Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit
| hal.structure.identifier | Observatoire Astronomique de l'Université de Genève [ObsGE] | |
| dc.contributor.author | TURBET, Martin | |
| hal.structure.identifier | Observatoire Astronomique de l'Université de Genève [ObsGE] | |
| dc.contributor.author | BOLMONT, Emeline | |
| hal.structure.identifier | Observatoire Astronomique de l'Université de Genève [ObsGE] | |
| dc.contributor.author | EHRENREICH, David | |
| hal.structure.identifier | AMOR 2020 | |
| dc.contributor.author | GRATIER, Pierre | |
| hal.structure.identifier | ECLIPSE 2020 | |
| dc.contributor.author | LECONTE, Jérémy | |
| hal.structure.identifier | ECLIPSE 2020 | |
| dc.contributor.author | SELSIS, Franck | |
| hal.structure.identifier | Observatoire Astronomique de l'Université de Genève [ObsGE] | |
| dc.contributor.author | HARA, Nathan | |
| hal.structure.identifier | Observatoire Astronomique de l'Université de Genève [ObsGE] | |
| dc.contributor.author | LOVIS, Christophe | |
| dc.date.issued | 2020-06 | |
| dc.identifier.issn | 0004-6361 | |
| dc.description.abstractEn | 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. | |
| dc.language.iso | en | |
| dc.publisher | EDP Sciences | |
| dc.subject.en | planets and satellites: atmospheres | |
| dc.subject.en | planets and satellites: composition | |
| dc.subject.en | planets and satellites: terrestrial planets | |
| dc.subject.en | planets and satellites: interiors | |
| dc.subject.en | planets and satellites: individual: TRAPPIST-1 | |
| dc.title.en | Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit | |
| dc.type | Article de revue | |
| dc.identifier.doi | 10.1051/0004-6361/201937151 | |
| dc.subject.hal | Planète et Univers [physics]/Astrophysique [astro-ph] | |
| dc.identifier.arxiv | 1911.08878 | |
| bordeaux.journal | Astronomy and Astrophysics - A&A | |
| bordeaux.page | A41 | |
| bordeaux.volume | 638 | |
| bordeaux.peerReviewed | oui | |
| hal.identifier | hal-02972902 | |
| hal.version | 1 | |
| hal.popular | non | |
| hal.audience | Internationale | |
| hal.origin.link | https://hal.archives-ouvertes.fr//hal-02972902v1 | |
| bordeaux.COinS | ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Astronomy%20and%20Astrophysics%20-%20A&A&rft.date=2020-06&rft.volume=638&rft.spage=A41&rft.epage=A41&rft.eissn=0004-6361&rft.issn=0004-6361&rft.au=TURBET,%20Martin&BOLMONT,%20Emeline&EHRENREICH,%20David&GRATIER,%20Pierre&LECONTE,%20J%C3%A9r%C3%A9my&rft.genre=article |
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