Origin of meteorites in the asteroid belt from meteor observations

An update is given reviewing asteroid, meteor, and meteorite-type links [1]. As of April 2025, 81 fireballs have been observed from which a meteorite was recovered. These fireballs record the meteoroid's orbit at the time of entering Earth's atmosphere. The number of observed falls has become sufficient to see that different meteorite types arrive on different orbits. Those show that our meteorites do not predominantly originate from a broad sampling of material from across the entire asteroid belt. Instead, the meteorites delivered to Earth are dominated by debris from the largest collisions among asteroids in the past 100 Ma. Collisions that also created km- and sub-km sized debris recognized as clusters in asteroid families. Following a collision, meter-sized meteoroids initially move more or less along the target asteroid orbit as does larger debris. Over time, Yarkovsky forces increase or decrease the semi-major axis until the orbit reaches one of the resonances, which takes about a million years. In resonance, the orbits quickly become eccentric with the perihelion distance moving in and the aphelion distance moving out. When the perihelion approaches Earth orbit, close encounters with Earth can lift the orbit out of the resonance, lower the semi-major axis and spread the inclination of the orbit over time. It can then still take a long time before meteoroids impact the small Earth. All this time, meteoroids smaller than 2-m in diameter are exposed to cosmic rays and built up cosmogenic nuclei that define the cosmic ray exposure (CRE) age. While in Earth-crossing orbits, CM chondrite meteoroids tend to fragment, but other meteoroids do not. Those have CRE ages that still correspond to the dynamical age of their young asteroid family source. In particular, 12 H chondrites have now been traced to three collision events in the Koronis family, at ~6, 11-14 and ~83 Ma, likely corresponding to the Karin, Koronis_2 and Koronis_3 clusters in that asteroid family. Most large km-sized Near Earth Asteroids (NEA) that are H-chondrite like do not. Those arrive at Earth via the 3:1 resonance from a source at high inclination in the Central Main Belt. Some H chondrites do too, four having a ~6 Ma CRE age that are possibly from the Nele (= Iannini) family. In addition, there is a source of H chondrites in the Inner Main Belt that have a ~35 Ma CRE age. These are likely from the Massalia family, which has a ~40 Ma cluster. All L chondrites observed to date appear to originate from the Inner Main Belt, likely from the Hertha (= Nysa) family. This is also the likely source of the larger km-sized L chondrite NEA, which arrive to Earth via the closer 3:1 resonance, rather than the nu-6 resonance from where most L chondrites are delivered. Most LL chondrites arrive from the Flora family in the Inner Main Belt (both small and large), but the meteorite Benesov likely arrived from the Eunomia family in the Central Main Belt. Unlike their larger cousins, most HED meteorites likely originated at asteroid Vesta, not the Vesta family. Possible source regions of other meteorite types will be discussed also. Based on these results, the meteorite type of a recent fall of a CK carbonaceous chondrites was anticipated because the observed orbit resembled that expected for meteorites delivered from the Eos family.

[1] Jenniskens P., Devillepoix H. A. R., 2025. Review of asteroid, meteor, and meteorite-type links. MAPS 60, 928-973.