Matching meteorites with their parents.Astronomers report the first direct link between a set of meteorites Meteorites See also astronomy. aerolithology the science of aerolites, whether meteoric stones or meteorites. Also called aerolitics. astrolithology the study of meteorites. Also called meteoritics. and a particular location in the main asteroid belt, which lies between Mars and Jupiter. Michael J. Gaffey, Kevin L. Reed and Michael S. Kelley of the Rensselaer Polytechnic Institute Rensselaer Polytechnic Institute, at Troy, N.Y.; coeducational; founded and opened 1824 as Rensselaer School; chartered 1826. It was called Rensselaer Institute from 1837 to 1861. in Troy, N.Y., made their chance discovery after observing the asteroid Apollo (3103) 1982BB as it passed within 30 million kilometers of Earth in July 1991. Obtaining the asteroid's spectra with the NASA NASA: see National Aeronautics and Space Administration. NASA in full National Aeronautics and Space Administration Independent U.S. Infrared Telescope atop Mauna Kea in Hawaii, the researchers found evidence that the body contained a type of iron-free, magnesium-rich silicate silicate, chemical compound containing silicon, oxygen, and one or more metals, e.g., aluminum, barium, beryllium, calcium, iron, magnesium, manganese, potassium, sodium, or zirconium. Silicates may be considered chemically as salts of the various silicic acids. known as enstatite enstatite Common silicate mineral in the pyroxene family. It is the stable form of magnesium silicate (MgSiO3, often with up to 10% iron) in magnesium- and iron-rich igneous rock types. . That mineral also predominates in a group of meteorites called enstatite achondrites. Gaffey's team believes these meteorites represent fragments of the kilometer-size asteroid they studied. At first glance, that identification wouldn't seem to link meteorites with main-belt asteroids This is a list of numbered minor planets, nearly all of them asteroids, in sequential order. As of late September 2007 there are 164,612 numbered minor planets, and many more not yet numbered. Most asteroids are ordinary and not particularly noteworthy. , since (3103) 1982BB does not now reside in the belt. But it may have once, says Gaffey, since this asteroid's orbit intersects the Hungaria region, one of the innermost parts of the asteroid belt. Researchers had previously suspected that enstatite achondrites came from the Hungaria region, but they discounted the idea because the surfaces of meteorites falling to Earth directly from this locale would have been bombarded by cosmic rays cosmic rays, charged particles moving at nearly the speed of light reaching the earth from outer space. Primary cosmic rays consist mostly of protons (nuclei of hydrogen atoms), some alpha particles (helium nuclei), and lesser amounts of nuclei of carbon, nitrogen, for tens of millions of years. Cosmic-ray studies, however, have shown that enstatite achondrites experienced such bombardment about 10 times longer. Gaffey's team conjectures that the Apollo asteroid represents a chip off an old rock, a runaway fragment of a larger resident of the Hungaria region. As such, it could have served as a reservoir for the enstatite meteorites, which at some point broke off its surface, accounting for their longer exposure in space. Thus, Hungaria asteroids indeed appear to be the parent bodies of these meteorites, Gaffey concludes. The link may enable researchers to infer the composition and temperature of this part of the solar system during the formation of the planets and asteroids, he notes. |
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