Ices in star forming regions

Abstract

IR spectra of sources associated with molecular cloud material show a variety of absorption features attributed to simple molecules, such as H 2 O, CO, CH 3 OH, CO 2 , CH 4 , and OCS in icy grain mantles. These identifications are reviewed. These molecules are formed through accretion and reaction of gas phase species on grain surfaces. The high abundance of CH 3 OH and CO 2 point towards the importance of hydrogenation and oxidation reactions in this process. Observations also show that thermal outgassing is of great importance for the composition of interstellar ice mantles. Both these processes are discussed in some detail.