Spectral analysis of the quadrangles Av-13 and Av-14 on Vesta

The Av-13 (Tuccia) and Av-14 (Urbinia) quadrangles are located in the south-west region of Vesta. They are characterized by a large topographic variability, from the highest (Vestalia terra highlands) to the lowest (Rheasilvia basin). Many geological units in these quadrangles are not associated with mineralogical variability, as shown by the color-composite maps. Maps of mafic absorption band-center position reveal that the principal lithology is eucrite-rich howardite, but diogenite-rich howardite areas are also present, corresponding to particular features such as Antonia and Justina craters, which are characterized by strong mafic absorptions. These quadrangles, especially Urbinia, contain many bright ejecta, such as those of Tuccia crater, which are the highest reflectance materials on Vesta (Zambon et al., 2014). Dark areas are present and correspond to regions with deeper OH-signature. The two quadrangles contain many vertical ridge crests associated with the Rheasilvia impact. These ridges do not show mineralogical differences with respect to their surroundings, but have a distinctive appearance in color-ratio composite images

Spectral Reflectance Measurements of Sulfides at the Planetary Emissivity Laboratory — Analogs for Hollow-Forming Material on Mercury?

We present spectral reflectance measurements at visible and near-infrared wavelengths of fresh and heated samples of MnS, CaS, and MgS, as well as elemental sulfur. We infer that sulfides display a diagnostic feature at or near 0.6 µm

Remote sensing and geologic studies of the Schiller-Schickard region of the Moon

Near-infrared reflectance spectra, multspectral images, and photogeologic data for the Schiller-Schickard (SS) region were obtained and analyzed in order to determine the composition and origin of a variety of geologic units. Thes include light plains deposits, Orientale-related deposits, mare units, and dark-haloed impact craters (DHCs). Spectral data indicate that the pre-Orientale highland surface was dominated by noritic anorthosite. Near-IR spectra show that DHCs in the region have excavated ancient (>3.8 Ga) mare basalts from beneath highland-bearing material emplaced by the Orientale impact. Acient mare basalts were widespread in the SS region prior to the Orientale event, and their distribution appears to have been controlled by the presence of several old impact basins,including the Schiller-Zucchius basin and a basin previously unrecognized. Both Near-IR spectra and multispectral images indicate that light plains and other Orientale-related units in the SS region contain major amounts of local pre-Orientale mare basalt. The amountsof local material in these deposits approach, but seldom exceed, the maximum values predicted by the local mixing hypothesis of Oberbeck and co-workers

Spectral and Multispectral Imaging Studies of Lunar Mantled Mare Deposits

Near-IR reflectance spectra (0.6-2.5 m) and CCD images in the extended visible range (0.4-1.0 m) obtained wth earth-based teles- copes have been used to investigate the composition and origin of formations in the Schiller-Schickard region of the Moon. Of particular interest are the Schickard light plains, which represent an area of mantled mare basalt, or crypto,are. Here local pre- existing mare basalts were eroded and incorporated into a highlands- rich deposit by ejecta from the Orientale Basin. Spectral observa- tions of mature and inmature highland and mare surfaces, as well as dark-halo crater materials provide information on the mafic mineralogy of features in the area. Analyses of the "1 m" absorptionband and spectral mixing models indicate that selected spots in the light plains contain on the order of 50% mare basalt. CCD image cubescan be used to map the amount of basalt in the light plains and evaluate changes with radial distance from Orientale

High-Resolution Regional Digital Elevation Models and Derived Products from MESSENGER MDIS Images

The Mercury Dual Imaging System (MDIS) on the Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has provided global images of Mercury’s surface. A subset of off-nadir observations acquired at different times resulted in near-global stereo coverage and enabled the creation of local area digital elevation models (DEMs). We derived fifty-seven DEMs covering nine sites of scientific interest and tied each to a geodetic reference derived from Mercury Laser Altimeter (MLA) profiles. DEMs created as part of this study have pixel scales ranging from 78 m/px to 500 m/px, and have vertical precisions less than the DEM pixel scale. These DEMs allow detailed characterizations of key Mercurian features. We present a preliminary examination of small features called “hollows” in three DEM sites. Depth measurements from the new DEMs are consistent with previous shadow and stereo measurements. © 2022 by the authors.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The geological nature of dark material on Vesta and implications for the subsurface structure

Abstract Deposits of dark material appear on Vesta’s surface as features of relatively low-albedo in the visible wavelength range of Dawn’s camera and spectrometer. Mixed with the regolith and partially excavated by younger impacts, the material is exposed as individual layered outcrops in crater walls or ejecta patches, having been uncovered and broken up by the impact. Dark fans on crater walls and dark deposits on crater floors are the result of gravity-driven mass wasting triggered by steep slopes and impact seismicity. The fact that dark material is mixed with impact ejecta indicates that it has been processed together with the ejected material. Some small craters display continuous dark ejecta similar to lunar dark-halo impact craters, indicating that the impact excavated the material from beneath a higher-albedo surface. The asymmetric distribution of dark material in impact craters and ejecta suggests non-continuous distribution in the local subsurface. Some positive-relief dark edifices appear to be impact-sculpted hills with dark material distributed over the hill slopes. Dark features inside and outside of craters are in some places arranged as linear outcrops along scarps or as dark streaks perpendicular to the local topography. The spectral characteristics of the dark material resemble that of Vesta’s regolith. Dark material is distributed unevenly across Vesta’s surface with clusters of all types of dark material exposures. On a local scale, some craters expose or are associated with dark material, while others in the immediate vicinity do not show evidence for dark material. While the variety of surface exposures of dark material and their different geological correlations with surface features, as well as their uneven distribution, indicate a globally inhomogeneous distribution in the subsurface, the dark material seems to be correlated with the rim and ejecta of the older Veneneia south polar basin structure. The origin of the dark material is still being debated, however, the geological analysis suggests that it is exogenic, from carbon-rich low-velocity impactors, rather than endogenic, from freshly exposed mafic material or melt, exposed or created by impacts