Compositional mapping of Vesta quadrangle V-23

Since the arrival of the Dawn space-craft [1] at Vesta the Visible and InfraRed Imaging Spectrometer (VIR) [2] has acquired hyperspectral images of Vesta’s surface in the wavelength range from 0.25 to 5.1μm. As part of the analysis of Vesta’s sur-face composition, a series of four quadrangle maps following the scheme of [3] have been produced show-ing the results derived from the spectroscopic analysis of the VIR data. We present the results of the spectro-scopic analysis achieved for the quadrangle V-23, which covers Vesta’s surface between 57°N - 57°S and 180° - 360°

Geoscientific mapping of Vesta by the Dawn mission

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 size-frequency distributions, provides the stratigraphic context for the structural and compositional mapping results into the stratigraphic context and thus revealing the geologic history of Vesta

Mineralogical analysis of the Ac-H-6 Haulani quadrangle of the dwarf planet Ceres

Ac-H-6 'Haulani' is one of five quadrangles that cover the equatorial region of the dwarf planet Ceres. This quadrangle is notable for the broad, spectrally distinct ejecta that originate from the crater Haulani, which gives the name to the quadrangle. These ejecta exhibit one of the most negative ('bluest') visible to near infrared spectral slope observed across the entire body and have distinct color properties as seen in multispectral composite images. Besides Haulani, here we investigate a broader area that includes other surface features of interest, with an emphasis on mineralogy as inferred from data obtained by Dawn's Visible InfraRed mapping spectrometer (VIR), combined with multispectral image products from the Dawn Framing Camera (FC) so as to enable a clear correlation with specific geologic features. Our analysis shows that crater Haulani stands out compared to other surface features of the quadrangle. Albedo maps obtained in the near infrared range at 1.2 μm and 1.9 μm reveal that the floor and ejecta of Haulani are indeed a patchwork of bright and dark material units. Visible to near-infrared spectral slopes display negative values in crater Haulani's floor and ejecta, highlighting bluish, younger terrains. Diagnostic spectral features centered at ∼2.7 μm and ∼3.1 μm respectively indicate a substantial decrease in the abundances of magnesium-bearing phyllosilicates and ammoniated phyllosilicates in crater Haulani's floor and bright ejecta. Similar, but less prominent, spectral behavior is observed in other geologic features of this quadrangle, while the general trend in quadrangle Ac-H-6 for these two mineral species is to increase from the northwest to the southeast. However, it is worth noting that the correlation between the ∼2.7 μm and ∼3.1 μm spectral parameters is generally strong in the Haulani crater's area, but much weaker elsewhere, which indicates a variable degree of mixing between these two major mineral phases in moving away from the crater. Finally, the region of crater Haulani displays a distinct thermal signature and a local enhancement in calcium and possibly sodium carbonate minerals, which is hardly found in the rest of the quadrangle and is likely the result of intense hydrothermal processes following the impact event. These evidences all together confirm the young age of crater Haulani, as they have not been erased or made elusive by space weathering processes

Dawn at Vesta: Accomplishments and Plans

Shortly after entering Vesta’s gravitational field in July 2011, Dawn was maneuvered by its ion propulsion system into Survey orbit at 2735 km altitude providing a complete map of the sunlit surface at low resolution. The fields of view of the Dawn instrument and the orbital phases are illustrated in Figure 1 and 2

Dawn Completes its Mission at 4 Vesta and Prepares for 1 Ceres

Dawn arrives at 1 Vesta and finds an amazing place with multiple large impact basins, a high south polar mountain rivaling Olympus Mons, and a colorful diverse surface, including unexpected dark material, light material, and pits

A preliminary global geologic map of Vesta based on high-altitude mapping orbit data

Previous maps of the asteroid Vesta were derived from albedo and elevation (Hubble Space Telescope, 38-52 km/pixel), and color data and Earthbased spectroscopy were utilized to generate mineralogic and lithologic maps [1-6]. The Dawn spacecraft has acquired images of Vesta at resolutions up to 500x higher, allowing us to advance from simple identification of the largest spatial and spectral features to complex geologic mapping of morphologic units and features, including stratigraphic and structural relationships. We here report on a 1:500,000-scale preliminary global map of Vesta, based on data from the High- Altitude Mapping Orbit (HAMO). This map is part of an iterative mapping effort; the geologic map is refined with each improvement in resolution [e.g., 7]. Geologic Setting: Vesta is an ellipsoidal asteroid with an equatorial radius of ~283 km. It has been identified as the parent body for the Vestoids and the HED (howardite-eucrite-diogenite) family of meteorites. By dating HEDs, Vesta has been determined to be ~4.56 by old [8-10]. Previous data revealed that it has a surface composed of pyroxene-bearing minerals [e.g. 1- 3]. Vesta has a heavily-cratered surface, with large basins evident in numerous locations. The south pole in particular is dominated by an impact basin so large it was identified before Dawn’s arrival; this basin has been named Rheasilvia. The surface is also characterized by a system of deep, globe-girdling equatorial troughs and ridges, as well as an older system to the north. Troughs and ridges are also evident cutting across, and spiraling arcuately from, the Rheasilvia central mound [11]