re: "That's a moon!"
Right up until the Voyager 1 and 2 flybys in 1979, when Amalthea was first imaged up close, there was semi-serious speculation that it was a giant alien spaceship, much as was once thought of regarding Mars's larger moon, Phobos.
Of course it COULD be a hollowed-out planetoid interstellar space ark that got stuck in Jovian orbit when the crew tried to replenish their supply of helium-3 for their fusion reactors but died when the giant planet's radiation proved too much for them.
All the more reason to send a lander to Amalthea with a serious drill on it.