NASA considered the possibility of establishing a base on one of these objects in its Human Outer Planet Exploration project.
A specific group of these objects was used by Giovanni Cassini to create ephemeris tables to help sailors determine longitude. Ole Rømer demonstrated that light has a finite speed by observing one of these objects. The innermost group of these objects is the Amalthea group, and the Himalia group is the outermost group of these objects orbiting in prograde. NASA considered the possibility of establishing a base on one of these objects in its Human Outer Planet Exploration project. The four largest of these objects are named for Galileo. For 10 points, name these objects that include Io, Europa, and Ganymede, a group of satellites that orbit a planet with a Great Red Spot
A specific group of these objects was used by Giovanni Cassini to create ephemeris tables to help sailors determine longitude.
moons of Jupiter [accept Galilean moons or Cosmica Sidera or Medicea Sidera before "Amalthea"; prompt on "moons"]