About the definition of meteoroid, asteroid, and related terms

The official definition of IAU Commission 22 from 1961 (see e.g. Millman, J. R. Astron. Soc. Can. 55, 265) says that meteoroid is a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom or molecule. In 1961, there was a huge gap between the smallest observed asteroids and the largest meteoroids observed as meteors in the atmosphere. Nowadays, the situation is different. The body, which caused the Chelyabinsk meteor (in fact a superbolide) of February 15, 2013, had a size of about 19 meters, while some cataloged asteroids observed telescopically in interplanetary space may be smaller than 1 meter. The current practice is to call objects observed telescopically asteroids and bodies detected in the atmosphere meteoroids irrespective of their size (which, anyway, is not precisely known at the time of observation). Nevertheless, some people tend to call the Chelyabinsk body asteroid because its size was obviously larger than the unofficial boundary of 10 meters. Another object with dual status is 2008 TC3, which was discovered as asteroid of the size of ~6 meters (the largest dimension), then detected as a meteoroid in the atmosphere and its remnants were found as meteorites Almahata Sitta.The subject was recently discussed with the Commission 22 with the aim to issue new definitions. Some other terms like meteor, meteorite, and dust needs to be refined to conform with the current usage and state of knowledge. We do not discourage the dual nomenclature asteroid/meteoroid according to the observation technique for the objects in the gray zone of 1-20 meters. On the other hand, some strict definition is desirable for generic bodies. It is obvious that there is no physical distinction between meteoroids and asteroids other than size. In practice, there are two choices for the boundary size: 1 meter or 10 meters.The possible definitions are:</u>Meteoroid: a solid object of a size between 100 microns and 1 meter moving in interplanetary space or coming from interplanetary space.Asteroid: a solid object of a size larger than 1 meter and smaller than a dwarf planet moving in interplanetary space and showing no activity (i.e. a release of gas, dust or meteoroids) or coming from interplanetary space.