Ice-coated Pebble Drift as a Possible Explanation for Peculiar Cometary CO/H₂O Ratios

Abstract To date, at least three comets—2I/Borisov, C/2016 R2 (PanSTARRS), and C/2009 P1 (Garradd)—have been observed to have unusually high CO concentrations compared water. We attempt explain these observations by modeling the effect of drifting solid (ice dust) material on ice compositions in protoplanetary disks. find that, independent exact disk model parameters, we always obtain a region enhanced ice-phase CO/H 2 O that spreads out radius over time. The inner edge this feature coincides with snowline. Almost every achieves unity, one reaches ratio >10. After running our simulations for 1 Myr, an average 40% mass contains more than H ice. In light this, population CO-ice-enhanced planetesimals are likely generally form outer regions disks, speculate aforementioned CO-rich comets may be common, both own solar system extrasolar systems, previously expected.