Compositional differences between meteorites and near-Earth asteroids

New spectral measurements of near-Earth asteroids reveal, as might be expected, overall compositions similar to the most commonly falling meteorites, the ordinary chondrites. But the compositional distribution is un-expected: about two-thirds of near-Earth asteroids, including those most likely to hit us, match the class of meteorites known as LL chondrites, which comprise only about 8% of all meteorite falls. This may reflect an origin at the asteroid belt's inner edge, where the family of asteroids produced by the break-up of the Flora parent body predominates. A possible explanation might lie in the involvement of size-dependent processes in the transport of material from the main asteroid belt to the vicinity of Earth's orbit.