First mineralogical maps of 4 Vesta

Before Dawn arrived at 4 Vesta only very low spatial resolution (~50 km) albedo and color maps were available from HST data. Also ground-based color and spectroscopic data were utilized as a first attempt to map Vesta’s mineralogical diversity [1-4]. The VIR spectrometer [5] onboard Dawn has ac-quired hyperspectral data while the FC camera [6] ob-tained multi-color data of the Vestan surface at very high spatial resolutions, allowing us to map complex geologic, morphologic units and features. We here re-port about the results obtained from a preliminary global mineralogical map of Vesta, based on data from the Survey orbit. This map is part of an iterative map-ping effort; the map is refined with each improvement in resolution

Mapping Vesta: First Results from Dawn’s Survey Orbit

The geologic objectives of the Dawn Mission [1] are to derive Vesta’s shape, map the surface geology, understand the geological context and contribute to the determination of the asteroids’ origin and evolution.Geomorphology and distribution of surface features will provide evidence for impact cratering, tectonic activity, volcanism, and regolith processes. Spectral measurements of the surface will provide evidence of the compositional characteristics of geological units. Age information, as derived from crater sizefrequency distributions, provides the stratigraphic context for the structural and compositional mapping results, thus revealing the geologic history of Vesta. We present here the first results of the Dawn mission from data collected during the approach to Vesta, and its first discrete orbit phase – the Survey Orbit, which lasts 21 days after the spacecraft had established a circular polar orbit at a radius of ~3000 km with a beta angle of 10°-15°

Compositional mapping of Vesta quadrangle V24

The Dawn spacecraft [1] entered orbit around Vesta in mid-July 2011. Since then, the Visible and InfraRed Imaging Spectrometer (VIR) [2] acquired hyperspectral images of Vesta’s surface in the overall wavelength range from 0.25 to 5.1 μm. During the Approach and Survey mission phases (23 July through 29 August 2011), VIR obtained resolved images of Vesta with spatial resolutions between 1.31 km and 0.68 km/pix. More than 65% of the surface, from the South Pole up to ∼40°N, was observed under different illumination conditions and local solar elevations. Based on this datasets, a series of four quadrangle maps following the scheme in [3] are being produced showing the results derived from the spectroscopic analysis of VIR data. In this work we present the results of the spectroscopic analysis achieved for the quadrangle V-24, which covers Vesta’s southern polar region 55°S - 90°S and longitude 0° - 360°

Geologic mapping of the AV-15 Rheasiliva quadrangle of asteroid 4 Vesta

NASA’s Dawn spacecraft entered orbit of the inner main belt asteroid 4 Vesta on July 16, 2011, and is spending one year in orbit to characterize the geology, elemental and mineralogical composition, topography, shape, and internal structure of Vesta be-fore departing to asteroid 1 Ceres in late 2012. As part of the Dawn data analysis the Science Team is con-ducting geologic mapping of the surface, in the form of 15 quadrangle maps. This abstract reports results from the mapping of quadrangle Av-15, named Rheasilvia. Data: The base for mapping this quadrangle is a monochrome Framing Camera (FC) mosaic produced from the High Altitude Mapping Orbit (HAMO) data with a spatial resolution of ~70 m/pixel. This base is supplemented by a Digital Terrain Model (DTM) de-rived from Survey orbit data (Figure 1). Also used to support the mapping are FC color ratio images from the Survey orbit with a spatial resolution of ~250 m/pixel, slope and contour maps derived from the DTM, and Visible and InfraRed (VIR) hyperspectral images from the Survey and HAMO orbits with spatial resolutions of 700 and 200 m/pixel, respectively. Geologic Setting: Av-15 Rheasilvia Quadrangle covers the southern pole of Vesta and stretches north to 21°S. This quadrangle is dominated by the central mound complex of the Rheasilvia impact basin. The quad is heterogeneous spectrally, and in terms of color and albedo [1-4]; these heterogeneities were originally interpreted to stem from extrusive volcanic activity and impact. Imaging by the Hubble Space Telescope (HST) in 1994 and 1996 revealed a crater at the south pole that excavated ~1% of the asteroid's volume; the presence of a 1-μm absorption feature was interpreted as coarse-grained plutonic pyroxene or pos-sibly olivine in a differentiated upper mantle [5]