What would the Cretaceous Impactor have looked like from the ground?
The object would have entered the atmosphere over 100 miles up, and in 5
seconds or so impacted the ground. A 2-mile across asteroid would have had a
bare angular diameter at a viewing distance 100 miles from the impact site of
twice the diameter of the Full Moon at contact with the atmosphere. The
fireball, however, would have been much larger than this, and by the time it
impacted, it would have filled 1/2 of the sky at this distance. Sound travels
at about 800 feet/sec, and the supersonic shock wave from the impact would
have taken about 10 minutes to reach you. It would look like a solid wall of
high temperature gas and rock mixed together into an incinerating 2000- 5000
degree wall of flames. The brightness of this impactor would have been
amazing. At contact with the atmosphere, its > 2000 degree heated disk would
have been larger than the Sun, which means at the surface you would be bathed
by light from a new, moving mini-Sun many times the apparent brightness of the
Sun itself. Just before impact, the > 5000 degree coma would subtend most of
the sky with a luminosity millions of times greater than the Sun itself! Even
the word 'blinding' fails to describe what you would have seen! These are my
best back of the envelope estimates.
The above artist rendition is by Don Davis, and can be found at the Asteroid Impacts and Hazards site at NASA/JPL.
Copyright 1997 Dr. Sten Odenwald
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