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Contemporary Meteoritics |
Earth and Physical Sciences, National Museums Liverpool, William Brown Street, Liverpool L3 8EN, UK alan.bowden{at}liverpoolmuseums.org.uk
The matching of meteorite types held in our collections to asteroid classes, and even individual asteroids, may perhaps be said to commence with Olmsted’s meteor researches and Wienek’s pioneering photographic meteor image taken in 1885. Photographic fireball network surveys started up during the 1960s and three major national programmes were initiated during this period; each resulting in the recovery of one meteorite, P
Dynamical considerations are paramount in connecting meteorites with cometary or asteroidal sources of supply. Ernst Öpik originally raised the question of locating the mechanism for delivering asteroid fragments to Earth within a timescale and flux that matches known meteorite falls. Several workers took up Öpik’s 1963 challenge, so that today the dynamical conditions and potential delivery mechanisms existing at the Kirkwood Gaps within the asteroid belt are better understood.
Pioneering work by Brobovnikoff in 1929 initiated the field of spectrophotometric studies of asteroid surfaces. He attempted to correlate asteroid spectra with the reflective properties of meteorites. Advances in instrumentation led McCord in 1969 to initiate the modern era of asteroid spectrophotometric studies. This is a burgeoning field of contemporary research that has had some success in identifying possible meteorite-asteroid class linkages and even possible meteorite-asteroid matches, i.e. Vesta and howardite-eucrite-diogenite (HED) meteorites. However, space weathering of asteroid surfaces may mask the true asteroidal reflectance characteristics.
In recent years spacecraft flyby missions have revealed more about the surface morphologies of asteroids: notably the S class asteroids (951) Gaspra, (243) Ida and the C class asteroid (253) Mathilde. Asteroids are no longer points of light or spectral curves but are bodies with distinct surface morphologies and geological histories. This was exemplified by the soft landing of the NEAR-Shoemaker spacecraft on (433) Eros in 2001 after a year-long orbital mission. However, it is still difficult to reconcile the meteorites held in our collections with the known distribution of asteroid classes and it may be that they are possibly incompatible sets.
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This 250-word extract was created in the absence of an abstract.
ibram, Lost City and Innisfree. Although photographic surveys had low meteorite recovery rates they, nevertheless, provided invaluable data on the population of meteoroids in near-Earth space.
