Editing Galilean moons (section)

=== Ganymede ===
{{main|Ganymede (moon)}}
[[File:PIA24682-Ganymede-DarkSide-JupiterMoon-20210607.jpg|thumb|Ancient tectonic features on Ganymede]]
Ganymede (Jupiter III), the third Galilean moon, is named after the mythological [[Ganymede (mythology)|Ganymede]], cupbearer of the [[Greek mythology|Greek gods]] and [[Zeus]]'s beloved.<ref>{{cite web| url = https://galileo.rice.edu/sci/observations/jupiter_satellites.html| title = Satellites of Jupiter| work = The Galileo Project| access-date = 2007-11-24| url-status = live| archive-url = https://web.archive.org/web/20120211140650/https://galileo.rice.edu/sci/observations/jupiter_satellites.html| archive-date = 2012-02-11}}</ref> Ganymede is the [[List of natural satellites by diameter|largest natural satellite]] in the Solar System at 5262.4 kilometers in diameter, which makes it larger than the planet [[Mercury (planet)|Mercury]] – although only at about half of its mass<ref name="nineplanets.org-Ganymede">{{cite web|publisher=nineplanets.org|title=Ganymede|date=October 31, 1997|url=https://www.nineplanets.org/ganymede.html|access-date=2008-02-27|url-status=live|archive-url=https://web.archive.org/web/20120208061056/https://nineplanets.org/ganymede.html|archive-date=February 8, 2012}}</ref> since Ganymede is an icy world. It is the only satellite in the Solar System known to possess a [[magnetosphere]], likely created through [[convection]] within the liquid iron core.<ref>{{cite journal |doi=10.1006/icar.2002.6834 |title=The Permanent and Inductive Magnetic Moments of Ganymede |journal=Icarus |volume=157 |issue=2 |pages=507–22 |year=2002 |last1=Kivelson |first1=M.G. |last2=Khurana |first2=K.K. |last3=Volwerk |first3=M. |bibcode=2002Icar..157..507K |hdl=2060/20020044825 |s2cid=7482644 |url=https://pdfs.semanticscholar.org/7c21/9bca2f2a0e98f1ee870903ef563c8c5d20ca.pdf |archive-url=https://web.archive.org/web/20200412144652/https://pdfs.semanticscholar.org/7c21/9bca2f2a0e98f1ee870903ef563c8c5d20ca.pdf |url-status=dead |archive-date=2020-04-12 |hdl-access=free }}</ref>

Ganymede is composed primarily of [[silicate|silicate rock]] and water ice, and a salt-water ocean is believed to exist nearly 200&nbsp;km below Ganymede's surface, sandwiched between layers of ice.<ref>{{cite web|url=https://www.jpl.nasa.gov/releases/2000/aguganymederoundup.html|title=Solar System's largest moon likely has a hidden ocean|access-date=2008-01-11|date=2000-12-16|work=Jet Propulsion Laboratory|publisher=NASA|url-status=live|archive-url=https://web.archive.org/web/20120117100414/https://www.jpl.nasa.gov/releases/2000/aguganymederoundup.html|archive-date=2012-01-17}}</ref> The metallic core of Ganymede suggests a greater heat at some time in its past than had previously been proposed. The surface is a mix of two types of terrain—highly cratered dark regions and younger, but still ancient, regions with a large array of grooves and ridges. Ganymede has a high number of craters, but many are gone or barely visible due to its icy crust forming over them. The satellite has a thin [[oxygen]] [[atmosphere]] that includes O, O<sub>2</sub>, and possibly O<sub>3</sub> ([[ozone]]), and some [[atomic hydrogen]].<ref>{{cite journal |doi=10.1086/305604 |title=The Far-Ultraviolet Oxygen Airglow of Europa and Ganymede |journal=The Astrophysical Journal |volume=499 |issue=1 |pages=475–481 |year=1998 |last1=Hall |first1=D. T. |last2=Feldman |first2=P. D. |last3=McGrath |first3=M. A. |last4=Strobel |first4=D. F. |bibcode=1998ApJ...499..475H |doi-access= }}</ref><ref>{{cite journal |doi=10.1016/S0032-0633(00)00154-9 |title=The ionosphere of Ganymede |journal=Planetary and Space Science |volume=49 |issue=3–4 |pages=327–36 |year=2001 |last1=Eviatar |first1=Aharon |last2=m. Vasyliūnas |first2=Vytenis |last3=a. Gurnett |first3=Donald |bibcode=2001P&SS...49..327E }}</ref>