A few days ago NASA announced that the largest moon in the solar system, Jupiter’s Ganymede, contains a huge, subsurface and saltwater ocean. Ganymede is larger even than the planet Mercury: an global ocean there could potentially be gargantuan.
This conclusion was reached thanks to new data on the moon from the Hubble Space Telescope.
This is utterly remarkable. There are now three places (Europa, Enceladus and Ganymede) with known oceans of liquid water other than Earth.
We’re starting to get a feel for how common liquid water is - it seems to be much more common than previously assumed.
If liquid water is fundamentally what it takes for life to begin than perhaps life is also much more common than we realize.