ASTRO-110 Lecture Notes - Lecture 15: Valles Marineris, Discovery Rupes, Tidal Locking
Document Summary
Mercury, like the moon, is too small for an atmosphere and has an ancient surface. Unlike the moon, it has a big iron core innermost of the terrestrial worlds. A tall cliff named discovery rupes: probably formed by extreme tectonic forces during the rapid cooling of the planet. Mercury shrunk very rapidly during heat loss. Sphere equations: volume: (4/3)(pi)(r^3, surface area: (4)(pi)(r^2) Relatively large planets have large volume but small surface area. Small planets lose heat quickly large surface area for small volume: mercury lost heat quickly and shrunk and since it is small, no atmosphere. Mercury"s orbit is rather eccentric (e=0. 206, the moon"s is 0. 055). This made it more difficult for mercury to become tidally locked to the sun instead mercury developed a 3-2 resonance (spin-orbit coupling). 3 times for every 2 times it revolves around the sun. Orbital resonance works almost as well as tidal locking (at minimalizing tidal surface motion)
