THERMAL STRESSES IN SMALL BODIESAPPROACHING THE SUN

Abstract

This study examines thermal stresses as one of the key physical mechanisms leading to the destruction of small Solar System bodies as they approach the Sun. The thermal destruction mechanism and its evolution are investigated in bodies of icy and silicate compositions of various sizes, along with their role in initiating cracking, fragmentation, and subsequent mass loss. Analytical and numerical solutions of the heat conduction equation for spherical bodies moving in highly eccentric orbits are used to describe temperature fields and resulting stresses. The analytical approach is based on the assumption of constant thermal diffusivity, whereas the numerical model accounts for its temperature dependence and the actual thermophysical properties of crystalline ice and meteoritic matter. A systematic comparison of the two methods was conducted for bodies ranging in size from decimeter-sized meteoroids to kilometer-sized cometary nuclei. It is shown that thermal stresses can exceed the material strength limits at significant heliocentric distances that is, well before reaching the tidal disruption zone. It is also shown that the analytical method performs effectively and exhibits minor discrepancies when compared with the numerical method. It was found that intermediate-sized bodies are the most vulnerable, as strong temperature gradients form between the cold core and heated surface layers. Small bodies heat up almost entirely and do not accumulate significant internal stresses, while large objects maintain stability due to the low penetration of heat into the interior. The results obtained confirm the significant role of thermal stresses in the evolution, activity, and destruction of both cometary nuclei and small asteroid bodies.