THEMISS · Thermal Evolution Modeling of Icy objects in the Solar System

Comets can be used as tracers of the conditions prevailing during the formation of the solar system. We have been studying them for decades, yet we still have not answered this foreground question: how do comets work? To answer that question is to understand which of comets properties are actually relevant to characterize the early solar system, and how primitive comets really are. Icy objects in the solar system are stored in different reservoirs, where they evolve very slowly owing irradiation, collisions and thermal processing. When they enter the inner solar system, they become comets, i.e. objects loosing mass. If comets are deemed very primitive due, for example, to their high content in very volatile species, some observations including ESA/Rosetta’s, have brought us a conundrum. Indeed, some comet properties indicate that they could have suffered from a long-term processing, which lead their basic properties (like shape, composition or size) to evolve significantly since the time they were formed. This proposal will explore the thermal processing of comets from their storage in the Oort Cloud, the Kuiper Belt and the Main Belt, and the thermally-induced variations in their physical and chemical characteristics, in order to understand whether such effects were important for shaping comets as we observe them today. Based on observational constraints obtained both from the ground and the latest space missions, an unprecedented modeling effort will be undertaken to evaluate under which conditions comets can preserve pristine material, what the long-lasting effects of thermal processing are for the various comet populations, and provide tools for deciphering between primitive properties and properties affected by evolution. Finally, this work will be shared via a web application, allowing the community to work from this foundation to prepare the future of our field, including the next generation of space missions exploring comets from sample returns.