Editing Europa (moon) (section)

=== Subsurface ocean ===
[[Image:Europa_poster.svg|thumb|upright=2|Model of Europa's possible interior structure, with a thin ice crust and a [[subsurface ocean]] atop a rocky mantle and metallic core]]
The scientific consensus is that a layer of liquid water exists beneath Europa's surface, and that heat from tidal flexing allows the [[subsurface ocean]] to remain liquid.<ref name="geology" /><ref name="greenberg" /> Europa's surface temperature averages about {{Convert|110|K|C F|-1|lk=on}} at the equator and only {{Convert|50|K|C F|-1|}} at the poles, keeping Europa's icy crust as hard as granite.<ref name="cyclo">{{cite book |title=The Encyclopedia of the Solar System |author1=McFadden, Lucy-Ann |author2=Weissman, Paul |author3=Johnson, Torrence |publisher=Elsevier |date=2007 |page=[https://archive.org/details/encyclopediaofso0000unse_m0r6/page/432 432] |isbn=978-0-12-226805-2 |url=https://archive.org/details/encyclopediaofso0000unse_m0r6/page/432 }}</ref> The first hints of a subsurface ocean came from theoretical considerations of tidal heating (a consequence of Europa's slightly eccentric orbit and orbital resonance with the other Galilean moons). ''Galileo'' imaging team members argue for the existence of a subsurface ocean from analysis of ''Voyager'' and ''Galileo'' images.<ref name="greenberg">{{cite book|last=Greenberg|first=Richard|year=2005|title=Europa: The Ocean Moon: Search for an Alien Biosphere|publisher=Springer + Praxis|isbn=978-3-540-27053-9|pages=7 ff|doi=10.1007/b138547|series=Springer Praxis Books}}</ref> The most dramatic example is "chaos terrain", a common feature on Europa's surface that some interpret as a region where the subsurface ocean has melted through the icy crust. This interpretation is controversial. Most geologists who have studied Europa favor what is commonly called the "thick ice" model, in which the ocean has rarely, if ever, directly interacted with the present surface.<ref name="greeley">Greeley, Ronald; ''et al.'' (2004) "Chapter 15: Geology of Europa", pp. 329 ff. in Bagenal, Fran; Dowling, Timothy E.; and McKinnon, William B., editors; ''Jupiter: The Planet, Satellites and Magnetosphere'', Cambridge University Press, {{ISBN|0-521-81808-7}}.</ref> The best evidence for the thick-ice model is a study of Europa's large craters. The largest impact structures are surrounded by concentric rings and appear to be filled with relatively flat, fresh ice; based on this and on the calculated amount of heat generated by Europan tides, it is estimated that the outer crust of solid ice is approximately {{cvt|10|to|30|km|mi|sigfig=1}} thick,<ref>{{cite journal |title=Improved detection of tides at Europa with radiometric and optical tracking during flybys |journal=Planetary and Space Science |date=July 2015 |last1=Park |first1=Ryan S. |last2=Bills |first2=Bruce |last3=Buffington |first3=Brent B. |volume=112 |pages=10–14 |doi=10.1016/j.pss.2015.04.005 |bibcode = 2015P&SS..112...10P }}</ref> including a ductile "warm ice" layer, which could mean that the liquid ocean underneath may be about {{Convert|100|km|mi|-1|abbr=on}} deep.<ref>{{cite news |first=Zaina |last=Adamu |title=Water near surface of a Jupiter moon only temporary |date=1 October 2012 |url=http://lightyears.blogs.cnn.com/2012/10/01/a-moon-of-jupiter-may-have-water-temporarily/?hpt=us_bn4 |work=CNN News |access-date=2 October 2012 |archive-date=5 October 2012 |archive-url=https://web.archive.org/web/20121005011205/http://lightyears.blogs.cnn.com/2012/10/01/a-moon-of-jupiter-may-have-water-temporarily/?hpt=us_bn4 |url-status=dead }}</ref> This leads to a volume of Europa's oceans of 3×10<sup>18</sup>m<sup>3</sup>, between two or three times the volume of Earth's oceans.<ref>{{Cite APOD|title=All the Water on Europa|date=24 May 2012|access-date=8 March 2016}}</ref><ref>{{cite web|author=Williams, Matt|url=http://www.universetoday.com/15201/jupiters-moon-europa/|title=Jupiter's Moon Europa|work=Universe Today|date=15 September 2015|access-date=9 March 2016|archive-date=10 March 2016|archive-url=https://web.archive.org/web/20160310022713/http://www.universetoday.com/15201/jupiters-moon-europa/|url-status=live}}</ref>

