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The presence of snow and ice at midlatitudes of Mars cannot be explained by current climatic conditions, as surface ice is unstable. However, a large variety of debris‐covered glaciers have been observed at both midlatitudes. Here, we report the presence of local, small‐scale, and debris‐covered stagnant ice deposits on the floor of a valley system in Terra Cimmeria. These deposits, termed valley fill deposits (VFD), have a distribution that is restricted to the host valley floor and to the extent of the ejecta blanket associated with Tarq impact crater. The VFD are characterized by convex‐upward morphology, various crevasses, sublimation pits, an average area of a few square kilometers, and occasional ejecta streaks on their surface. Our model age estimation points to two possible time frames for the Tarq impact event; thus, we suggest two formation scenarios for VFD: (I) distribution of ice due to impact into shallow ice during the Middle Amazonian and (II) post‐impact deposition of VFD due to precipitation. In both scenarios, ice preservation is most likely due to a lag of dust and debris deposited in the valley's topographic lows. Scenario I is more consistent with our geomorphological observation of the VFD being overlain by ejecta streaks. Our results highlight the importance of local geological events and conditions in the distribution and preservation of buried ice deposits on Mars and suggest that more small‐scale and debris‐covered ice deposits may exist in the midlatitudes than previously thought. These deposits are of high importance for future human exploration missions to Mars. In the last two decades with the increase of high‐resolution imagery data, more studies report the presence of ice deposits covered by dust and debris on the Martian surface, in both midlatitudes. These deposits must have been formed under different atmospheric conditions, since water ice is not stable in the current surface environment. One of the generally accepted hypotheses for their formation is precipitation induced by variations of Mars' axial tilt known as obliquity. During high obliquity phases, ice would have sublimated from the poles and redeposited in the midlatitudes. Here, we report the presence of small‐scale ice deposits, located on the floor of a valley system in Terra Cimmeria. Although it is clear that these deposits were formed in different climatic conditions, their formation seems to be related to an impact into a shallow subsurface ice layer, redistributing a mixture of ejected material and ice across the region around the impact site. This study shows the importance of local geological processes, for example, impact cratering, in investigations of water ice distribution on Mars. Near‐surface ice reservoirs are of high importance in the search for life and for future human exploration on Mars. Small debris‐covered stagnant ice deposits (termed valley fill deposits or VFD) are located inside a valley system in Terra Cimmeria, MarsMorphological properties (convex upward morphology, crevasses, and sublimation pits) suggest a current degradational stage of VFD evolutionThe location of VFD within the ejecta blanket of Middle Amazonian Tarq crater points to impact into shallow ice as a likely formation process

Chaos terrains are geologically young and extensively disrupted surface features of Europa, thought to be an expression of the subsurface ocean interacting with the surface. The most prominent examples of this terrain on Europa are Conamara Chaos, and Thera and Thrace Maculae, all prime targets for the upcoming JUICE and Europa Clipper missions to assess the astrobiological potential of Europa. Of the three features, Thrace Macula is currently the least studied and understood. It intersects both Agenor Linea to the north and Libya Linea to the south, two important regional‐scale bands whose interaction with Thrace is yet to be fully unraveled, especially in terms of their relative ages of emplacement and activity. Using Galileo Solid State Imager data and Digital Terrain Models, we conducted detailed structural mapping and terrain analysis to develop a novel hypothesis on the mechanisms involved in the study area. We find that Thrace Macula is bordered along most sides by preexisting strike‐slip faults that have constrained its emplacement and areal distribution. We determine a sequence of events in the area involving the formation of Agenor Linea, followed by that of Libya Linea first and Thrace Macula later, and ultimately by strike‐slip tectonic activity likely driven by Libya Linea, that displaced a portion of Thrace Macula. Therefore, Thrace's subsurface material, uprising along faults postdating its formation, represents the freshest possible that could be sampled by future spacecraft in this region, a major consideration for the upcoming Europa Clipper mission. Europa, an icy moon of Jupiter with a large subterranean water reservoir, has unique surface features known as chaos terrains, believed to result from interactions between its subsurface ocean and surface. Of these terrains, Conamara Chaos and Thera and Thrace Maculae are prime targets for upcoming missions to investigate the astrobiological potential of Europa. However, Thrace Macula, which is situated between Agenor Linea to the north and Libya Linea to the south (two large‐scale bands, linear geological features), remains poorly understood. In this study, we used detailed mapping of faults and lineaments, together with topographical analysis, to propose a new hypothesis for the formation and evolution of Thrace Macula. Our findings suggest that preexisting tectonic faults constrained its emplacement and distribution, while a sequence of events starting with the formation of Agenor Linea, followed by Libya Linea first and Thrace Macula later, culminated in strike‐slip tectonic activity likely driven by Libya Linea that displaced a portion of Thrace Macula. These results imply that future spacecraft could sample Thrace's subsurface material uplifting along faults postdating its formation, the freshest available in this region. This research sheds light on Europa's regional history and its astrobiological potential. We conducted structural analysis on Thrace Macula, a chaotic terrain on Europa, based on imaging and newly processed topographic dataWe found that preexisting strike‐slip faults border Thrace Macula and have constrained its emplacement and areal distributionWe provide insights into the history of Thrace and identify it as a prime location for future missions to sample fresh subsurface material We conducted structural analysis on Thrace Macula, a chaotic terrain on Europa, based on imaging and newly processed topographic data We found that preexisting strike‐slip faults border Thrace Macula and have constrained its emplacement and areal distribution We provide insights into the history of Thrace and identify it as a prime location for future missions to sample fresh subsurface material

