The search for solid O 2 and N 2 with ISO

Abstract

Theoretical models for the composition of icy grain mantles predict that O 2 and N 2 can be important grain mantle molecules in apolar ices. Large amounts of oxygen and nitrogen are apparently missing from the gas phase and could be depleted on grains likely in the form of O 2 and N 2. Molecules such as O 2 and N 2 are infrared inactive and radio quiet and only interactions in the solid state allow observations of the weak fundamental vibrations of solid O 2 and N 2. These molecules can also be indirectly traced by studying infrared active daughter molecules such as O 3, N 2O and NO 2. Solid CO 2 and CO profiles (at 4.27 and 4.67 μm, respectively) and the position of isolated water ice bands around 2.7 μm may indicate the presence of solid O 2 and N 2. We discuss methods — recently studied in the laboratory — which will allow searches for solid O 2 and N 2 with ISO.