Welcome to this new webpage, where I hope I’ll be able to share some of my research! Articles published in peer-reviewed journals can be found here. I have two main areas of expertise: observations of small bodies, and modeling of their thermo-physical evolution. Let’s talk about the latter. Indeed, my recent paper “On the evolution of comets” has just been published. It started with a workshop I had organized while I was still working at ESA: Surface-Interior Interactions on Small Bodies. Back in 2006, some colleagues had been writing a book, part of the ISSI collection: Heat and Gas Diffusion in Comet Nuclei (Huebner et al. 2006). The book is dressing a big picture of thermal evolution modeling after the Giotto mission, and before Rosetta (it remains my bible). Now our idea was to assess where thermal modeling had been heading since that book had been written, what remained to be understood, and how the Rosetta mission (which would start to give results in the coming months at that time) would perhaps be able to address our questions. After lots of interesting discussions, we decided to write a review paper for the Space Science Reviews. I’d like to summarize here the discussion, so to explain why studying the thermal evolution of comets is relevant and important.
We study comets because we believe that they hold invaluable clues on the formation and evolution of our planetary system. In comparison to planets, they have undergone much less alteration, having been exposed to fewer evolutionary processes that acted preferentially at their surface. Therefore, they should have retained a relatively pristine record of the conditions prevailing during the early phases of the solar system. However, we still have not been able to determine which of the observed physical, chemical and orbital characteristics of comets will provide the best clues to their origin, after they have evolved for more than 4 Gyr in a time-varying radiative and collisional environment. Comet nuclei could be formed of a single component, either relatively uniform in composition, or heterogeneous if comets accreted material from different regions when migrating through the protoplanetary disk. Alternatively, comet nuclei may be made of multiple components loosely bound together. These sub-units may similarly be relatively uniform, or could originate from different regions of the protoplanetary disk. Furthermore, some of the observed nuclei might be collisional debris of larger, possibly chemically differentiated parent bodies. The subsequent evolution of comet nuclei involves some processing from radiogenic heating, space weathering and large- and small-scale collisions, which could have modified their primordial structures and compositions to various degrees. When comets enter the inner solar system and become active, they start to loose mass at a very high rate. The effects of activity on comet nuclei involve a layering of the composition, a substantial non-even erosion and modification of their size and shape, and may eventually result in the death of comets.
From an orbital point of view, it is clear that the evolution of comets is dominated by chaos. Ultimately, it is entirely possible that the evolutionary track may be specific to each comet, which would complicate the task of constraining their origins as a whole population. Because evolutionary processes may lead to so many different outcomes, we need to focus on their long-lasting effects, with statistical significance. But before we are able to track back the origins of comet nuclei, we have identified two issues that do need to be addressed before we can make any progress: how does activity actually work? what is the role of collisions?