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

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Sat, 3 Apr 2010 19:37:58 -0700 (MST)
Message-ID: <28cc93c72c43b8abeca838a4e4a4879c.squirrel_at_webmail.lpl.arizona.edu>

Hi Alan:

Thanks for this. Where was this published? Some of the numbers did not
come though. This works fine with me other than,if read this correctly, it
does not classify anything larger than a meter. What are those objects?

There was a discussion of this topic some time ago and one needs to take
into account some that has been observed and has its orbit determined.
Technically this is an asteroid since the IAU does not number/name
meteoroids. This can be down to about 5 meters (not sure what the smallest
NEO observed is). I would be hard pressed to call everything larger than 1
meter (if I read this right) an asteroid.

My two cents.


> 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)
> ??
> 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.
> ??
> 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).
> ??
> 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.
> ??
> 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.
> ??
> 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.
> ??
> Shawn Alan
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Received on Sat 03 Apr 2010 10:37:58 PM PDT

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