The thin-ice model suggests that Europa's ice shell may be only a few kilometers thick. However, most planetary scientists conclude that this model considers only those topmost layers of Europa's crust that behave elastically when affected by Jupiter's tides.<ref name="Billings"/> One example is flexure analysis, in which Europa's crust is modeled as a plane or sphere weighted and flexed by a heavy load. Models such as this suggest the outer elastic portion of the ice crust could be as thin as {{Convert|200|m|ft}}. If the ice shell of Europa is really only a few kilometers thick, this "thin ice" model would mean that regular contact of the liquid interior with the surface could occur through open ridges, causing the formation of areas of chaotic terrain.<ref name="Billings">{{cite journal |title=The great thickness debate: Ice shell thickness models for Europa and comparisons with estimates based on flexure at ridges |author=Billings, Sandra E. |author2=Kattenhorn, Simon A. |journal=Icarus |volume=177 |issue=2 | pages=397–412 |date=2005 |doi=10.1016/j.icarus.2005.03.013 |bibcode=2005Icar..177..397B}}</ref> Large impacts going fully through the ice crust would also be a way that the subsurface ocean could be exposed.<ref name=":0" /><ref name=":1" />

====Composition====
[[File:Europa PIA2387x - Chaos Transition, Crisscrossing Bands & Chaos Near Agenor Linea.jpg|thumb|300px|Closeup views of Europa obtained on 26 September 1998; images clockwise from upper left show locations from north to south as indicated at lower left.]]
The ''Galileo'' orbiter found that Europa has a weak [[magnetic moment]], which is induced by the varying part of the Jovian magnetic field. The field strength at the magnetic equator (about 120 [[Tesla (unit)|nT]]) created by this magnetic moment is about one-sixth the strength of Ganymede's field and six times the value of Callisto's.<ref name="Zimmer">{{cite journal |last1=Zimmer |first1=C |title=Subsurface Oceans on Europa and Callisto: Constraints from Galileo Magnetometer Observations |journal=Icarus |date=October 2000 |volume=147 |issue=2 |pages=329–347 |doi=10.1006/icar.2000.6456 |bibcode=2000Icar..147..329Z |citeseerx=10.1.1.366.7700 }}</ref> The existence of the induced moment requires a layer of a highly electrically conductive material in Europa's interior. The most plausible candidate for this role is a large subsurface ocean of liquid saltwater.<ref name="Kivelson" />
{{Multiple image |header=Europa Closeups |caption_align=center |align=left |width=150 |direction=vertical |image1=PIA26332-JupiterMoonEuropaCloseupA.jpg |caption1=29 September 2022 |width1= |image2=PIA25696-Europa-JupiterMoon-20220929.jpg |caption2=9 September 2022 |width2= |footer= }}
Since the ''Voyager'' spacecraft flew past Europa in 1979, scientists have worked to understand the composition of the reddish-brown material that coats fractures and other geologically youthful features on Europa's surface.<ref>{{cite news |url=http://www.jpl.nasa.gov/news/news.php?feature=4602 |title=Europa Mission to Probe Magnetic Field and Chemistry |work=Jet Propulsion Laboratory |date=27 May 2015 |access-date=29 May 2015 |archive-date=2 December 2020 |archive-url=https://web.archive.org/web/20201202163713/https://www.jpl.nasa.gov/news/news.php?feature=4602 |url-status=live }}</ref> Spectrographic evidence suggests that the darker, reddish streaks and features on Europa's surface may be rich in salts such as [[magnesium sulfate]], deposited by evaporating water that emerged from within.<ref name="McCord1998">{{cite journal |title=Salts on Europa's Surface Detected by Galileo's Near Infrared Mapping Spectrometer |author1=McCord, Thomas B. |author2=Hansen, Gary B. |display-authors=etal |date=1998 |doi=10.1126/science.280.5367.1242 |volume=280 |issue=5367 |journal=Science |pages=1242–1245|pmid=9596573 |bibcode=1998Sci...280.1242M }}</ref> [[Sulfuric acid]] hydrate is another possible explanation for the contaminant observed spectroscopically.<ref name="Carlson2005">{{Cite journal | last1 = Carlson | first1 = R. W. | last2 = Anderson | first2 = M. S. | last3 = Mehlman | first3 = R. | last4 = Johnson | first4 = R. E. | title = Distribution of hydrate on Europa: Further evidence for sulfuric acid hydrate | doi = 10.1016/j.icarus.2005.03.026 | journal = Icarus | volume = 177 | issue = 2 | page = 461 | year = 2005 |bibcode = 2005Icar..177..461C }}</ref> In either case, because these materials are colorless or white when pure, some other material must also be present to account for the reddish color, and [[sulfur]] compounds are suspected.<ref name="Calvin">{{cite journal |last=Calvin |first=Wendy M. |author2=Clark, Roger N. |author3=Brown, Robert H. |author4= Spencer, John R. |title=Spectra of the ice Galilean satellites from 0.2 to 5 μm: A compilation, new observations, and a recent summary |journal=Journal of Geophysical Research |date=1995 |volume=100 |issue=E9 |pages=19,041–19,048 |bibcode=1995JGR...10019041C|doi=10.1029/94JE03349 }}</ref>

