Callisto Crater Chains.
I wanted to depict the impact of a Shoemaker-Levy 9 like comet on the
Jovian moon Callisto. A long standing mystery from the first flyby of
the Voyager spacecraft in the late 1970's was the discovery of crater
chains, called ``Catena'' on Callisto and Ganymede. Crater chains
found elsewhere were found to be secondary impacts from a large impact
structure and tended to point back to the source crater, but that was
not found to be the case on Callisto. Finally, in March 1993, Carolyn
Shoemaker along with her husband Gene and David Levy discovered their
now famous comet which was quickly confirmed to be a string of over 20
individual nuclei that resulted from the tidal breakup of the progenitor
body and which impacted on Jupiter in July 1994. After working on and
thinking about the problem without a satisfactory answer since the Voyager
days, Paul Schenk of the Johnson Spaceflight Center in Houston figured he
might never find an answer to these mysteries. Shortly after their
discovery, the S-L 9 images reminded Jay Melosh of the Lunar and Planetary
Laboratory in Tucson Arizona of the Callisto crater chains and a
discussion I had with him one afternoon in April 1993 got the ball
rolling on the answer. Melosh designed a tidal breakup model which he
used in collaboration with Paul Schenk to describe the crater chains on
Ganymede and Callisto. Melosh and I collaborated on applying the model
to the observations of S-L 9 that I had made which resulted in a direct
measurement of the size of the original object which broke up to form
the doomed comet. We found that the object must have been only 2 kilometers
in diameter. Later work by Eric Asphaug and Willy Benz and others have
confirmed the size estimate and filled in more details.
This painting was started in December, 1995 and completed on March 31, 1996
and is a 24 by 24 inch acrylic on foam board. It is intended to be viewed
either as shown here or rotated clockwise 45 degrees from this view.
Last update: May 7, 2003