Editing Europa (moon) (section)

=====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"/>