[[File:Europa_%28NIRCam_image,_cropped%29_%28weic2323b%29.jpg|right|thumb|upright|[[Near-infrared spectroscopy|NIR]] image of Europa by the [[James Webb Space Telescope]], confirming the presence of carbon dioxide on the moon<ref>{{cite web | url=https://www.nasa.gov/solar-system/nasas-webb-finds-carbon-source-on-surface-of-jupiters-moon-europa/#:~:text=life%2C%20particularly%20carbon.-,Astronomers%20using%20data%20from%20NASA%27s%20James%20Webb%20Space%20Telescope%20have,meteorites%20or%20other%20external%20sources | title=NASA's Webb Finds Carbon Source on Surface of Jupiter's Moon Europa - NASA | date=21 September 2023 }}</ref>]]
Another hypothesis for the colored regions is that they are composed of abiotic [[organic compounds]] collectively called [[tholins]].<ref name='Tholins Europa'>{{cite journal|doi=10.1029/2002JE001841 | bibcode=2002JGRE..107.5114B | volume=107 | issue=E11 | title=A new energy source for organic synthesis in Europa's surface ice | year=2002 | journal=Journal of Geophysical Research: Planets | pages=24–1–24–5 | last1 = Borucki | first1 = Jerome G. | last2 = Khare | first2 = Bishun | last3 = Cruikshank | first3 = Dale P.| doi-access=free }}</ref><ref name='amino acids'>{{cite conference |bibcode=2017AAS...22913804W |title=MISE: A Search for Organics on Europa |conference=American Astronomical Society Meeting Abstracts #229 |volume=229 |pages=138.04 |last1=Whalen |first1=Kelly |last2=Lunine |first2=Jonathan I. |last3=Blaney |first3=Diana L.|author3-link= Diana Blaney |year=2017 }}</ref><ref name='JPL2015'>{{cite news |url=http://www.jpl.nasa.gov/news/news.php?feature=4602 |title=Europa Mission to Probe Magnetic Field and Chemistry |work=Jet Propulsion Laboratory |date=27 May 2015 |access-date=23 October 2017 |archive-date=2 December 2020 |archive-url=https://web.archive.org/web/20201202163713/https://www.jpl.nasa.gov/news/news.php?feature=4602 |url-status=live }}</ref> The morphology of Europa's impact craters and ridges is suggestive of fluidized material welling up from the fractures where [[pyrolysis]] and [[radiolysis]] take place. In order to generate colored tholins on Europa, there must be a source of materials (carbon, nitrogen, and water) and a source of energy to make the reactions occur. Impurities in the water ice crust of Europa are presumed both to emerge from the interior as [[Cryovolcano|cryovolcanic]] events that resurface the body, and to accumulate from space as interplanetary dust.<ref name='Tholins Europa'/> Tholins bring important [[Astrobiology|astrobiological]] implications, as they may play a role in prebiotic chemistry and [[abiogenesis]].<ref name='prebiotic chem'>{{cite journal| pmc=3796891 | pmid=24143126 | doi=10.2174/13852728113179990078 | volume=17 | issue=16 | title=Atmospheric Prebiotic Chemistry and Organic Hazes | year=2013 | journal=Curr Org Chem | pages=1710–1723 | last1 = Trainer | first1 = MG}}</ref><ref name='Coll 2010'>{{cite conference |bibcode=2010cosp...38..777C |title=Prebiotic chemistry on Titan ? The nature of Titan's aerosols and their potential evolution at the satellite surface |conference=38th Cospar Scientific Assembly |volume=38 |pages=11 |last1=Coll |first1=Patrice |last2=Szopa |first2=Cyril |last3=Buch |first3=Arnaud |last4=Carrasco |first4=Nathalie |last5=Ramirez |first5=Sandra I. |last6=Quirico |first6=Eric |last7=Sternberg |first7=Robert |last8=Cabane |first8=Michel |last9=Navarro-Gonzalez |first9=Rafael |last10=Raulin |first10=Francois |last11=Israel |first11=G. |last12=Poch |first12=O. |last13=Brasse |first13=C. |year=2010 }}</ref><ref>{{cite journal |last1=Ruiz-Bermejo |first1=Marta |last2=Rivas |first2=Luis A. |last3=Palacín |first3=Arantxa |last4=Menor-Salván |first4=César |last5=Osuna-Esteban |first5=Susana |title=Prebiotic Synthesis of Protobiopolymers Under Alkaline Ocean Conditions |journal=Origins of Life and Evolution of Biospheres |date=16 December 2010 |volume=41 |issue=4 |pages=331–345 |doi=10.1007/s11084-010-9232-z |pmid=21161385 |bibcode=2011OLEB...41..331R |s2cid=19283373 }}</ref>

