Olivine or Impact Melt: Nature of the "Orange" Material on Vesta from Dawn

NASA's Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types, a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), b) lobate patches with well-defined edges, and c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed "Leslie feature" first identified by Gaffey (1997) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt

VIS-NIR Imaging Spectroscopy of Mercury\u2019sSurface: SIMBIO-SYS/VIHI ExperimentOnboard the BepiColombo Mission

The Visible and Infrared Hyperspectral Imager (VIHI) is one of the three optical heads of the Spectrometers and Imagers for MPO BepiColombo Integrated Observatory SYStem (SIMBIO-SYS) experiment onboard European Space Agency\u2019s BepiColombo cornerstone mission to Mercury. The other two optical heads of SIMBIO-SYS are a stereo camera and a highresolution image camera. The experiment is designed to scan the Hermean surface from a polar orbit with the three channels to map the physical, morphological, tectonic, and compositional properties of the planet. The main scientific objectives of SIMBIO-SYS are the study of Mercury\u2019s surface geology and stratigraphy, the surface composition, the regolith properties, the crustal differentiation, impact, and volcanic processes. The VIHI experiment uses a high-performance optical layout (Schmidt telescope and spectrometer in Littrow configuration) which allows investigating the 400\u20132000-nm spectral range with 256 spectral channels (6.25 nm/band sampling). The instrument has an instrument field of view (FOV) of 250 \u3bcrad corresponding to a spatial scale of about 100 m/pixel at periherm and 375 m at apoherm. The instrument operates in pushbroom configuration, sampling the surface of Mercury with an FOV of 64 7 0.25 mrad. The main technical challenges of this experiment are focal-plane design (cadmium\u2013mercury\u2013telluride thinned to improve the efficiency at visible wavelengths), short dwell time (from about 40 ms at equator to about 100 ms at poles), thermal control, mechanical miniaturization, radiation hardening, high data rate, and compression. A description of the internal calibration unit concept and functionalities is given

The mineralogy of Ceres’ Nawish quadrangle

Quadrangle Ac-H-08 Nawish is located in the equatorial region of Ceres (Lat 22°S-22°N, Lon 144°E- 216°E), and it has variable mineralogy and geology. Here, we report on the mineralogy using spectra from the Visible and InfraRed (VIR) mapping spectrometer onboard the NASA Dawn mission. This quadrangle has two generally different regions: the cratered highlands of the central and eastern sector, and the eastern lowlands. We find this dichotomy is also associated with differences in the NH4-phyllosilicates distribution. The highlands, in the eastern part of the quadrangle, appear depleted in NH4-phyllosilicates, conversely to the lowlands, in the north-western side. The Mg-phyllosilicates distribution is quite homogeneous across Nawish quadrangle, except for few areas. The 2.7 µm band depth is lower in the south-eastern part, e.g. in the Azacca ejecta and Consus crater ejecta, and the band depth is greatest for the Nawish crater ejecta, and indicates the highest content of Mg-phyllosilicates of the entire quadrangle. Our analysis finds an interesting relationship between geology, mineralogy, topography, and the age in this quadrangle. The cratered terrains in the highlands, poor in NH4 phyllosilicates, are older (̴2 Ga). Conversely, the smooth terrain, such as with Vindimia Planitia, is richer in ammonia-bearing phyllosilicates and is younger (̴1 Ga). At the local scale, Ac-H-8 Nawish, displays several interesting mineralogical features, such as at Nawish crater, Consus crater, Dantu and Azzacca ejecta, which exhibit localized Na-carbonates deposits. This material is superimposed on the cratered terrains and smooth terrains and shows the typical depletion of phyllosilicates, already observed on Ceres in the presence of Na-carbonates