Cratered Worlds: The Moon and Mercury (Astronomy)

Recall cards studying the Moon and Mercury, the airless, heavily cratered worlds closest to home. The Moon's bulk properties: its diameter, mass, surface gravity, escape velocity, low density, and synchronous rotation, and why it holds no atmosphere. Its two terrains: the dark basaltic maria that flooded impact basins, the bright, ancient, heavily cratered highlands of anorthosite, the regolith, and its extreme day and night temperatures. The physics of impact cratering: impact speeds, the nuclear-scale blast, crater and ejecta sizes, bright rays, secondary craters, and how often craters of a given size form. The competing ideas for the Moon's origin, from the fission, sister, and capture hypotheses to the leading giant impact hypothesis. And Mercury: its eccentric orbit, huge iron core, 3-to-2 spin-orbit resonance, temperature extremes, shrinkage scarps, the Caloris basin, polar ice, and the Mariner 10 and MESSENGER missions that mapped it.