1. Meteors and Meteorites

2. “Meteoroids” - still in space…

3. “Shooting Stars” Size of a pea velocities of 10’s km/sec ~ 6/hour sporadic rate (any night)

4. “Bolides” or “fireballs”

5. Sometimes seen in daytime

6. Sometimes break up

7. Meteor “train” can persist

8. If hit: “meteorites”

9. Meteor showers occur when we cross paths of a broken up comet Here the “Persieds” named …

10. … named for constellation containing the radiant point Leonids shown here or plotted…

11. …plotted back to radiant in Leo

12. Caused by perspective – the artist’s “vanishing point” Driving in snow

13. Major showers Handout

14. Leonids spectacular every 33 years Due to lumpiness in distribution of old comet within orbit This woodcut from 1833 – 100,000/hour My first chance – 1966 Most recent 2000-2002-who saw?

15. Meteors better after midnight But…

16. Meteorites: types Carbonaceous Stony Iron-nickel Iron

17. Iron most commonly found but more stony meteorites more common!

18. Widmanstatten patterns

19. Stony meteorites – 93% of all meteorites

20. Show chondrules (round stones) when cut and polished

21. Stony-irons show a mix

22. Carbonaceous chondrites this at right from 1969 Allende’ fall in Mexico Primordial in content Contain volatiles Organics Radioactive nuclei – 26 Al may be from supernova that sparked the formation of our solar system

23. Model to explain the variety

24. Barringer crater in Arizona 1.2 km diameter, 25,000 years ago, 11 km/s = 20 Mton bomb

25. Drilling found the rock

26. 41-mile diameter crater in Quebec

27. Tunguska Heard for 1000 km. Small comet? What if had happened 60 – 70 years later?

28. Walter and Luis Alvarez found iridium clay layer at Cretacous-Tertiary boundary (65My ago) Traced impact to …

29. Chicxulub Impact structure A bad day for dinosaurs Expect such hits every ~ 8 million years May find a kilometer within 10-20 years Need to look for 100-m objects Need a wakeup call?

30. That’s all. Have a nice day!