Mimas looks identical to the Death Star in photographs, and its heat signature from the Cassini orbiter glows in the shape of Pac-Man. This episode explores Saturn's innermost major moon, the smallest known body rounded by its own gravity at about 396 kilometers across, with a surface area smaller than Spain and a density of just 1.15 grams per cubic centimeter. The conversation examines the 139-kilometer Herschel crater that spans a third of the moon's diameter, why ice at 64 Kelvin behaves like granite and let Mimas survive an impact that should have shattered it, and how William Herschel first spotted the moon in 1789 with his 40-foot telescope.

The episode then unpacks the physics of orbital resonance that lets this tiny moon carve the 4,800-kilometer Cassini Division out of Saturn's rings, along with its 3:1, 7:6, and 2:1 resonances wi ...