New simulation of Phobos Stickney crater

In this work we model the Phobos Stickney impact crater using the iSALE hydrocode and considering different scenarios that could form the well-studied crater

Phobos spectral clustering: first results using the MRO-CRISM 0.4-2.5 micron dataset

Whether Phobos is a captured asteroid or it formed in situ around Mars, is still an outstanding question within the scientific community. The proposed Japanese Mars Moon eXploration (MMX) sample return mission has the chief scientific objective to solve this conundrum, reaching Phobos in early 2020s and returning Phobos samples to Earth few years later. Nonetheless, well before surface samples are returned to Earth, there are important spectral datasets that can be mined in order to constrain Phobos' surface properties and address implications regarding Phobos' origin. One of these is the MRO-CRISM multispectral observations of Phobos. The MRO-CRISM visible and infrared observations (0.4-2.5 micron) are here corrected for incidence and emission angles of the observation. Unlike previous studies of the MRO-CRISM data that selected specific regions for analyses, we apply a statistical technique that identifies different clusters based on a K-means partitioning algorithm. Selecting specific wavelength ranges of Phobos' reflectance spectra permits identification of possible mineralogical compounds and the spatial distribution of these on the surface of Phobos. This work paves the way to a deeper analysis of the available dataset regarding Phobos, potentially identifying regions of interest on the surface of Phobos that may warrant more detailed investigation by the MXX mission as potential sampling areas. Acknowledgments: M. Pajola was supported for this research by an appointment to the NASA Postdoctoral Program at the Ames Research Center administered by USRA

Lermontov crater on Mercury: Geology, morphology and spectral properties of the coexisting hollows and pyroclastic deposits

Abstract We present a multidisciplinary analysis of Lermontov crater, located at 15.24°N, −48.94°E in the Kuiper quadrangle of Mercury. By means of MESSENGER multiband MDIS-WAC and monochrome MDIS-NAC images, we prepare a high-resolution geological map of the crater and its closest surroundings, highlighting the presence of coexisting hollows and pyroclastic deposits on its floor. On the photometrically corrected MDIS-WAC multiband dataset, we apply an unsupervised clustering technique that spectrally separates the different materials located both inside and outside Lermontov crater. We observe that the pyroclastic deposits located on the crater's floor have a steep, red spectral behaviour dominated by the presence of a mixture of various pyroxenes containing Ti and Ni. On the contrary, the vents' rims are characterised by several hollows whose spectral slope is bluer than that of the pyroclastic deposits. By comparing the vent hollows to the hollows located farther out on the crater floor, we observe a steeper 0.62–0.82 μm spectral trend for those within the vents. The vent hollows' spectrum is more similar to the pyroclastic one in the above mentioned wavelength range. In addition, the vent hollows 0.55 μm absorption band could be related to CaS, while the small differences in slope at 0.48 μm and 0.62 μm could be due to the presence of other volatiles compounds, such as MgS or chlorides. When compared to hollows located in other hermean geological settings, Lermontov hollows are characterised by steeper spectra. This supports the interpretation that when hollows form, their bright deposits do not completely overwrite the spectral signature of the surrounding terrain, and their spectroscopic appearance is mixed with the composition of the terrain where they form

Spectral Clustering and Geomorphological Analysis on Mercury Hollows

Characterization of hollows located in different craters to understand whether there is a similar trend from a compositional point of view, and whether a possible correlation exists between spectral behavior of hollows and geomorphological units

Multidisciplinary Analysis of Lermontov Crater on Mercury

We present the geological, age determination, and spectrophotometric analysis of the Lermontov Crater on Mercury

Main Belt Comets as Clues to the Distribution of Water in the Early Solar System

n/

Asteroids Inside Out: Radar Tomography

n/

Hydrothermal Alteration of Ultramafic Rocks in Ladon Basin, Mars—Insights From CaSSIS, HiRISE, CRISM, and CTX

The evolution of the Ladon basin has been marked by intense geological activity and the discharge of huge volumes of water from the Martian highlands to the lowlands in the late Noachian and Hesperian. We explore the potential of the ExoMars Trace Gas Orbiter/Color and Stereo Surface Imaging System color image data set for geological interpretation and show that it is particularly effective for geologic mapping in combination with other data sets such as HiRISE, Context, and Compact Reconnaissance Imaging Spectrometer for Mars. The study area displays dark lobate flows of upper Hesperian to early Amazonian age, which were likely extruded from a regional extensional fault network. Spectral analysis suggests that these flows and the underlying rocks are ultramafic. Two distinct altered levels are observed below the lobate flows. The upper, yellow-orange level shows hundreds of structurally controlled narrow ridges reminiscent of ridges of listwanite, a suite of silicified, fracture-controlled silica-carbonate rocks derived from an ultramafic source and from serpentine. In addition to serpentinite, the detected mineral assemblages may include chlorite, carbonates, and talc. Kaolin minerals are detected in the lower, white level, which could have formed by groundwater alteration of plagioclase in the volcanic pile. Volcanism, tectonics, hydrothermal activity, and kaolinization are interpreted to be coeval, with hydrothermal activity and kaolinization controlled by the interactions between the aquifer and the hot, ultramafic lobate flows. Following our interpretations, East Ladon may host the first listwanite ridges described on Mars, involving a hydrothermal system rooted in a Hesperian aquifer and affecting ultramafic rocks from a magmatic source yet to be identified