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NASA’s Dawn spacecraft entered orbit of Ceres on March 6, 2015, to spend one year characterizing the geology, elemental and mineralogical composition, topography, shape, and internal structure of the Ceres [1]. Ceres is supposed to be differentiated into a silicate core, a liquid water mantle and a solid ice crust with a surface temperature from 130K to 235K [2,3]. At the time of writing, the acquired image data from Ceres provide a spatial resolution of up to 2.1 km/pixel. The surface of Ceres reveals some albedo features that seem to be related to geomorphology. Those features show either a high or a low albedo compared to the surrounding.

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NASA's Dawn spacecraft is providing unprecedented views of the surface of 4 Vesta since it went into orbit in July 2011. Dawn is actively gathering an abundance of image, spectral and topographic data to characterize the geology, composition, shape and internal structure of the ~560-km-diameter asteroid. Geologic mapping of Vesta's surface is being undertaken at the global and regional scales by subdividing Vesta into 15 quadrangles. Here, we report the mapping results for quadrangle Av-14, the Urbinia quadrangle of Vesta, derived from data acquired during the High Altitude Mapping Orbit (HAMO) and Survey orbit. Base materials for mapping include HAMO-derived monochrome (clear filter) Framing Camera (FC) mosaic (~70 m/pixel and a Digital Terrain Model (DTM) derived from Survey orbit FC data (450 m/pixel). We also use FC color ratio images (~250 m/pixel) from Survey orbit and Visible and InfraRed (VIR) hyperspectral images from Survey (700 m/pixel) and HAMO (200 m/pixel) orbits to provide information on surface composition and refine unit boundaries. The Av-14 Quadrangle covers the region between 21°-66°S latitude and 270°-360°E longitude. The quadrangle is named after crater Urbinia (D=24 km; 30°S, 276°E), which displays an ejecta blanket with moderate albedo and a smooth, lightly cratered surface. The map area is dominated by moderately cratered equatorial terrains and lightly cratered, but highly deformed, southern terrains. The topographic gradient of the map area is declined toward the south from the more elevated equatorial terrain to the relatively lower interior of the Rheasilivia impact basin. Av-14 contains two dominant terrains - (1) intermediately-cratered equatorial terrain bearing flat-floored, E-W-trending troughs, and (2) relatively lightly-cratered south polar terrain, which contains the Rheasilvia impact basin and related terrains. The northern part of the quadrangle is covered by the moderately cratered equatorial ridge-and-trough terrain and equatorial cratered terrain. The ridge-and-trough terrain forms a thin exposure along the northeastern edge of the map area that displays a handful of troughs. The equatorial cratered terrain extends the width of the quadrangle in a narrow band near the northern part of the map area; this unit contains a few short troughs and is more heavily cratered than the ridge-and-trough terrain. The south polar region contains materials that comprise the Rheasilvia formation, which includes the Rheasilvia ridge-and-groove terrain and the Rheasilvia central mound terrain. The ridge-and-groove terrain is characterized by lineations exhibiting two main orientations: One set is oriented radial to the central mound (N-S) and includes broad ridges and narrow grooves, as well as low-relief scarps. The second set is more arcuate and is oriented circumferential to the central mound (E-W), and consists of ridges and grooves generally a few tens of kilometers in length. Av-14 contains numerous "large" (D>5 km) impact craters, many of which are surrounded by distinct ejecta deposits. Most ejecta deposits display albedos similar to the underlying material and are recognizable by identification of lobate terminations. However, several craters display ejecta with moderate albedo and rays with higher albedo than the underlying surface. In general, these craters appear morphologically fresh.

NASA's Dawn spacecraft arrived at the asteroid 4 Vesta in July 2011 and is now collecting imaging and spectroscopic data during its one-year orbital mission. The maps we present are based on information obtained by the Visible and Infrared Mapping Spectrometer VIR-MS and the multi-color Framing Camera FC. VIR covers the wavelength range between 0.25 to 5.1 µm while FC covers the range 0.4 to 1.0 µm. The VIR instrument has a significant higher spectral resolution than FC but the latter achieves higher spatial resolution data. As part of the geological and mineralogical analysis of the surface, a series of 15 quadrangles have been defined covering the entire surface of Vesta. We report about the mapping results of quadrangle Av-6 (Gegania) and Av-7 (Lucaria). The Gegania quadrangle is dominated by old craters showing no ejecta blankets and rays while several small fresh craters do. The most obvious geologic features are a set of equatorial troughs, a group of three ghost craters of similar diameter (~57 km), an ejecta mantling of the Gegania crater and three smaller craters showing bright and dark ejecta rays. The quadrangle contains two main geologic units: 1) the northern cratered trough terrain and 2) the equatorial ridge and trough terrain. The quadrangle shows moderate variation in Band II center wavelength and Band II depth. FC color ratio variations of some recent craters and their ejecta are linked to the bright and dark material. The bright material is possibly excavated eucritic material while the dark material could be remnants of a CM2 impator(s) or an excavated subsurface layer of endogenic origin. The most prominent geologic features in the Lucaria quadrangle are the 40 km long hill Lucaria Tholus, a set of equatorial troughs, some relatively fresh craters with bright and dark material and mass wasting. The quadrangle contains three main geologic units: 1) the northern cratered trough terrain, 2) the equatorial ridge and trough terrain, and 3) the equatorial cratered terrain. The quadrangle exhibits moderate variation in Band II center wavelength and only small variation in Band II depth. FC ratio maps show a distinct variation of the pseudo 1-µm band depth. Ejecta material showing steeper VIS spectral slope is located in the western part of the quadrangle.

