Asteroids, Meteors and Comets - PowerPoint PPT Presentation

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Asteroids, Meteors and Comets

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  1. Asteroids, Meteors and Comets

  2. Definitions: Meteor: A solid body heated to incandescence by its passage through the Earth’s atmosphere. Meteoroid: The same solid body in space, before reaching the Earth. Meteorite: Parts of the solid body that actually reach the ground. Asteroid: A small, generally rocky body that orbits the Sun. Comet: A small body in orbit around the Sun, consisting of a tiny icy core and tail of gas and dust.

  3. Largest Asteroids:

  4. Types of Asteroids: • C-type, includes more than 75% of known asteroids: extremely dark (albedo 0.03); similar approximately the same chemical composition as the Sun minus hydrogen, helium and other volatiles; • S-type, 17%: relatively bright (albedo .10-.22); metallic nickel-iron mixed with iron- and magnesium-silicates; • M-type, most of the rest: bright (albedo .10-.18); pure nickel-iron. • There are also a dozen or so other rare types.

  5. Location of the Asteroids: • Main Belt: located between Mars and Jupiter roughly 2 - 4 AU from the Sun; • Near-Earth Asteroids (NEAs): ones that closely approach the Earth • Atens: semimajor axes less than 1.0 AU and aphelion distances greater than 0.983 AU; • Apollos: semimajor axes greater than 1.0 AU and perihelion distances less than 1.017 AU • Amors: perihelion distances between 1.017 and 1.3 AU; • Trojans: located near Jupiter's Lagrange points (60 degrees ahead and behind Jupiter in its orbit).

  6. Asteroid-like Satellites:

  7. Ida and Dactyl

  8. Comets:

  9. The Oort Cloud:

  10. Kuiper Belt Objects:

  11. The Structure of a Comet:

  12. Hale-Bopp

  13. Comet’s Orbit:

  14. Meteor Crater

  15. Meteor Crater from above

  16. Meteor Impacts Impact Diameter Yield Interval Consequences (in meters) (in megatons) (x 1000 years) ----------------------------------------------------------------------------------------------------------------------------------------- <500 <10 <1 meteors in upper atmosphere most don't reach surface 750 10-100 1,000 irons make craters like Meteor Crater; stones produce airbursts like Tunguska; land impacts destroy area size of city 1600 100-1,000 5,000 irons, stones hit ground; comets produce airbursts; land impacts destroy area size of large urban area (New York, Tokyo) 3500 1,000-10,000 15,000 land impacts destroy area size of small state; ocean impact produces mild tsunamis 7000 10,000-100,000 63,000 land impacts destroy area size of moderate state (Virginia) ocean impact makes big tsunamis 17000 100,000-1,000,000 250,000 land impact raises dust with global implication; destroys area size of large state (California, France)

  17. Yucatan Peninsula