Tidal Heating in Io

Matsuyama, Isamu N.; Steinke, Teresa; Nimmo, F.

doi:10.2138/gselements.18.6.374

Cited by 7 publications

(9 citation statements)

References 26 publications

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“…New observations of Io's thermal emission by the Juno spacecraft Jovian Infrared Auroral Mapper suggest that polar hot spots emit less energy than hot spots at lower latitudes (Davies et al., 2024). This finding is consistent with the presence of a magma ocean, although enhanced tidal heating at low latitudes can also be predicted by models with a dissipative asthenosphere (e.g., Kervazo et al., 2021; Matsuyama et al., 2022; Tyler et al., 2015).…”

Section: Discussionsupporting

confidence: 84%

“…This equatorial zone is clearly separated from the low‐dissipation regions at higher latitudes and its position shows a remarkable correspondence with Io's yellow bright plains (Williams et al., 2011, see Figure 2 below). The purely zonal character of dissipation (i.e., independent of the longitude) is unusual in the context of eccentricity tides and, to our knowledge, has not been reported in previous studies of tidal flow in subsurface (water or magma) oceans (e.g., Chen et al., 2014; Hay & Matsuyama, 2019; Matsuyama et al., 2018, 2022; Tyler et al., 2015), except for a study including the moon‐moon tidal interaction (Hay et al., 2020, based on the communication with Hamish Hay). Although the zonal distribution of dissipation is obtained for models with a thin ocean ( d ≈ 1 km), the velocity field has a strong radial component ( v r / v θ ≈ v r / v ϕ ≈ 0.2) that cannot be found by solving the LTE.…”

Section: Resultssupporting

confidence: 43%

“…The presence of a magma ocean on Io has recently been supported by new observations by the Juno spacecraft, which show that Io's hot spots are more or less evenly distributed over the surface, but polar volcanoes emit less energy than volcanoes at lower latitudes (Davies et al, 2024). Such a heat flux distribution cannot be explained by tidal dissipation in the deep interior, but it is consistent with the presence of a global magma ocean and/or shallow asthenospheric heating (e.g., Matsuyama et al, 2022;Tyler et al, 2015).…”

Section: Introductionmentioning

confidence: 72%

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Tidal Heating in a Subsurface Magma Ocean on Io Revisited

Aygün,

Čadek

2024

Geophysical Research Letters

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We investigate the tidal dissipation in Io's hypothetical fluid magma ocean using a new approach based on the solution of the 3D Navier‐Stokes equations. Our results indicate that the presence of a shallow magma ocean on top of a solid, partially molten layer leads to an order of magnitude increase in dissipation at low latitudes. Tidal heating in Io's magma ocean does not correlate with the distribution of hot spots, and is maximum for an ocean thickness of about 1 km and a viscosity of less than 104 Pa s. Due to the Coriolis effect, the k2 Love number can depend on the harmonic order. We show that the analysis of k2 may not reveal the presence of a fluid magma ocean if the ocean thickness is less than 2 km. If the fluid layer is thicker than 2 km, k20 ≈ k22/2 ≈ 0.7.

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Section: Discussionsupporting

confidence: 84%

Section: Resultssupporting

confidence: 43%

Section: Introductionmentioning

confidence: 72%

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Tidal Heating in a Subsurface Magma Ocean on Io Revisited

Aygün,

Čadek

2024

Geophysical Research Letters

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“…Power outputs are given in the Appendix (Table A1). Ross et al 1990;Tyler et al 2015;Matsuyama et al 2022). However, JIRAM is only sensitive to part of the thermal emission from Io's volcanic centers, being limited (as was NIMS) to surface temperatures above approximately 200 K. The methodology of deriving JIRAM hot spot spectral radiances is provided in Davies et al (2024).…”

Section: Io's Polar Volcanoesmentioning

confidence: 99%

“…As described above, tidal heating in the deep mantle results in polar regions that are preferentially heated, and tidal heating in the asthenosphere results in equatorial regions that are preferentially heated. If the partial melt fraction in the asthenosphere is larger than ∼30%, dissipation associated with volume changes modifies the surface tidal heating pattern, but equatorial regions remain preferentially heated (Kervazo et al 2022;Matsuyama et al 2022).…”

Section: Correlation With Heat Flow Modelsmentioning

confidence: 99%

New Global Map of Io’s Volcanic Thermal Emission and Discovery of Hemispherical Dichotomies

Davies,

Perry,

Williams

et al. 2024

Planet. Sci. J.

