AST-1002 Lecture 8: Terrestrial Planets
Document Summary
Crater: caused by the impact of an object when it heats and compresses the surface it hits. Material is thrown from the site of impact. Ejected material lands around the crater, forming rays and secondary craters. Rebound of the deformed surface may form a central peak in the crater, while melted rock pools in the crater floor, giving it a flat bottom. Happens kind of randomly-- the half-life is the same everywhere. Measure daughter and parent to get the life. Radioactive dating of samples from apollo missions calibrates the timescale. Seismic waves help probe structure of interior. Earth"s dynamo: rotation, convection, and electric currents generate magnetic fields. Moon, venus, and mars have no magnetic field. Earth"s magnetic field flips about every 300,000 years or so. Hot enough so that at some point, heavy stuff sinks and light stuff rises. Sending out photons (light) and taking away energy. Cores are hot because left overt heat from initial formation (accretion)
