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Composition of the Rheasilvia basin, a window into Vesta's interior
Author(s) -
McSween Harry Y.,
Ammannito Eleonora,
Reddy Vishnu,
Prettyman Thomas H.,
Beck Andrew W.,
Cristina De Sanctis M.,
Nathues Andreas,
Corre Lucille Le,
O'Brien David P.,
Yamashita Naoyuki,
McCoy Timothy J.,
Mittlefehldt David W.,
Toplis Michael J.,
Schenk Paul,
Palomba Ernesto,
Turrini Diego,
Tosi Federico,
Zambon Francesca,
Longobardo Andrea,
Capaccioni Fabrizio,
Raymond Carol A.,
Russell Christopher T.
Publication year - 2013
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/jgre.20057
Subject(s) - geology , olivine , mantle (geology) , crust , geochemistry , meteorite , basalt , partial melting , incompatible element , petrology , astrobiology , physics
The estimated excavation depth of the huge Rheasilvia impact basin is nearly twice the likely thickness of the Vestan basaltic crust, so the mantle should be exposed. Spectral mapping by the Dawn spacecraft reveals orthopyroxene‐rich materials, similar to diogenite meteorites, in the deepest parts of the basin and within its walls. Significant amounts of olivine are predicted for the mantles of bulk‐chondritic bodies like Vesta, and its occurrence is demonstrated by some diogenites that are harzburgite and dunite. However, olivine has so far escaped detection by Dawn's instruments. Spectral detection of olivine in the presence of orthopyroxene is difficult in samples with <25% olivine, and olivine in Rheasilvia might have been diluted during impact mixing or covered by the collapse of basin walls. The distribution of diogenite inferred from its exposures in and around Rheasilvia provides a geologic context for the formation of these meteorites, but does not clearly distinguish between a magmatic cumulate versus partial melting restite origin for diogenites. The former is favored by geochemical arguments, and crystallization in either a magma ocean or multiple plutons emplaced near the crust‐mantle boundary is permitted by Dawn observations.