NASA's Dawn spacecraft is collecting a variety of imaging, spectral, and elemental abundance data to characterize the geology, geochemistry, shape and internal structure of Vesta. Geologic mapping of Vesta's surface is being conducted at the global scale and as a series of 15 regional quadrangles. We report results from the mapping of quadrangle Av-10 (Oppia). A mosaic of monochrome (clear filter) Framing Camera (FC) images from the High Altitude Mapping Orbit (HAMO) (70 m/pixel) serves as the base image with additional information about the surface gathered from Visible and Infra-Red (VIR) hyperspectral images, FC color ratio images, and a Digital Terrain Model (DTM: lateral spacing of 450 m/pixel and vertical accuracy of ~30 meters) derived from FC images. Quadrangle Av-10 Oppia is located within the equatorial region of Vesta, and covers 22°S to 22°N latitude and 288° to 0°/360°E longitude. The four global units in Av-10 are 1) cratered terrain in the north, 2) a broad, topographic low (Feralia Planitia) that dominates the central portion of the quadrangle and 3) a topographically higher area towards the south, and 4) equatorial troughs and ridges that cut across the quadrangle between 10°S and 10°N latitude. The northern cratered terrain is one of the older geologic units in Av-10. A portion of this terrain was excavated by the impact that formed Feralia Planitia, one of the larger basin-like features on Vesta. Feralia Planitia is 270 km across and ~15 km deep in relation to the surrounding topographically higher terrain. This topographic low, which is bound by Vestalia Terra to the west (see quadrangle Av-9 Numisia), has been reshaped by Oppia crater on the southern basin boundary, an unnamed crater (50 km) on the northern basin boundary, and by the ridge and trough terrain. A portion of a large northern trough (Saturnalia Fossa) is present in the northwest corner of the quadrangle (see quadrangles Av-4 Domitia and Av-9 Numisia) and E-W-trending equatorial troughs (Divalia Fossa) are located in the eastern half of the (see quadrangle Av-6 Gegania). Oppia crater (D=34 km, 8°S, 309°E) has a sharp rim and a smooth ejecta blanket with a low abundance of impact craters that indicates the crater is relatively young. In FC color-ratio images using approximations of Clementine ratios (Red: 750/430 nm; Green: 750/920 nm; Blue: 430/750 nm), the ejecta blanket has a distinct coloration in comparison to the surrounding terrain. Further study is underway to better understand the nature of this ejecta blanket. The authors gratefully acknowledge the support of the Dawn Instrument, Operations, and Science Teams. This work is supported by NASA through Dawn at Vesta Participating Scientist grant #NNH09ZDA001N.

NASA's Dawn spacecraft is spending one year in orbit around asteroid 4 Vesta to characterize its geology, chemical and mineralogical composition, topography, shape, and internal structure. The Dawn Team is conducting geological mapping of the surface in the form of one global and 15 quadrangle maps. Here we report results from the mapping of Rheasilvia quadrangle Av-15. Mapping is based on a Framing Camera (FC) mosaic produced from High Altitude Mapping Orbit (HAMO) data with a spatial resolution of ~70 m/pixel, supplemented by a Digital Terrain Model (DTM: lateral spacing of 450 m/pixel and vertical accuracy of ~30 meters), FC color images, and Visible and InfraRed (VIR) hyperspectral images. Av-15 Rheasilvia Quadrangle covers the southern pole of Vesta and stretches north to -21°S. Vesta has three dominant terrains: A heavily-cratered northern terrain with ancient troughs and grooves, an intermediately-cratered equatorial terrain bearing prominent flat-floored, E-W-trending troughs, and the relatively lightly-cratered south polar region, containing the Rheasilvia impact basin and related terrains. This quadrangle is dominated by the central mound complex of the Rheasilvia impact basin. Primary geologic features of this region include: (1) the Rheasilvia complex, including the central mound terrain, ridge-and-groove terrain, and smoother terrain; (2) slump material; and (3) impact craters and associated material. The Rheasilvia formation encompasses the central mound complex, two trends of ridges and grooves (only 5% of the quad area is covered by this terrain), and patches of smoother, less-cratered terrain on the mound itself. The mound, which covers nearly 60% of the quadrangle area, is ~22 km high and ~180 km wide, with a discontinuous bounding scarp and low crater density. The ridge-and groove terrain consists of ridges and grooves radiating approximately 90°-270°, and ridges and troughs or ridge and groove complexes that arch or curve as they extend out from from the central mound unit. VIR data indicates that the basin's central mound has a uniform mineralogy, while the basin floor shows more heterogeneity, though both indicate the presence of howardite-diogenite rich materials. Along the base of the bounding scarp occur patches of material characterized by a low crater density and smoother, somewhat granular-textured morphology. Irregularly-bounded patches of very smooth material 25-35 km across are also present, often located on slopes or topographically lower regions. We interpret most of these deposits as slump material emplaced as a result of the effects of basin formation and settling. Most terrain in the quadrangle is heavily cratered. The authors gratefully acknowledge the support of the Dawn Instrument, Operations, and Science Teams. This work is supported by NASA through Dawn at Vesta Participating Scientist grant #NNX10AR19G.