* Astronomy

Title: Meteorite and meteoroid: New comprehensive definitions
Authors: Alan E. Rubin and Jeffrey N. Grossman

Meteorites have traditionally been defined as solid objects that have fallen to Earth from 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 and Mars, and small interplanetary objects have impacted orbiting spacecraft. Taking these facts and other potential complications into consideration, we offer new comprehensive definitions of the terms "meteorite,""meteoroid," and their smaller counterparts: A meteoroid is a 10-m to 1-m-size natural solid object moving in interplanetary space. A micrometeoroid is a meteoroid 10 m to 2 mm in size. A meteorite is a natural, solid object larger than 10 m in size, derived from a celestial body, that was transported by natural means 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 recognisable 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 m 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 has been directly observed to have fallen down to the Earth's surface" (translated from Cohen 1894); "[a] solid body which came to the earth from space" (Farrington 1915); "A mass of solid matter, too small to be considered an asteroid; either travelling 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 vaporised" (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 body which reaches 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 survives passage through the atmosphere and falls to earth" (Burke 1986); "a recovered fragment of a meteoroid that has survived transit through the earth's atmosphere" (McSween 1987); "[a] solid body of extraterrestrial material that penetrates the atmosphere and reaches the Earth's surface" (Krot et al. 2003).

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