Editing Europa (moon) (section)

==== Lineae ====
{{See also|List of lineae on Europa}}
[[File:Europa - PJ45-1.png|alt=|thumb|300x300px|True color mosaic of Europa's numerous [[lineae]]. The region of lineae at the center of this image is the [[List of geological features on Europa#Regiones|Annwn Regio]].<ref>{{cite web | url=https://planetarynames.wr.usgs.gov/Feature/14291 | title=Planetary Names }}</ref><ref>{{cite web|url=https://asc-planetarynames-data.s3.us-west-2.amazonaws.com/europa_15m_100ppi.pdf|title=Europa Nomenclature|website=asc-planetarynames|access-date=25 February 2024}}</ref> ]]
Europa's most striking surface features are a series of dark streaks crisscrossing the entire globe, called [[lineae]] ({{langx|en|lines}}). Close examination shows that the edges of Europa's crust on either side of the cracks have moved relative to each other. The larger bands are more than {{Convert|20|km|mi|0|abbr=on}} across, often with dark, diffuse outer edges, regular striations, and a central band of lighter material.<ref name="Geissler1998">{{cite journal |last1=Geissler |first1=P.E. |last2=Greenberg |first2=R. |last3=Hoppa |first3=G. |last4=McEwen |first4=A. |last5=Tufts |first5=R. |last6=Phillips |first6=C. |author6-link=Cynthia B. Phillips|last7=Clark |first7=B. |last8=Ockert-Bell |first8=M. |last9=Helfenstein |first9=P. |last10=Burns |first10=J. |last11=Veverka |first11=J. |last12=Sullivan |first12=R. |last13=Greeley |first13=R. |last14=Pappalardo |first14=R.T. |last15=Head |first15=J.W. |last16=Belton |first16=M.J.S. |last17=Denk |first17=T. |s2cid=15375333 |title=Evolution of Lineaments on Europa: Clues from Galileo Multispectral Imaging Observations |journal=Icarus |date=September 1998 |volume=135 |issue=1 |pages=107–126 |doi=10.1006/icar.1998.5980 |bibcode=1998Icar..135..107G |doi-access=free }}</ref>

The most likely hypothesis is that the lineae on Europa were produced by a series of eruptions of warm ice as Europa's crust slowly spreads open to expose warmer layers beneath.<ref name="Figueredo2003">{{cite journal |last1=Figueredo |first1=Patricio H. |last2=Greeley |first2=Ronald |title=Resurfacing history of Europa from pole-to-pole geological mapping |journal=Icarus |date=February 2004 |volume=167 |issue=2 |pages=287–312 |doi=10.1016/j.icarus.2003.09.016 |bibcode=2004Icar..167..287F }}</ref> The effect would have been similar to that seen on Earth's [[oceanic ridge]]s. These various fractures are thought to have been caused in large part by the tidal flexing exerted by Jupiter. Because Europa is tidally locked to Jupiter, and therefore always maintains approximately the same orientation towards Jupiter, the stress patterns should form a distinctive and predictable pattern. However, only the youngest of Europa's fractures conform to the predicted pattern; other fractures appear to occur at increasingly different orientations the older they are. This could be explained if Europa's surface rotates slightly faster than its interior, an effect that is possible due to the subsurface ocean mechanically decoupling Europa's surface from its rocky mantle and the effects of Jupiter's gravity tugging on Europa's outer ice crust.<ref name="Hurford2006">{{cite journal |last1=Hurford |first1=T.A. |last2=Sarid |first2=A.R. |last3=Greenberg |first3=R. |title=Cycloidal cracks on Europa: Improved modeling and non-synchronous rotation implications |journal=Icarus |date=January 2007 |volume=186 |issue=1 |pages=218–233 |doi=10.1016/j.icarus.2006.08.026 |bibcode=2007Icar..186..218H }}</ref> Comparisons of ''[[Voyager program|Voyager]]'' and ''Galileo'' spacecraft photos serve to put an upper limit on this hypothetical slippage. A full revolution of the outer rigid shell relative to the interior of Europa takes at least 12,000 years.<ref name="Kattenhorn1">{{cite journal |last=Kattenhorn |first=Simon A. |title=Nonsynchronous Rotation Evidence and Fracture History in the Bright Plains Region, Europa |journal=Icarus |volume=157 |issue=2 |pages=490–506 |date=2002 |doi=10.1006/icar.2002.6825 |bibcode=2002Icar..157..490K }}</ref> Studies of ''Voyager'' and ''Galileo'' images have revealed evidence of [[subduction]] on Europa's surface, suggesting that, just as the cracks are analogous to ocean ridges,<ref name="Schenk1989">{{cite journal |last1=Schenk |first1=Paul M. |last2=McKinnon |first2=William B. |title=Fault offsets and lateral crustal movement on Europa: Evidence for a mobile ice shell |journal=Icarus |date=May 1989 |volume=79 |issue=1 |pages=75–100 |doi=10.1016/0019-1035(89)90109-7 |bibcode=1989Icar...79...75S }}</ref><ref name="Katternhorn2">{{cite journal |last1=Kattenhorn |first1=Simon A. |last2=Prockter |first2=Louise M. |title=Evidence for subduction in the ice shell of Europa |journal=Nature Geoscience |date=7 September 2014 |volume=7 |issue=10 |pages=762–767 |doi=10.1038/ngeo2245 |bibcode=2014NatGe...7..762K }}</ref> so plates of icy crust analogous to [[tectonic plate]]s on Earth are recycled into the molten interior. This evidence of both crustal spreading at bands<ref name="Schenk1989" /> and convergence at other sites<ref name="Katternhorn2" /> suggests that Europa may have active [[plate tectonics]], similar to Earth.<ref name="NASA-20140908" /> However, the physics driving these plate tectonics are not likely to resemble those driving terrestrial plate tectonics, as the forces resisting potential Earth-like plate motions in Europa's crust are significantly stronger than the forces that could drive them.<ref>{{cite journal |last1=Howell |first1=Samuel M. |last2=Pappalardo |first2=Robert T. |title=Can Earth-like plate tectonics occur in ocean world ice shells? |journal=Icarus |date=1 April 2019 |volume=322 |pages=69–79 |doi=10.1016/j.icarus.2019.01.011 |bibcode=2019Icar..322...69H |s2cid=127545679 }}</ref>