Sub-surface dust thickness and ice content in the nucleus of comet 67P/Churyumov-Gerasimenko constrained with Rosetta observations

We computed the total water vapor outgassing rate for comet 67P/Churyumov-Gerasimenko for a time period spanning several months before and after the perihelion in 2015. The two-layer surface model includes time-dependent solar illumination, thermal emission, sublimation, heat transport into the nucleus, and gas diffusion through the dust layer. The model parameters include among others the thickness of the top dust layer and the ice content in the bottom layer. We fitted the model parameters so that the temporal evolution of the computed water outgassing rate matches published outgassing rates derived from observations with the Microwave Instrument for the Rosetta Orbiter (MIRO). We will discuss the evolution of the retrieved dust thickness and ice content before and after perihelion and the variations between the northern and southern hemispheres of the nucleus.