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. ¿American Geophysical Union 1991