Astronomy 23/223 Homework:

Meteorites

1. What information should you collect if you see a meteorite fall?
 
2. What should you do if you find a rock that appears to be a meteorite? How will you convince your listeners that this really is a meteorite? (I.e., how do you tell a meteorite from a "meteorwrong"?)
 
   
3. Artifacts from the iron age that are preserved in museums have been identified as having been made from iron in meteorites. How can we tell?
 
   
4. Examine the data in this table...
 
  Notice how the relative abundances of stones vs. irons is different between falls and finds. Which set of numbers do you think represents the true abundance of irons vs. stones out in space? Which set do you expect is closer to abundances seen in Antarctic meteorites?
   
5. By analogy with high explosive and nuclear craters, the size of a crater may be estimated on the basis of Lampson's Relation:
 
 
  where D and D0 are the diameters of two different craters (assuming a hemispherical force) and W and W0 are the explosive yield (equivalent to the kinetic energy of the projectile) in kilatons. The 300 m Sedan crater in Nevada was the product of a 100 kilaton nuclear explosion. What explosive charge would have been necessary to produce Meteor Crater with a diameter of 1 km? (Note that before we had data on nuclear explosions, this calculation as not possible!)

More complicated models exist for making this estimate, considering such things as planetary gravity, the geometry of the crater, strength of the materials, the mass/velocity relationships of the projectile, and depth of burial of the explosion. Of these, the most important is probably depth of burial. There are (at least) four published estimates of the yield (energy) for Sedan crater:

1960 Shoemaker 1.7 megatons

1963 Baldwin 8.1 megatons

1978 Bryan et al. 4.5 megatons

1980 Schmidt 10-60 megatons



The depths of projectiles for these four studies, in units of projectile diameter, were 0 (at the surface); O.9; 2-3; and 4-5. Which depth matches which study?

   

 

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