dc.contributor.author Nixon, MC dc.contributor.author Nikku, Madhusudhan dc.date.accessioned 2022-01-11T00:32:20Z dc.date.available 2022-01-11T00:32:20Z dc.date.issued 2021-08 dc.identifier.issn 0035-8711 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/332606 dc.description.abstract Understanding the internal structures of planets with a large H$_2$O component is important for the characterisation of sub-Neptune planets. The finding that the mini-Neptune K2-18b could host a liquid water ocean beneath a mostly hydrogen envelope motivates a detailed examination of the phase structures of water-rich planets. To this end, we present new internal structure models for super-Earths and mini-Neptunes that enable detailed characterisation of a planet's water component. We use our models to explore the possible phase structures of water worlds and find that a diverse range of interiors are possible, from oceans sandwiched between two layers of ice to supercritical interiors beneath steam atmospheres. We determine how the bulk properties and surface conditions of a water world affect its ocean depth, finding that oceans can be up to hundreds of times deeper than on Earth. For example, a planet with a 300 K surface can possess H$_2$O oceans with depths from 30-500 km, depending on its mass and composition. We also constrain the region of mass-radius space in which planets with H/He envelopes could host liquid H$_2$O, noting that the liquid phase can persist at temperatures up to 647 K at high pressures of $218$-$7\times10^4$ bar. Such H/He envelopes could contribute significantly to the planet radius while retaining liquid water at the surface, depending on the planet mass and temperature profile. Our findings highlight the exciting possibility that habitable conditions may be present on planets much larger than Earth. dc.publisher Oxford University Press (OUP) dc.rights Attribution 4.0 International dc.rights.uri https://creativecommons.org/licenses/by/4.0/ dc.subject planets and satellites: composition dc.subject planets and satellites: general dc.subject planets and satellites: interiors dc.subject planets and satellites: oceans dc.subject planets and satellites: surfaces dc.title How deep is the ocean? Exploring the phase structure of water-rich sub-Neptunes dc.type Article dc.publisher.department Institute of Astronomy dc.date.updated 2022-01-09T07:33:32Z prism.endingPage 3432 prism.issueIdentifier 3 prism.publicationDate 2021 prism.publicationName Monthly Notices of the Royal Astronomical Society prism.startingPage 3414 prism.volume 505 dc.identifier.doi 10.17863/CAM.80053 rioxxterms.versionofrecord 10.1093/mnras/stab1500 rioxxterms.version VoR dc.contributor.orcid Nixon, MC [0000-0001-8236-5553] dc.contributor.orcid Nikku, Madhusudhan [0000-0002-4869-000X] dc.identifier.eissn 1365-2966 dc.publisher.url http://dx.doi.org/10.1093/mnras/stab1500 rioxxterms.type Journal Article/Review cam.issuedOnline 2021-06-17 cam.depositDate 2022-01-09 pubs.licence-identifier apollo-deposit-licence-2-1 pubs.licence-display-name Apollo Repository Deposit Licence Agreement
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Except where otherwise noted, this item's licence is described as Attribution 4.0 International