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Abstract: The Optical Microscope (OM) on the Phoenix Mars lander (operated from May through October 2008) was used to search for visible-wavelength luminescence of soil particles excited by ultraviolet (UV) illumination (λ=360–390nm). No luminescent particles were found, with the possible exception of a few potentially luminescent features comprising about 0.02% of the total soil volume. The luminescence quantum efficiency of bulk soil as well as individual soil particles at the Phoenix site is constrained to less than 0.04%. A similar UV experiment will be performed by the Mars Hand Lens Imager (MAHLI) on the upcoming Mars Science Laboratory (MSL) mission. We compare OM and MAHLI UV experiments to each other and suggest a strategy to search for UV-excited luminescence with MAHLI. [Copyright &y& Elsevier]

Abstract: The limited depth of focus of microscope optics precludes the observation of a three-dimensional surface in a single view. For an efficient operation of a planetary microscope observing a highly irregular surface, an autofocus algorithm must detect partially focused views and merge them into a completely focused image (extended depth of focus). In this paper we investigate the suitability of different algorithms for autonomous image focusing onboard a Mars lander. We show that all methods under study, except for the Variance method, produce reasonable results and that their performance depends (amongst other factors) on sample morphology. For reasons of simplicity and reduced computational requirements we favor Gradient and Roberts methods and present an efficient implementation thereof. [ABSTRACT FROM AUTHOR]

The microscope for the Beagle 2 lander, which was launched as part of the European Space Agency''s Mars Express mission on 2 June 2003, will provide images of the Martian surface at around 6 μm resolution. It will provide optical images of the surface of Mars at a resolution 5 times higher than any other experiment currently planned. The device has a working distance of 12 mm and uses a set of 12 light-emitting diodes which surround the aperture to illuminate the sample in four colours. The target is brought into focus using a stepper motor. This article describes the scientific objectives and the design of the microscope. It also discusses initial results from ground calibration exercises which were designed to validate the system and describes aspects of its operation. [Copyright &y& Elsevier]

Abstract The previously defined regions on the nucleus of comet 67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7 model of the nucleus (Preusker et al., 2017). The resulting regional definition is therefore self-consistent with boundaries that are well defined in 3 dimensions. The facets belonging to each region are provided as supplementary material. The shape model has then been used to assess inhomogeneity of nucleus surface morphology within individual regions. Several regions show diverse morphology. We propose sub-division of these regions into clearly identifiable units (sub-regions) and a comprehensive table is provided. The surface areas of each sub-region have been computed and statistics based on grouping of unit types are provided. The roughness of each region is also provided in a quantitative manner using a technique derived from computer graphics applications. The quantitative method supports the sub-region definition by showing that differences between sub-regions can be numerically justified. Highlights • Regions are defined upon the latest 3D shape model (SHAP7) of comet 67P/Churyumov-Gerasimenko. • The definition is provided in a publicly accessible shape file. • Sub-regions of similar properties are defined to support more detailed work. • Roughness calculations are performed to quantify differences between regions and sub-regions. [ABSTRACT FROM AUTHOR]

Context Pinnacles, local promontories of varied shapes including spires with pointed tops, are observed on the surface of the 67P's cometary nucleus in the OSIRIS and NavCam images. Their presence and characteristics allow to infer the magnitude of the surface erosion and the degree of heterogeneity of the consolidated nucleus material. Aims To identify these pinnacles and consider implications, which follow from their presence and characteristics. Methods Identification of pinnacles in the available OSIRIS and NavCam images, as well as in the model images of the nucleus built from the digital terrain model, and an investigation of their morphology. Results We identified and measured 49 pinnacles in 13 regions of the studied part of the nucleus. The pinnacles are typically asymmetric with somewhat different slope angles at different slopes whose maximum values range from 40 to 90°, sometimes with small overhangs. Their heights vary from 10 to 20 to 100–200 m and the foot diameters from 30 to 300 m. Our analysis of the OSIRIS images of the pinnacles showed that they have surface texture similar to that of consolidated nucleus material and are probably composed of it. Conclusions The observed characteristics of pinnacles found on 67P agree with the suggestion that they are erosion remnants formed due to a slowdown of erosion in places where nucleus material is more resistant to sublimational erosion than the material around it. In this case the maximum heights of pinnacles (100–200 m) gives a lower boundary for the amount of surface material lost and their diameters (typically tens of meters) are a measure of the size of the erosion-resistant parts. [ABSTRACT FROM AUTHOR]

