Ice in the Outer Solar System

Ice is stable in the Solar System at all distances larger than a few AU (e.g. the Main-Belt Comets recently identified in the outer asteroid belt). It may be a dominant component of the most distant bodies for which we have useful physical observations, namely the Kuiper belt objects located beyond Neptune. It is accessible to observational study using near infrared spectroscopy on the largest telescopes. In this talk we will discuss recent observations pertaining to ice in the outer Solar system, with a particular focus on the physical state of the ice. The state (crystalline vs. amorphous) is of great importance in determining the temperature history and the gas-carrying capacity of the ice. We will present the observations and inferences, and discuss on-going laboratory work from the UH Ultra-High Vacuum Machine concerning the stability of the crystalline phase in the Kuiper belt environment.