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File:Europa-like turbulence simulation.jpg
The figures portray convective flow structures, zonal flows and temperature fields (left to right) in a Europa-like convection models. Credit: Nature Geoscience.

The figures above portray convective flow structures, zonal flows and temperature fields (left to right, respectively) in Europa-like convection models.

The "odd surface terrain patterns [of Europa] likely come about due to convection. [...] The ice shell of Jupiter’s moon Europa is marked by regions of disrupted ice known as chaos terrains that cover up to 40% of the satellite’s surface, most commonly occurring within 40° of the equator. Concurrence with salt deposits implies a coupling between the geologically active ice shell and the underlying liquid water ocean at lower latitudes. Europa’s ocean dynamics have been assumed to adopt a two-dimensional pattern, which channels the moon’s internal heat to higher latitudes. [...] heterogeneous heating promotes the formation of chaos features through increased melting of the ice shell and subsequent deposition of marine ice at low latitudes."[1]

Gaseous objects

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Main resource: Gases/Gaseous objects
This graphic shows the location of water vapor detected over Europa's south pole in observations taken by NASA's Hubble Space Telescope in December 2012. Credit: NASA/ESA/L. Roth/SWRI/University of Cologne.

"This [image at the right] is the first strong evidence of water plumes erupting off Europa's surface."[2]

"Hubble didn't photograph plumes, but spectroscopically detected auroral emissions from oxygen and hydrogen. The aurora is powered by Jupiter's magnetic field. This is only the second moon in the solar system found ejecting water vapor from the frigid surface. The image of Europa is derived from a global surface map generated from combined observations taken by NASA's Voyager and Galileo space probes."[2]

Liquid objects

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Main resources: Liquids/Liquid objects and Liquid objects
File:Europa-ocean-model-1.jpg
This rendering of Europa shows the temperature field in a simulation of the icy moon's global ocean dynamics, where hot plumes (red) rise from the seafloor and cool fluid (blue) sinks down from the ice-ocean border. Credit: K. M. Soderlund/NASA/JPL/University of Arizona.
File:Subsurface Water Model of Europa.jpg
This rendering of Jupiter's icy moon Europa shows so-called isosurfaces of warmer (red) and cooler (blue) temperatures in a simulation of Europa’s global ocean dynamics. Credit: J. Wicht/NASA/JPL/University of Arizona.

"This rendering [at the right] of Europa shows the temperature field in a simulation of the icy Jupiter moon's global ocean dynamics, where hot plumes (red) rise from the seafloor and cool fluid (blue) sinks down from the ice-ocean border. More heat is delivered to the ice shell near the equator, consistent with the distribution of chaos terrains on Europa."[3]

"This rendering [at the left] of Jupiter's icy moon Europa shows so-called isosurfaces of warmer (red) and cooler (blue) temperatures in a simulation of Europa’s global ocean dynamics. More heat is delivered to the ice shell near the equator where convection is more vigorous, consistent with the distribution of chaos terrains on Europa."[4]

Astrognosy

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The image portrays two possible models of the interior of Europa. Credit: NASA/JPL.

"These artist's drawings [at the right] depict two proposed models of the subsurface structure of the Jovian moon, Europa. Geologic features on the surface, imaged by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft might be explained either by the existence of a warm, convecting ice layer, located several kilometers below a cold, brittle surface ice crust (top model), or by a layer of liquid water with a possible depth of more than 100 kilometers (bottom model). If a 100 kilometer (60 mile) deep ocean existed below a 15 kilometer (10 mile) thick Europan ice crust, it would be 10 times deeper than any ocean on Earth and would contain twice as much water as Earth's oceans and rivers combined. Unlike the Earth, magnesium sulfate might be a major salt component of Europa's water or ice, while the Earth's oceans are salty due to sodium chloride (common salt)."[5]

"While data from various instruments on the Galileo spacecraft indicate that an Europan ocean might exist, no conclusive proof has yet been found. To date Earth is the only known place in the solar system where large masses of liquid water are located close to a solid surface. Other sources are especially interesting since water is a key ingredient for the development of life."[5]

