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Published August 20, 2014 | Submitted + Published
Journal Article Open

Multiple and Fast: The Accretion of Ordinary Chondrite Parent Bodies

Abstract

Although petrologic, chemical, and isotopic studies of ordinary chondrites and meteorites in general have largely helped establish a chronology of the earliest events of planetesimal formation and their evolution, there are several questions that cannot be resolved via laboratory measurements and/or experiments alone. Here, we propose the rationale for several new constraints on the formation and evolution of ordinary chondrite parent bodies (and, by extension, most planetesimals) from newly available spectral measurements and mineralogical analysis of main-belt S-type asteroids (83 objects) and unequilibrated ordinary chondrite meteorites (53 samples). Based on the latter, we suggest that spectral data may be used to distinguish whether an ordinary chondrite was formed near the surface or in the interior of its parent body. If these constraints are correct, the suggested implications include that: (1) large groups of compositionally similar asteroids are a natural outcome of planetesimal formation and, consequently, meteorites within a given class can originate from multiple parent bodies; (2) the surfaces of large (up to ~200 km) S-type main-belt asteroids mostly expose the interiors of the primordial bodies, a likely consequence of impacts by small asteroids (D < 10 km) in the early solar system; (3) the duration of accretion of the H chondrite parent bodies was likely short (instantaneous or in less than ~10^5 yr, but certainly not as long as 1 Myr); (4) LL-like bodies formed closer to the Sun than H-like bodies, a possible consequence of the radial mixing and size sorting of chondrules in the protoplanetary disk prior to accretion.

Additional Information

© 2014 American Astronomical Society. Received 2014 March 28; accepted 2014 May 16; published 2014 August 6. We thank the referee for his pertinent and constructive remarks. The research leading to these results has received funding from the European Community's Seventh Framework Programme. The work by the MIT coauthors was supported by the National Science Foundation. The near infrared data were acquired by the authors operating as Visiting Astronomers at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program. We warmly thank the Antarctic meteorite collection for providing the ordinary chondrite samples. We thank Cecilia Satterwhite for preparing the samples. We thank Zibulle for producing Figure 6's artwork. We thank Tom Burbine for useful discussions and encouragement. This paper is dedicated to the late Paul Pellas who energetically defended the idea that S-type asteroids are the parent bodies of OCs.

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Published - 0004-637X_791_2_120.pdf

Submitted - 1405.6850.pdf

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August 22, 2023
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