A recently formed ocean inside Saturn's moon Mimas

• 成果类型: Article
• 署名作者: Lainey, V.; Rambaux, N.; Tobie, G.; Cooper, N.; Zhang, Q.; Noyelles, B.; Baillie, K.
• 署名单位: Sorbonne Universite; Universite de Lille; Universite PSL; Observatoire de Paris; Centre National de la Recherche Scientifique (CNRS); Nantes Universite; Centre National de la Recherche Scientifique (CNRS); CNRS - National Institute for Earth Sciences & Astronomy (INSU); University of London; Queen Mary University London; University College London; Jinan University; Universite Marie et Louis Pasteur; Centre National de la Recherche Scientifique (CNRS); CNRS - National Institute for Earth Sciences & Astronomy (INSU)
• 刊物名称: Nature
• ISSN/ISSBN: 0028-4752
• DOI: 10.1038/s41586-023-06975-9
• 发表日期: 2024-02-08
• 关键词: cassini division; icy satellites; gravity-field; interior; astrometry; constraints; libration; orbit; shape

摘要

Moons potentially harbouring a global ocean are tending to become relatively common objects in the Solar System1. The presence of these long-lived global oceans is generally betrayed by surface modification owing to internal dynamics2. Hence, Mimas would be the most unlikely place to look for the presence of a global ocean3. Here, from detailed analysis of Mimas's orbital motion based on Cassini data, with a particular focus on Mimas's periapsis drift, we show that its heavily cratered icy shell hides a global ocean, at a depth of 20-30 kilometres. Eccentricity damping implies that the ocean is likely to be less than 25 million years old and still evolving. Our simulations show that the ocean-ice interface reached a depth of less than 30 kilometres only recently (less than 2-3 million years ago), a time span too short for signs of activity at Mimas's surface to have appeared. An analysis of the orbital motion of Saturn's moon Mimas shows that a recently formed global subsurface ocean lies beneath its cratered icy shell and that this ocean is probably still evolving.