Tidal controls on the lithospheric thickness and topography of Io from magmatic segregation and volcanism modelling

TL;DR

This study models how tidal heating influences Io's lithospheric thickness and topography, revealing correlations that can help interpret surface observations and constrain tidal heating distribution.

Contribution

It couples 3D tidal heating calculations with magmatic and volcanic models to predict lithospheric thickness variations and their impact on surface topography.

Findings

Lithospheric thickness can be correlated or anti-correlated with tidal heating depending on intrusion rates.

Long-wavelength topography anti-correlates with lithospheric thickness under certain density assumptions.

Results provide a framework for interpreting Io's surface features in terms of tidal heating distribution.

Abstract

Tidal heating is expected to impart significant, non-spherically-symmetric structure to Jupiter's volcanic moon Io. A signature of spatially variable tidal heating is generally sought in observations of surface heat fluxes or volcanic activity, an exploration complicated by the transient nature of volcanic events. The thickness of the lithosphere is expected to change over much longer timescales, and so may provide a robust link between surface observations and the tidal heating distribution. To predict long-wavelength lithospheric thickness variations, we couple three-dimensional tidal heating calculations to a suite of one-dimensional models of magmatic segregation and volcanic eruption. We find that the lithospheric thickness could either be correlated with the radially integrated heating rate, or weakly anti-correlated. Lithospheric thickness is correlated with radially integrated heating rate if magmatic intrusions form at a constant rate in the lithosphere, but is weakly anti-correlated if intrusions form at a rate proportional to the flux through volcanic conduits. Utilising a simple isostasy model we show how variations in lithospheric thickness can predict long-wavelength topography. The relationship between lithospheric thickness and topography depends on the difference in chemical density between the lithosphere and mantle. Assuming that this difference is small, we find that long-wavelength topography anti-correlates with lithospheric thickness. These results will allow future observations to critically evaluate models for Io's lithospheric structure, and enable their use in constraining the distribution of tidal heating.