The July edition of Meteoritics & Planetary Science (vol. 60, #7) has been posted:
Laforet, S. Leroux, H. Le Guillou, C. et al. Silicate–sulfide interaction within quenched melts of space weathered Ryugu grains Pgs 1480 .14366
Rubin, A. E. Selective sampling of asteroids, the Moon, and Mars: Factors affecting the numerical abundances of members of meteorite groups Pgs 1502 .14367
Chaves, L. C. Thompson, M. S. Dukes, C. A. et al. Experimental simulations of space weathering on pentlandite Pgs 1555 .14371
Miyahara, M. Noguchi, T. Yamaguchi, A. et al. Djerfisherite in a Ryugu grain: A clue to localized heterogeneous conditions or material mixing in the early solar system Pgs 1666 .14370
Most asteroids, like most planets, are partly composed of silicates. Unlike planets, they retain much sulfide- possibly the next most-common component after silicates, for some meteorites. Chondritic asteroids, then, are some part familiar, some part uncanny. Also un-Earthly: airless asteroids are directly exposed to bombardments, like micrometeorites. This is a form of erosion unlike what we experience in our terrestrial lives. The question, then, is what happens to this strange mixture, in this strange situation? Laforet et al. try to answer; so do Chaves et al.
“Most asteroids” is, by necessity, a hedge: there isn’t one asteroid, one type, or even one region in the Solar System to lump together. Meteorites being samples of asteroids and other silicate bodies, what were/are those bodies? Over the decades, we have homed in on a strange hypothesis: the meteorites that have landed on Earth and been collected and studied may come from just dozens of parent asteroids (plus Earth’s satellite, Mars, and, it was once proposed, Mars’ satellites). Rubin 2025 again asks the question- how many(/few) parent bodies have made it to our meteorite collections?
“Most asteroids” have that sulfide in the form of troilite, pentlandite, or very similar metal-sulfur compounds. Ryugu, though, contains a minority of djerfisherite- a rare sulfide mineral that tends to be found in other meteorite classes. Why does Ryugu have djerfisherite, unexpectedly? The simplest, most direct answer is mixing. The Zag/Monahans meteorites had water, unexpectedly, which looks cometary. Ryugu was seen to have ‘foreign’ boulders resting on its surface, as did Bennu. Alternately, this spot of sulfide may just happen to be a freak spot on Ryugu- weird things happen.