Most Super-Earths Have Less Than 3% Water
Super-Earths are highly irradiated, small planets with bulk densities approximately consistent with Earth. We construct combined interior-atmosphere models of super-Earths that trace the partitioning of water throughout a planet, including an iron-rich core, silicate-rich mantle, and steam atmosphere.
We compare these models with exoplanet observations to infer a 1σ upper limit on total water mass fraction of ≲3% at the population level. We consider end-member scenarios that may change this value, including the efficiency of mantle outgassing and escape of high mean-molecular weight atmospheres.
Although our constraints are agnostic as to the origin of water, we show that our upper limits are consistent with its production via chemical reactions of primordial hydrogen-dominated atmospheres with magma oceans. This mechanism has also been hypothesised to explain Earth’s water content, possibly pointing to a unified channel for the origins of water on small terrestrial planets.
Our sample of planets from the PlanetS catalogue (Otegi et al. 2020; Parc et al. 2024) are shown as white circles. We distinguish super-Earths from sub-Neptunes using the definition of the radius valley from Ho et al. (2024), which accounts for the radius dependence of the radius valley on orbital period and stellar mass. Orange contours and grey points show the underlying Kepler sample from Ho et al. (2024). The 1σ uncertainties on the radius valley are shown in blue, projected through the stellar mass axis. — astro-ph.EP
James G. Rogers, Caroline Dorn, Vivasvaan Aditya Raj, Hilke E. Schlichting, Edward D. Young
Comments: Submitted to ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2409.17394 [astro-ph.EP] (or arXiv:2409.17394v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2409.17394
Focus to learn more
Submission history
From: James Rogers
[v1] Wed, 25 Sep 2024 22:12:36 UTC (1,242 KB)
https://arxiv.org/abs/2409.17394
Astrobiology, Astrogeology, Astrochemistry,
