Estimating the Density of Intermediate Size KBOs from Considerations of Volatile Retention

By using a hydrodynamic atmospheric escape mechanism \citep{amit09} we show how the unusually high mass density of Quaoar could have been predicted (constrained), without any knowledge of a binary companion. We suggest an explanation of the recent spectroscopic observations of Orcus and Charon \citep{delsanti10,cook07}. We present a simple relation between the detection of certain volatile ices and the body mass density and diameter. As a test case we implement the relations on the KBO 2003 AZ$_{84}$ and give constraints on its mass density. We also present a method of relating the latitude-dependence of hydrodynamic gas escape to the internal structure of a rapidly rotating body and apply it to Haumea.