How many different parent bodies do meteorites come from?

Every meteorite group is thought to come from a separate parent body, or a family of closely related bodies. Counting groups therefore gives a rough idea of how many parent bodies are represented.

For chondrites, there are about 15 recognised groups: H, L and LL ordinary chondrites; EH and EL enstatite chondrites; CI, CM, CO, CV, CK, CR, CH and CB carbonaceous chondrites; and the R and K chondrites. Some groups, such as the CR, CH and CB clan, may be related.

Achondrites add many more: the HED meteorites from Vesta; angrites; aubrites; ureilites; brachinites; acapulcoites and lodranites, which share a parent body; winonaites; and Martian and lunar meteorites from known bodies.

Iron meteorites are remarkable. There are about 14 recognised chemical groups, but many iron meteorites are ungrouped. Studies suggest the irons alone represent perhaps 50 or more separate parent bodies.

Stony-irons include main-group pallasites, several small pallasite groups and mesosiderites.

Adding ungrouped meteorites, each potentially from a different body, the total may well exceed a hundred and perhaps approach 150 parent bodies.

This is surprising given that the asteroid belt contains millions of asteroids: it suggests meteorites sample only a small, biased fraction. Fragments from bodies near orbital resonances or from recently broken asteroids are over-represented, while others may never reach us. Each new group or ungrouped meteorite adds another world to the list.

More about the science of meteorites

• Why do iron meteorites come from so many parent bodies?
• Can meteorites tell us what is inside Earth?
• How do scientists cut and study a meteorite?
• What is a regolith breccia and what can it tell us?
• Why do some meteorites contain gas from the Sun?
• What are short-lived radioactive isotopes and why do they matter?

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