On the origin & thermal stability of Arrokoth's and Pluto's ices

We discuss in a thermodynamic, geologically empirical way the long-term nature of stable majority ices that could be present Kuiper Belt Object 2014 MU69 after its 4.6 Gyr residence EKB as cold classical object. Considering stability versus sublimation into vacuum for suite commonly found on comets, Centaurs, and KBOs at average ~40K sunlit surface temperature over Myr to Gyr, we find only 3 common are truly refractory: HCN, CH3OH, H2O (in order increasing stability). NH3 H2CO marginally may removed by any positive excursions EKB, produced every 1e8 - 1e9 yrs nearby supernovae passing O/B stars. To date NH team has reported presence abundant CH3OH evidence MU69s (Lisse et al. 2017, Grundy 2020). been searched for, but not found. predict future absorption feature detections will due an HCN or poly-H2CO based species. Consideration conditions region during formation era lead us infer it formed "in dark", optically thick mid-plane, unable see nascent, variable, highly luminous Young Stellar Object-TTauri Sun, contain ice phases addition their Short Period comet descendants. Finally, when apply our thermal analysis bodies/populations related MU69, methanol ubiquitous outer solar system; if Pluto is fully differentiated body, then must have gained hypervolatile from proto-planetary disk sources first few systems existence; rich, primordial C/2016 R2 was placed onto Oort Cloud orbit similar timescale.