The Formation and Evolution of Ordinary Chondrite Parent Bodies

TL;DR

This paper reviews the origin and evolution of ordinary chondrite parent bodies, highlighting how space weathering and recent asteroid missions have clarified their connection to S-type asteroids, informing planetesimal formation theories.

Contribution

It synthesizes recent observational and sample return data to resolve longstanding debates about the formation and evolution of ordinary chondrite parent bodies.

Findings

Space weathering explains spectral differences between S-type asteroids and OCs.

Most S-type asteroids have mineralogies similar to OCs.

Recent missions support the S-type--OC link, constraining planetesimal formation models.

Abstract

Ordinary chondrites (OCs) are by far the most abundant meteorites (80% of all falls). Their origin has long been the matter of a heated debate. About thirty years ago (e.g., Pellas 1988), it was proposed that OCs should originate from S-type bodies (the most abundant asteroid spectral types in the inner part of the asteroid belt), but the apparent discrepancy between S-type asteroid and OC reflectance spectra generated what was known as the S-type--OC conundrum. This paradox has gradually been resolved over the years. It is now understood that space weathering processes are responsible for the spectral mismatch between S-type bodies and OCs. Furthermore, both telescopic observations and the first asteroid sample return mission (Hayabusa) indicate that most S-type bodies have mineralogies similar to those of OCs. Importantly, the S-type/OC link, which has remained sterile for more than 30 years, has been delivering fundamental constraints on the formation and evolution of planetesimals over the recent years.