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| comment | | "parent_author":"",<br>"parent_permlink":"steemstem",<br>"author":"terrylovejoy",<br>"permlink":"europa-the-ocean-moon-of-jupiter",<br>"title":"Europa - The Ocean Moon of Jupiter",<br>"body":"![steemit-intro.jpg (https:\/\/steemitimages.com\/DQmUMST2LTUSbjzepvjbndAsEDYky7LYfsDhER75zGwaX8f\/steemit-intro.jpg)\n*Europa and it\u2019s fractured ice shell is shown in fine detail in this image. Credits: NASA\/JPL-Caltech\/SETI Institute*\n\nEuropa is an exciting world orbiting Jupiter and is the subject of considerable interest in whether life could exist in it\u2019s warm subsurface oceans. The possibility of life on Europa even formed part of the plot for Authur C Clarkes 1982 novel 2010: Odyssey Two which was later adapted to film. In that film the intrepid human explorers were given a chilling warning by a higher intelligence \u201cAll these worlds are yours \u2013 except Europa. attempt no landings there\u201d! Thankfully in the real world we have received no such warnings yet and exploration of Europa is exciting prospect we look forward to in the coming decade!\n\nOf Jupiter\u2019s large moons,<br> Europa is the smallest but is still almost the size of our own moon (see the diagram below). On the outside it appears to be an almost perfect sphere of water ice 3120 km across. However,<br> beneath the ice is an immense ocean of salt water that covers the entire moon and appears to completely decouple the moons exterior from its interior. Nobody knows exactly how deep the ice,<br> but some observations suggest in the order of 20km,<br> with 60-130km of liquid ocean beneath it. Beneath the ocean appears to be a silicate mantle,<br> and then at center an Iron\/Nickel core.\n\n\n![steemit-moonsizes.jpg (https:\/\/steemitimages.com\/DQmRC3m62jshvabr3VCgE6MwraKnvGWnXfKwrgfSmKDR2RU\/steemit-moonsizes.jpg)\n*Comparitive size of Jupiters largest moons and some of the inner planets. Credit:Author\/NASA*\n\nFor a brief introduction to Europa please view this [short video the author created using Celestia (https:\/\/d.tube\/#!\/v\/terrylovejoy\/ztm9im58) showing how the moon fits into the rest of the Jovian system.\n\n## Tidal Heating and Subsurface Ocean\n\n![steemit-tyre.jpg (https:\/\/steemitimages.com\/DQmerckXTR6vLXbxoYBgPCi97AzypjRKMkxJvnpC7tXA7Dm\/steemit-tyre.jpg)\n*Tyre is the feature where the icesheet has been smashed by an impact. Galileo\/NASA*\n\nThe moons Ganymede,<br> Io and Europa all orbit in a tidal tug of war that keeps their orbits synchronised in a 4:2:1 resonance that in turn generates stresses within them sufficient to cause heating. This tidal stress in Europa maintains a subsurface ocean of salt water. Jupiter\u2019s magnetic field generate eddy current\u2019s in the ocean which in turn induces a magnetic field around Europa.\n\nCloser inspection of the surface shows evidence of blocks of ice that have been shattered from the ice crust,<br> upturned,<br> translated and then frozen in place. Evidence from Hubble telescope observation indicate that at least occasionally water is released from the surface indicating fissures open to the ocean below. It is quite possibly the Galileo spacecraft was simply not lucky enough to capture such an event during its Jupiter mission.