Sublimation of ice-dust mixtures in cooled vacuum environments to reproduce cometary morphologies

Abstract

Aims. The morphology of cometary surfaces can provide important information to constrain the composition and evolution of comets. In this work, we investigate the sublimation behavior of comet analog materials and how the sample composition affects the evolution of morphological features in laboratory experiments. In our experiments, we used dust ice mixtures as analog material to form observed cometary morphologies. Methods. We used ice-dust mixtures in different mixing ratios as cometary analog material. In order to obtain realistic results, we scaled the expected cohesive and gravitational forces on comets to laboratory conditions. The samples were placed in a vacuum sublimation chamber and permanently cooled down to temperatures below 150 K to simulate the space environment. In the experiment, the samples were insolated with a light source from two different directions and alterations on the surface were recorded with a camera. Results. We find that the morphology of sublimation residues of ice-dust mixtures is strongly dependent on the ice-dust ratio as well as the insolation direction. High amounts of ice cause constant surface alteration and lead to exotic morphologies. Low amounts cause fewer and more episodic surface changes during its sublimation. Collapse events resulting in irregular and very rough surfaces occur during horizontal insolation.