Editing Galilean moons (section)

=== Europa ===
{{main|Europa (moon)}}
[[File:PIA25696-Europa-JupiterMoon-20220929.jpg|thumb|Closeup of Europan lineae]]
Europa (Jupiter II), the second of the four Galilean moons, is the second closest to Jupiter and the smallest at 3121.6 kilometers in diameter, which is slightly smaller than [[Moon|Earth's Moon]]. The name comes from a mythical [[Phoenicia]]n noblewoman, [[Europa (mythology)|Europa]], who was courted by [[Zeus]] and became the queen of [[Crete]], though the name did not become widely used until the mid-20th century.<ref name="marazzini"/>

It has a smooth and bright surface,<ref>{{cite web|url=https://solarsystem.nasa.gov/planets/europa/indepth|title=Europa: In Depth|last=Hefler|first=Michael|date=2001|publisher=[[NASA]], Jet Propulsion Laboratory|access-date=9 August 2007|work=NASA, Solar system Exploration|url-status=live|archive-url=https://web.archive.org/web/20151114055431/https://solarsystem.nasa.gov/planets/europa/indepth|archive-date=14 November 2015}}</ref> with a layer of water surrounding the mantle of the planet, thought to be 100 kilometers thick.<ref>{{Cite book |last1=Schenk |first1=Paul M. |url=https://lasp.colorado.edu/mop/files/2015/08/jupiter_ch18-1.pdf |title=Jupiter: the planet, satellites, and magnetosphere |last2=Chapman |first2=Clark R. |last3=Zahnle |first3=Kevin |last4=Moore |first4=Jeffrey M. |date=2004 |publisher=[[Cambridge University Press]] |isbn=978-0-521-81808-7 |editor-last=Bagenal |editor-first=Fran |series=Cambridge planetary science |location=Cambridge, UK; New York |chapter=Ages and Interiors: the Cratering Record of the Galilean Satellites |bibcode=2004jpsm.book..427S |editor-last2=Dowling |editor-first2=Timothy E. |editor-last3=McKinnon |editor-first3=William B.}}</ref> The smooth surface includes a layer of ice, while the bottom of the ice is theorized to be liquid water.<ref name="EuropaAlbedo">{{cite web|url=https://www.solarviews.com/eng/europa.htm|author=Hamilton, C. J.|title=Jupiter's Moon Europa|url-status=live|archive-url=https://web.archive.org/web/20120124013342/https://www.solarviews.com/eng/europa.htm|archive-date=2012-01-24}}</ref> The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, which could conceivably serve as an abode for [[extraterrestrial life]].<ref>{{cite web|url=https://people.msoe.edu/~tritt/sf/europa.life.html |title=Possibility of Life on Europa |last=Tritt |first=Charles S. |access-date=10 August 2007 |publisher=Milwaukee School of Engineering |date=2002 |url-status=dead |archive-url=https://web.archive.org/web/20070609150109/https://people.msoe.edu/~tritt/sf/europa.life.html |archive-date=9 June 2007 }}</ref> Heat energy from [[tidal flexing]] ensures that the ocean remains liquid and drives geological activity.<ref name=geology>{{cite web| url=https://geology.asu.edu/~glg_intro/planetary/p8.htm |title=Tidal Heating|access-date=2007-10-20|work=geology.asu.edu |archive-url = https://web.archive.org/web/20060329000051/https://geology.asu.edu/~glg_intro/planetary/p8.htm |archive-date = 2006-03-29}}</ref> Life may exist in Europa's under-ice ocean. So far, there is no evidence that life exists on Europa, but the likely presence of liquid water has spurred calls to send a probe there.<ref>{{cite web|last=Phillips|first=Cynthia|author-link=Cynthia B. Phillips|url=https://www.space.com/2954-time-europa.html|title=Time for Europa|publisher=Space.com|date=28 September 2006|access-date=5 January 2014|url-status=live|archive-url=https://web.archive.org/web/20111211091904/https://www.space.com/2954-time-europa.html|archive-date=11 December 2011}}</ref>

[[File:Hubble sees recurring plume erupting from Europa.jpg|thumb|Recurring plume erupting from Europa.<ref>{{cite web|title=Hubble sees recurring plume erupting from Europa|url=https://www.spacetelescope.org/images/opo1717a/|website=www.spacetelescope.org|access-date=24 April 2017|url-status=live|archive-url=https://web.archive.org/web/20170425031144/https://www.spacetelescope.org/images/opo1717a/|archive-date=25 April 2017}}</ref>]]

The prominent markings that criss-cross the moon seem to be mainly [[albedo feature]]s, which emphasize low topography. There are few [[Impact crater|craters]] on Europa because its surface is tectonically active and young.<ref>{{cite journal |doi=10.1006/icar.1998.5986 |title=Tectonic Processes on Europa: Tidal Stresses, Mechanical Response, and Visible Features |journal=Icarus |volume=135 |issue=1 |pages=64–78 |year=1998 |last1=Greenberg |first1=Richard |last2=Geissler |first2=Paul |last3=Hoppa |first3=Gregory |last4=Tufts |first4=B.Randall |last5=Durda |first5=Daniel D. |last6=Pappalardo |first6=Robert |last7=Head |first7=James W. |last8=Greeley |first8=Ronald |last9=Sullivan |first9=Robert |last10=Carr |first10=Michael H. |bibcode=1998Icar..135...64G |s2cid=7444898 |url=https://pdfs.semanticscholar.org/fad2/aceb725eec9e700ac791063633c99796d903.pdf |archive-url=https://web.archive.org/web/20200412144704/https://pdfs.semanticscholar.org/fad2/aceb725eec9e700ac791063633c99796d903.pdf |url-status=dead |archive-date=2020-04-12 }}</ref> Some theories suggest that Jupiter's gravity is causing these markings, as one side of Europa is constantly facing Jupiter. Volcanic water eruptions splitting the surface of Europa and even geysers have also been considered as causes. The reddish-brown color of the markings is theorized to be caused by sulfur, but because no data collection devices have been sent to Europa, scientists cannot yet confirm this.<ref>{{cite journal|title=Distribution of hydrate on Europa: Further evidence for sulfuric acid hydrate|doi=10.1016/j.icarus.2005.03.026|first1=R.W.|last1=Carlson|author2=M.S. Anderson |date=2005|bibcode=2005Icar..177..461C|volume=177|issue=2|journal=Icarus|pages=461–471}}</ref> Europa is primarily made of [[silicate]] rock and likely has an [[iron]] core. It has a tenuous atmosphere composed primarily of [[oxygen]].<ref>{{Cite web|url=https://phys.org/news/2015-06-moons-jupiter.html|title=The moons of Jupiter|access-date=2020-02-26|archive-date=2020-02-26|archive-url=https://web.archive.org/web/20200226071614/https://phys.org/news/2015-06-moons-jupiter.html|url-status=live}}</ref>