Ganymede: Ganymede is both the largest moon of Jupiter, our Solar System's planetary behemoth, as well as the largest moon in our entire Solar system. Observations of Ganymede by the HST in 2015 suggested the existence of a subsurface saline ocean. This is because patterns in auroral belts and rocking of the magnetic field hinted at the presence of an ocean. It is estimated to be approximately 100 kilometers deep with a surface situated below a crust of 150 kilometers.
It makes sense, then, that the most potent example of astrological synastry (harmony between two birth charts) involves contact between one person's Sun and the other person's Moon, or contact between the two Moons. Carl Jung, the renowned Swiss Psychologist, famously conducted a 'marriage experiment' in which he studied the birth charts of over 500 couples. What he found was an unmistakable trend of Sun-Moon contact between partners. To most astrologers, this came as no surprise-it has long been understood that when one person's Moon hits another person's chart in a significant way, there exists a strong possibility of lasting and meaningful romance.
Despite this oddball moon's many exotic attributes, it actually sports one of the most Earth-like surfaces in our Solar System. Titan may also experience volcanic activity, but its volcanoes would erupt with different ingredients than the molten-rock lava that shoots out from the volcanoes of Earth. In dramatic contrast to what occurs on our own planet, Titan's volcanoes erupt icy water "lava" (cryovolcanism). Titan's entire alien surface has been sculpted by gushing methane and ethane, which carves river channels, and fills its enormous great lakes with liquid natural gas.