Faults and fractures may emplace fresh material onto Europa's surface, originating from shallow reservoirs within the ice shell or directly from the subsurface ocean. Ménec Fossae is a region of particular interest as it displays the interaction of several geological features, including bands, double ridges, chaotic terrains, and fossae, within a relatively small area. These features might affect the emplacement of buried material and subsequent exposure of fresh volatiles, prime targets for the upcoming JUICEand Europa Clippermissions in order to assess Europa's astrobiological potential. Previous studies have already revealed that a deep central trough is present at Ménec Fossae, flanked by several subparallel minor troughs and by a few asymmetrical scarps with lobate planforms. The presence of such features has motivated this study, given its potential to provide clear indications on the tectonic regime involved. Through detailed geomorphological‐structural mapping using GalileoSolid State Imager data and terrain analysis on Digital Terrain Models, we could develop a novel hypothesis on the formation mechanisms that might have been involved in the study area. We propose that Ménec Fossae has been shaped by transtensional (strike‐slip with an extensional component) tectonic activity, as indicated by the orientation and relationship of the tectonic features present. Likely, such transtensional tectonism occurred above or associated with shallow subsurface water, consistent with the overall morphology and topography of the study area and the presence of chaotic terrains and double ridges. These results strengthen the case for widely distributed shallow water reservoirs within Europa's ice shell. Tectonic cracks, which can originate from shallow water bodies within the icy crust or directly from the subsurface ocean, may emplace fresh material onto Europa's surface. This kind of material is a prime target for upcoming space missions to assess Europa's habitability. We investigated the area of Ménec Fossae, which is characterized by many different geological features and structures within a relatively small area and can therefore provide clues on the mechanisms that shaped it. Our analyses were based on imaging and new topographic data, we developed a new hypothesis involving a combination of different tectonic styles as the driving processes for the formation of this area. This kind of tectonic activity could be related to a liquid water pocket located at a shallow depth within Europa's icy crust, which might explain the concurrent presence of some particular geological features in the area. These findings strengthen the case for the wide distribution of shallow water pockets distributed within the icy crust, which could allow future space missions to more easily assess Europa's habitability. Detailed geomorphological‐structural analysis of Ménec Fossae has been conducted, using imaging and newly processed topographic dataMénec Fossae has been shaped by transtensional tectonic activity, potentially related to the emplacement of a shallow water reservoirThe hypothesis that shallow water reservoirs are widely distributed within Europa's ice shell is strengthened Detailed geomorphological‐structural analysis of Ménec Fossae has been conducted, using imaging and newly processed topographic data Ménec Fossae has been shaped by transtensional tectonic activity, potentially related to the emplacement of a shallow water reservoir The hypothesis that shallow water reservoirs are widely distributed within Europa's ice shell is strengthened

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.

