Evidence for a subsurface ocean on Europa

Carr, M. H.; Belton, M. J. S.; Chapman, C. R.; Davies, Merton E.; Geissler, P. E.; Greenberg, R.; McEwen, A. S.; Tufts, B. R.; Greeley, R.; Sullivan, Robert; Head, J. W.; Pappalardo, R.; Klaasen, K. P.; Johnson, T. V.; Kaufman, James M.; Senske, D. A.; Moore, Jeffrey M.; Neukum, G.; Schubert, G.; Burns, Joseph A.; Thomas, P. C.; Veverka, J.

doi:10.1038/34857

Cited by 516 publications

(292 citation statements)

References 13 publications

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“…Galileo images show that among the stratigraphically most recent features on Europa's surface are circular to elliptical pits, domes, and dark spots -7 to 15 km in diameter, spaced -5 to 20 km apart (Figure 6) [Carr et al, 1998;Greeley et al, 1998b;Pappalardo et al, 1998a]. These features, collectively termed "lenticulae," generally modify and disrupt the preexisting ridged plains, which are widespread and consist of subparallel ridges and grooves that overlap in successive generations.…”

Section: Solid-state Convectionmentioning

confidence: 99%

Does Europa have a subsurface ocean? Evaluation of the geological evidence

Pappalardo¹,

Belton²,

Breneman³

et al. 1999

J. Geophys. Res.

387

269

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Abstract. It has been proposed that Jupiter's satellite Europa currently possesses a global subsurface ocean of liquid water. Galileo gravity data verify that the satellite is differentiated into an outer H20 layer about 100 km thick but cannot determine the current physical state of this layer (liquid or solid). Here we summarize the geological evidence regarding an extant subsurface ocean, concentrating on Galileo imaging data. We describe and assess

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Section: Solid-state Convectionmentioning

confidence: 99%

Does Europa have a subsurface ocean? Evaluation of the geological evidence

Pappalardo¹,

Belton²,

Breneman³

et al. 1999

J. Geophys. Res.

387

269

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“…The chaos regions (e.g., Conamara Chaos) are possibly the remnants of such catastrophic events, with ''ice rafts'' preserving temporarily floating blocks that were frozen in place in the refreezing ice layer [Carr et al, 1998;Greenberg et al, 1999]. Assuming the ice rafts were floating in liquid at the time of their formation (consistent with the record of significant lateral motion preserved in the surface), buoyancy considerations require that the blocks were <3 km thick when they were formed [Williams and Greeley, 1998].…”

Section: Introductionmentioning

confidence: 99%

Persistence of thin ice regions in Europa's ice crust

Buck

Chyba

Goulet

et al. 2002

Geophysical Research Letters

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[1] Extensive data from planetary spacecraft as well as celestial mechanics models support the existence of a subsurface ocean on Europa $100 km thick, maintained by a tidal heat flux. Models in which the overlying ice crust is less than 20 km thick permit breaches in the ice due to impact events or thermal plumes from the tidally heated core. We apply a two-dimensional thermal model to the analysis of the refreezing of a hole in the ice crust following a breach event. Our model incorporates heat produced by tidal heating of Europa in two ways: a basal heat flux from Europa's silicate and iron core, together with volumetric heating of the ice shell. We compare our refreezing timescales to those obtained from a model where viscous flow in the base of the ice crust fills the hole. We find that catastrophic breaches in Europa's ice crust may produce regions of relatively thin ice persisting up to $1 My. These breaches are closed by viscous flow when radii are small (<10-50 km) and by conductive refreezing for larger radii, especially if Europa's crust has a high basal heat flow due to a hot core. Detection of the ice/ocean interface by orbital detection of the temperature anomalies or radar sounding would be most probable in the vicinity of these events.

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“…Remote observations of the jovian satellite Europa indicate that a liquid water ocean may lie beneath its solid ice surface [Khurana et al, 1998;Cart et al, 1998;Pappalardo et al, 1998]. Furthermore, the ocean appears to be underlain by a differentiated, rocky interior [Anderson et al, 1998].…”

Section: Introductionmentioning

confidence: 99%

Methanogenesis as a potential source of chemical energy for primary biomass production by autotrophic organisms in hydrothermal systems on Europa

McCollom¹

1999

J. Geophys. Res.

176

127

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Abstract. Geochemical models are used to explore the possibility that lithoautotrophic methanogenesis (the conversion of CO2 plus H2 to methane) could be a source of metabolically useful chemical energy for the production of biomass at putative Europan hydrothermal systems. Two cases are explored: a relatively reduced methane-rich ocean and a relatively oxidized sulfate-and bicarbonate-rich ocean. In the case of a methane-rich ocean, a source of CO2 for methanogenesis is provided by conversion of dissolved methane to CO2 during reaction of ocean water with igneous rocks at high temperatures in the subsurface. Fluid-rock reactions also provide a source of dissolved H2 in the hydrothermal fluid. When this fluid circulates back to the ocean floor and mixes with seawater, conversion of the dissolved CO2 and H2 to methane provides a potential source of chemical energy that can be used to drive metabolic processes. For the case of a sulfate-and carbonate-rich ocean, reaction with reduced igneous rocks at high temperatures will also produce hydrothermal fluids with high H2 concentrations (as occurs in hydrothermal systems on Earth). Mixing of the resulting hydrothermal fluid with seawater in a relatively oxidized ocean could supply energy from either methanogenesis or sulfate reduction. For plausible compositions of a Europan ocean, methanogenesis can supply similar amounts of energy to that which supports the prolific ecosystems surrounding submarine hydrothermal vents on Earth. Even in the most optimistic case, however, the total amount of biomass that could be supported globally by lithoautotrophic microbes on Europa is extremely small compared to the biomass produced photosynthetically on Earth. Nevertheless, sufficient metabolic energy could apparently be available at hydrothermal systems on Europa to support an origin of life and localized ecosystems.Lime and limpid green, a second scene A fight between the blue you once lmew Floating down, the sound resounds Around the icy waters underground.

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Evidence for a subsurface ocean on Europa

Cited by 516 publications

References 13 publications

Does Europa have a subsurface ocean? Evaluation of the geological evidence

Does Europa have a subsurface ocean? Evaluation of the geological evidence

Persistence of thin ice regions in Europa's ice crust

Methanogenesis as a potential source of chemical energy for primary biomass production by autotrophic organisms in hydrothermal systems on Europa

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