Our Solar System is so much more than just the eight planets that inhabit it.  One of the things I learned a bit later in my career as an astronomer (my teenage years; been doing this for awhile) is how unique and diverse the natural satellites are.  Our own moon seems somewhat tame, and it’s easy to think the same of all moons.  Many of them are boring quiescent rocks with little more scientific value than asteroids, but the largest hide deep and profound secrets that we are just starting to unlock.  Four moons in our solar system are larger...