Internal structures of the Galilean satellites

Schubert, G.; Stevenson, D. J.; Ellsworth, K.

doi:10.1016/0019-1035(81)90090-7

Cited by 119 publications

(85 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both bodies had surface radiogenic heat fluxes of about 15 − 20 mW m −2 four billion years ago 277 (Schubert et al, 2004;McKinnon, 2006), comparable to our estimate for Triton at the present day.…”

supporting

confidence: 84%

Powering Triton’s recent geological activity by obliquity tides: Implications for Pluto geology

Nimmo

Spencer

2015

Icarus

View full text Add to dashboard Cite

We investigate the origins of Triton's deformed and young surface. Assuming Triton was captured early in solar system history, the bulk of the energy released during capture will have been lost, and cannot be responsible for its present-day activity. Radiogenic heating is sufficient to maintain a long-lived ocean beneath a conductive ice shell, but insufficient to cause convective deformation and yielding at the surface. However, Triton's high inclination likely causes a significant (≈ 0.7• ) obliquity, resulting in large heat fluxes due to tidal dissipation in any subsurface ocean. For a 300 km thick ice shell, the estimated ocean heat production rate (≈0.3 TW) is capable of producing surface yielding and mobile-lid convection. Requiring convection places an upper bound on the ice shell viscosity, while the requirement for yielding imposes a lower bound. Both bounds can be satisfied with an ocean temperature ≈240 K for our nominal temperature-viscosity relationship, suggesting the presence of an antifreeze such as NH 3 . In our view, Triton's geological activity is driven by obliquity tides, which arise because of its inclination. In contrast, Pluto is unlikely to be experiencing significant tidal heating. While Pluto may have experienced ancient tectonic deformation, we do not anticipate seeing the kind of young, deformed surfaces seen at Triton.

show abstract

supporting

confidence: 84%

Powering Triton’s recent geological activity by obliquity tides: Implications for Pluto geology

Nimmo

Spencer

2015

Icarus

View full text Add to dashboard Cite

show abstract

“…1 The current work focuses specifically on the longitudinal libration in so-called synchronized systems where the secondary body's rotation rate undergoes periodic oscillations about its orbital rate. Additionally, some librating bodies are differentiated and contain liquid metal cores such as those of Mercury, 2 Io, 3 Ganymede, 4 as well as subsurface oceans in Europa, 5 Ganymede, 4 and Enceladus. 6 The fluid layer response to the librational forcing through viscous, 7-9 topographic, 10,11 and electromagnetic coupling [12][13][14] is important for understanding the thermal, magnetic, and orbital evolution of the body.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of global-scale turbulence in a librating ellipsoid

et al. 2014

View full text Add to dashboard Cite

We present laboratory experimental results demonstrating that librational forcing of an ellipsoidal container of water can produce intense motions through the mechanism of a libration driven elliptical instability (LDEI). These libration studies are conducted using an ellipsoidal acrylic container filled with water. A particle image velocimetry method is used to measure the 2D velocity field in the equatorial plane over hundreds libration cycles for a fixed Ekman number, E = 2 × 10 −5 . In doing so, we recover the libration induced base flow and a time averaged zonal flow. Further, we show that LDEI in non-axisymmetric container geometries is capable of driving both intermittent and saturated turbulent motions in the bulk fluid. Additionally, we measure the growth rate and amplitude of the LDEI induced excited flow in a fully ellipsoidal container at more extreme parameters than previously studied [Noir

show abstract

“…The existence of an iron-rich core is further supported by the small mean moment-of-inertia factor (MoI = 0.3105) derived from Galileo gravity and rotation data (e.g., Anderson et al 1996;Sohl et al 2002;Schubert et al 2004). Fixing the Liquidus temperatures for core S contents of 10.6, 14.2, and 16.2 wt.% are presented as solid black lines.…”

Section: Ganymedementioning

confidence: 77%

“…13). As a light and siderophile element, sulfur is the main candidate (e.g., Schubert et al 2004). Assuming a composition identical to a type I carbonaceous chondrite (CI), experiments by Scott et al (2002) indicate that the alloying of iron and sulfur may form FeS-dominated cores.…”

Section: Ganymedementioning

confidence: 99%

Iron snow, crystal floats, and inner-core growth: modes of core solidification and implications for dynamos in terrestrial planets and moons

Breuer

Rueckriemen

Spohn

2015

Prog. in Earth and Planet. Sci.

View full text Add to dashboard Cite

Recent planetary space missions, new experimental data, and advanced numerical techniques have helped to improve our understanding of the deep interiors of the terrestrial planets and moons. In the present review, we summarize recent insights into the state and composition of their iron (Fe)-rich cores, as well as recent findings about the magnetic field evolution of Mercury, the Moon, Mars, and Ganymede. Crystallizing processes in iron-rich cores that differ from the classical Earth case (i.e., Fe snow and iron sulfide (FeS) crystallization) have been identified and found to be important in the cores of terrestrial bodies. The Fe snow regime occurs at pressures lower than that in the Earth's core on the iron-rich side of the eutectic, where iron freezes first close to the core-mantle boundary rather than in the center. FeS crystallization, instead, occurs on the sulfur-rich side of the eutectic. Depending on the core temperature profile and the pressure range considered, FeS crystallizes either in the core center or close to the core-mantle boundary. The consequences of the various crystallizing mechanisms for core dynamics and magnetic field generation are discussed. For the Moon, revised paleomagnetic data obtained with advanced techniques suggest a peculiar history of its internal dynamo, with an early strong field persisting between 4.25 and 3.5 Ga, and subsequently a much weaker field. In addition, the long-lasting dynamo and the possible presence of an inner core, as inferred from a revised interpretation of Apollo seismic data, suggest core crystallization as a viable process of magnetic field generation for a substantial period during lunar evolution. The present-day magnetic fields of Mercury and Ganymede (if they occur on the iron-rich side of the Fe-FeS eutectic) and the related dynamo action are likely generated in the Fe snow regime and seem to be recent features. An earlier dynamo in Mercury would have been powered differently. For Mercury, MESSENGER data further suggest core formation under reducing conditions that may have resulted in an Fe-S-Si composition, further complicating the core crystallization process. Mars, with its early and strong paleo-field, likely has not yet started to freeze out an inner iron core.

show abstract

Internal structures of the Galilean satellites

Cited by 119 publications

References 40 publications

Powering Triton’s recent geological activity by obliquity tides: Implications for Pluto geology

Powering Triton’s recent geological activity by obliquity tides: Implications for Pluto geology

Experimental study of global-scale turbulence in a librating ellipsoid

Iron snow, crystal floats, and inner-core growth: modes of core solidification and implications for dynamos in terrestrial planets and moons

Contact Info

Product

Resources

About