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  • 11
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    Investigating the Origin of Bright Materials on Vesta: Synthesis, Conclusions, and Implications (2012)
    In:  CASI
    Details
    Publication Date: 2019-08-26
    Description: The Dawn spacecraft started orbiting the second largest asteroid (4) Vesta in August 2011, revealing the details of its surface at an unprecedented pixel scale as small as approx.70 m in Framing Camera (FC) clear and color filter images and approx.180 m in the Visible and Infrared Spectrometer (VIR) data in its first two science orbits, the Survey Orbit and the High Altitude Mapping Orbit (HAMO) [1]. The surface of Vesta displays the greatest diversity in terms of geology and mineralogy of all asteroids studied in detail [2, 3]. While the albedo of Vesta of approx.0.38 in the visible wavelengths [4, 5] is one of the highest among all asteroids, the surface of Vesta shows the largest variation of albedos found on a single asteroid, with geometric albedos ranging at least from approx.0.10 to approx.0.67 in HAMO images [5]. There are many distinctively bright and dark areas observed on Vesta, associated with various geological features and showing remarkably different forms. Here we report our initial attempt to understand the origin of the areas that are distinctively brighter than their surroundings. The dark materials on Vesta clearly are different in origin from bright materials and are reported in a companion paper [6].
    Keywords: Astronomy
    Type: JSC-CN-25701 , 43rd Lunar and Planetary Science Conference; Mar 19, 2012 - Mar 23, 2012; The Woodlands, TX; United States
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  • 12
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    Visible Color and Photometry of Bright Materials on Vesta (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Dawn Framing Camera (FC) collected images of the surface of Vesta at a pixel scale of ~70 m in the High Altitude Mapping Orbit (HAMO) phase through its clear and seven color filters spanning from 430 nm to 980 nm. The surface of Vesta displays a large diversity in its brightness and colors, evidently related to the diverse geology [1] and mineralogy [2]. Here we report a detailed investigation of the visible colors and photometric properties of the apparently bright materials on Vesta in order to study their origin. The global distribution and the spectroscopy of bright materials are discussed in companion papers [3, 4], and the synthesis results about the origin of Vestan bright materials are reported in [5].
    Keywords: Astronomy
    Type: JSC-CN-25715 , 43rd Lunar and Planetary Science Conference; Mar 19, 2012 - Mar 23, 2012; The Woodlands, TX; United States
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  • 13
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    Types and Distribution of Bright Materials in 4 Vesta (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A strong case can be made that Vesta is the parent asteroid of the howardite, eucrite and diogenite (HED) meteorites [1]. As such, we have over a century of detailed sample analysis experience to call upon when formulating hypotheses regarding plausible lithologic diversity on Vesta. It thus came as a surprise when Dawn s Framing Camera (FC) first revealed distinctly localized materials of exceptionally low and high albedos, often closely associated. To understand the nature and origin of these materials, and how they inform us of the geological evolution of Vesta, task forces began their study. An initial step of the scientific endeavor is to develop a descriptive, non-genetic classification of objects to use as a basis for developing hypotheses and observational campaigns. Here we present a catalog of the types of light-toned deposits and their distribution across Vesta. A companion abstract [2] discusses possible origins of bright materials and the constraints they suggest for vestan geology.
    Keywords: Astronomy
    Type: JSC-CN-25711 , 43rd Lunar and Planetary Science Conference; Mar 19, 2012 - Mar 23, 2012; The Woodlands, TX; United States
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  • 14
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    Comparison of Observed Surface Temperatures of 4 Vesta to the KRC Thermal Model (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this work, we will compare ob-served temperatures of the surface of Vesta using data acquired by the Dawn [1] Visible and Infrared Map-ping Spectrometer (VIR-MS) [2] during the approach phase to model results from the KRC thermal model. High thermal inertia materials, such as bedrock, resist changes in temperature while temperatures of low thermal inertia material, such as dust, respond quickly to changes in solar insolation. The surface of Vesta is expected to have low to medium thermal inertia values, with the most commonly used value being extremely low at 15 TIU [4]. There are several parameters which affect observed temperatures in addition to thermal inertia: bond albedo, slope, and surface roughness. In addition to these parameters, real surfaces are rarely uniform monoliths that can be described by a single thermal inertia value. Real surfaces are often vertically layered or are mixtures of dust and rock. For Vesta's surface, with temperature extremes ranging from 50 K to 275 K and no atmosphere, even a uniform monolithic surface may have non-uniform thermal inertia due to temperature dependent thermal conductivity.
    Keywords: Astronomy
    Type: JSC-CN-25899 , 43rd Lunar and Planetary Science Conference; Mar 19, 2012 - Mar 23, 2012; The Woodlands, TX; United States
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  • 15
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    Surface Water-Ice Deposits in the Northern Shadowed Regions of Ceres (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Ceres, a dwarf planet located in the main asteroid belt, has a low bulk density, and models predict that a substantial amount of water ice is present in its mantle and outer shell. The Herschel telescope and the Dawn spacecraft have observed the release of water vapor from Ceres, and exposed water ice has been detected by Dawn on its surface at mid-latitudes. Water molecules from endogenic and exogenic sources can also be cold-trapped in permanent shadows at high latitudes, as happens on the Moon and Mercury. Here we present the first image-based survey of Ceres's northern permanent shadows and report the discovery of bright deposits in cold traps. We identify a minimum of 634 permanently shadowed craters. Bright deposits are detected on the floors of just 10 of these craters in multiscattered light. We spectroscopically identify one of the bright deposits as water ice. This detection strengthens the evidence that permanently shadowed areas have preserved water ice on airless planetary bodies.
    Keywords: Astronomy
    Type: GSFC-E-DAA-TN38267 , Nature Astronomy Letters (e-ISSN 2397-3366); 1; 7; 1-6
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