The presence of [[sodium chloride]] in the internal ocean has been suggested by a 450&nbsp;nm absorption feature, characteristic of irradiated NaCl crystals, that has been spotted in [[Hubble Space Telescope|HST]] observations of the chaos regions, presumed to be areas of recent subsurface upwelling.<ref name="Trumbo2019">{{cite journal |last1=Trumbo |first1=Samantha K. |last2=Brown |first2=Michael E. |last3=Hand |first3=Kevin P. |title=Sodium chloride on the surface of Europa |journal=Science Advances |date=12 June 2019 |volume=5 |issue=6 |pages=eaaw7123 |doi=10.1126/sciadv.aaw7123 |pmid=31206026 |pmc=6561749 |bibcode=2019SciA....5.7123T }}</ref> The subterranean ocean of Europa contains carbon<ref>{{Cite news |last=Devlin |first=Hannah |date=21 September 2023 |title=Scientists excited to find ocean of one of Jupiter's moons contains carbon |newspaper=The Guardian |url=https://www.theguardian.com/science/2023/sep/21/scientists-excited-to-find-ocean-of-one-of-jupiters-moons-contains-carbon }}</ref> and was observed on the surface ice as a concentration of [[carbon dioxide]] within Tara Regio, a geologically recently resurfaced terrain.<ref>{{Cite journal |last=Trumbo |first=Samantha |date=September 2023 |title=The distribution of CO2 on Europa indicates an internal source of carbon |journal=Science |volume=381 |issue=6664 |pages=1308–1311|doi=10.1126/science.adg4155 |pmid=37733851 |arxiv=2309.11684 }}</ref> JWST [[NIRSpec]] observations show that the northern hemisphere show crystalline water [[ice]] beneath the surface and amorphous ice dominating the surface. In the southern hemisphere Regiones Tara and Powys crystalline water ice dominates both the surface and the deeper layers. These two regiones likely experience ongoing thermal (re)crystallization, as the radiation near Jupiter cause particle amorphization at the top 10 microns over a period of less than 15 days.<ref name="Cartwright2025">{{cite arXiv|eprint=2504.05283 |last1=Cartwright |first1=Richard J. |last2=Hibbits |first2=Charles A. |last3=Holler |first3=Bryan J. |last4=Raut |first4=Ujjwal |last5=Nordheim |first5=Tom A. |last6=Neveu |first6=Marc |last7=Protopapa |first7=Silvia |last8=Glein |first8=Christopher R. |last9=Leonard |first9=Erin J. |last10=Roth |first10=Lorenz |last11=Beddingfield |first11=Chloe B. |last12=Villanueva |first12=Geronimo L. |title=JWST Reveals Spectral Tracers of Recent Surface Modification on Europa |date=2025 |class=astro-ph.EP }}</ref>
[[File:CO2_Europa.png|thumb|upright=4|center|A series of images of Europa in different wavelengths by the James Webb Space Telescope. The different wavelengths show the presence of different forms of carbon dioxide on Europa.]]

====Sources of heat====

Europa receives thermal energy from [[tidal heating]], which occurs through the tidal friction and tidal flexing processes caused by [[tidal acceleration]]: orbital and rotational energy are dissipated as heat in the [[Planetary core|core]] of the moon, the internal ocean, and the ice crust.<ref name="Europa FAQ 2012">{{cite news |url=http://solarsystem.nasa.gov/europa/faq.cfm |title=Frequently Asked Questions about Europa |work=NASA |date=2012 |access-date=18 April 2016 |archive-url=https://web.archive.org/web/20160428110229/http://solarsystem.nasa.gov/europa/faq.cfm |archive-date=28 April 2016 |url-status=dead }}</ref>

=====Tidal friction=====
Ocean tides are converted to heat by frictional losses in the oceans and their interaction with the solid bottom and with the top ice crust. In late 2008, it was suggested Jupiter may keep Europa's oceans warm by generating large planetary tidal waves on Europa because of its small but non-zero obliquity. This generates so-called [[Rossby wave]]s that travel quite slowly, at just a few kilometers per day, but can generate significant kinetic energy. For the current axial tilt estimate of 0.1 degree<!-- and assuming a linear dependency -->, the resonance from Rossby waves would contain 7.3{{E|18}} J of kinetic energy, which is two thousand times larger than that of the flow excited by the dominant tidal forces.<ref name="Zyga2008">{{cite web |title=Scientist Explains Why Jupiter's Moon Europa Could Have Energetic Liquid Oceans |url=http://www.physorg.com/news148278114.html |first=Lisa |last=Zyga |publisher=PhysOrg.com |date=12 December 2008 |access-date=28 July 2009 |archive-date=17 February 2009 |archive-url=https://web.archive.org/web/20090217213351/http://www.physorg.com/news148278114.html |url-status=live }}</ref><ref name="Tyler2008">{{cite journal |last=Tyler |first=Robert H. |title=Strong ocean tidal flow and heating on moons of the outer planets |journal=Nature |date=11 December 2008|volume=456 | pages=770–772 |doi=10.1038/nature07571 |pmid=19079055 |issue=7223 |bibcode =2008Natur.456..770T |s2cid=205215528 }}</ref> Dissipation of this energy could be the principal heat source of Europa's ocean.<ref name="Zyga2008"/><ref name="Tyler2008"/>

