Radius Inflation in Super-Earths Born with Polluted Envelopes

The characterization of super-Earth to Neptune-sized exoplanets depends critically on understanding their formation and thermal evolution. We investigate the evolutionary pathways of super-Earths formed with compositionally polluted envelopes, focusing on the role of silicate rainout and its impact on the observed mass-radius relation. Our results show that the energy released during silicate rainout inflates the planetary radius during early evolutionary stages, when stellar irradiation is most intense. This radius inflation enhances atmospheric mass loss by a factor of 2–8 compared to planets with initially clean envelopes. Moreover, neglecting this effect can lead to overestimates of hydrogen-helium content in young super-Earths. These findings highlight the need for accurate age measurements—such as those anticipated from the PLATO mission—to reliably interpret the observed properties of young exoplanets.