lunar mare basalts were not well constrained in the past, because as craters and rilles age, downslope movement of loose material tends to mix and bury stratigraphy, obscuring the three dimensional nature of the maria. New Lunar Reconnaissance Orbiter Camera high resolution images unambiguously reveal thicknesses of mare basalt layers exposed in impact craters, rilles, and steep-walled pits. Pits up to one hundred meters deep present relatively unmodified, near-vertical sections of mare in three cases, and many young impact craters also expose well preserved sections of mare. Oblique views of each pit and many of these craters reveal multiple layers, 3 to 14m thick, indicating that eruptions typically produced a series of ∼10m thick flows (or flow lobes) rather than flows many tens to hundreds of meters thick. Additionally, these images unambiguously show that the floors of two pits extend beneath the mare surfaces, thus revealing sublunarean voids of unknown lateral extent. We also document the occurrence of pits that may be expressions of collapse into subsurface voids in non-mare impact melt deposits. These voids are compelling targets for future human and robotic exploration, with potential as temporary shelters, habitations, or geologic museums. [Copyright &y& Elsevier]

Abstract: For a future Moon landing, a concept for an in-situ NAA involving age determination using the 40Ar–39Ar method is developed. A neutron source 252Cf is chosen for sample irradiation on the Moon. A special sample-in-source irradiation geometry is designed to provide a homogeneous distribution of neutron flux at the irradiation position. Using reflector, the neutron flux is likely to increase by almost 200%. Sample age of 1Ga could be determined. Elemental analysis using INAA is discussed. [Copyright &y& Elsevier]

Abstract: Syrtis Major Planum is a volcanic plain dominated by lava flows. High resolution stereo camera (HRSC) images of the northern Syrtis Major region display erosional features such as grooves, teardrop-shaped islands and valleys. These landforms are characteristics of outflow channels seen on Mars, therefore implying that a flood event took place in this region. The flow of 100km long and a few kilometer wide followed the local slopes in most locations. Maximum flood discharges estimated from images and topography vary from about 0.3×106 to 8×106 m3/s, and therefore are in the range of terrestrial mega-floods in the Scablands or Lake Bonneville. In North Syrtis Major, the relationships with surrounding lava flows and the timing of the flood coeval to Syrtis Major volcanic activity suggest that it could be related to the subsurface water discharge mobilized by the volcanic activity. The proximity of Noachian age basement rocks 20km away from the flood and below lava flows might have played a role in its formation and water presence. [Copyright &y& Elsevier]

Abstract: The European SMART-1 mission to the Moon, primarily a testbed for innovative technologies, was launched in September 2003 and will reach the Moon in 2005. On board are several scientific instruments, including the point-spectrometer SMART-1 Infrared Spectrometer (SIR). Taking into account the capabilities of the SMART-1 mission and the SIR instrument in particular, as well as the open questions in lunar science, a selection of targets for SIR observations has been compiled. SIR can address at least five topics: (1) Surface/regolith processes; (2) Lunar volcanism; (3) Lunar crust structure; (4) Search for spectral signatures of ices at the lunar poles; and (5) Ground truth and study of geometric effects on the spectral shape. For each topic we will discuss specific observation modes, necessary to achieve our scientific goals. The majority of SIR targets will be observed in the nadir-tracking mode. More than 100 targets, which require off-nadir pointing and off-nadir tracking, are planned. It is expected that results of SIR observations will significantly increase our understanding of the Moon. Since the exact arrival date and the orbital parameters of the SMART-1 spacecraft are not known yet, a more detailed planning of the scientific observations will follow in the near future. [Copyright &y& Elsevier]