Craters
Crater formation vg 67
- a) 10 km body traveling 30 km/s
- typical orbital speed near earth
- implies kinetic energy of 200 Million Megatons of TNT
- enormous energy (Oklahoma City bomb 1 ton TNT)
- b) surface rock: compressed, shocked, melted
- c) subterranean explosion
- excavates circular, 100 km crater
- ejects debris (radial rays)
- d) compressed rock rebounds
Crater density => surface age Fig. 7
- Apollo/Luna missions returned Moon rocks
- radioactive dating determined age
- similar curve expected to elsewhere (Mercury, Galilean satellites, etc.)