Gas Flux of Minor Volatiles from the Inside of a Porous Comet Nucleus

J. Benkhoff (DLR)

Sublimation of minor gases (CO, tex2html_wrap_inline13 , tex2html_wrap_inline15 ) from ices inside of a porous comet nucleus may be important to explain activity a larger heliocentric distances (>3 AU) and to understand observationally results.
A new model to describe the gas flux inside the porous nucleus more accurately has been developed. We obtain a set of conservation equations for each of the different volatiles which are solved simultaneously under appropriate boundary conditions. As a result, one get the gas flux from volatile, icy components inside the porous nucleus, temperature profiles and changes in relative chemical abundances, porosity and pore size distribution as a function of depth, and the gas flux into the interior and into the atmosphere for each of the volatiles at various positions of the comet in its orbit. From the calculations we derive higher values of the gas flux into the interior and lower values of the gas flux into the atmosphere than from our previous models (Benkhoff and Huebner, ICARUS 114, 1995; Benkhoff and Huebner, Planet. Space Sci.44, 1996 ). Diurnal effects on the mixing ratio of minor gases to water depend on the structure of the body and the rotation period.