# Mass-Radius relationships of small, highly irradiated exoplanets with small water mass fractions

Hugo Vivien, Artem Aguichine, Olivier Mousis, M. Deleuil, Emmanuel Marcq

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Hugo Vivien, Artem Aguichine, Olivier Mousis, M. Deleuil, Emmanuel Marcq. Mass-Radius relationships of small, highly irradiated exoplanets with small water mass fractions. European Planetary Science Congress. EPSC 2021, Sep 2021, Virtual Meeting, France. 10.5194/epsc2021-249. insu-03317763

HAL Id: insu-03317763

https://insu.hal.science/insu-03317763

Submitted on 7 Aug 2021

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# Mass-Radius relationships of small, highly irradiated exoplanets with small water mass fractions

Hugo Vivien<fnref n="1" />, Artem Aguichine<fnref n="1" />, Olivier Mousis<fnref n="1" />, Magali Deleuil<fnref n="1" />, and Emmanuel Marcq<fnref n="2" />

This work aims to determine the mass-radius relationships of highly irradiated (500< Tirr<2000K) small planets (0.2<M<2.3M☉) with water contents up to 5%. To do so, we coupled an internal model of small terrestrial planets (Brugger et al., 2017) to the atmosphere model elaborated by Marcq et al. (2017, 2019), following the approach depicted in Aguichine et al. (2021) and Mousis et al. (2020).

We show that these planets, even with small water contents, can become strongly inflated and produce large radii for small masses. We also show that strongly irradiated small planets cannot sustain their atmospheres due to the lack of hydrostatic stability, implying they cannot preserve any hydrosphere. The temperature and the water mass fraction are the key parameters controlling the extent of inflation and the thickness of the supercritical layer. An important amount of water also leads to the contraction of the rocky interior. However, the composition of the rocky interior only has a limited impact on the final mass-radius relationship, and barely impacts the behavior of the hydrosphere.

<footnote n="1">¹Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France</footnote>

<footnote n="2">²LATMOS/IPSL, UVSQ Université Paris-Saclay, Sorbonne Université, CNRS, Guyancourt, France</footnote>