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