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Impact

Impact. The Solar System. Nine Eight Planets Over 170,000 catalogued asteroids ???? Centaurs ???? KBO’s (including one disgruntled ex-planet) Millions of Comets. Impact Mechanics. Energy of motion turns into heat 10-m rock at 20 km/sec = 150 kt = 10 Hiroshima atomic bombs

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Impact

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  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)

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