Spontaneous formation of geysers at only one pole on Enceladus’s ice shell

© 2020 National Academy of Sciences. All rights reserved. The ice shell on Enceladus, an icy moon of Saturn, exhibits strong asymmetry between the northern and southern hemispheres, with all known geysers concentrated over the south pole, even though the expected pattern of tidal forced deformation...

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Main Authors: Kang, Wanying, Flierl, Glenn
Format: Article
Language:English
Published: Proceedings of the National Academy of Sciences 2021
Online Access:https://hdl.handle.net/1721.1/133635
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author Kang, Wanying
Flierl, Glenn
author_facet Kang, Wanying
Flierl, Glenn
author_sort Kang, Wanying
collection MIT
description © 2020 National Academy of Sciences. All rights reserved. The ice shell on Enceladus, an icy moon of Saturn, exhibits strong asymmetry between the northern and southern hemispheres, with all known geysers concentrated over the south pole, even though the expected pattern of tidal forced deformation should be symmetric between the north and south poles. Using an idealized ice-evolution model, we demonstrate that this asymmetry may form spontaneously, without any noticeable a priori asymmetry (such as a giant impact or a monopole structure of geological activity), in contrast to previous studies. Infinitesimal asymmetry in the ice shell thickness due to random perturbations are found to be able to grow indefinitely, ending up significantly thinning the ice shell at one of the poles, thereby allowing fracture formation there. Necessary conditions to trigger this hemispheric symmetry-breaking mechanism are found analytically. A rule of thumb we find is that, for Galilean and Saturnian icy moons, the ice shell can undergo hemispheric symmetry breaking only if the mean shell thickness is around 10 to 30 km.
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spelling mit-1721.1/1336352021-10-28T05:00:19Z Spontaneous formation of geysers at only one pole on Enceladus’s ice shell Kang, Wanying Flierl, Glenn © 2020 National Academy of Sciences. All rights reserved. The ice shell on Enceladus, an icy moon of Saturn, exhibits strong asymmetry between the northern and southern hemispheres, with all known geysers concentrated over the south pole, even though the expected pattern of tidal forced deformation should be symmetric between the north and south poles. Using an idealized ice-evolution model, we demonstrate that this asymmetry may form spontaneously, without any noticeable a priori asymmetry (such as a giant impact or a monopole structure of geological activity), in contrast to previous studies. Infinitesimal asymmetry in the ice shell thickness due to random perturbations are found to be able to grow indefinitely, ending up significantly thinning the ice shell at one of the poles, thereby allowing fracture formation there. Necessary conditions to trigger this hemispheric symmetry-breaking mechanism are found analytically. A rule of thumb we find is that, for Galilean and Saturnian icy moons, the ice shell can undergo hemispheric symmetry breaking only if the mean shell thickness is around 10 to 30 km. 2021-10-27T19:53:56Z 2021-10-27T19:53:56Z 2020 2021-09-16T14:51:20Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/133635 en 10.1073/PNAS.2001648117 Proceedings of the National Academy of Sciences of the United States of America Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf Proceedings of the National Academy of Sciences PNAS
spellingShingle Kang, Wanying
Flierl, Glenn
Spontaneous formation of geysers at only one pole on Enceladus’s ice shell
title Spontaneous formation of geysers at only one pole on Enceladus’s ice shell
title_full Spontaneous formation of geysers at only one pole on Enceladus’s ice shell
title_fullStr Spontaneous formation of geysers at only one pole on Enceladus’s ice shell
title_full_unstemmed Spontaneous formation of geysers at only one pole on Enceladus’s ice shell
title_short Spontaneous formation of geysers at only one pole on Enceladus’s ice shell
title_sort spontaneous formation of geysers at only one pole on enceladus s ice shell
url https://hdl.handle.net/1721.1/133635
work_keys_str_mv AT kangwanying spontaneousformationofgeysersatonlyonepoleonenceladussiceshell
AT flierlglenn spontaneousformationofgeysersatonlyonepoleonenceladussiceshell