[meteorite-list] "Meteorite and meteoroid: New comprehensive definitions"

From: Shawn Alan <photophlow_at_meteoritecentral.com>
Date: Sat, 3 Apr 2010 16:40:50 -0700 (PDT)
Message-ID: <653025.82873.qm_at_web113618.mail.gq1.yahoo.com>

Hello Listers,

Here is an intersting artical I found that explains new comprehensive definitions about meteorites. Down below is an abstract from the artical and a short introduction into the what is disussed about new definitions.


Meteorite and meteoroid: New comprehensive definitions

Alan E. RUBIN1* and Jeffrey N. GROSSMAN2
1Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095?1567, USA
2U.S. Geological Survey, 954 National Center, Reston, Virginia 20192, USA
*Corresponding author. E-mail: aerubin at ucla.edu
(Received 05 May 2009; revision accepted 14 September 2009)
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Abstract?Meteorites have traditionally been defined as solid objects that have fallen to Earthfrom space. This definition, however, is no longer adequate. In recent decades, man-made objects have fallen to Earth from space, meteorites have been identified on the Moon andMars, and small interplanetary objects have impacted orbiting spacecraft. Taking these factsand other potential complications into consideration, we offer new comprehensive definitions of the terms ??meteorite,?? ??meteoroid,?? and their smaller counterparts: A meteoroid is a 10-lm to 1-m-size natural solid object moving in interplanetary space. Amicrometeoroid is a meteoroid 10 lm to 2 mm in size. A meteorite is a natural, solid object
larger than 10 lm in size, derived from a celestial body, that was transported by naturalmeans from the body on which it formed to a region outside the dominant gravitational influence of that body and that later collided with a natural or artificial body larger than
itself (even if it is the same body from which it was launched). Weathering and other secondary processes do not affect an object?s status as a meteorite as long as something recognizable remains of its original minerals or structure. An object loses its status as a
meteorite if it is incorporated into a larger rock that becomes a meteorite itself. A micrometeorite is a meteorite between 10 lm and 2 mm in size.
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Meteorite???a solid substance or body falling from the high regions of the atmosphere??(Craig 1849); ??[a] mass of stone and iron that ha[s] been directly observed to have fallen down to the Earth?s surface?? (translated from Cohen 1894); ??[a] solid bod[y] which came to the earth from space?? (Farrington 1915); ??A mass of solid matter, too small to be
considered an asteroid; either traveling through space as an unattached unit, or having landed on the earth and still retaining its identity?? (Nininger 1933); ??[a meteoroid] which has reached the surface of the Earth without being vaporized?? (1958 International
Astronomical Union (IAU) definition, quoted by Millman 1961); ??a solid body which has arrived on the Earth from outer space?? (Mason 1962); ??[a] solid bod[y] which reach[es] the Earth (or the Moon, Mars, etc.) from interplanetary space and [is] large enough to survive
passage through the Earth?s (or Mars?, etc.) atmosphere?? (Gomes and Keil 1980); ??[a meteoroid] that survive[s] passage through the atmosphere and fall[s] to earth?? (Burke1986); ??a recovered fragment of a meteoroid that has survived transit through the earth?satmosphere?? (McSween 1987); ??[a] solid bod[y] of extraterrestrial material that penetrate[s]
the atmosphere and reach[es] the Earth?s surface?? (Krot et al. 2003).
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INTRODUCTION
Since Chladni (1794) published On the Origin of the
Pallas Iron and Others Similar to it, and on Some
Associated Natural Phenomena and made plausible the
hypothesis that rocks could fall from the sky, the
definition of the word meteorite has remained essentially
unchanged, as reflected in the ten quotations given
above. Nearly all modern reference works use a similar
definition. Meteorites are almost always defined to be
solid bodies that have fallen through the Earth?s
atmosphere and landed on the Earth?s surface.
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Many recent definitions of meteorite, including the
one adopted by the International Astronomical Union
(IAU), specify that meteorites originated as meteoroids.
The latter term was defined by the IAU as ??a solid
object moving in interplanetary space, of a size
considerably smaller than an asteroid and considerably
larger than an atom or molecule?? (Millman 1961). Beech
and Steel (1995) suggested modifying this definition to
include only natural objects in the size range 100 lm to
10 m. Because modern usage frequently ties these two
terms together, with meteoroids forming the pre-impact
precursors of meteorites, it is imperative that the
definitions be consistent.
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With the advent of the Space Age and the discovery
of new sources of extraterrestrial material, it is clear
that most existing definitions of the term meteorite are
too restrictive. Indeed, there are already three objects
recognized by the Meteoritical Society?s Committee on
Meteorite Nomenclature (NomCom) that violate most
traditional definitions of meteorite (with the exception
of the one given in Gomes and Keil 1980) because they
were not found on Earth?s surface. Two millimeter-size
chondrites discovered among samples returned from the
Moon during the Apollo missions have been described
and named as meteorites: Bench Crater (McSween 1976;
Zolensky et al. 1996) and Hadley Rille (Haggerty 1972;
Grossman 1997; Rubin 1997). A IAB-complex iron
identified on the surface of Mars by the Opportunity
rover was recently given a formal meteorite name:
Meridiani Planum (Connolly et al. 2006; Schro? der et al.
2008). The existence of these objects, combined with
other probable meteorites from the Moon and Mars
that have not yet been formally named (as well as other
conceivable examples), has led us to re-examine the
term meteorite and the related term meteoroid in a
search for precise, comprehensive definitions.
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Shawn Alan
Received on Sat 03 Apr 2010 07:40:50 PM PDT