[meteorite-list] Mystery Meteorite with a Molten Past (NWA 011)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:50:29 2004
Message-ID: <200204251706.KAA17409_at_zagami.jpl.nasa.gov>

http://skyandtelescope.com/news/current/article_585_1.asp

Mystery Meteorite with a Molten Past
Sky & Telescope News Brief
April 25, 2002

Planetary scientists suspect that many primordial asteroids must
have grown large enough to melt completely, yielding iron-rich
cores and silicate crusts before being shattered to pieces. After
all, the iron meteorites reaching Earth comprise dozens of unique
compositional types. Yet, among the thousands of known meteorites,
only a relative handful consist of basalt, the igneous rock type
that would be most common in those asteroidal crusts - and until
recently all of them seemed to have come from a single source,
4 Vesta. In the April 12th issue of Science, Akira Yamaguchi
(National Institute of Polar Research, Tokyo) and nine colleagues
argue that a 40-gram stone called Northwest Africa 011 is a basaltic
meteorite entirely unlike those from Vesta. Its parent body is unknown;
one candidate is 1459 Magnya, an outer-belt object that was found to
have a basalt spectrum two years ago. Still, though lacking a pedigree,
NWA 011 is a significant find. As asteroid expert Richard P. Binzel
(MIT) explains, "Yamaguchi's results (and those for 1459 Magnya) are the
'eureka' that complement what the iron meteorites have been telling us:
there must have been other Vestas out there."

Online access to Science is restricted, but Yamaguchi's abstract can be
found at:

http://www.sciencemag.org/cgi/content/short/296/5566/334.

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http://www.sciencemag.org/cgi/content/short/296/5566/334

A New Source of Basaltic Meteorites Inferred from Northwest Africa 011

  Akira Yamaguchi,[12*] Robert N. Clayton,[3] Toshiko K. Mayeda,[3]
  Mitsuru Ebihara,[4] Yasuji Oura,[4] Yayoi N. Miura,[5] Hiroshi Haramura,[1]
  Keiji Misawa,[12] Hideyasu Kojima,[12] Keisuke Nagao[6]

  Eucrites are a class of basaltic meteorites that share common
  mineralogical, isotopic, and chemical properties and are thought to
  have been derived from the same parent body, possibly asteroid 4 Vesta.
  The texture, mineralogy, and noble gas data of the recently
  recovered meteorite, Northwest Africa (NWA) 011, are similar to those
  of basaltic eucrites. However, the oxygen isotopic composition of
  NWA011 is different from that of other eucrites, indicating that NWA011
  may be derived from a different parent body. The presence of basaltic
  meteorites with variable oxygen isotopic composition suggests the
  occurrence of multiple basaltic meteorite parent bodies, perhaps
  similar to 4 Vesta, in the early solar system.

  1 Antarctic Meteorite Research Center, National Institute of Polar
    Research, Tokyo 173-8515, Japan.
  2 The Graduate University for Advanced Studies, Tokyo 173-8515, Japan.
  3 Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA.
  4 Department of Chemistry, Tokyo Metropolitan University, Hachioji,
    Tokyo 192-0397, Japan.
  5 Earthquake Research Institute, University of Tokyo, Tokyo 113-0032, Japan.
  6 Laboratory for Earthquake Chemistry, University of Tokyo, Tokyo
    113-0033, Japan.

  * To whom correspondence should be addressed. E-mail: yamaguch_at_nipr.ac.jp
Received on Thu 25 Apr 2002 01:06:55 PM PDT