Dynamics of the global meridional ice flow of Europa’s icy shell

Ashkenazy, Yosef; Sayag, Roiy; Tziperman, Eli

doi:10.1038/s41550-017-0326-7

Cited by 37 publications

(66 citation statements)

References 42 publications

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“…This heat may come from hydrothermal activity at the seafloor (Goodman et al, 2004;Vance and Goodman, 2009;Goodman and Lenferink, 2012) or from global Hadley circulation (Soderlund et al, 2014). Large-scale variations in ice thickness may lead to latitudinal overturning circulation and saline stratification (Ashkenazy et al, 2017;Zhu et al, 2017). The ice shell thickness has been mapped at Enceladus and ranges from 5 to 40 km (Čadek et al, 2016).…”

Section: Brinicles In Icy Ocean Worldsmentioning

confidence: 99%

Self-Assembling Ice Membranes on Europa: Brinicle Properties, Field Examples, and Possible Energetic Systems in Icy Ocean Worlds

et al. 2019

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Brinicles are self-assembling tubular ice membrane structures, centimeters to meters in length, found beneath sea ice in the polar regions of Earth. We discuss how the properties of brinicles make them of possible importance for chemistry in cold environments-including that of life's emergence-and we consider their formation in icy ocean worlds. We argue that the non-ice composition of the ice on Europa and Enceladus will vary spatially due to thermodynamic and mechanical properties that serve to separate and fractionate brines and solid materials. The specifics of the composition and dynamics of both the ice and the ocean in these worlds remain poorly constrained. We demonstrate through calculations using FREZCHEM that sulfate likely fractionates out of accreting ice in Europa and Enceladus, and thus that an exogenous origin of sulfate observed on Europa's surface need not preclude additional endogenous sulfate in Europa's ocean. We suggest that, like hydrothermal vents on Earth, brinicles in icy ocean worlds constitute ideal places where ecosystems of organisms might be found.

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Section: Brinicles In Icy Ocean Worldsmentioning

confidence: 99%

Self-Assembling Ice Membranes on Europa: Brinicle Properties, Field Examples, and Possible Energetic Systems in Icy Ocean Worlds

et al. 2019

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“…It is possible to provide a very rough estimate of Europa's ice thickness based on the above; see Section 3.2 . This estimate may be a reference thickness for studying the effect of both the vertical and horizontal ice flows due to both tidal heating within the ice and ice flow due to pressure gradients that are associated with variations in ice thickness (see, e.g., Ashkenazy et al, 2018 ).…”

Section: Modelmentioning

confidence: 99%

“…The dependence of the thickness of the ice on latitude is not trivial as ice may flow due to gradients in ice thickness (see, for example, Tziperman et al, 2012 , Ashkenazy et al, 2018 ). To bypass this complexity, we only estimate the mean ice thickness by performing a spatial mean on Eq.…”

Section: Modelmentioning

confidence: 99%

“…Still, the diurnal mean temperature for latitudes poleward of 15 ∘ and the temperatures at the high latitudes were not measured. The polar region temperatures are important as in these regions, the internal heating significantly affects the surface temperatures, and measurements of surface temperatures in these regions may help to estimate the internal heating rate and, consequently, the thickness of the ice (see, e.g., Ashkenazy et al, 2018 ). The dependence of surface temperature on the internal heating is studied here.…”

Section: Introductionmentioning

confidence: 99%

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The surface temperature of Europa

Ashkenazy

2019

Heliyon

Self Cite

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Previous estimates of the annual mean surface temperature of Jupiter's moon, Europa, neglected the effect of the eccentricity of Jupiter's orbit around the Sun, the effect of the emissivity and heat capacity of Europa's ice, the effect of the eclipse of Europa (i.e., the relative time that Europa is within the shadow of Jupiter), the effect of Jupiter's radiation, and the effect of Europa's internal heating. Other studies concentrated on the diurnal cycle but neglected some of the above factors. In addition, to our knowledge, the seasonal cycle of the surface temperature of Europa was not estimated. Here we systematically estimate the diurnal, seasonal and annual mean surface temperature of Europa, when Europa's obliquity, emissivity, heat capacity, and eclipse, as well as Jupiter's radiation, internal heating, and eccentricity, are all taken into account. For a typical internal heating rate of 0.05 , the equator, pole, and the global and mean annual mean surface temperatures are 96 K, 46 K, and 90 K, respectively. We found that the temperature at the high latitudes is significantly affected by the internal heating, especially during the winter solstice, suggesting that measurements of high latitude surface temperatures can be used to constrain the internal heating. We also estimate the incoming solar radiation to Enceladus, the moon of Saturn.

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“…In this process, foreign bodies present in liquid water are naturally embedded in the ice matrix; among them are metallic ions. The subsequent transfer of the metals to the top ice layers can occur via an ice convection (Pappalardo et al 1998;Ashkenazy et al 2018), often referred to as diapirism. Because convection is a physical process, the metals are pushed up to the surface accompanied by their close water environment.…”

Section: Introductionmentioning

confidence: 99%

Sodium, Potassium, and Calcium in Europa: An Atomic Journey through Water Ice

Ozgurel

Mousis

Pauzat

et al. 2018

ApJL

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Sodium and potassium are known to be present as neutral elements in the exosphere of Europa. The question of the origin of these alkalis-endogenous or exogenous-remains open. They have been ascribed to exogenous contamination due to volcanism from nearby Io, or the accretion of meteorites and dust. However, these mechanisms fail to fit the observed sodium-to-potassium ratio. Sodium and potassium have also been considered to originate from Europa's putative subsurface ocean, generated by past rock-water leaching. The latter scenario implies a journey of the ions and atoms throughout the ice covering Europa. This raises questions about their stability into the bulk as well as on top of ice. These questions are addressed with first principle periodic solid-state density functional theory simulations describing the relative propensities of sodium, potassium, and calcium for being trapped in the bulk. The evolution of the ionic character of these atoms is followed by means of a topological analysis as they come up to the surface of the ice crust. We find that the metals, almost totally ionized in the ice bulk (net charge ∼+0.8) where they are stabilized by ∼1 eV or more, recover a quasi-neutrality (net charge ∼+0.2) when weakly adsorbed at the surface by ∼0.15 eV. Our results are consistent with the assumption that sodium and potassium observed in Europa exosphere come from the sputtering of materials issued from the underlying ocean and exposed by resurfacing events. They also suggest that calcium should be searched for by future missions.

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Dynamics of the global meridional ice flow of Europa’s icy shell

Cited by 37 publications

References 42 publications

Self-Assembling Ice Membranes on Europa: Brinicle Properties, Field Examples, and Possible Energetic Systems in Icy Ocean Worlds

Self-Assembling Ice Membranes on Europa: Brinicle Properties, Field Examples, and Possible Energetic Systems in Icy Ocean Worlds

The surface temperature of Europa

Sodium, Potassium, and Calcium in Europa: An Atomic Journey through Water Ice

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