Oceans

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The apparent youth and smoothness of the surface have led to the hypothesis that a subsurface water ocean exists beneath the surface, which could conceivably harbor extraterrestrial life.[6] The predominant model suggests that heat from tidal flexing causes the ocean to remain liquid and drives ice movement similar to plate tectonics, absorbing chemicals from the surface into the ocean below.[7][8] Sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the sea floor, which may be important in determining whether Europa could be habitable.[9] In addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturn's moon Enceladus, which are thought to be caused by erupting cryogeysers.[10] In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated analysis of data obtained from the Galileo space probe, which orbited Jupiter from 1995 to 2003. Such plume activity could help researchers in a search for life from the subsurface Europan ocean without having to land on the moon.[11][12][13][14] Such plume activity could help researchers in a search for life from the subsurface Europan ocean without having to land on the moon.[11]

Liquids

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Animation shows the Laplace resonance of Io, Europa and Ganymede (conjunctions are highlighted by color changes). Credit: WolfmanSF.

Europa is tidally locked to Jupiter, with one hemisphere of Europa constantly facing Jupiter, as such, there is a sub-Jovian point on Europa's surface, from which Jupiter would appear to hang directly overhead with Europa's prime meridian passing through this point.[15]

The tidal locking may not be full, as a non-synchronous rotation has been proposed: Europa spins faster than it orbits, or at least did so in the past. This suggests an asymmetry in internal mass distribution and that a layer of subsurface liquid separates the icy crust from the rocky interior.[16]

The orbital eccentricity of Europa is continuously pumped by its mean-motion resonance with Io.[17] Thus, the tidal flexing kneads Europa's interior and gives it a source of heat, possibly allowing its ocean to stay liquid while driving subsurface geological processes.[7][17] The ultimate source of this energy is Jupiter's rotation, which is tapped by Io through the tides it raises on Jupiter and is transferred to Europa and Ganymede by the orbital resonance.[17][18]

It is estimated that Europa has an outer layer of water around 100 km (62 mi) thick; a part frozen as its crust, and a part as a liquid ocean underneath the ice. Recent magnetic-field data from the Galileo orbiter showed that Europa has an induced magnetic field through interaction with Jupiter's, which suggests the presence of a subsurface conductive layer.[19] This layer is likely to be a salty liquid-water ocean. Portions of the crust are estimated to have undergone a rotation of nearly 80°, nearly flipping over, which would be unlikely if the ice were solidly attached to the mantle.[20] Europa probably contains a metallic iron core.[21][22]

Hypotheses

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Main resource: Hypotheses
  1. Europa is a solid ice ball.

