Magnetic Induction Responses of Jupiter's Ocean Moons Including Effects From Adiabatic Convection

Vance, S.; Styczinski, Marshall J.; Bills, B. G.; Cochrane, Corey J.; Soderlund, K. M.; Pérez, Nelly Diego; Paty, C. S.

doi:10.1029/2020je006418

Cited by 34 publications

(79 citation statements)

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“…The physical meaning of the amplitude and phase parameters is that they represent the relative magnitude and phase delay or lag of the induced magnetic moment with respect to that which would be induced by a perfectly conducting sphere of radius M E R . For additional background, we refer the reader to the Supporting Information of Vance et al (2021), where it is shown that the complex response function…”

Section:  I K K Ementioning

confidence: 99%

In Search of Subsurface Oceans Within the Uranian Moons

et al. 2021

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The Galileo mission to Jupiter discovered magnetic signatures associated with hidden subsurface oceans at the moons Europa and Callisto using the phenomenon of magnetic induction. These induced magnetic fields originate from electrically conductive layers within the moons and are driven by Jupiter's strong time‐varying magnetic field. The ice giants and their moons are also ideal laboratories for magnetic induction studies. Both Uranus and Neptune have a strongly tilted magnetic axis with respect to their spin axis, creating a dynamic and strongly variable magnetic field environment at the orbits of their major moons. Although Voyager 2 visited the ice giants in the 1980s, it did not pass close enough to any of the moons to detect magnetic induction signatures. However, Voyager 2 revealed that some of these moons exhibit surface features that hint at recent geologically activity, possibly associated with subsurface oceans. Future missions to the ice giants may therefore be capable of discovering subsurface oceans, thereby adding to the family of known “ocean worlds” in our Solar System. Here, we assess magnetic induction as a technique for investigating subsurface oceans within the major moons of Uranus. Furthermore, we establish the ability to distinguish induction responses created by different interior characteristics that tie into the induction response: ocean thickness, conductivity and depth, and ionospheric conductance. The results reported here demonstrate the possibility of single‐pass ocean detection and constrained characterization within the moons of Miranda, Ariel, and Umbriel, and provide guidance for magnetometer selection and trajectory design for future missions to Uranus.

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Section:  I K K Ementioning

confidence: 99%

In Search of Subsurface Oceans Within the Uranian Moons

et al. 2021

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“…The imaginary part of the conductivity must be zero to obtain a steady-state solution for the inductive response, as we have assumed the oscillations are slow enough that displacement currents may be ignored. The assumption that the conductivity is uniform within each layer holds approximately for any planetary body with layers that are global in extent, although geophysical conditions changing with depth require a greater number of radial layers in order to be adequately represented ( Vance et al, 2021 ). The consequence of this assumption is that our model is not expected to be capable of predicting the induced field of a body containing localized melt lenses ( Schmidt et al, 2011 ), sills ( Michaut and Manga, 2014 ), etc.…”

Section: Methodsmentioning

confidence: 99%

“…For simplicity in deriving our model, we neglect movement of conducting material within the body (as in the case of ocean currents) and rotation of the body within the external field, each of which can induce secondary fields ( Saur et al, 2010 ; Vance et al, 2021 ). We also neglect currents outside the body.…”

Section: Methodsmentioning

confidence: 99%

“…Here, we generalize the approach to apply to cases of arbitrary conductivity, described by uniformly conducting layers with boundaries of arbitrary, but near-spherical shape 2 . Then, we apply our mathematical result to plausible models of asymmetry within the conductivity structure of the moons Europa, Miranda, Callisto, and Triton, informed by the literature and calculated using the geophysical modeling framework PlanetProfile ( Vance et al, 2018 , 2021 ). A summary of the results from the example cases studied is in Section 3.2 ; a full collection of the model results is contained in the Supplemental Text , Section S4 .…”

Section: Introductionmentioning

confidence: 99%

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A perturbation method for evaluating the magnetic field induced from an arbitrary, asymmetric ocean world analytically

Styczinski

Vance

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“…Similar to the hypothesized Triton ocean, the icy Galilean moons possess subsurface oceans with conductances on the order of 𝐴𝐴 10 4 S, sustained by thermal contributions from accretional and radiogenic sources in addition to tidal heating-except for Callisto, which receives negligible tidal heat (see, e.g., Schilling et al, 2007;Seufert et al, 2011;Saur et al, 2015;Vance et al, 2021). Each of these moons displays strong inductive responses to the changing magnetic field of their ambient magnetospheric environments (e.g., Saur et al, 2010) which, outside of their conducting layers, are well-represented using a magnetic moment located at the center of each moon (e.g., Zimmer et al, 2000).…”

Section: Triton's Induced Magnetic Fieldmentioning

confidence: 99%

Triton’s Variable Interaction With Neptune’s Magnetospheric Plasma

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Neptune's largest moon Triton (radius 𝐴𝐴 𝐴𝐴𝑇𝑇 = 1, 353 km) is thought to be an erstwhile Kuiper belt object that was captured by the ice giant (Agnor & Hamilton, 2006). Orbiting at a radial distance of 𝐴𝐴 14.4𝑅𝑅𝑁𝑁 (radius of Neptune 𝐴𝐴 𝐴𝐴𝑁𝑁 = 24, 622 km), Triton is always located within Neptune's magnetosphere (Curtis & Ness, 1986;Mejnertsen et al., 2016;Ness et al., 1989;Richardson, 1993). The moon's highly inclined orbit-tilted nearly 𝐴𝐴 157 • with respect to its parent planet's rotational equator-results in a retrograde orbital motion around Neptune. Triton possesses the second-most dense moon atmosphere in the solar system after Titan (Broadfoot et al., 1989;Strobel et al., 1990;Strobel & Zhu, 2017). Mainly comprised of neutral 𝐴𝐴 N2 , its maximum surface number density is on the order of 𝐴𝐴 10 15 cm −3 , with a scale height between 10 and 70 km (Broadfoot et al., 1989). Additionally, trace gases including methane are present, with surface densities below 𝐴𝐴 10 11 cm −3 (e.g., Summers & Strobel, 1991;Trafton, 1984;Krasnopolsky et al., 1992). This neutral envelope is predominantly ionized by a combination of magnetospheric electron impacts and photoionization, resulting in an ionospheric Pedersen conductance that may exceed 𝐴𝐴 10 4 S (Strobel et al., 1990). In addition to this global atmosphere, observations during the Voyager 2 encounter of Neptune in 1989 indicated localized, geyser-like vapor plumes emanating from the surface to an altitude of ∼10 km (Smith et al., 1989). Since the moon's interior is likely differentiated in a hydrosphere and rocky mantle, it is possible that these plumes originate from a global, deep ocean sustained via radiogenic heating and/or tidal forcing (Nimmo & Spencer, 2015).

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Magnetic Induction Responses of Jupiter's Ocean Moons Including Effects From Adiabatic Convection

Cited by 34 publications

References 69 publications

In Search of Subsurface Oceans Within the Uranian Moons

In Search of Subsurface Oceans Within the Uranian Moons

A perturbation method for evaluating the magnetic field induced from an arbitrary, asymmetric ocean world analytically

Triton’s Variable Interaction With Neptune’s Magnetospheric Plasma

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