近日，美国加州大学洛杉矶分校Stixrude, Lars团队研究了亚海王星和超级地球的地核-包层混溶性。2026年1月21日出版的《自然》杂志发表了这项成果。
亚海王星与超级地球作为银河系中最普遍的行星类型，其半径介于地球与海王星之间，在太阳系中并无对应天体。关于它们的结构和形成机制仍存在根本性疑问。虽然超级地球主要由岩石构成，但半径更大的亚海王星构成独特族群，被认为由富氢包层覆盖岩石核心形成。在核幔交界处的极端条件下（压力超数吉帕、温度达数千开尔文），核幔间可能发生反应，但反应性质与程度尚不明确。
研究组采用基于密度泛函理论的第一性原理分子动力学模拟，证明硅酸盐与氢在广泛的核幔压力温度条件下可实现完全混溶。研究组发现这种混溶源于氢与硅酸盐发生的大规模化学反应，生成硅烷、一氧化硅和水等产物，这些产物可能通过当前或未来的观测任务被探测到。核幔混溶现象会溶解行星大部分氢进入地核，并在行星演化过程中驱动核幔间的氢交换，从而深刻影响亚海王星与超级地球的演化进程。
附：英文原文
Title: Core–envelope miscibility in sub-Neptunes and super-Earths
Author: Gilmore, Travis, Stixrude, Lars
Issue&Volume: 2026-01-21
Abstract: Sub-Neptunes and super-Earths, the most abundant types of planet in the galaxy, are unlike anything in the Solar System, with radii between those of Earth and Neptune1,2. Fundamental questions remain regarding their structure and origin. Although super-Earths have a rocky composition3, sub-Neptunes form a distinct population at larger radii and are thought to consist of a rocky core overlain by a hydrogen-rich envelope4,5. At the extreme conditions of the core–envelope interface (exceeding several gigapascals and several thousand kelvin4,6), reaction between core and envelope seems possible, but the nature and extent of these reactions are unknown. Here we use first-principles molecular dynamics driven by density functional theory to show that silicate and hydrogen are completely miscible over a wide range of plausible core–envelope pressure–temperature conditions. We find the origin of miscibility in extensive chemical reaction between hydrogen and silicate, producing silane, SiO and water species, which may be observable with ongoing or future missions. Core–envelope miscibility profoundly affects the evolution of sub-Neptunes and super-Earths, by dissolving a large fraction of the hydrogen of the planet in the core and driving exchange of hydrogen between core and envelope as the planet evolves.
DOI: 10.1038/s41586-025-09970-4