Fizzy Planets: Mass-Radius Relationships for Carbonated and Hydrous Magma Oceans

Terrestrial planets are thought to transition through a magma ocean phase during their evolution in which they exhibit globally molten mantles. These magma oceans have the capacity to store a significant amount of volatiles (i.e, H₂O , CO₂ , etc.), thereby affecting the observed properties of the planet. Volatile storage is a particular concern for planets on close-in orbits because the magma ocean phase can be long-lived due to the planet’s proximity to its star. To date, many terrestrial planets have been discovered on close-in orbits making them likely hosts of global magma oceans. However, there has been minimal research into the observational impacts that the storage of volatiles within a magma ocean has on the mass and radius of the planet. We present the first mass-radius relationships for carbonated magma ocean planets along with updated relationships for hydrous magma oceans using ExoPlex, a thermodynamically self-consistent planet interior software.