1. Impact

2. The Solar System Nine Eight Planets Over 170,000 catalogued asteroids ???? Centaurs ???? KBO’s (including one disgruntled ex- planet) Millions of Comets

3. Impact Mechanics Energy of motion turns into heat 10-m rock at 20 km/sec = 150 kt = 10 Hiroshima atomic bombs Energy released in seconds Impacting object destroyed Crater 20-30 times diameter of impacting object Crater is round regardless of approach path

4. The Impact Process Atmospheric Entry Contact-Compression Penetration – Transient Crater Excavation Collapse

5. Impacts on Earth

6. Small Impacts Make Simple Pit Craters

7. A Simple Lunar Crater - Bessel

8. Recent Impact – Meteor Crater

9. Medium Impacts Create Central- Peak Craters

10. How Central Peaks Form

11. Tycho (93 km) Moon

12. Upheaval Dome, Utah

13. Peak Ring Craters

14. Schrodinger: A Peak-Ring Crater

15. Clearwater Lakes, Quebec

16. Large Impacts Result in Multiple- Ring Basins

17. Mare Orientale, Moon

18. Comets and Planetary History Superposition Crater Saturation Crater Degradation

19. Superposition

20. Crater Saturation

21. Crater Degradation

22. Recognizing Craters on Earth Craters rapidly destroyed by erosion Circular geologic structures Impact melts Impact breccias Shock metamorphism Shatter cones

23. Manicouagan, Quebec

24. Sudbury, An Ancient Impact Site

25. A Shatter Cone

26. Fallback Breccia

27. Mega-Impacts: As Usual, Gary Larson Gets There First

28. Computer Simulations by H.J. Melosh (University of Arizona)