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Analysis of Io’s global volcanic hotspot flux from the JIRAM instrument aboard Juno

Presentation #103.01 in the session Fire and Ice: Io and Beyond (Oral Presentation)

Published onOct 23, 2023
Analysis of Io’s global volcanic hotspot flux from the JIRAM instrument aboard Juno

In the fifty years since the prediction and discovery of tidally-generated volcanism on Io (Morabito 1979, Peale 1979), key questions have arisen that can only be answered by first understanding the spatial distribution of volcanism Io. Io exhibits high-temperature, short-lived, extremely bright outbursts, but also hosts effusive, relatively cool volcanoes that are active for decades; previous studies have suggested that these behaviors may be linked to latitude (Milazzo 2005, de Kleer & de Pater 2016). Furthermore, models of Io’s interior heating regimes suggest that the depth at which tidal friction generates heat controls surface heat flow distribution, which we assume correlates to volcanic flux distribution (de Kleer 2019, Lopes-Gautier 1999, Veeder 2012, Hamilton 2013). However, constraining the differences between high- and low-latitude volcanoes and discriminating between tidal heating model regimes depends on accurate global measurements of volcanism. All previous ground-based and spacecraft missions to Io have had an equatorial bias. Juno’s polar orbit around Jupiter has provided, for the first time, direct viewing of Io’s poles. Using the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard Juno, we have created a global map of Io’s volcanic hotspots visible from Juno. We have carefully measured the M-band infrared flux associated with each hotspot over 11 orbits and created a global saturation-corrected map of the volcanic flux. Analysis of this map allows us to answer questions about how high- and low-latitude volcanoes differ and how Io’s volcanism compares to predictive models for tidal heating and surface heat flow. We’ve found that the poles have significantly more volcanic flux than has been reported previously in the literature. The vast majority of volcanic flux comes through the mid-latitude regions and can mostly be attributed to three areas of high volcanic flux. We’ve found a system of bright, high-latitude, persistent volcanoes that may contradict previous expectations for the behavior of high-latitude volcanoes. There appears to be a hemispheric dichotomy; the trailing hemisphere is uniformly brighter than the leading hemisphere, whose volcanic flux is concentrated mostly in the volcano Loki. While a shallow mantle heating regime and a global magma ocean best matches the distribution of volcanic flux on Io, spherical harmonic analysis suggest that the model end members do not match the observed distribution of Ionian heat flow well. A paper describing the results of this study is in preparation and is expected to be available by the DPS fall meeting.

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