Io's polar volcanic thermal emission indicative of magma ocean and shallow tidal heating models

TL;DR

This study uses Juno spacecraft data to map Io's volcanic thermal emissions, supporting models of a global magma ocean or shallow tidal heating, and reveals polar lithospheric differences affecting volcanic activity.

Contribution

It provides the first near-infrared global thermal emission map of Io's volcanoes, supporting the presence of a magma ocean or shallow heating and highlighting polar lithospheric effects.

Findings

Volcanic heat flow distribution supports magma ocean or shallow heating models.

Polar volcanoes are less energetic but similarly numerous per area compared to lower latitudes.

North polar volcanic heat flow exceeds that in the south, indicating lithospheric dichotomies.

Abstract

The distribution of Io's volcanic activity likely reflects the position and magnitude of internal tidal heating. We use new observations of Io's polar regions by the Juno spacecraft Jovian Infrared Auroral Mapper (JIRAM) to complete near-infrared global coverage, revealing the global distribution and magnitude of thermal emission from Io's currently erupting volcanoes. We show that the distribution of volcanic heat flow from 266 active hot spots is consistent with the presence of a global magma ocean, and/or shallow asthenospheric heating. We find that Io's polar volcanoes are less energetic but about the same in number per unit area than at lower latitudes. We also find that volcanic heat flow in the north polar cap is greater than that in the south. The low volcanic advection seen at Io's poles is therefore at odds with measurements of background temperature showing Io's poles are anomalously warm. We suggest that the differences in volcanic thermal emission from Io's poles compared to that at lower latitudes is indicative of lithospheric dichotomies that inhibit volcanic advection towards Io's poles, particularly in the south polar region.