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|Title:||Detection of new olivine-rich locations on Vesta||Authors:||PALOMBA, Ernesto
DE SANCTIS, MARIA CRISTINA
CAPRIA, MARIA TERESA
Russell, Christopher T.
Raymond, Carol A.
Cloutis, Edward A.
|Issue Date:||2015||Journal:||ICARUS||Number:||258||First Page:||120||Abstract:||The discovery of olivine on Vesta's surface by the VIR imaging spectrometer onboard the Dawn space mission has forced us to reconsider our views of Vestan petrogenetic models. Olivines were expected to be present in the interior of Vesta: in the mantle of a vertically layered body as invoked by the magma ocean models, or at the base (or within) the mantle-crust boundary as proposed by fractionation models. Olivines have been detected by VIR-Dawn in two wide areas near Arruntia and Bellicia, regions located in the northern hemisphere. Interestingly, these olivine-rich terrains are far from the Rheasilvia and the more ancient Veneneia basins, which are expected to have excavated the crust down to reach the mantle. In this work we present our attempts to identify other undetected olivine rich areas on Vesta by using spectral parameters sensitive to olivine such as the Band Area Ratio (BAR) and other specific parameters created for the detection of olivines on Mars (forsterite, fayalite and a generic olivine index). As a preliminary step we calibrated these parameters by means of VIS-IR spectra of different HED meteorite samples: behaviors versus sample grain size and albedo were analyzed and discussed. We selected the BAR and the Forsterite Index as the best parameters that can be used on Vesta. A cross-correlation analysis has been applied in order to detect olivine signature on the VIR hyperspectral cubes. These detections have then been confirmed by an anti-correlation analysis between the BAR and one of the olivine parameters, independent of the first method applied. <P />In agreement with the recent discovery, Arruntia and Bellicia were found to be as the most olivine-rich areas, i.e. where the parameter values are strongest. In addition we detected 6 new regions, all but one located in the Vesta north hemisphere. This result confirms again that the old petrogenetic models cannot be straightforwardly applied to Vesta and should be reshaped in the view of these new detections. An alternative and very recent option can be represented by the model according to which surface "eruption" of material from the mantle, including olivine can reach the surface of Vesta.||Acknowledgments:||Acknowledgments In Loving memory of my Dad, Gianni Palomba. The authors acknowledge the support of the Dawn Science, Instrument, and Operations Teams. This work was supported by ASI and NASA . A portion of this work was performed at the NASA/JPL. The data used in this paper are available from the website http://dawndata.igpp.ucla.edu . We warmly thank Robert Gaskell for providing the Vesta shape model and Anton Ermakov for providing map of the Vesta Bouguer anomaly. Thanks to Tom McCord (Bear Fight Institute) and to another anonymous reviewer for suggestions and comments that improved our manuscript. Diego Turrini (IAPS-INAF) is thanked for an helpful discussion about exogenous origin of olivine. VIR is funded by the Italian Space Agency ASI and was developed under the leadership of INAF-Istituto di Astrofisica e Planetologia Spaziali, Rome-Italy. The instrument was built by Selex-Galileo, Florence-Italy.||URI:||http://hdl.handle.net/20.500.12386/29731||URL:||https://www.sciencedirect.com/science/article/abs/pii/S0019103515002559?via%3Dihub||ISSN:||0019-1035||DOI:||10.1016/j.icarus.2015.06.011||Bibcode ADS:||2015Icar..258..120P||Fulltext:||reserved|
|Appears in Collections:||1.01 Articoli in rivista|
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