Oh look, an article in Nature. Well, a Nature-family title, Nature Communications Earth & Environment. In vol. 6:
Kawasaki, N. Arakawa, S. Miyamoto, Yushi et al. Solar System’s earliest solids as tracers of the accretion region of Ryugu and Ivuna-type carbonaceous chondrites 537 s43247-025-02511-x
It’s hard to emphasize it enough: small bodies, having never been melted like the planets, preserve the traces from the early Solar System. The CI chondrite meteorites are the most representative of that early Solar System elemental inventory, and are used as reference standards for workers trying to assay other Solar System materials. (Note that “C” is for carbonaceous, as in carbonaceous chondrite meteorites, and “I” is for Ivuna, since the Ivuna meteorite, specifically, had been the standard bearer for establishing the CI group.) And Ryugu samples, brought back by Hayabusa2, are considered to be CI-type material which never suffered the ills of atmospheric entry, Earth impact, and exposure to our hydrosphere and biosphere.
So what can we say about these traces from ~4.5 billion years ago? We are putting together a picture of a Solar System with an inner and outer chemistry, roughly separated by Jupiter. …Except, that Jupiter moved in the early years, jumbling the pieces. Those pieces included in them CAIs (Calcium-Aluminum rich Inclusions), considered the first true solids to form. Their formation is taken to be the ‘birthday’ of this System, and all other timescales start at the condensation of the CAIs. CAIs are rare in CI meteorites… but not completely gone, and we have found CAIs in the Haya2 sample of Ryugu, as well. Kawasaki et al. take the Ryugu sample, and try to deduce not just the formation region of Ryugu and the CIs, but their timeline since CAI formation.