This paper is based on geologic analysis of the surface morphology of nucleus of the Jupiter family comet 67P. This comet was visited by the ESA mission Rosetta, which escorted the comet since May 2014 till the end of September 2016 and studied it by 11 instruments of the mission orbiter and 10 instruments of the lander. The nucleus is ~4 km in diameter, has a bilobate shape with the smaller (Head) and larger (Body) lobes, and the narrow neck between them. For the analysis, primarily images taken by the Rosetta Navigation camera (NavCam) were used and then complemented by selected images from the ROLIS and OSIRIS cameras. Two major types of the nucleus material are distinguished by us and other researchers: 1) the consolidated nucleus material and 2) the loose material, a kind of cometary regolith, covering the nucleus consolidated material. On the surface of the consolidated material rather long (up to hundreds meters) straight lineaments are distinguishable. They probably correspond to fractures and in some cases to strata. Their presence suggests that the consolidated material is rather compact and lacks voids larger than tens of meters across. Surfaces of consolidated nucleus material typically show knobby appearance at the scales from tens of meters and meters to centimeters and millimeters. This suggests that this material is grainy, consisting of more and less resistant (to surface weathering) “particles” on the scale of the visible knobs. The geometric analysis of steep slopes based on the nucleus shape model allowed us to estimate a tensile, shear and compressive strength of the consolidated material. It was shown that the 67P consolidated nucleus material is very fragile, and taking into account the scale effect one can conclude that it is as fragile as fresh fallen snow and maybe even more fragile. In addition, estimates of the compressive strength of the surface material were considered at the sites of the first and the last contacts of the Philae lander with the surface. Observations also showed evidence of various downslope and lateral movements of rather large material masses (landslide? avalanche?) as well as boulders and “fines”, which are driven primarily by gravity and then by the acquired inertia, but in some cases a material transport by dust-gas jets/outbursts could play a role. The latter could also be responsible for formation of the eolian-type ripples. [ABSTRACT FROM AUTHOR]

Abstract: The OSIRIS camera onboard Rosetta successfully acquired images of asteroid 2867 Steins through a variety of color filters during the flyby on 5 September 2008. The best images of this 5km diameter asteroid have a resolution of 78m per pixel. We process the images by deconvolving with the point spread function and enlarging through the Mitchell–Netravali filter. The enhanced set is analyzed by means of various techniques (PCA, band ratios, stereo anaglyphs) to study surface morphology and search for variegation. We identify a landslide, which supports a YORP origin for Steins’ unusual diamond shape. In addition, we find that the interior of one of two large craters on the south pole is bluer than the rest of the body. [Copyright &y& Elsevier]

Abstract: The Venus Express mission will focus on a global investigation of the Venus atmosphere and plasma environment, while additionally measuring some surface properties from orbit. The instruments PFS and SPICAV inherited from the Mars Express mission and VIRTIS from Rosetta form a powerful spectrometric and spectro-imaging payload suite. Venus Monitoring Camera (VMC)—a miniature wide-angle camera with 17.5° field of view—was specifically designed and built to complement these experiments and provide imaging context for the whole mission. VMC will take images of Venus in four narrow band filters (365, 513, 965, and 1000nm) all sharing one CCD. Spatial resolution on the cloud tops will range from 0.2km/px at pericentre to 45km/px at apocentre when the full Venus disc will be in the field of view. VMC will fulfill the following science goals: (1) study of the distribution and nature of the unknown UV absorber; (2) determination of the wind field at the cloud tops (70km) by tracking the UV features; (3) thermal mapping of the surface in the 1μm transparency “window” on the night side; (4) determination of the global wind field in the main cloud deck (50km) by tracking near-IR features; (5) study of the lapse rate and H2O content in the lower 6–10km; (6) mapping O2 night-glow and its variability. [Copyright &y& Elsevier]