Meteors and Meteorites

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Meteors and Meteorites
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Meteoroids - still in space
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Shooting Stars

• Size of a pea
• velocities of 10s km/sec
• 6/hour sporadic rate (any night)

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Bolides or fireballs
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Sometimes seen in daytime
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Sometimes break up
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Meteor train can persist
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If hit meteorites
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Meteor showers occur when we cross paths of a
broken up comet
Here the Persieds named
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named for constellation containing the radiant
point
Leonids shown here or plotted
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plotted back to radiant in Leo
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Caused by perspective the artists vanishing
point
Driving in snow
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Major showers
Handout
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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?

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Meteors better after midnight
But
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Meteorites types
Carbonaceous
Iron-nickel
Iron
Stony
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Iron most commonly found but more stony
meteorites more common!
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Widmanstatten patterns
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Stony meteorites 93 of all meteorites
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Show chondrules (round stones) when cut and
polished
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Stony-irons show a mix
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Carbonaceous chondrites

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

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Model to explain the variety
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Barringer crater in Arizona
1.2 km diameter, 25,000 years ago, 11 km/s 20
Mton bomb
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Drilling found the rock
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41-mile diameter crater in Quebec
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Tunguska
Heard for 1000 km. Small comet? What if
had happened 60 70 years later?
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Walter and Luis Alvarez found iridium clay layer
at Cretacous-Tertiary boundary (65My ago)
Traced impact to
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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?

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Thats all. Have a nice day!