Missed Meteoritics & Planetary Science for February (vol. 60 #2):
Jenkins, L. E. Lee, M. R. Daly, L et al. Petrofabrics in the CM chondrite Kolang: Evidence for non-spherical chondrules in the protoplanetary disk p. 190 .14297
Dionnet, Z. Djouadi, Z. Delaye, L. et al. Methylene-to-methyl ratio variability in Ryugu samples: Clues to a heterogeneous aqueous alteration p. 273 .14304
Floyd, C. J. Jenkins, L. E. Martin, P.-E. et al. CM carbonaceous chondrite petrofabrics and their implications for understanding the relative chronologies of parent body deformation and aqueous alteration p. 324 .14303
We have a rather interesting claim on the agenda. Previously, it was assumed that petrofabrics (aligned textures in a rock mass, aligning its components) found in chondrite meteorites were caused by the parent rock getting smashed and smeared by impact. Jenkins et al. and Floyd et al. (including some of the same et al.s) have seen intriguing evidence in multiple, separate meteorites: our understanding of petrofabrics is significantly off. The petrofabric includes nonround chondrules, assumed to be deformed from their original, round state. However, by other lines of evidence in the meteorites, the workers now claim that the chondrules were oval to begin with; mild pressure then aligned their long axes to their current directions. Over time, they then froze in place when the asteroid material lithified. This is a bold claim; there must be something making nontrivial numbers of chondrules into ovals, despite them being free-floating or in microgravity. We’ll see what other scientists say (and find) in turn.
By contrast, Dionnet et al. seems rather pedestrian. They report the processing of organic chemicals in Ryugu, based on their Hayabusa2 sample allocation. Organics are, variously, mildly durable or not stable at all. It is unsurprising that they’ve been processed; if anything, it testifies to the value of carbonaceous chondrites that they preserve organic compounds as well as they do. But what, exactly, happened to the organics, and can we back-trace it to the original chemicals in the Solar Nebula (and before)?