The legacy of SWAS: Water and molecular oxygen in the interstellar medium

The Submillimeter Wave Astronomy Satellite has recently completed 5.5 years of successful operation. Among the legacies of the mission has been a greater understanding of the abundance and spatial distribution of H2O and O2 within molecular clouds. The model summarized here provides an explanation for the relatively low gaseous H2O abundance and the high H2O-ice abundance in cold dense clouds, the higher H2O abundance toward diffuse clouds, the low O2 abundance toward all clouds observed.