2020A&A...638A..41T


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.09CEST11:48:44

2020A&A...638A..41T - Astronomy and Astrophysics, volume 638A, 41-41 (2020/6-1)

Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit.

TURBET M., BOLMONT E., EHRENREICH D., GRATIER P., LECONTE J., SELSIS F., HARA N. and LOVIS C.

Abstract (from CDS):

Mass-radius relationships for water-rich rocky planets are usually calculated assuming most water is present in condensed (either liquid or solid) form. Planet density estimates are then compared to these mass-radius relationships, even when these planets are more irradiated than the runaway greenhouse irradiation limit (around 1.1 times the insolation at Earth for planets orbiting a Sun-like star), for which water has been shown to be unstable in condensed form and would instead form a thick H2O-dominated atmosphere. Here we use a 1-D radiative-convective inverse version of the LMD generic numerical climate model to derive new theoretical mass-radius relationships appropriate for water-rich rocky planets that are more irradiated than the runaway greenhouse irradiation limit, meaning planets endowed with a steam, water-dominated atmosphere. As a result of the runaway greenhouse radius inflation effect introduced in previous work, these new mass-radius relationships significantly differ from those traditionally used in the literature. For a given water-to-rock mass ratio, these new mass-radius relationships lead to planet bulk densities much lower than calculated when water is assumed to be in condensed form. In other words, using traditional mass-radius relationships for planets that are more irradiated than the runaway greenhouse irradiation limit tends to dramatically overestimate -possibly by several orders of magnitude- their bulk water content. In particular, this result applies to TRAPPIST-1 b, c, and d, which can accommodate a water mass fraction of at most 2, 0.3 and 0.08%, respectively, assuming planetary core with a terrestrial composition. In addition, we show that significant changes of mass-radius relationships (between planets less and more irradiated than the runaway greenhouse limit) can be used to remove bulk composition degeneracies in multiplanetary systems such as TRAPPIST-1. Broadly speaking, our results demonstrate that non-H2/He-dominated atmospheres can have a first-order effect on the mass-radius relationships, even for rocky planets receiving moderate irradiation. Finally, we provide an empirical formula for the H2O steam atmosphere thickness as a function of planet core gravity and radius, water content, and irradiation. This formula can easily be used to construct mass-radius relationships for any water-rich, rocky planet (i.e., with any kind of interior composition ranging from pure iron to pure silicate) more irradiated than the runaway greenhouse irradiation threshold.

Abstract Copyright: © ESO 2020

Journal keyword(s): planets and satellites: terrestrial planets - planets and satellites: composition - planets and satellites: atmospheres - planets and satellites: individual: TRAPPIST-1 - planets and satellites: interiors - methods: numerical

Simbad objects: 6

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Number of rows : 6

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME G 139-21b Pl 17 15 18.9337265994 +04 57 50.064695682           ~ 573 1
2 TRAPPIST-1 LM* 23 06 29.3684052886 -05 02 29.031690445     18.798 16.466 14.024 M7.5e 583 0
3 TRAPPIST-1d Pl 23 06 29.3684052886 -05 02 29.031690445           ~ 133 0
4 TRAPPIST-1b Pl 23 06 29.3684052886 -05 02 29.031690445           ~ 140 0
5 TRAPPIST-1c Pl 23 06 29.3684052886 -05 02 29.031690445           ~ 113 0
6 TRAPPIST-1e Pl 23 06 29.3684052886 -05 02 29.031690445           ~ 158 0

    Equat.    Gal    SGal    Ecl

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2021.05.09-11:48:44

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