=====Tidal flexing=====
Tidal flexing kneads Europa's interior and ice shell, which becomes a source of heat.<ref>{{cite news |url=http://solarsystem.nasa.gov/europa/energy.cfm |title=Europa: Energy |work=NASA |date=2012 |access-date=18 April 2016 |quote=Tidal flexing of the ice shell could create slightly warmer pockets of ice that rise slowly upward to the surface, carrying material from the ocean below. |archive-url=https://web.archive.org/web/20160428191605/https://solarsystem.nasa.gov/europa/energy.cfm |archive-date=28 April 2016 |url-status=dead }}</ref> Depending on the amount of tilt, the heat generated by the ocean flow could be 100 to thousands of times greater than the heat generated by the flexing of Europa's rocky core in response to the gravitational pull from Jupiter and the other moons circling that planet.<ref>{{cite news |last=Tyler |first=Robert |url=https://www.sciencedaily.com/releases/2008/12/081212092056.htm |title=Jupiter's Moon Europa Does The Wave To Generate Heat |work=University of Washington |publisher=Science Daily |date=15 December 2008 |access-date=18 April 2016 |archive-date=14 May 2016 |archive-url=https://web.archive.org/web/20160514044845/https://www.sciencedaily.com/releases/2008/12/081212092056.htm |url-status=live }}</ref> Europa's seafloor could be heated by the moon's constant flexing, driving hydrothermal activity similar to undersea volcanoes in Earth's oceans.<ref name="Europa FAQ 2012"/>

Experiments and ice modeling published in 2016, indicate that tidal flexing dissipation can generate one order of magnitude more heat in Europa's ice than scientists had previously assumed.<ref name="Stacey 2016">{{cite news |last=Stacey |first=Kevin |url=https://news.brown.edu/articles/2016/04/europa |title=Europa's heaving ice might make more heat than scientists thought |work=Brown University |date=14 April 2016 |access-date=18 April 2016 |archive-date=21 April 2016 |archive-url=https://web.archive.org/web/20160421003232/https://news.brown.edu/articles/2016/04/europa |url-status=live }}</ref><ref name="McCarthy 2016">{{cite journal |title=Tidal dissipation in creeping ice and the thermal evolution of Europa |journal=Earth and Planetary Science Letters |date=1 June 2016 |last1=McCarthy |first1=Christine |last2=Cooper |first2=Reid F. |volume=443 |pages=185–194 |doi=10.1016/j.epsl.2016.03.006 |bibcode = 2016E&PSL.443..185M |doi-access=free }}</ref> Their results indicate that most of the heat generated by the ice actually comes from the ice's [[Crystal structure|crystalline structure]] (lattice) as a result of deformation, and not friction between the ice grains.<ref name="Stacey 2016"/><ref name="McCarthy 2016"/> The greater the deformation of the ice sheet, the more heat is generated.

=====Radioactive decay=====
In addition to tidal heating, the interior of Europa could also be heated by the decay of radioactive material ([[radiogenic heating]]) within the rocky mantle.<ref name="Europa FAQ 2012"/><ref>{{cite book |last1=Barr |first1=Amy C. |last2=Showman |first2=Adam P. |chapter=Heat transfer in Europa's icy shell |pages=405–430 |bibcode=2009euro.book..405B |citeseerx=10.1.1.499.6279 |editor-last=Pappalardo |editor-first=Robert T. |editor2-last=McKinnon |editor2-first=William B. |editor3-last=Khurana |editor3-first=Krishan |title=Europa |publisher=University of Arizona Press |year=2009 |isbn=978-0-8165-2844-8 }}</ref> But the models and values observed are one hundred times higher than those that could be produced by radiogenic heating alone,<ref>{{cite journal |title=Hydrothermal systems on Europa |journal=Geophysical Research Letters |date=9 March 2005 |last1=Lowell |first1=Robert P. |last2=DuBosse |first2=Myesha |volume=32 |issue=5 |pages=L05202 |doi=10.1029/2005GL022375 |bibcode = 2005GeoRL..32.5202L |s2cid=129270513 }}</ref> thus implying that tidal heating has a leading role in Europa.<ref>{{cite journal |last1=Ruiz |first1=Javier |title=The heat flow of Europa |journal=Icarus |date=October 2005 |volume=177 |issue=2 |pages=438–446 |doi=10.1016/j.icarus.2005.03.021 |bibcode=2005Icar..177..438R |url=https://eprints.ucm.es/id/eprint/10490/1/15-Europa_5.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://eprints.ucm.es/id/eprint/10490/1/15-Europa_5.pdf |archive-date=9 October 2022 |url-status=live }}</ref>

