NASAのジュノー計画、木星の衛星イオの火山活動の中心を発見(NASA’s Juno Mission Uncovers Heart of Jovian Moon’s Volcanic Rage)

2024-12-12 NASA

The north polar region of Jupiter’s volcanic moon Io was captured by NASA’s Juno during the spacecraft’s 57th close pass of the gas giant on Dec. 30, 2023. Data from recent flybys is helping scientists understand Io’s interior.
Image data: NASA/JPL-Caltech/SwRI/MSSS
Image processing by Gerald Eichstädt

＜関連情報＞

• https://www.nasa.gov/missions/juno/nasas-juno-mission-uncovers-heart-of-jovian-moons-volcanic-rage/
• https://www.nature.com/articles/s41586-024-08442-5

イオの潮汐反応により浅いマグマの海は存在しない Io’s tidal response precludes a shallow magma ocean

R. S. Park,R. A. Jacobson,L. Gomez Casajus,F. Nimmo,A. I. Ermakov,J. T. Keane,W. B. McKinnon,D. J. Stevenson,R. Akiba,B. Idini,D. R. Buccino,A. Magnanini,M. Parisi,P. Tortora,M. Zannoni,A. Mura,D. Durante,L. Iess,J. E. P. Connerney,S. M. Levin & S. J. Bolton
Nature  Published:12 December 2024
DOI:https://doi.org/10.1038/s41586-024-08442-5

We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

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 emission¹. 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 interior². 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 Juno^3,4 and Galileo^5-7 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 mantle². 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^8,9, 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.