1. Comets, Meteors, and Asteroids

2. Structure of a Comet
Ion Tail
Dust Tail
Coma
To Sun

3. Comet Structure Nucleus Coma Tail 10 km “Dirty Snowball”
Cloud of evaporated ices and ions
may be 100,000 km in diameter
Tail
Always points away from Sun
Solar Wind and Radiation Pressure

4. The Oort Cloud In 1950 Jan Oort noticed that
no comet has been observed with an orbit that indicates that it came from interstellar space,
there is a strong tendency for aphelia of long period comet orbits to lie at a distance of about 50,000 AU, and
there is no preferential direction from which comets come.

5. The Oort Cloud

6. Comet Halley

7. Bayeaux Tapestry Norman Invasion of 1066

8. 164 BCE, Babylon

9. Comet Nucleus

10. Comet of 1577

11. Hale-Bopp

12. Comet West

13. The Cause of Meteor Showers
P55/Tempel-Tuttle

14. Why After Midnight is Best
Orbital Velocity
Rotational Velocity

15. The 1833 storm

16. The 1966 storm

17. 1997 Leonids from Orbit

18. Two Showers for Halley

19. Carbonaceous Chondrite
Sporadic Meteors
Irons
Stony-Irons
Chondrites
Carbonaceous Chondrite
Achondrite

20. Barringer’s Crater
An iron meteorite 100 feet across and 70,000 tons slamed into the Earth at about 43,000mph in the Arizona desert near Flagstaff 40,000 years ago. Barringer Crater is 4,100 feet wide and 571 feet deep.

21. Other Impact Craters

22. Tunguska, 1908

23. How Much Damage?

24. Asteroids
Apollo
Trojans

25. Ida - Dactyl

26. Gaspra

27. Asteroids Elsewhere

29. Asteroid: A relatively small, inactive body, composed of rock, carbon or metal, which is orbiting the Sun.
Comet: A relatively small, sometimes active object, which is composed of dirt and ices. Comets are characterised by dust and gas tails when in proximity to the Sun. Far from the Sun it is difficult to distinguish an asteroid from a comet.
Meteoroid: A small particle from an asteroid or comet orbiting he Sun.
Meteor: A meteoroid that is observed as it burns up in the Earth's atmosphere - a shooting star.
Meteorite: A meteoroid that survives its passage through the Earth's atmosphere and impacts the Earth's surface.