From the latest MAPS (Meteoritics and Planetary Science), too new to have article numbers yet:
Schönbächler, M. Fehr, M. A. Yokoyama, T. et al. Zirconium isotope composition indicates s-process depletion in samples returned from asteroid Ryugu .14279
S-process isotopes are components from the “slow process,” found in Asymptotic Giant Branch stars. Why are S-isotopes important? The newborn Sun was in a star cluster with AGB stars; those stars left their imprint in the form of AGB components (like S-isotopes) in certain parts of the Solar System. Carbonaceous chondrites are one of those parts. C-chondrites formed in the outer Solar System, where they were exposed to gases and dust from other stars. (In the inner Solar System, the heat and light and excess gas and such was able to shield/deflect bodies from these ‘foreign’ influxes.) The trace amounts of stellar chemicals is one piece of evidence that tells us where C-chondrites formed, and in turn the detection of certain isotopes, and not others, is one piece of evidence of what happens in AGB stars. Very interesting detective work, I must say.
Yet this piece doesn’t fit. Some Ryugu particles test low for these isotopes. Granted, the research group admits there could be some sort of error; in geochemistry/cosmochemistry, isotopes are measured as ‘enriched’ or ‘depleted’ versus each other. One possibility not ruled out is that it’s the gauge isotope that’s off, not the S-one (here, zirconium). But there are lots of isotopes, of lots of elements. It would take a mighty coincidence for the whole picture to be off. Rather, it seems we’re on to something here, something which may be of interest. I told you meteoriticists drill deep, in both the tool-sense, and in the sense of decimal places. Let’s wait and see where this puzzle piece takes the picture.