TY - JOUR
T1 - Olivine or impact melt
T2 - Nature of the "Orange" material on Vesta from Dawn
AU - Le Corre, Lucille
AU - Reddy, Vishnu
AU - Schmedemann, Nico
AU - Becker, Kris J.
AU - O'Brien, David P.
AU - Yamashita, Naoyuki
AU - Peplowski, Patrick N.
AU - Prettyman, Thomas H.
AU - Li, Jian Yang
AU - Cloutis, Edward A.
AU - Denevi, Brett W.
AU - Kneissl, Thomas
AU - Palmer, Eric
AU - Gaskell, Robert W.
AU - Nathues, Andreas
AU - Gaffey, Michael J.
AU - Mittlefehldt, David W.
AU - Garry, William B.
AU - Sierks, Holger
AU - Russell, Christopher T.
AU - Raymond, Carol A.
AU - De Sanctis, Maria C.
AU - Ammanito, Eleonora
N1 - Funding Information:
The authors would like to thank the Dawn Flight Operations team for a successful Dawn at Vesta mission. L.L. work is supported by Dawn UCLA subcontract# 2090-S-MB170. V.R. work is supported by NASA Dawn Participating Scientist Program Grant NNH09ZDA001N-DAVPS and NASA Planetary Geology and Geophysics Grant NNX07AP73G. D.P.O. is supported by Dawn at Vesta Participating Scientist Program Grant NNX10AR21G. NS and TK work is supported by the German Space Agency (DLR) on behalf of the Federal Ministry of Economics and Technology, Grant 50OW1101. The research utilizes spectra acquired with the NASA RELAB facility at Brown University. The authors would like to thank Guneshwar S. Thangjam for his help gathering laboratory spectral data from RELAB. E.A.C. thanks CSA, CFI, MRIF and the University of Winnipeg for supporting HOSERLab. The authors are grateful to Nicholas Moskovitz and Tom Burbine for their suggestions to improve the manuscript. The Dawn mission is led by the University of California, Los Angeles under the auspices of the NASA Discovery Program. The Framing Camera project is financially supported by the Max Planck Society and the German Space Agency, DLR. VIR is funded by the Italian Space Agency and was developed under the leadership of INAF-Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy. GRaND is operated by the Planetary Science Institute.
PY - 2013/11
Y1 - 2013/11
N2 - NASA's Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types: (a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), (b) lobate patches with well-defined edges (nicknamed "pumpkin patches"), and (c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed "Leslie feature" first identified by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130-157) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Several possible options for the composition of the orange material are investigated including, cumulate eucrite layer exposed during impact, metal delivered by impactor, olivine-orthopyroxene mixture and impact melt. Based on our analysis, the orange material on Vesta is unlikely to be metal or olivine (originally proposed by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130-157)). Analysis of the elemental composition of Oppia ejecta blanket with GRaND suggests that its orange material has ~25% cumulate eucrite component in a howarditic mixture, whereas two other craters with orange material in their ejecta, Octavia and Arruntia, show no sign of cumulate eucrites. Morphology and topography of the orange material in Oppia and Octavia ejecta and orange patches suggests an impact melt origin. A majority of the orange patches appear to be related to the formation of the Rheasilvia basin. Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt.
AB - NASA's Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types: (a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), (b) lobate patches with well-defined edges (nicknamed "pumpkin patches"), and (c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed "Leslie feature" first identified by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130-157) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Several possible options for the composition of the orange material are investigated including, cumulate eucrite layer exposed during impact, metal delivered by impactor, olivine-orthopyroxene mixture and impact melt. Based on our analysis, the orange material on Vesta is unlikely to be metal or olivine (originally proposed by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130-157)). Analysis of the elemental composition of Oppia ejecta blanket with GRaND suggests that its orange material has ~25% cumulate eucrite component in a howarditic mixture, whereas two other craters with orange material in their ejecta, Octavia and Arruntia, show no sign of cumulate eucrites. Morphology and topography of the orange material in Oppia and Octavia ejecta and orange patches suggests an impact melt origin. A majority of the orange patches appear to be related to the formation of the Rheasilvia basin. Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt.
KW - Asteroid Vesta
KW - Asteroids, composition
KW - Asteroids, surfaces
KW - Mineralogy
KW - Spectroscopy
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U2 - 10.1016/j.icarus.2013.08.013
DO - 10.1016/j.icarus.2013.08.013
M3 - Article
AN - SCOPUS:84884324637
SN - 0019-1035
VL - 226
SP - 1568
EP - 1594
JO - Icarus
JF - Icarus
IS - 2
ER -