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Reliable detection and characterization of water ice on the Martian surface is pivotal to not only understand its present and past climate, but to also provide valuable information on in-situ resource availability and distribution for future human exploration missions. Ice-rich features are currently identified with visible/near-IR (VNIR), thermal IR and radar data. However, their coarse spatial scale sometimes limits confident characterization of small (i.e., meter-scale) icy exposures resulting from recent activity like new impacts. Water ice bearing materials possess weaker spectral characteristics at wavelengths shorter than ∼1030 nm that may be resolved by VNIR imaging instruments like the High Resolution Imaging Science Experiment (HiRISE) and the Colour and Stereo Surface Imaging System (CaSSIS). Our study assesses the spectral capability of HiRISE colour observations to help distinguish high purity water ice exposures from ice-poor materials. We report detailed methodologies for reliable colour characterization of icy surface using unfiltered HiRISE images. We present the first quantitative approach to uniquely characterize high-purity ice-rich materials through spectral shape and spectral parameterization methods at high spatial resolution (∼50 cm/pixel). We also present three spectral parameters to aid detection of pure water ice features, while also providing statistical constraints to enable a quantitative interpretation scheme. Our methods are observed to work well in characterizing and separating ice-rich features uniquely from ice-poor and ferrous materials. However, we do observe that these methods have a lower grain size detection limit of ∼250–300 μm, and may not be able to uniquely separate frosts from ground ice exposures. We also apply these methods to better constrain the composition of bright materials exposed by recent impacts identified in previous surveys, where substantial evidence for ice-bearing materials was previously unavailable. Overall, our work proposes HiRISE colour-based methods as a novel approach for high-resolution multispectral characterization of ice-rich features on the Martian surface, which is of particular value since the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) has ceased operations. • Reliable characterization of water ice on the Martian surface is crucial for understanding its climate, resource availability, and future human exploration. • HiRISE colour observations offer a spectral capability to distinguish high-purity water ice exposures from ice-poor materials at high spatial resolution (∼50 cm/pixel). • The study presents a quantitative approach to aid in the detection and characterization of pure water ice features. [ABSTRACT FROM AUTHOR]

The distribution of gullies on Mars has been used to support different modes of formation involving CO 2 , H 2 O or entirely dry processes. We mapped the extent of gullied hillslope using a global mosaic of ConTeXt camera (CTX) at 6 m/pixel and High Resolution Imaging Science Experiment (HiRISE) browse products at ∼3 m/pixel. Our new global catalog of gullied hillslopes allows for quantitative, area-based analysis of gullies both at global and regional scale, which was not possible with point-based or more localized previous datasets. We analyzed aspect and gradient information derived from MOLA topography for every mapped gullied hillslope. We have confirmed the trends identified in previous works, which are that the mean gradient of gullied hillslopes is lower than 30°, the angle of repose of dry material on Mars, and that the preferred aspect of gullied hillslopes is latitude-dependent, with a shift between pole-facing to equator-facing happening around 40° in both hemispheres. We established a hierarchy of factors that can explain the global distribution of gullied hillslopes: Latitude is the strictest control because gullies are constrained between 26°-83°S and 28°-76°N. The availability of steep slopes is a strong control over gully distribution, and we observed that gullied hillslopes aspect reflects the orientation of large regional reliefs, which implies that hillslope aspect is less of a factor than the hillslope gradient in explaining gully distribution. We analyzed the correlation of gully distribution with a subsurface water ice consistency map, and we found that gullies are preferentially distributed on areas with some ground ice rather than no ice at all. We identified for the first time a bias toward an east-facing trend for southern hemisphere gullies poleward of ∼40° of latitude. We also linked our gullied hillslopes dataset with a global crater morphometry dataset: 63% of the gullied area on Mars is found in craters, and we find that the area covered by gullies in a given crater is positively correlated with the depth and diameter ratio of this crater. Our observations point toward a complex interplay between local slope, insolation, and thermal properties of the substrate to explain the spatial distribution of the current population of gullies. Finally, we have assessed the very high resolution (sub-meter) imagery coverage of gullies to be 36% and that the repeated coverage reaches 21% of gullies, hence this would need expanding to better understand the spatial trends in active gullies. • We present a new catalog of gullied hillslopes, mapped using CTX and HiRISE data. • We establish a hierarchy of factors explaining the distribution of gullied hillslopes. • Gullies are found in areas with some ice rather than no ice at all. • Gullies tend to be east-facing poleward of 40°. • We assess the HiRISE coverage of gullies to be 36%. [ABSTRACT FROM AUTHOR]

