A model of the activity of comet wild 2 Original Research Article

A numerical model of the thermal evolution and chemical differentiation of cometary nuclei was developed to help in the preparation of future comet missions. To better describe the microstructure of cometary matter we modified the way in which bulk thermal conductivity is expressed. The matter is now described as an aggregate of grains, formed by a refractory core and an ice mantle. In this way the evolution of the microstructure due to various physical processes, such as sintering, can be better simulated. With this kind of formulation, bulk conductivity could be very low, orders of magnitude lower than in our previous versions of the model. In order to test this expression and its consequences, we present here a simulation of the thermal evolution of comet Wild 2, the target of the STARDUST mission. We can see that a much lower conductivity changes the internal stratigraphy and the flux of low volatile gases, but does not affect surface properties and consequently water and dust fluxes.