The new Meteoritics & Planetary Science (May – volume 60, #5) is now online:
Connolly Jr, H. C. Lauretta, D. S. McCoy, T. J. et al. An overview of the petrography and petrology of particles from aggregate sample from asteroid Bennu P. 979 .14335
Patzek, M. Kadlag, Y. Rüfenacht, M. et al. Multi-isotope (N, O, Ti, and Cr) study of C1 and CM-like clasts—Probing unsampled C1 material P. 1073 .14343
Imae, N. Kimura, M. Yamaguchi, A. Hydration and dehydration of CM chondrites revealed by X-ray diffraction combined with textural observations and compositional data P. 1194 .14348
The CM meteorites are a group within the carbonaceous chondrites- rich in carbon and organics, and soft and wet due to a “clay-like” (phyllosilicate) composition. Numerous examples of CM meteorites have fallen and been recovered, the most famous being the large, 1970 Murchison meteorite- large enough to enable detection of meteorite organics, even with the crude analytical chemistry tools of the ’70s.
Samples from asteroid Bennu don’t exactly match CM meteorites, but they’re close- somewhere in between CM and the related CI meteorites (also classified as C1). No less of an authority than OSIRIS-REx principal investigator Dante Lauretta (et al., of course) publish the Bennu analysis- soft and wet, and rich in carbon and organics.
As well as the OSIRIS-REx material, fragile phyllosilicate astromaterials have reached Earth as clasts (rock inclusions) in stronger meteorites. Between true CM/CI meteorites, smaller clast samples, and the Bennu/Ryugu grains, we are piecing together the history of these preserved Solar System traces.