==== Plumes ====
<!---[[File:Water vapour plumes on Jupiter's moon Europa (artist's impression).jpg|thumb|Water vapor plumes on Jupiter's moon Europa (artist's impression)<ref name="Plumes2013" />]] --->[[File:Photo composite of suspected water plumes on Europa.jpg|thumb|Photo composite of suspected water plumes on Europa<ref name="Plumes2013">{{cite web|title=Photo composite of suspected water plumes on Europa|url=https://www.spacetelescope.org/images/opo1633a/|website=www.spacetelescope.org|access-date=6 October 2016|archive-date=9 October 2016|archive-url=https://web.archive.org/web/20161009104726/https://www.spacetelescope.org/images/opo1633a/|url-status=live}}</ref>]]
The [[Hubble Space Telescope]] acquired an image of Europa in 2012 that was interpreted to be a plume of water vapour erupting from near its south pole.<ref>{{Cite web|url=https://www.spacetelescope.org/news/heic1322/|title=Hubble discovers water vapour venting from Jupiter's moon Europa|date=12 December 2013|website=www.spacetelescope.org|publisher=Hubble Space Telescope/European Space Agency|language=en|access-date=16 April 2019|archive-date=16 April 2019|archive-url=https://web.archive.org/web/20190416012613/https://www.spacetelescope.org/news/heic1322/|url-status=live}}</ref><ref name="Plumes2013"/> The image suggests the plume may be {{convert|200|km|mi|abbr=on}} high, or more than 20 times the height of Mt. Everest.,<ref name="NASA-20131212-EU" /><ref>{{cite news | first = Leigh | last = Fletcher | title = The Plumes of Europa | date = 12 December 2013 | url = http://www.planetary.org/blogs/guest-blogs/2013/1212-fletcher-the-plumes-of-europa.html | work = The Planetary Society | access-date = 17 December 2013 | archive-date = 15 December 2013 | archive-url = https://web.archive.org/web/20131215041956/http://www.planetary.org/blogs/guest-blogs/2013/1212-fletcher-the-plumes-of-europa.html | url-status = live }}</ref><ref>{{cite news | first = Charles Q. | last = Choi | title = Jupiter Moon Europa May Have Water Geysers Taller Than Everest | date = 12 December 2013 | url = http://www.space.com/23923-europa-water-geyers-taller-than-everest.html | work = Space.com | access-date = 17 December 2013 | archive-date = 15 December 2013 | archive-url = https://web.archive.org/web/20131215173940/http://www.space.com/23923-europa-water-geyers-taller-than-everest.html | url-status = live }}</ref> though recent observations and modeling suggest that typical Europan plumes may be much smaller.<ref>{{Cite journal|last1=Fagents|first1=Sarah A.|last2=Greeley|first2=Ronald|last3=Sullivan|first3=Robert J.|last4=Pappalardo|first4=Robert T.|last5=Prockter|first5=Louise M.|date=30 June 1999|title=Cryomagmatic Mechanisms for the Formation of Rhadamanthys Linea, Triple Band Margins, and Other Low-Albedo Features on Europa|url=https://www.sciencedirect.com/science/article/abs/pii/S0019103599962541|journal=Icarus|volume=144|issue=1 |pages=54–88|doi=10.1006/icar.1999.6254|access-date=16 June 2022|archive-date=16 June 2022|archive-url=https://web.archive.org/web/20220616235235/https://www.sciencedirect.com/science/article/abs/pii/S0019103599962541|url-status=live}}</ref><ref>{{Cite journal|last1=Quick|first1=Lynnae C.|author-link=Lynnae Quick|last2=Barnouin|first2=Olivier S.|last3=Prockter|first3=Louise|author-link3=Louise Prockter|last4=Patterson|first4=G. Wesley|date=15 September 2013|title=Constraints on the Detection of Cryovolcanic Plumes on Europa|url=https://www.sciencedirect.com/science/article/abs/pii/S0032063313001803|journal=Planetary and Space Science|volume=86|issue=1 |pages=1–9|doi=10.1006/icar.1999.6254|access-date=16 June 2022|archive-date=16 June 2022|archive-url=https://web.archive.org/web/20220616235322/https://www.sciencedirect.com/science/article/abs/pii/S0032063313001803|url-status=live}}</ref><ref>{{Cite journal|last1=Paganini|first1=L.|last2=Villanueva|first2=G.L.|last3=Mandell|first3=A.M.|last4=Hurford|first4=T.A.|last5=Retherford|first5=K.D.|last6=Mumma|first6=M.A.|title=CA measurement of water vapour amid a largely quiescent environment on Europa|date=18 November 2019|url=https://www.nature.com/articles/s41550-019-0933-6|journal=Nature Astronomy|volume=4|issue=3|pages=266–272|doi=10.1038/s41550-019-0933-6|s2cid=210278335|access-date=16 June 2022|archive-date=18 June 2022|archive-url=https://web.archive.org/web/20220618112026/https://www.nature.com/articles/s41550-019-0933-6|url-status=live}}</ref> It has been suggested that if plumes exist, they are episodic<ref>{{cite news |last=Dyches |first=Preston |url=http://www.nasa.gov/jpl/signs-of-europa-plumes-remain-elusive-in-search-of-cassini-data |title=Signs of Europa Plumes Remain Elusive in Search of Cassini Data |work=NASA |date=30 July 2015 |access-date=18 April 2016 |archive-date=16 April 2016 |archive-url=https://web.archive.org/web/20160416214519/http://www.nasa.gov/jpl/signs-of-europa-plumes-remain-elusive-in-search-of-cassini-data/ |url-status=live }}</ref> and likely to appear when Europa is at its farthest point from Jupiter, in agreement with [[tidal force]] modeling predictions.<ref name='Europa tidal forces 2013'>{{cite journal |last1=Roth |first1=L. |last2=Saur |first2=J. |last3=Retherford |first3=K. D. |last4=Strobel |first4=D. F. |last5=Feldman |first5=P. D. |last6=McGrath |first6=M. A. |last7=Nimmo |first7=F. |title=Transient Water Vapor at Europa's South Pole |journal=Science |date=12 December 2013 |volume=343 |issue=6167 |pages=171–174 |doi=10.1126/science.1247051 |pmid=24336567 |bibcode=2014Sci...343..171R |s2cid=27428538 }}</ref> Additional imaging evidence from the Hubble Space Telescope was presented in September 2016.<ref name="plumes 2016">{{cite news |last=Berger |first=Eric |url=https://arstechnica.com/science/2016/09/hubble-finds-additional-evidence-of-water-vapor-plumes-on-europa/ |title=Hubble finds additional evidence of water vapor plumes on Europa |work=NASA |publisher=ARS Technica |date=26 September 2016 |access-date=26 September 2016 |archive-date=26 September 2016 |archive-url=https://web.archive.org/web/20160926202346/http://arstechnica.com/science/2016/09/hubble-finds-additional-evidence-of-water-vapor-plumes-on-europa/ |url-status=live }}</ref><ref>{{cite news |last=Amos |first=Jonathan |url=https://www.bbc.com/news/science-environment-37473617 |title=Europa moon 'spewing water jets' |work=BBC News |date=26 September 2016 |access-date=26 September 2016 |archive-date=26 September 2016 |archive-url=https://web.archive.org/web/20160926204050/http://www.bbc.com/news/science-environment-37473617 |url-status=live }}</ref>

