Olivine-dominated asteroids: Mineralogy and origin

Juan A. Sanchez, Vishnu Reddy, Michael S. Kelley, Edward A. Cloutis, William F. Bottke, David Nesvorný, Michael P. Lucas, Paul S. Hardersen, Michael J. Gaffey, Paul A. Abell, Lucille Le Corre

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

Olivine-dominated asteroids are a rare type of objects formed either in nebular processes or through magmatic differentiation. The analysis of meteorite samples suggest that at least 100 parent bodies in the main belt experienced partial or complete melting and differentiation before being disrupted. However, only a few olivine-dominated asteroids, representative of the mantle of disrupted differentiated bodies, are known to exist. Due to the paucity of these objects in the main belt their origin and evolution have been a matter of great debate over the years. In this work we present a detailed mineralogical analysis of twelve olivine-dominated asteroids. We have obtained near-infrared (NIR) spectra (0.7-2.4μm) of asteroids (246) Asporina, (289) Nenetta, (446) Aeternitas, (863) Benkoela, (4125) Lew Allen and (4490) Bamberry. Observations were conducted with the Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i. This sample was complemented with spectra of six other olivine-dominated asteroids including (354) Eleonora, (984) Gretia, (1951) Lick, (2501) Lohja, (3819) Robinson and (5261) Eureka obtained by previous workers. Within our sample we distinguish two classes, one that we call monomineralic-olivine asteroids, which are those whose spectra only exhibit the 1μm feature, and another referred to as olivine-rich asteroids, whose spectra exhibit the 1μm feature and a weak (Band II depth ~4%) 2μm feature. For the monomineralic-olivine asteroids the olivine chemistry was found to range from ~Fo49 to Fo70, consistent with the values measured for brachinites and R chondrites. In the case of the olivine-rich asteroids we determined their olivine and low-Ca pyroxene abundance using a new set of spectral calibrations derived from the analysis of R chondrites spectra. We found that the olivine abundance for these asteroids varies from 0.68 to 0.93, while the fraction of low-Ca pyroxene to total pyroxene ranges from 0.6 to 0.9. A search for dynamical connections between the olivine-dominated asteroids and asteroid families found no genetic link (of the type core-mantel-crust) between these objects.

Original languageEnglish (US)
Pages (from-to)288-300
Number of pages13
JournalIcarus
Volume228
DOIs
StatePublished - Jan 15 2014
Externally publishedYes

Keywords

  • Asteroids
  • Infrared observations
  • Meteorites
  • Spectroscopy

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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