The majority of hydrated silicate occurrences on Mars are associated with impact craters (Ehlmann et al., 2011; Carter et al., 2013). Three formation mechanisms have been suggested to account for this correlation: (1) aqueous alteration occurred pre-impact, and was subsequently exposed via the impact (pre-impact; Bibring et al., 2006; Ehlmann et al., 2011), (2) heat generated from the impact facilitated the formation of a hydrothermal system, leading to alteration products (syn-impact; e.g. Marzo et al., 2010; Osinski et al., 2013), and/or (3) altered materials were deposited after crater formation, or formed within the crater well after the impact had taken place (post-impact). In this study, we analyze the central uplift of Elorza Crater, a ∼40 km diameter impact crater located ∼300 km north of Valles Marineris. To determine whether hydrated minerals found within the uplift were generated pre-, syn-, or post-impact, we used a data synthesis approach, utilizing High Resolution Imaging Science Experiment (HiRISE), Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), Context Camera (CTX), and Thermal Emission Imaging System (THEMIS) imagery. Opaline silica is observed in two locations on the southwestern side of the uplift and is interpreted to have been pre-existing or formed via hydrothermal alteration due to stratigraphic relationships with the overlying impact melt unit. Both Fe/Mg smectite and low-calcium pyroxene (LCP) are found throughout the uplift. Bedrock exposures on the northern wall of Coprates Chasma containing Fe/Mg smectite and LCP suggest an uplifted origin for these units. In all cases, although a pre-existing origin is probable, it is difficult to rule out the possibility of an impact-generated hydrothermal origin. Using the observed stratigraphy exposed in Coprates Chasma and bedrock exposures analyzed in nearby craters, we were able to constrain the pre-impact stratigraphy around Elorza. The near-subsurface consists of Hesperian-aged, discontinuous lava/ash deposits that may be interposed with opaline silica-bearing deposits, overlying Noachian basement consisting of smectite-bearing bedrock and LCP- bearing light-toned fractured bedrock. [ABSTRACT FROM AUTHOR]

Abstract Approaches to rover mission operations were investigated in the framework of the CanMars Mars Sample Return (MSR) analogue mission deployments. Improving the efficiency of operations is a necessity for future planetary missions, including Mars 2020, which seek to combine sample targeting with in situ investigations in the fixed amount of time available in primary science operations and with increasingly high public and science community expectations for results. Analogue missions provide an important opportunity to experiment with mission operation strategies and learn lessons that can be incorporated in future missions. Improving the efficiency of operations was a key objective of the 2015 and 2016 CanMars mission deployment. The mission overall operations organisation for CanMars is described with comparison to current implementation of Mars Exploration Rover and Mars Science Laboratory missions. Approaches being tested included 3-sol plan sequences with increased use of waypoints for teach and return as part of a global Walkabout approach, use of Strategic Observation days to focus the Science Team's efforts, and consideration to improvements in how information is exchanged tactically and strategically in operations. Highlights • Rover mission operation strategies are tested during an analogue mission in Utah. • Fully pre-developed strategic traverse plans were prepared days ahead of time. • Consecutive multi-sol plans were executed with increased autonomous capabilities. • Post-drive autonomous target selection greatly enhances the value of multi-sol plans. • A "walkabout-first" strategy allowed for rapid determination of potential targets. [ABSTRACT FROM AUTHOR]

Abstract: Thermal contraction crack polygons and scalloped depressions, two of the most common landforms found in Utopia Planitia, Mars, have previously been linked to the presence of ice-rich deposits in the subsurface. Although the formation and evolution of these features individually are relatively well understood, little to no effort has been directed towards elucidating possible interactions that occur between them during their development. Thus, the overarching goal of this research was to investigate if there is an evolutionary link between polygonal and scalloped terrains by correlating metrics representing polygon and scallop maturity. A variety of statistical analyses were performed using HiRISE and MOLA datasets to quantify interactions between four sets of polygonal and scalloped terrains. Our results demonstrate the existence of a negative relationship between polygonal subdivision and surface elevation, indicating that polygon networks become more ‘evolved’ as the surface subsides. These results suggest that the permafrost landscape in Utopia Planitia may once have been extremely ice-rich, and that multiple geomorphic processes may be responsible for its evolution. Ultimately, this work demonstrates that landscape reconstruction is more complete when a system approach is followed, quantifying interactions between landforms as opposed to examining an individual landform in isolation. [Copyright &y& Elsevier]