Science and Exploration

A Subsurface Magma Ocean On Io: Exploring The Steady State Of Partially Molten Planetary Bodies

By Keith Cowing
Press Release
November 20, 2022
A Subsurface Magma Ocean On Io: Exploring The Steady State Of Partially Molten Planetary Bodies
Schematic illustration of Io’s interior with (a) a magmatic sponge and (b) a subsurface magma ocean. An enlarged view of eruption through the crust is also shown on the right. Parameters defined in Sections 2 and 4.1 are labeled to the corresponding reservoirs. Our results suggest that a magmatic sponge would swiftly separate into two phases and create a magma ocean, which is a rheologically liquid layer with φ>0.4. It is noted that the crust and the partially molten layer are connected by a transition zone, where upwelling magma solidifies to heat the subsiding crust (Section 4.2). — astro-ph.EP

Intense tidal heating within Io produces active volcanism on the surface, and its internal structure has long been a subject of debate.

A recent reanalysis of the Galileo magnetometer data suggested the presence of a high melt fraction layer with >50~km thickness in the subsurface region of Io. Whether this layer is a magmatic sponge'' with interconnected solid or a rheologically liquidmagma ocean” would alter the distribution of tidal heating and would also influence the interpretation of various observations.

To this end, we explore the steady state of a magmatic sponge and estimate the amount of internal heating necessary to sustain such a layer with a high degree of melting. Our results show that the rate of tidal dissipation within Io is insufficient to sustain a partial melt layer of ϕ>0.2 for a wide range of parameters, suggesting that such a layer would swiftly separate into two phases.

Unless melt and/or solid viscosities are at the higher end of the estimated range, a magmatic sponge would be unstable, and thus a high melt fraction layer suggested in Khurana et al. (2011) is likely to be a subsurface magma ocean.

Yoshinori Miyazaki, David J. Stevenson

Comments: 19 pages, 8 figures, Accepted to Planetary Science Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2211.06945 [astro-ph.EP] (or arXiv:2211.06945v1 [astro-ph.EP] for this version)
Submission history
From: Yoshinori Miyazaki
[v1] Sun, 13 Nov 2022 16:39:02 UTC (2,139 KB)

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