The composition of the interiors of rocky exoplanets is difficult to assess observationally. However, knowledge of this composition is important to understand how planets formed, as well as how they evolve over their lifetimes, particularly the evolution of secondary atmospheres. One avenue of investigation is through observations of catastrophically evaporating planets. These systems are detected through dusty tails which condense from outflows driven from the planets. These outflows come from the molten surface of these worlds, meaning the composition of the dusty tails must be related to the solid planet below. Here we present our model of the interior structure of these planets, and use it to argue that the planets have only a shallow lava pool on their daysides from which material is evaporated. Therefore, the dust composition samples a snapshot of the upper portion of the planets’ mantle at a given time. We further use our model to predict the occurrence rate of progenitor planets, which must have initial masses of less than around 10% of Earth, and suggest they are more common than, but within an order of magnitude of, Super-Earths in the same region of parameter space. We also find that the substellar temperatures of the known systems can be well explained by dust production models.
[Poster PDF File]