ASTRON 10 Lecture Notes - Lecture 12: Apollo 15, Late Heavy Bombardment, Continental Drift
Document Summary
Crust is the first thing to form. Crust thickens through time, but below is still molten, leading to cracks and holes in the crust. As size of a planet increases, the insulation for a planet"s warmth in its core increases. Mercury receives tidal forces from the sun, venus. Moon has light, cratered areas and dark smooth areas. Initial impact causes explosion, the ejection at high speed of some rocks, shock waves. Followed by seismic waves, the falling of the rocks (ejecta) and the creation of small, neighboring craters. Newest craters have white rays around them. Glass spheres reflect light in the direction from which it came. As time passes, these spheres become disrupted by solar wind particles and micrometeorite impact, removing their reflective properties - why old craters don"t have rays around them. Crater walls have terraces, the center can have a central peak. Central peaks are made of target material, which is unmelted.
