Io's tidal response precludes a shallow magma ocean.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39667409.
- Also identified by DOI 10.1038/s41586-024-08442-5 and PMC identifier 11798835.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Io experiences tidal deformation as a result of its eccentric orbit around Jupiter, which provides a primary energy source for Io's continuing volcanic activity and infrared emission<sup>1</sup>. The amount of tidal energy dissipated within Io is enormous and has been suggested to support the large-scale melting of its 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<sup>2</sup>. Here we report the measurement of Io's tidal deformation, quantified by the gravitational tidal Love number k<sub>2</sub>, enabled by two recent flybys of the Juno spacecraft. By combining Juno<sup>3,4</sup> and Galileo<sup>5-7</sup> Doppler data from the NASA Deep Space Network and astrometric observations, we recover Re(k<sub>2</sub>) 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<sup>2</sup>. Our results indicate that tidal forces do not universally create global magma oceans, which may be prevented from forming owing to rapid melt ascent, intrusion and eruption<sup>8,9</sup>, so even strong tidal heating-such as that expected on several known exoplanets and super-Earths<sup>10</sup>-may not guarantee the formation of magma oceans on moons or planetary bodies.