\n\n## Uplifted crust and other features\n![ice-rafts.jpg (https:\/\/steemitimages.com\/DQmSpu487pYskemDSkdK8tDyT16aC8g6FSBxtGnAdS2NPAA\/ice-rafts.jpg)\n\n*Blocks of ice have been fractured,<br> upturned,<br> rotated and frozen back in place. Galileo\/NASA*\n\nEstimates for the thickness of the icy crust of Europa range from 4-25km,<br> and there is plenty of evidence for fracturing of the crust as can be seen from the various images. Some structures called lineae run across the moon and are reminiscent of plate tectonics,<br> appearing to be lines where the ice has pulled apart of slipped. Water upwells from the ocean below and freezes in these cracks. Some liquid is lost to space as vapour and minerals in that water color the cracks a brown color (the mineral composition is still not certain).\n\n![steemit-lineae.jpg (https:\/\/steemitimages.com\/DQmRwBpxTvgn17HXo9DecfqQh3jdPSovWKq9aiTrjChr1BZ\/steemit-lineae.jpg)\n*Lineae run the length of the planet and show where the ice sheet has fracture and moved. If you look carefully you can see evidence of sideways slippage. Image Credit: NASA\/JPL\/University of Arizona*\n\n\n## Search for Life\n\nThe presence of a warm subsurface ocean is of great interest as it may be the best chance of finding life outside the earth within our own solar system. There are a number of upcoming space missions which will study Europa in more detail,<br> including NASA\u201ds Clipper mission which is planned to launch 2022-2025. It is hoped this mission in conjunction with ESA\u2019s JUICE mission will enable us to characterise the properties of the ice shell and ocean. There is also discussion on probing underneath the ice,<br> depending on what the next missions uncover.\n\n## Conclusion\n\nEuropa is an exciting geologically active world,<br> like Io but manifesting in a different way. We look forward to the future space missions in a decade\u2019s time which will hopefully discover more about the oceans underneath Europa\u2019s exterior.\n\n## References\n\n1.\tPhillips,<br> Cynthia B.; Pappalardo,<br> Robert T. (20 May 2014). \"Europa Clipper Mission Concept:\". Eos,<br> Transactions American Geophysical Union. 95 (20): 165\u2013167. Bibcode:2014EOSTr..95..165P\n2.\tRoth,<br> Lorenz & Saur,<br> Joachim & Retherford,<br> Kurt & F Strobel,<br> Darrell & D Feldman,<br> Paul & A McGrath,<br> Melissa & Nimmo,<br> F. (2013). Transient Water Vapor at Europa's South Pole. Science (New York,<br> N.Y.). 343. . 10.1126\/science.1247051.\n3.\tGreenberg,<br> R. (2011),<br> Europa,<br> edited by R. T. Pappalardo,<br> W. B. McKinnon,<br> and K. Khurana. Meteoritics & Planetary Science,<br> 46: 765\u2013766. doi:10.1111\/j.1945-5100.2011.01193.x",<br>"json_metadata":" \"tags\":[\"steemstem\",<br>\"science\",<br>\"space\",<br>\"astronomy\",<br>\"teamaustralia\" ,<br>\"image\":[\"https:\/\/steemitimages.com\/DQmUMST2LTUSbjzepvjbndAsEDYky7LYfsDhER75zGwaX8f\/steemit-intro.jpg\",<br>\"https:\/\/steemitimages.com\/DQmRC3m62jshvabr3VCgE6MwraKnvGWnXfKwrgfSmKDR2RU\/steemit-moonsizes.jpg\",<br>\"https:\/\/steemitimages.com\/DQmerckXTR6vLXbxoYBgPCi97AzypjRKMkxJvnpC7tXA7Dm\/steemit-tyre.jpg\",<br>\"https:\/\/steemitimages.com\/DQmSpu487pYskemDSkdK8tDyT16aC8g6FSBxtGnAdS2NPAA\/ice-rafts.jpg\",<br>\"https:\/\/steemitimages.com\/DQmRwBpxTvgn17HXo9DecfqQh3jdPSovWKq9aiTrjChr1BZ\/steemit-lineae.jpg\" ,<br>\"links\":[\"https:\/\/d.tube\/#!\/v\/terrylovejoy\/ztm9im58\" ,<br>\"app\":\"steemit\/0.1\",<br>\"format\":\"markdown\" " |
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