Do icy dust aggregates break up when they pass the snow line?

Abstract

Icy dust aggregates can break up when they pass the snow line or when a heating event occurs because of the sublimation of H${}_2$O ice. However, the original aggregate may absorb the fragment conducting the Brownian motion because the thickness of the icy mantle of a grain is less than the typical grain radius of $\sim 10^{-5}$cm. On the other hand, the vapor pressure caused by the sublimated H${}_2$O molecules accelerates the fragment to escape. Rotation of the aggregate and electrostatic repulsion may also promote the escape of the fragment aggregate. Here, I determined a lower bound of the escaping fragment radius, including the effects of the vapor pressure, rotation, and electrostatic repulsion. It has been found that the breakup to the single grain does not occur, and the fragment radius strongly depends on the thickness of the icy mantle. The vapor pressure and the rotation produce fragments from large aggregates. The fragments escape from small aggregates by the electrostatic repulsion. Possible consequences of the breakup are discussed.