Understanding Io’s high-latitude volcanoes using JIRAM data

Tidal heating is the most important energy process on known ocean worlds. However, we do not fully understand the heat output on the body where tidal heating is most readily observed, Jupiter’s moon Io. Comparisons of tidal heating models with observations of heat output are hampered by the lack of a global dataset, including the brightness of each volcano and how it varies with time.

Current datasets come from ground-based telescopes and spacecraft that generally orbited in the moon's orbital plane, resulting
in observational biases, particularly in latitude. This is particularly important because the largest and most diagnostic difference between the two end-member tidal heating models occurs at high latitudes. With 13.4% of Io’s surface at latitudes higher than 60°, we expect that percentage of volcanoes in the distribution is uniform. However, most observations have detected fewer than 3% of volcanoes at those latitudes. Only the Galileo Photopolarimeter Radiometer (PPR), which considers cooling flows that may be decades old, found 5.8% of detected volcanoes at high latitudes.

Juno, with its polar orbit, is in a unique position to determine the differences between high latitude and low latitude volcanoes on Io. The Jovian Infrared Auroral Mapper (JIRAM) instrument is sensitive to wavelengths between 2 and 5 microns, similar to previous observations by the Galileo Near Infrared Mapping Spectrometer (NIMS). It also takes images in L and M bands, which are generally used from ground-based telescopes like the Infrared Telescope Facility (IRTF) and Keck.

This investigation will enhance the scientific return from [the Juno mission] by broadening scientific participation in the analysis and interpretation of data returned by [this mission]. The Juno science goals do not include any questions related to Io science, despite the fact that the JIRAM instrument can observe Io’s volcanoes, so this study will clearly broaden the existing mission investigations.

It will address outstanding science questions within the Jupiter system not within the Juno mission science objectives. Visions and Voyages mentioned three main questions for the study of planetary satellites, including What processes control the present-day behavior of these bodies? This study will enhance our understanding of tidal heating, the primary heating process in the outer solar system, and the key to possible habitability of ocean worlds.

In order to determine what Io’s high latitude volcanoes can tell us about tidal heating, I propose to: 1. Determine if and how Io’s high latitude volcanoes are different from low latitude volcanoes. 2. Determine what these differences in volcanic style by latitude tell us about tidal heating. 3. Determine eruption style for several Ionian volcanoes by looking at variations in activity with time. To accomplish these goals we propose two major tasks. Task 1: Obtaining volcano brightnesses from JIRAM images and Task 2: Analyzing volcano brightnesses.