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Thermal and topographic tests of Europa chaos formation models from Galileo E15 observations

Nimmo, Francis and Giese, Bernd (2005) Thermal and topographic tests of Europa chaos formation models from Galileo E15 observations. Icarus: International Journal of Solar System Studies, 177 (2), pp. 327-340. Elsevier. DOI: 10.1016/j.icarus.2004.10.034. ISSN 0019-1035.

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Stereo topography of an area near Tyre impact crater, Europa, reveals chaos regions character- ized by marginal cli s and domical topography, rising to 100-200 m above the background plains. The regions contain blocks which have both rotated and tilted. We tested two models of chaos formation: a hybrid diapir model, in which chaos topography is caused by thermal or composi- tional buoyancy, and block motion occurs due to the presence of near-surface (1-3 km) melt; and a melt-through model, in which chaos regions are caused by melting and refreezing of the ice shell. None of the hybrid diapir models tested generate any melt within 1-3 km of the surface, owing to the low surface temperature. A model of the refreezing following melt-through gives e ective elastic thicknesses and ice shell thicknesses of 0.1-0.3 km and 0.5-2 km, respectively. However, for such low shell thicknesses the refreezing model requires implausibly large lateral density contrasts (50-100 kg m-3) to explain the elevation of the centres of the chaos regions. Although a global equilibrium ice shell thickness of ~2 km is possible if Europa's mantle resembles that of Io, it is unclear whether local melt-through events are energetically possible. Thus, neither of the models tested here gives a completely satisfactory explanation for the formation of chaos regions. We suggest that surface extrusion of warm ice may be an important component of chaos terrain formation, and demonstrate that such extrusion is possible for likely ice parameters.

Document Type:Article
Title:Thermal and topographic tests of Europa chaos formation models from Galileo E15 observations
AuthorsInstitution or Email of Authors
Nimmo, FrancisDepartment of Earth and Space Sciences, UCLA, USA
Date:May 2005
Journal or Publication Title:Icarus: International Journal of Solar System Studies
Refereed publication:Yes
In ISI Web of Science:Yes
Page Range:pp. 327-340
Keywords:Europa, Satellites of Jupiter, Ices, Geophysics, Tectonics
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EW - Erforschung des Weltraums
DLR - Research area:Space
DLR - Program:W EW - Erforschung des Weltraums
DLR - Research theme (Project):W - Vorhaben Vergleichende Planetologie (old)
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Planetary Geodesy
Deposited By: Dr.rer.nat. Bernd Giese
Deposited On:24 Nov 2005
Last Modified:14 Jan 2010 20:05

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