It is the hot gas molecules that act as the radiators and the icy mantles of the interstellar grains are the main reservoirs where the gas molecules can come from.

BBC: University of Nottingham

Even though they account for only about 1% of the mass of a typical interstellar cloud, interstellar dust grains play a crucial role in the creation of this rich variety of molecules and in the process of star formation.

BBC: University of Nottingham