- 1Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169–007 Porto, Portugal
- 2Instituto de Astrofísica e Ciências do Espaço, Centro de Astrofísica da Universidade do Porto, Rua das Estrelas 4150-762 Porto, Portugal
- 3Institute for Particle Physics and Astrophysics, ETH Zürich, Otto-Stern-Weg 5, 8093 Zürich, Switzerland
- 4Centro de Astrobiología (CAB), CSIC-INTA, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada (Madrid), Spain
As the number of exoplanets found gradually increases, so does the types of planets existing, leading to a very diverse population. While the formation processes of some are thought to be known, others remain yet to be explained. Such is the case of steam worlds, planets mostly composed by rocky material but with a non-negligible atmosphere partially composed of water.
The planetary radius distribution is well known due to its bimodal shape, with one peak centred around super-Earths and the other around sub-Neptunes. The unexpected lack of planets in between is known as the radius valley. This valley is often explained by Neptune-like planets that had their atmosphere removed due to proximity with their host star. The resulting planet would be similar to super-Earths due to the lack of atmosphere and rocky interior, populating the first peak. However, the existence of steam worlds might also help to better understand this puzzling gap.
In this talk I will discuss the conditions under which this type of planets may exist. I will also debate if these planets are consequence of the evolution of other planets, or if, surprisingly, they might be instead a different population on their own.
How to cite: Soares, B., Dorn, C., Adibekyan, V., Sousa, S., Delgado-Mena, E., and Santos, N.: Neither rocky nor icy: Exploring the nature of steam worlds, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-1792, https://doi.org/10.5194/epsc-dps2025-1792, 2025.
