Mimas is a moon of Saturn. Discovered late in the 18th century by the astonishing Sir William Herschel, Mimas is the smallest (known) astronomical body which is spherical from self-gravitation (here is an explanation of what that means). The moon’s most noteworthy feature is an enormous impact crater named Herschel which is 130 kilometres (81 mi) across–about the same as the distance between New York and Philadelphia. Wikipedia gives some additional dimensions of the crater:
Herschel’s diameter is almost a third of [Mimas’] diameter; its walls are approximately 5 kilometres (3.1 mi) high, parts of its floor measure 10 kilometres (6.2 mi) deep, and its central peak rises 6 kilometres (3.7 mi) above the crater floor.
If you were standing in the crater (which you should not do!) it would be a great broken plain surrounded by cliffs thirteen times taller than the Empire State Building. In the middle you could see a huge mountain slightly shorter than the tallest mountain in North America. Jagged craters and valleys as deep as Lake Baikal would lie around you.
A great series of impact cracks on the opposite side of the moon would seem to indicate that the collision which created Herschel nearly shattered Mimas (which is composed principally of ice).
The moon’s name might be of passing interest to followers of my Deities of the Underworld category. In Greek mythology, Mimas was one of the monstrous sons of Gaia. He was born with snakes for legs and he was clad in full armor. In the Aeneid, Virgil tells the story of how Hephaestus imprisoned Mimas under Vesuvius during Gaia’s great rebellion against the Olympian gods. As the imprisoned giant shakes so to does the area around the Bay of Naples.
As I was researching this article, I was struck by how many moons Saturn has! As a special bonus feature, here is an alphabetic list of Saturn’s named moons (several more remain anonymous): Aegaeon, Aegir, Albiorix, Anthe, Atlas, Bebhionn, Bergelmir, Bestla, Calypso, Daphnis, Dione, Enceladus, Epimetheus, Erriapus, Farbauti, Fenrir, Fornjot, Greip, Hati, Helene, Hyperion, Hyrrokkin, Iapetus, Ijiraq, Janus, Jarnsaxa, Kari, Kiviuq, Loge, Methone, Mimas, Mundilfari, Narvi, Paaliaq, Pallene, Pan, Pandora, Phoebe, Polydeuces, Prometheus, Rhea, Siarnaq, Skadi, Skoll, Surtur, Suttung, Tarqeq, Tarvos, Telesto, Tethys, Thrym, Titan and Ymir.