Tristan Guillot

The 2023 Runcorn-Florensky Medal is awarded to Tristan Guillot for fundamental contributions to the study of the formation, interior and atmosphere of giant planets and exoplanets, and for his inspirational leadership across multiple fields in planetary sciences.

Tristan Guillot, a research director at the Observatoire de la Côte d’Azur, is an exceptionally creative planetary scientist who uses complex and innovative physics to advance our understanding of the interior of giant planets, the nature of exoplanets, the behaviour of convective clouds in exotic contexts, and the formation of planetesimals and planets. He also led the creation of a unique observatory in the middle of the Antarctic ice sheet that enables unprecedented long duration observations of exoplanetary systems.

Guillot has been a reference in the field of interior structure and internal dynamics of giant planets since his earliest works in the 1990s. He has explored the interior and composition of giant planets from a combination of theoretical modelling, laboratory data and observations. He pioneered investigations of how convection works in hydrogen-dominated atmospheres, where the condensates are heavier than the surrounding dry air, and he explored how convective inhibition might explain differences in storm activity and heat flux between planets. More recently, his contributions to the interpretation of data from the NASA Juno mission are exceptionally broad. He developed a sophisticated new theory to explain puzzling discoveries that Jupiter’s volatiles like ammonia (and possibly water) are not distributed uniformly below their cloud bases. He was the first to determine the depth of the zonal winds in Jupiter by analysing Jupiter’s gravity field. His early idea during the 2000s that giant planets might have a diluted core has also become more firmly established by Juno’s data. His research results also provide strong motivations for future missions.

Guillot is also a leading researcher in exoplanetary research, with strong responsibilities in exoplanetary missions like PLATO (PLAnetary Transits and Oscillations of stars) and CoRoT (Convection, Rotation and planetary Transits). He helped lay the groundwork for understanding the thermal evolution of hot Jupiters and discovered the possibility of an internal radiative zone. He explained the atmospheric structure of irradiated planets and successfully predicted the day-night contrast effect on hot Jupiters. He published several landmark papers and review papers on the interiors of giant planets inside and outside the Solar System, which continue to serve as guides to the planetary community.

Guillot has published more than 200 articles, many of them are among the most cited articles in his field, in top peer reviewed journals. He has received several prestigious prizes for his research activities and publications. He wrote white papers supporting comparative planetology to both ESA and NASA and was called to represent the community on the Giant Planet Systems Panel for the Planetary Science and Astrobiology Decadal Survey, where he helped secure a future mission to an ice giant planet.

Tristan Guillot has made diverse and exceptional contributions to planetary and exoplanetary sciences thanks to his very creative work to understand uncharted areas.  In recognition of his multiple remarkable and pioneering scientific achievements, his superb creativity and ability to identify and solve complex interdisciplinary research questions, his talent in bringing people together in novel collaborations, and his outstanding leadership and services to the community, Tristan Guillot is a very worthy Runcorn-Florensky Medal recipient.