Gas release from ice/dust mixtures

Abstract

Gas fluxes from insolated ice/dust mixtures were measured by pressure gauges and a mass spectrometer placed one meter in front of the sample. As soon as the insolation of about one solar constant was started a fast rise in H₂O and CO₂ emissions from the fresh surface was observed. Thereafter gas fluxes slowly decreased. When intermittent dark periods occurred, water emission dropped rapidly while CO₂ fluxes were measured for hours. Results from labeled isotope layers gave information on sublimation depth and temperature and showed that sublimated CO₂ migrated also toward deeper parts of the sample where it recondensed, producing an enrichment. A simple model is presented which describes the redistribution of CO₂ within the sample consistent with the gas phase and solid phase measurements of CO₂ abundances.