Interior layered deposits (ILDs) of the eastern Valles Marineris and adjacent chaos regions were analysed using high-resolution imagery, topography and spectral data in order to detect possible correlations. We find that ILDs are susceptible to erosion and weathering, as proven by their shapes (mesa, buttes), surface structures (pitted, fluted, yardangs), stair-stepped morphologies at different scales, and metre-sized boulders and talus. ILDs bear hydrated sulphates; consequently, we conclude that aqueous conditions dominated during their formation. Subhorizontal layering and parallel bedding of the ILDs could then indicate that deposition took place under low-energy aquatic conditions. Their superposition on chaotic terrain suggests that they are younger than chaotic terrain and, hence, younger than Late Hesperian. For the hydrated ILDs, which show polyhydrated on top of monohydrated sulphates, we think that formation within an evaporative body is not conceivable and we assume instead that a conversion of sulphates by post-formational humidity changes took place. As hydrated ILDs correlate well with rock fragmentation, we suppose that volume changes due to water content are responsible for rock fragmentation. Despite the different ILD settings, the basic conditions during sedimentation and erosion of ILDs could not have varied greatly because comparable mineralogies and morphologies are found among ILDs.

The recently approved ExoMars rover is the first element of the ESA Aurora programme and is scheduled to deliver the Pasteur exobiology payload to Mars by 2015. The 0.7 kg Panoramic Camera will provide multi-spectral stereo images with 65 ° field-of-view (1.1 mrad/pixel) and high-resolution (85 μrad/pixel) monoscopic ‘zoom’ images with 5 ° field-of-view. The stereo wide-angle cameras (WAC) are based on the Beagle 2 Stereo Camera System heritage (Griffiths et al. (2005). Planet. Space Sci. 53, 1466–1488). The Panoramic Camera instrument is designed to fulfil the digital terrain mapping requirements of the mission as well as to provide multi-spectral geological imaging, colour and stereo panoramic images, water vapour abundance and dust optical depth measurements. It can also be used for high-resolution imaging of inaccessible locations on crater walls and to observe retrieved subsurface samples before ingestion into the rest of the Pasteur payload.

Besides Earth, Mars is the only planet with a record of resurfacing processes and environmental circumstances that indicate the past operation of a hydrologic cycle. However the present-day conditions on Mars are far apart of supporting liquid water on the surface. Although the large-scale morphology of the Martian channels and valleys show remarkable similarities with fluid-eroded features on Earth, there are major differences in their size, small-scale morphology, inner channel structure and source regions indicating that the erosion on Mars has its own characteristic genesis and evolution. The different landforms related to fluvial, glacial and periglacial activities, their relations with volcanism, and the chronology of water-related processes, are presented.

The evolution of Mars is discussed using results from the recent Mars Global Surveyor (MGS) and Mars Pathfinder missions together with results from mantle convection and thermal history models and the chemistry of Martian meteorites. The new MGS topography and gravity data and the data on the rotation of Mars from Mars Pathfinder constrain models of the present interior structure and allow estimates of present crust thickness and thickness variations. The data also allow estimates of lithosphere thickness variation and heat flow assuming that the base of the lithosphere is an isotherm. Although the interpretation is not unambiguous, it can be concluded that Mars has a substantial crust. It may be about 50 km thick on average with thickness variations of another ±50 km. Alternatively, the crust may be substantially thicker with smaller thickness variations. The former estimate of crust thickness can be shown to be in agreement with estimates of volcanic production rates from geologic mapping using data from the camera on MGS and previous missions. According to these estimates most of the crust was produced in the Noachian, roughly the first Gyr of evolution. A substantial part of the lava generated during this time apparently poured onto the surface to produce the Tharsis bulge, the largest tectonic unit in the solar system and the major volcanic center of Mars. Models of crust growth that couple crust growth to mantle convection and thermal evolution are consistent with an early 1 Gyr long phase of vigorous volcanic activity. The simplest explanation for the remnant magnetization of crustal units of mostly the southern hemisphere calls for an active dynamo in the Noachian, again consistent with thermal history calculations that predict the core to become stably stratified after some hundred Myr of convective cooling and dynamo action. The isotope record of the Martian meteorites suggest that the core formed early and rapidly within a few tens of Myr. These data also suggest that the silicate rock component of the planet was partially molten during that time. The isotope data suggest that heterogeneity resulted from core formation and early differentiation and persisted to the recent past. This is often taken as evidence against vigorous mantle convection and early plate tectonics on Mars although the latter assumption can most easily explain the early magnetic field. The physics of mantle convection suggests that there may be a few hundred km thick stagnant, near surface layer in the mantle that would have formed rapidly and may have provided the reservoirs required to explain the isotope data. The relation between the planform of mantle convection and the tectonic features on the surface is difficult to entangle. Models call for long wavelength forms of flow and possibly a few strong plumes in the very early evolution. These plumes may have dissolved with time as the core cooled and may have died off by the end of the Noachian.