Do we know which asteroids ordinary chondrites came from?
Increasingly, yes. Recent studies link many L chondrites to the Massalia asteroid family and many H chondrites to young families in the Koronis region.
Ordinary chondrites make up most falls, so identifying their source asteroids has long been a major goal.
Spectral evidence. Stony S-type asteroids have spectra resembling ordinary chondrites once space weathering is taken into account. Japan's Hayabusa mission confirmed in 2010 that Itokawa, an S-type, is made of LL chondrite material. That established the general link.
Specific families. In 2024, two studies published in the journal Nature combined fireball orbits, asteroid family ages, computer models of how fragments drift into resonances, and cosmic-ray exposure ages. They concluded that about 70 per cent of meteorite falls come from just a few young asteroid families. The L chondrites were linked to the Massalia family in the inner belt, whose formation in a collision about 470 million years ago matches the time of a famous shower of L chondrites seen in fossil meteorites in Sweden. A more recent collision in the same family, about 40 million years ago, may supply many L chondrites today. Many H chondrites were linked to the Karin and Koronis families, formed around 5.8 million and 7.6 million years ago respectively in the outer part of the belt.
LL chondrites. These may come from the Flora family or similar groups in the inner belt, consistent with Itokawa's origin.
Caution. These links are based on models and statistics. Individual meteorites cannot yet be traced to a specific asteroid with certainty. Future spacecraft and better fireball data will test these conclusions.