近日，美国加州理工学院的R. S. Park及其研究团队取得一项新进展。经过不懈努力，他们发现木卫一的潮汐响应能够排除浅层岩浆海洋的存在。相关研究成果已于2024年12月12日在国际权威学术期刊《自然》上发表。

本研究报道了利用“朱诺”号探测器最近两次飞掠艾奥（Io）所测得的艾奥潮汐形变，该形变通过引力潮汐洛夫数k₂来量化。通过结合来自深空网络的“朱诺”号和“伽利略”号的多普勒数据以及天体测量观测数据，研究人员得出k₂的实部Re(k2)为0.125±0.047（1σ），以及潮汐耗散参数Q为11.4±3.6（1σ）。

这些测量结果证实艾奥并不存在浅层的全球性岩浆海洋，而是拥有一个主要为固态的地幔。这项研究结果表明，潮汐力并不总是能创造出全球性岩浆海洋，由于岩浆的快速上升、侵入和喷发，岩浆海洋的形成可能会受到阻碍。因此，即使是像在一些已知系外行星和超级地球上预期的那样强烈的潮汐加热，也可能无法保证卫星或行星体上岩浆海洋的形成。

据悉，木卫一艾奥（Io）因其绕木星运行的偏心轨道而发生潮汐形变，这为艾奥持续的火山活动和红外辐射提供了主要的能量来源。艾奥内部耗散的潮汐能量巨大，据推测足以支持其内部的大规模熔化，以及形成一个全球性的地下岩浆海洋。如果艾奥拥有一个浅层的全球岩浆海洋，那么其潮汐形变将会比内部更加坚硬、主要为固态的情况大得多。

附：英文原文

Title: Io’s tidal response precludes a shallow magma ocean

Author: Park, R. S., Jacobson, R. A., Gomez Casajus, L., Nimmo, F., Ermakov, A. I., Keane, J. T., McKinnon, W. B., Stevenson, D. J., Akiba, R., Idini, B., Buccino, D. R., Magnanini, A., Parisi, M., Tortora, P., Zannoni, M., Mura, A., Durante, D., Iess, L., Connerney, J. E. P., Levin, S. M., Bolton, S. J.

Issue&Volume: 2024-12-12

Abstract: Io experiences tidal deformation due to its eccentric orbit around Jupiter, which provides a primary energy source for Io’s ongoing volcanic activity and infrared emission. The amount of tidal energy dissipated within Io is enormous and has been hypothesized to support the large-scale melting of Io’s interior and the formation of a global subsurface magma ocean. If Io has a shallow global magma ocean, its tidal deformation would be much larger than in the case of a more rigid, mostly solid interior. Here we report the measurement of Io’s tidal deformation, quantified by the gravitational tidal Love number k₂, enabled by two recent flybys of the Juno spacecraft. By combining Junoand Galileo Doppler data from the Deep Space Network and astrometric observations, we recover Re(k₂) of 0.125±0.047 (1σ) and the tidal dissipation parameter Q of 11.4±3.6 (1σ). These measurements confirm that a shallow global magma ocean in Io does not exist and are consistent with Io having a mostly solid mantle. Our results indicate that tidal forces do not universally create global magma oceans, which may be prevented from forming due to rapid melt ascent, intrusion, and eruption, so even strong tidal heating – like that expected on several known exoplanets and super-Earths10 – may not guarantee the formation of magma oceans on moons or planetary bodies.

DOI: 10.1038/s41586-024-08442-5

Source: https://www.nature.com/articles/s41586-024-08442-5