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|Title:||Lithologic variation within bright material on Vesta revealed by linear spectral unmixing||Authors:||Blewett, D. T.
Russell, C. T.
Raymond, C. A.
DE SANCTIS, MARIA CRISTINA
|Issue Date:||2016||Journal:||ICARUS||Number:||272||First Page:||16||Abstract:||Vesta's surface is mostly composed of pyroxene-rich lithologies compatible with howardite, eucrite and diogenite (HED) meteorites (e.g., McCord et al.  Science, 168, 1445-1447; Feierberg & Drake  Science, 209, 805-807). Data provided by the Visible and Infrared (VIR) spectrometer, onboard the NASA Dawn spacecraft, revealed that all Vesta reflectance spectra show absorption bands at ∼0.9 and ∼1.9 μm, which are typical of iron-bearing pyroxenes (De Sanctis et al.  Science, 336, 697-700). Other minerals may be present in spectrally significant concentrations; these include olivine and opaque phases like those found in carbonaceous chondrites. These additional components modify the dominant pyroxene absorptions. We apply linear spectral unmixing on bright material (BM) units of Vesta to identify HEDs and non-HED phases. We explore the limits of applicability of linear spectral unmixing, testing it on laboratory mixtures. We find that the linear method is applicable at the VIR pixel resolution and it is useful when the surface is composed of pyroxene-rich lithologies containing moderate quantities of carbonaceous chondrite, olivine, and plagioclase. We found three main groups of BM units: eucrite-rich, diogenite-rich, and olivine-rich. For the non-HED spectral endmember, we choose either olivine or a featureless component. Our work confirms that Vesta's surface contains a high content of pyroxenes mixed with a lower concentration of other phases. In many cases, the non-HED endmember that gives the best fit is the featureless phase, which causes a reduction in the strength of both bands. The anticorrelation between albedo and featureless endmember indicates that this phase is associated with low-albedo, CC-like opaque material. Large amounts of olivine have been detected in Bellicia, Arruntia and BU14 BM units. Other sites present low olivine content (<30%) mostly with a high concentration of diogenite.||Acknowledgments:||VIR is funded by the Italian Space Agency (ASI) and was de- veloped under the leadership of INAF-Istituto di Astrofisica e Plan- etologia Spaziale, Rome-Italy. The instrument was built by Selex- Galileo, Florence-Italy. The authors acknowledge the support of the Dawn Science, Instrument, and Operations Teams. This work was supported by ASI and NASA’s.||URI:||http://hdl.handle.net/20.500.12386/26158||URL:||https://www.sciencedirect.com/science/article/pii/S0019103516000130?via%3Dihub||ISSN:||0019-1035||DOI:||10.1016/j.icarus.2016.01.009||Bibcode ADS:||2016Icar..272...16Z||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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|Zambon et al_in press_Lithologic variation within bright material on Vesta_linear unmixing.pdf||postprint||11.78 MB||Adobe PDF||View/Open|
|Zambon et al2016_Icarus_Lithologic variation within bright material on Vesta.pdf||[Administrators only]||4.06 MB||Adobe PDF|
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