Oops, missed Astrophysical Journal Letters for April 10 (vol. 983, #1):
Mousis, O. Werlen, A. Benest Couzinou, T. et al. Primordial Origin of Methane on Eris and Makemake Supported by D/H Ratios L12 adc134
Lim, B. Ishiguro, M. Takahashi, J. et al. Optical and Near-infrared Contemporaneous Polarimetry of C/2023 A3 (Tsuchinshan-ATLAS) L19 adc2f9
What is the nature and history of small bodies (and in turn, the planets that formed from them)? Mousis et al. look at one aspect: the organics on primitive (unmelted) small bodies. Carbonaceous chondrite asteroids, comets, and outer Solar System bodies (Centaurs and KBOs) contain various hydrocarbons, and thus hydrogen. The richness in the deuterium isotope (2H) indicates outer-Solar System hydrogen, from the edge of the presolar nebula and the surrounding galaxy. Relative to the inner Solar System (and Comet 67P/C-G), KBO methanes appear deuterium-rich, making it nebular, not scattered outward from the Sun or inner Solar System.
Polarimetry: the stepchild of astronomy. Plenty of people do spatial resolution (imaging), and magnitudes/lightcurves. But the polarization of light is information that often goes un-“read”. In the case of small bodies, polarized light can tell us of surfaces and emitted dust (poly-surfaces). Lim et al. tell us, in turn, what they’ve read at Comet C/2023 A3.