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标题：Herschel map of Saturn’s stratospheric water, delivered by the plumes of Enceladus ★
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作者：T. Cavalié ; V. Hue ; P. Hartogh 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：630
页码：1-15
DOI：10.1051/0004-6361/201935954
语种：English
出版社：EDP Sciences
摘要：Context.The origin of water in the stratospheres of giant planets has been an outstanding question ever since its first detection by the Infrared Space Observatory some 20 years ago. Water can originate from interplanetary dust particles, icy rings and satellites, and large comet impacts. Analyses ofHerschelSpace Observatory observations have proven that the bulk of Jupiter’s stratospheric water was delivered by the Shoemaker-Levy 9 impacts in 1994. In 2006, theCassinimission detected water plumes at the South Pole of Enceladus, which made the moon a serious candidate for Saturn’s stratospheric water. Further evidence was found in 2011 whenHerscheldemonstrated the presence of a water torus at the orbital distance of Enceladus that was fed by the moon’s plumes. Finally, water falling from the rings onto Saturn’s uppermost atmospheric layers at low latitudes was detected during the final orbits ofCassini’send-of-mission plunge into the atmosphere.Aims.In this paper, we useHerschelmapping observations of water in Saturn’s stratosphere to identify its source.Methods.We tested several empirical models against theHerschel-HIFI and -PACS observations, which were collected on December 30, 2010, and January 2, 2011, respectively.Results.We demonstrate that Saturn’s stratospheric water is not uniformly mixed as a function of latitude, but peaks at the equator and decreases poleward with a Gaussian distribution. We obtain our best fit with an equatorial mole fraction 1.1 ppb and a half width at half maximum of 25°, when accounting for a temperature increase in the two warm stratospheric vortices produced by Saturn’s Great Storm of 2010–2011.Conclusions.This work demonstrates that Enceladus is the main source of Saturn’s stratospheric water.
关键词：Key wordsenplanets and satellites: individual: Saturnplanets and satellites: individual: Enceladusplanets and satellites: atmospheres