Icy Grains in the Solar System: Cometary and Asteroidal Environments

Icy grains have been directly detected or inferred in the circumnuclear region of various short- and long-period comets. In particular, comets 103P/Hartley 2, C/2002 T7 (LINEAR), and, recently C/2013 OS10 (Catalina) and 67P/Churyumov–Gerasimenko have been found to eject dust particles with a variable proportion of ice content. In this chapter, we report on the theoretical computation of the equilibrium temperature of sublimating grains composed by a varying amount of water ice, silicate, and carbon materials, and its variation with grain size and heliocentric distance. It is shown that even a small addition of absorbing impurities to a pure water ice grain reduces dramatically its survival. A particular application to comet 67P, the ESA Rosetta Mission target, is provided.