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Tidal Heating: Lessons from Io and the Jovian System - Final Report

de Kleer, Katherine and McEwen, Alfred S. and Park, Ryan S. and Bierson, Carver J. and Davies, Ashley G. and DellaGustina, Daniella N. and Ermakov, Anton I. and Fuller, Jim and Hamilton, Christopher W. and Harris, Camilla D. K. and Hay, Hamish C. F. C. and Jacobson, Robert A. and Keane, James T. and Kestay, Laszlo P. and Khurana, Krishan K. and Kirby, Karen W. and Lainey, Valeriy J. and Matsuyama, Isamu and McCarthy, Christine and Nimmo, Francis and Panning, Mark P. and Pommier, Anne and Rathbun, Julian and Steinbrügge, Gregor and Stevenson, David J. and Tsai, Victor C. and Turtle, Elizabeth P. and Eiler, John M. and Young, Edward D. and Zahnle, Kevin J. and Adkins, Jess F. and Mandt, Kathy E. and McGrath, Melissa A. and Moullet, Arielle and Waite, J. Hunter and Schneider, Nicholas M. (2019) Tidal Heating: Lessons from Io and the Jovian System - Final Report. , Pasadena, CA.

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Tidal heating is key to the evolution and habitability of many worlds across our solar system and beyond. However, there remain fundamental gaps in our understanding of tidal heating and coupled orbital evolution, which motivated a Keck Institute for Space Studies (KISS) workshop on this topic. The Cassini mission has led to many recent results about ocean worlds and what may become a new paradigm for understanding orbital evolution with tidal heating, the model of resonance locking in the parent planet (Fuller et al., 2016). Resonance locking explains how subsurface oceans may persist over much of geologic time, even in tiny Enceladus. The discovery of the Laplace resonance of Io, Europa, and Ganymede orbiting Jupiter led to the prediction of intense tidal heating of Io (Peale et al., 1979); this system provides the greatest potential for advances in the next few decades. Europa Clipper and JUpiter ICy moons Explorer (JUICE) will provide in-depth studies of Europa and Ganymede in the 2030s. The easily observed heat flow of Io, from hundreds of continually erupting volcanoes, makes it an ideal target for further investigation, and the missing link—along with missions in development—to understand the Laplace system. We identified five key questions to drive future research and exploration: (Q1) What do volcanic eruptions tell us about the interiors of tidally heated bodies (e.g., Io, Enceladus, and perhaps Europa and Triton)? (Q2) How is tidal dissipation partitioned between solid and liquid materials? (Q3) Does Io have a melt-rich layer, or “magma ocean”, that mechanically decouples the lithosphere from the deeper interior? (Q4) Is the Jupiter/Laplace system in equilibrium (i.e., does the satellite’s heat output equal the rate at which energy is generated)? (Q5) Can stable isotope measurements inform long-term evolution of tidally heated bodies? The most promising avenues to address these questions include a new spacecraft mission making close flybys of Io, missions orbiting and landing on key worlds such as Europa and Enceladus, technology developments to enable advanced techniques, closer coupling between laboratory experiments and tidal heating theory, and advances in Earth-based telescopic observations of solar system and extrasolar planets and moons. All of these avenues would benefit from technological developments. An Io mission should: characterize volcanic processes (Q1); test interior models via a set of geophysical measurements coupled with laboratory experiments and theory (Q2 and Q3); measure the rate of Io’s orbital migration (to complement similar measurements expected at Europa and Ganymede) to determine if the Laplace resonance is in equilibrium (Q4); and determine neutral compositions and measure stable isotopes in Io’s atmosphere and plumes (Q5). No new technologies are required for such an Io mission following advances in radiation design and solar power realized for Europa Clipper and JUICE. Seismology is a promising avenue for future exploration, either from landers or remote laser reflectometry, and interferometric synthetic aperture radar (InSAR) could be revolutionary on these active worlds, but advanced power systems plus lower mass and power-active instruments are needed for operation in the outer solar system.

Item Type:Report or Paper (Report)
de Kleer, Katherine0000-0002-9068-3428
Davies, Ashley G.0000-0003-1747-8142
Fuller, Jim0000-0002-4544-0750
Keane, James T.0000-0002-4803-5793
Khurana, Krishan K.0000-0002-2856-1171
Nimmo, Francis0000-0003-3573-5915
Panning, Mark P.0000-0002-2041-3190
Stevenson, David J.0000-0001-9432-7159
Tsai, Victor C.0000-0003-1809-6672
Adkins, Jess F.0000-0002-3174-5190
Moullet, Arielle0000-0002-9820-1032
Waite, J. Hunter0000-0002-1978-1025
Additional Information:© June 2019. We especially thank Michele Judd and others at the Keck Institute for Space Studies for supporting this effort. This research was in part carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Group:Keck Institute for Space Studies, Astronomy Department
Funding AgencyGrant Number
Keck Institute for Space Studies (KISS)UNSPECIFIED
Record Number:CaltechAUTHORS:20191023-151847724
Persistent URL:
Official Citation:de Kleer, et al. Tidal Heating: Lessons from Io and the Jovian System, Final Report for the Keck Institute for Space Studies, 2019.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99419
Deposited By: Katherine Johnson
Deposited On:23 Oct 2019 22:37
Last Modified:24 Oct 2019 21:07

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