Natural Satellites
Ganymede (moon)
Ganymede is the largest moon in the Solar System and a satellite of Jupiter, notable for being the only moon with an intrinsic magnetic field. Observations from Voyager, Galileo, Hubble, Juno, and the James Webb Space Telescope indicate a differentiated interior, a subsurface ocean, and a tenuous atmosphere with oxygen, water vapor, and carbon dioxide.
Triton (moon)
Triton is the largest moon of Neptune and the only large satellite in the Solar System with a retrograde orbit, indicating capture rather than in‑situ formation. Discovered on October 10, 1846 by William Lassell, Triton is an icy world with a thin nitrogen atmosphere, active geysers observed by Voyager 2 in 1989, and surface terrains suggesting ongoing cryovolcanic and tectonic processes.