See also

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References

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  1. ↑ Jason Goodman (December 2, 2013). Scientists Detect Hidden Ocean on Jupiter’s Moon. Astro Watch. http://www.astrowatch.net/2013/12/scientists-detect-hidden-ocean-on.html. Retrieved 2014-06-11. 
  2. ↑ 2.0 2.1 L. Roth (12 December 2013). Water Vapor Over Europa. Greenbelt, Maryland USA: Goddard Space Flight Center. http://www.nasa.gov/content/goddard/water-vapor-over-europa/. Retrieved 2014-06-11. 
  3. ↑ Charles Q. Choi (December 9, 2013). Hidden Oceans on Jupiter's Icy Moon Europa May Explain Strange Terrain. Space.com. http://www.space.com/23880-jupiter-moon-europa-hidden-oceans.html. Retrieved 2014-06-11. 
  4. ↑ J. Wicht (December 9, 2013). Hidden Oceans on Jupiter's Icy Moon Europa May Explain Strange Terrain. Space.com. http://www.space.com/23880-jupiter-moon-europa-hidden-oceans.html. Retrieved 2014-06-11. 
  5. ↑ 5.0 5.1 Sue Lavoie (18 January 1999). PIA01669: Model of Europa's Subsurface Structure. Pasadena, California USA: NASA/JPL. http://photojournal.jpl.nasa.gov/catalog/PIA01669. Retrieved 2014-06-11. 
  6. ↑ Tritt, Charles S. (2002). "Possibility of Life on Europa". Milwaukee School of Engineering. Archived from the original on 9 June 2007. Retrieved 10 August 2007.
  7. ↑ 7.0 7.1 "Tidal Heating". geology.asu.edu. Archived from the original on 29 March 2006.
  8. ↑ Dyches, Preston; Brown, Dwayne; Buckley, Michael (8 September 2014). "Scientists Find Evidence of 'Diving' Tectonic Plates on Europa". NASA. Retrieved 8 September 2014.
  9. ↑ Dyches, Preston; Brown, Dwayne (12 May 2015). "NASA Research Reveals Europa's Mystery Dark Material Could Be Sea Salt". NASA. Retrieved 12 May 2015.
  10. ↑ Cook, Jia-Rui C.; Gutro, Rob; Brown, Dwayne; Harrington, J. D.; Fohn, Joe (12 December 2013). "Hubble Sees Evidence of Water Vapor at Jupiter Moon". NASA.
  11. ↑ 11.0 11.1 Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S. (14 May 2018). "Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures". Nature Astronomy 2 (6): 459–464. doi:10.1038/s41550-018-0450-z. 
  12. ↑ McCartney, Gretchen; Brown, Dwayne; Wendel, JoAnna (14 May 2018). "Old Data Reveal New Evidence of Europa Plumes". Retrieved 14 May 2018.
  13. ↑ Chang, Kenneth (14 May 2018). "NASA Finds Signs of Plumes From Europa, Jupiter's Ocean Moon". The New York Times. Retrieved 14 May 2018.
  14. ↑ Wall, Mike (14 May 2018). "This May Be the Best Evidence Yet of a Water Plume on Jupiter's Moon Europa". Space.com. Retrieved 14 May 2018.
  15. ↑ "Planetographic Coordinates". Wolfram Research. 2010. Archived from the original on 1 March 2009. Retrieved 29 March 2010.
  16. ↑ Geissler, P. E.; Greenberg, R.; Hoppa, G.; Helfenstein, P.; McEwen, A.; Pappalardo, R.; Tufts, R.; Ockert-Bell, M. et al. (1998). "Evidence for non-synchronous rotation of Europa". Nature 391 (6665): 368–70. doi:10.1038/34869. PMID 9450751. 
  17. ↑ 17.0 17.1 17.2 Showman, Adam P.; Malhotra, Renu (May 1997). "Tidal Evolution into the Laplace Resonance and the Resurfacing of Ganymede". Icarus 127 (1): 93–111. doi:10.1006/icar.1996.5669. 
  18. ↑ Moore, W. B. (2003). "Tidal heating and convection in Io". Journal of Geophysical Research 108 (E8): 5096. doi:10.1029/2002JE001943. 
  19. ↑ Phillips, Cynthia B.; Pappalardo, Robert T. (20 May 2014). "Europa Clipper Mission Concept". Eos, Transactions American Geophysical Union 95 (20): 165–167. doi:10.1002/2014EO200002. 
  20. ↑ Cowen, Ron (7 June 2008). "A Shifty Moon". Science News.
  21. ↑ Kivelson, Margaret G.; Khurana, Krishan K.; Russell, Christopher T.; Volwerk, Martin; Walker, Raymond J.; Zimmer, Christophe (2000). "Galileo Magnetometer Measurements: A Stronger Case for a Subsurface Ocean at Europa". Science 289 (5483): 1340–1343. doi:10.1126/science.289.5483.1340. PMID 10958778. 
  22. ↑ Bhatia, G.K.; Sahijpal, S. (2017). "Thermal evolution of trans-Neptunian objects, icy satellites, and minor icy planets in the early solar system". Meteoritics & Planetary Science 52 (12): 2470–2490. doi:10.1111/maps.12952. 
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{{Radiation astronomy resources}}

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