In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated critical analysis of data obtained from the ''Galileo'' space probe, which orbited Jupiter between 1995 and 2003. ''Galileo'' flew by Europa in 1997 within {{convert|206|km|mi|abbr=on}} of the moon's surface and the researchers suggest it may have flown through a water plume.<ref name="NA-20180514">{{cite journal |last1=Jia |first1=Xianzhe |last2=Kivelson |first2=Margaret G. |last3=Khurana |first3=Krishan K. |last4=Kurth |first4=William S. |title=Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures |date=14 May 2018 |journal=[[Nature Astronomy]] |volume=2 |issue=6 |pages=459–464 |doi=10.1038/s41550-018-0450-z |bibcode=2018NatAs...2..459J |s2cid=134370392 }}</ref><ref name="NASA-20180514">{{cite web |last1=McCartney |first1=Gretchen |last2=Brown |first2=Dwayne |last3=Wendel |first3=JoAnna |title=Old Data Reveal New Evidence of Europa Plumes |website=[[Jet Propulsion Laboratory]] |url=https://www.jpl.nasa.gov/news/news.php?feature=7122 |date=14 May 2018 |access-date=14 May 2018 |archive-date=17 June 2019 |archive-url=https://web.archive.org/web/20190617213109/https://www.jpl.nasa.gov/news/news.php?feature=7122 |url-status=live }}</ref><ref name="NYT-20180514">{{cite news |last=Chang |first=Kenneth |title=NASA Finds Signs of Plumes From Europa, Jupiter's Ocean Moon |url=https://www.nytimes.com/2018/05/14/science/europa-plumes-water.html |date=14 May 2018 |work=[[The New York Times]] |access-date=14 May 2018 |archive-date=14 May 2018 |archive-url=https://web.archive.org/web/20180514165834/https://www.nytimes.com/2018/05/14/science/europa-plumes-water.html |url-status=live }}</ref><ref name="SP-20180514">{{cite web |last=Wall |first=Mike |title=This May Be the Best Evidence Yet of a Water Plume on Jupiter's Moon Europa |url=https://www.space.com/40575-jupiter-moon-europa-plume-galileo-spacecraft.html |date=14 May 2018 |work=[[Space.com]] |access-date=14 May 2018 |archive-date=14 May 2018 |archive-url=https://web.archive.org/web/20180514183300/https://www.space.com/40575-jupiter-moon-europa-plume-galileo-spacecraft.html |url-status=live }}</ref> Such plume activity could help researchers in a [[Life|search for life]] from the subsurface Europan ocean without having to land on the moon.<ref name="NA-20180514"/>

