In the journal Geochimica et Cosmochimica Acta, 15 Nov (vol. 409):
Jordan, F. Timms, N. E. Nakamura, T. et al. Asteroid Itokawa … but when and how did it form exactly? Pg. 178 .2025.09.020
Our first asteroid sample- not a meteorite, with unknown provenance and zero context- just keeps on giving. Despite being a wisp of dust, barely a milligram, our Hayabusa grains from (25143) Itokawa are still delivering results… in a way. Jordan et al. use argon isotopes to date the grains; one isotopes is a decay product, one is not; the relative isotope budget (each acts as a gauge against the other) can give the number of half-lives since the “clock” was reset. Less convincingly, the authors search for signs of shock in the particles. Not finding many, they presume the collisional history of the body. I, personally, find this weak evidence. The Hayabusa spacecraft accidentally knocked loose dust off one spot on the asteroid. There’s a possibility that this particular sample is unrepresentative, and of course it’s a small sample. A larger total mass (or one, large rock) might give different results. Oh well, you can read the paper yourself and decide your own ‘sigma’ on it.