1. Four Basic Geological Processes Impact cratering –Impacts by asteroids or comets Volcanism –Eruption of molten rock onto surface Tectonics –Disruption of a planet’s surface by internal stresses Erosion –Surface changes made by wind, water, or ice

3. Impact Cratering High kinetic energy of impacting object  Excavation  Heat Shape round for all impact directions

4. Crater Morphology: Impactor in the inner solar system can have 10s of km/sec relative velocity May vaporize or liquefy a significant amount of the target for a large impactor “Simple” craters are bowl shaped “Complex” craters are flatter, and have a central uplift or peak

5. Meteor Crater (Arizona) Tycho (Moon) Impact Craters

6. The Impact Process 1.Detonation - shockwave propagates through target, projectile vaporized 2.Excavation - target is heated, vaporized, liquified, solid material is ejected (possibly above escape velocity!) 3.Rebound - in larger craters, the target may “bounce back” viscously, forming a central uplift 4.Relaxation - crater walls subside, melt pools in the crater

7. Few Hundred Confirmed Craters on Earth

8. Meteor Crater

11. Manicouigan Crater

12. Moon Near Side

13. Moon Far Side

14. Lunar Highlands

15. Mare Imbrium Lunar Mare

16. Crater modification

17. Mars Rampart Crater 3

18. Venus Craters 1

19. Ganymede Crater Chain

20. Shoemaker-Levy 9

21. SL-9 Aftermath

22. Hyperion

23. Mercury - lots of craters, little volcanism Venus completely re-surfaced by volcanism ~600 MY ago Earth - heavily re-worked surface Moon - volcanism stopped 3.2 BYago Lots of craters Mars - some volcanism, south heavily cratered Terrestrial Planets

24. Processes that HEAT planets