The tidal forces are about 1,000 times stronger than the Moon's effect on [[Earth]]. The only other moon in the Solar System exhibiting water vapor plumes is [[Enceladus]].<ref name="NASA-20131212-EU" /> The estimated eruption rate at Europa is about 7000&nbsp;kg/s<ref name='Europa tidal forces 2013'/> compared to about 200&nbsp;kg/s for the plumes of Enceladus.<ref name="Hansen2006">{{Cite journal | last1 = Hansen | first1 = C. J. | last2 = Esposito | first2 = L. | last3 = Stewart | first3 = A. I. | last4 = Colwell | first4 = J. | last5 = Hendrix | first5 = A. | last6 = Pryor | first6 = W. | last7 = Shemansky | first7 = D. | last8 = West | first8 = R. | s2cid = 2954801 | doi = 10.1126/science.1121254 | title = Enceladus' Water Vapor Plume | journal = Science | volume = 311 | issue = 5766 | pages = 1422–1425 | date = 10 March 2006| pmid = 16527971|bibcode = 2006Sci...311.1422H }}</ref><ref name="Spencer2013">{{Cite journal | last1 = Spencer | first1 = J. R. | last2 = Nimmo | first2 = F. | s2cid = 140646028 | doi = 10.1146/annurev-earth-050212-124025 | title = Enceladus: An Active Ice World in the Saturn System | journal = [[Annual Review of Earth and Planetary Sciences]]| volume = 41 | page = 693 | date = May 2013| issue = 1 |bibcode = 2013AREPS..41..693S }}</ref> If confirmed, it would open the possibility of a flyby through the plume and obtain a sample to analyze ''in situ'' without having to use a lander and drill through kilometres of ice.<ref name="plumes 2016"/><ref>{{cite news |last=O'Neill |first=Ian |url=http://www.space.com/34151-nasa-activity-spied-on-europa-but-its-not-aliens.html |title=NASA: Activity Spied on Europa, But It's 'NOT Aliens' |work=Discovery News |publisher=Space |date=22 September 2016 |access-date=23 September 2016 |archive-date=23 September 2016 |archive-url=https://web.archive.org/web/20160923011825/http://www.space.com/34151-nasa-activity-spied-on-europa-but-its-not-aliens.html |url-status=live }}</ref><ref name="europa_plume_in_situ">{{cite journal |title=On the in-situ detectability of Europa's water vapour plumes from a flyby mission |author1=Huybrighs, Hans |author2=Futaana, Yoshifumi |author3=Barabash, Stas |author4=Wieser, Martin |author5=Wurz, Peter|author6=Krupp, Norbert|author7=Glassmeier, Karl-Heinz|author8=Vermeersen, Bert |journal=Icarus |date=June 2017 |volume=289 |pages=270–280 |doi=10.1016/j.icarus.2016.10.026|arxiv=1704.00912|bibcode=2017Icar..289..270H|s2cid=119470009 }}</ref>

In November 2020, a study was published in the peer-reviewed scientific journal ''[[Geophysical Research Letters]]'' suggesting that the plumes may originate from water within the crust of Europa as opposed to its subsurface ocean. The study's model, using images from the Galileo space probe, proposed that a combination of freezing and pressurization may result in at least some of the cryovolcanic activity. The pressure generated by migrating briny water pockets would thus, eventually, burst through the crust, thereby creating these plumes. The hypothesis that cryovolcanism on Europa could be triggered by freezing and pressurization of liquid pockets in the icy crust was first proposed by Sarah Fagents at the University of Hawai'i at Mānoa, who in 2003, was the first to model and publish work on this process.<ref>{{Cite journal|last1=Fagents|first1=Sarah A.|date=27 December 2003|title=Considerations for effusive cryovolcanism on Europa:The post-Galileo perspective|url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2003JE002128|journal=Icarus|language=en|volume=108|issue=E12|pages=5139|doi=10.1029/2003JE002128|bibcode=2003JGRE..108.5139F|access-date=16 June 2022|archive-date=16 June 2022|archive-url=https://web.archive.org/web/20220616235245/https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2003JE002128|url-status=live}}</ref> A press release from NASA's Jet Propulsion Laboratory referencing the November 2020 study suggested that plumes sourced from migrating liquid pockets could potentially be less hospitable to life. This is due to a lack of substantial energy for organisms to thrive off, unlike proposed hydrothermal vents on the subsurface ocean floor.<ref name="JPL20201113">{{cite web |last1=McCartney |first1=Gretchen |last2=Hautaluoma |first2=Grey |last3=Johnson |first3=Alana |last4=Tucker |first4=Danielle |title=Potential Plumes on Europa Could Come From Water in the Crust |website=[[Jet Propulsion Laboratory]] |url=https://www.jpl.nasa.gov/news/news.php?feature=7785 |date=13 November 2020 |access-date=13 November 2020 |archive-date=13 November 2020 |archive-url=https://web.archive.org/web/20201113191732/https://www.jpl.nasa.gov/news/news.php?feature=7785 |url-status=live }}</ref><ref name="GRL20201105">{{cite journal |last1=Steinbrügge |first1=G. |last2=Voigt |first2=J. R. C. |last3=Wolfenbarger |first3=N. S. |last4=Hamilton |first4=C. W. |last5=Soderlund |first5=K. M. |last6=Young D. |first6=D. A. |last7=Blankenship |first7=D. |last8=Vance D. |first8=S. D. |last9=Schroeder |first9=M. |title=Brine Migration and Impact-Induced Cryovolcanism on Europa |date=5 November 2020 |journal=[[Geophysical Research Letters]] |volume=47 |issue=21 |pages={e2020GL090797} |doi=10.1029/2020GL090797|bibcode=2020GeoRL..4790797S |s2cid=228890686 }}</ref>