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Bolides and crater diameters



Eugene Shoemaker describes a formula for calculating the
relationships between a bolide's kinetic energy and what
the associated crater diameter would be if it should hit
mother Earth.

The calculations are slightly involved so I will only summarize
how his model works. Get the article if you want to try this
at home ;-)

D = C Kn W

where   D=crater diameter in km

        C=collapse factor(1 for craters <=3km and 1.3 for those >=4km
        Kn=(0.074 km kilotons)^-1/3.4
        W = the kinetic energy of the incoming body...

The constant (Kn) was derived using empirical data from the Jangle U 
nuclear test site in Yucca Flat, Nevada. 

I did a few simulations using this formula. The first three
cases assume a bolide with a density of 3grams/cc hits Earth.

CASE 1  bolide diameter = 10km
        bolide velocity = 20km/sec
        resultant crater= 136km diameter

CASE 2  Same bolide at twice the velocity(40 km/sec)
        resultant crater= 205km diameter

Note: You can see why 10km is a convenient estimate for the size of
      the bolide that resulted in the Chicxulub(180km) structure.

CASE 3  What if fragment "G" of SL9 which recently hit Jupiter
        were to hit the Earth instead?
        resultant crater= 60km diameter

CASE 4  "Reverse engineer" the Barringer Crater(Meteor Crater, AZ).
        Since we have evidence for an iron/nickel body, let's assume
        the density to be 10g/cc. The original bolide would then have 
        a diameter of 40meters.
        
-Paul
---
References:

Asteroid and Comet Bombardment of the Earth,
Eugene M. Shoemaker, Ann. Rev. Earth Planet Sci., 1983,41.