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By combining multiple spacecraft and telescope data sets, the first fully global volcanic heat flow map of Io has been created, incorporating data down to spatial resolutions of ∼10 km pixel−1 in Io’s polar regions. Juno Jovian Infrared Auroral Mapper data have filled coverage gaps in Io’s polar regions and other areas poorly imaged by Galileo instruments. A total of 343 thermal sources are identified in data up to mid-2023. While poor correlations are found between the longitudinal distribution of volcanic thermal emission and radially integrated end-member models of internal heating, the best correlations are found with shallow asthenospheric tidal heating and magma ocean models and negative correlations with the deep-mantle heating model. The presence of polar volcanoes supports, but does not necessarily confirm, the presence of a magma ocean on Io. We find that the number of active volcanoes per unit area in polar regions is no different from that at lower latitudes, but we find that Io’s polar volcanoes are smaller, in terms of thermal emission, than those at lower latitudes. Half as much energy is emitted from polar volcanoes as from those at lower latitudes, and the thermal emission from the north polar cap volcanoes is twice that of those in the south polar cap. Apparent dichotomies in terms of volcanic advection and resulting power output exist between sub- and anti-Jovian hemispheres, between polar regions and lower latitudes, and between the north and south polar regions, possibly due to internal asymmetries or variations in lithospheric thickness.

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Origin and Evolution of Enceladus’s Tidal Dissipation

Nimmo,

Neveu,

Howett

2023

Space Sci Rev

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Enceladus possesses a subsurface ocean beneath a conductive ice shell. Based on shell thickness models, the estimated total conductive heat loss from Enceladus is 25–40 GW; the measured heat output from the South Polar Terrain (SPT) is 4–19 GW. The present-day SPT heat flux is of order $100\text{ mW}\,\text{m}^{-2}$ 100 mW m − 2 , comparable to estimated paleo-heat fluxes for other regions of Enceladus. These regions have nominal ages of about 2 Ga, but the estimates are uncertain because the impactor flux in the Saturnian system may not resemble that elsewhere. Enceladus’s measured rate of orbital expansion implies a low dissipation factor $Q_{p}$ Q p for Saturn, with $Q_{p} \approx 3\times 10^{3}$ Q p ≈ 3 × 10 3 (neglecting the role of Dione). This value implies that Enceladus’s present-day equilibrium tidal heat production (roughly 50 GW, but with large uncertainties) is in approximate balance with its heat loss. If $Q_{p}$ Q p is constant, Enceladus cannot be older than 1.5 Gyr (because otherwise it would have migrated more than is permissible). However, Saturn’s dissipation may be better described by the “resonance-locking” theory, in which case Enceladus’s orbit may have only evolved outwards by about 35% over the age of the Solar System. In the constant-$Q_{p}$ Q p scenario, any ancient tidal heating events would have been too energetic to be consistent with the observations. Because resonance-locking makes capture into earlier mean-motion orbital resonances less likely, the inferred ancient heating episodes probably took place when the current orbital resonance was already established. In the resonance-locking scenario, tidal heating did not change significantly over time, allowing for a long-lived ocean and a relatively stable ice shell. If so, Enceladus is an attractive target for future exploration from a habitability standpoint.

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Tidal Heating in Io

Cited by 7 publications

References 26 publications

Tidal Heating in a Subsurface Magma Ocean on Io Revisited

Tidal Heating in a Subsurface Magma Ocean on Io Revisited

New Global Map of Io’s Volcanic Thermal Emission and Discovery of Hemispherical Dichotomies

Origin and Evolution of Enceladus’s Tidal Dissipation

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