Presentation #350.13 in the session The Sun and the Solar System — iPoster Session.
Comets are leftover materials from the formation of the solar system. Among comet phenomena that are still poorly understood is outbursts. In contrast to regular out-gassing, outbursts cause comets to brighten a factor of few magnitudes over a few days. Outbursts could be caused by a range of phenomena, including mechanical events such as cliffs on the surface that might collapse and expose crystalline ice to the sunlight, or as a result of heat wave propagation into the comet’s subsurface.
To study outbursts, we developed a model to examine how heat diffusion occurs at the comet’s subsurface by considering comet 67P/Churyumov-Gerasimenko. Based on its orbital properties, we looked at the diffusion of heat on the surface of crystalized ice and measured how much heat on the surface can penetrate into the subsurface through porous ice. Crystallization under the subsurface generates extra heat, which can move the crystalline front towards the surface or deeper into the nucleus. This effect increases the rate of evaporation at the subsurface. This also causes a thick mantle of ice with a lower rate of porosity to build up on the surface, which traps evaporated gas in the layers below. Over time, this gas builds up until the mantle can no longer withstand the gas pressure, and it breaks, creating the outburst event. We used percolation theory to find the critical point that the trapped gas propagates to the surface from the subsurface. Our results suggest that two parameters are critical to the gas buildup: the porosity at the local area of investigation and the level of gas production in the subsurface layer. The results of our simulations will be discussed.