Comet Hit Suspected For 536 AD

["Richard W. Travsky" <rtravsky@uwyo.edu>]

If so, this gives one a little bit more to conjecture with for
whatever happened 65 mya...


http://www.cardiff.ac.uk/news/03-04/040204.html

Scientists at Cardiff University believe they have discovered the cause of
crop failures and summer frosts some 1,500 years ago - a comet colliding
with Earth.

The team in the School of Physics and Astronomy, has been studying
evidence from tree rings, which suggests that the earth underwent a series
of very cold summers around 536 540 AD, indicating an effect rather like a
nuclear winter.

They believe this was caused by a comet hitting the earth and exploding in
the upper atmosphere. The debris from this giant explosion was such that
it enveloped the earth in soot and ash, blocking out the sunlight and
causing the very cold weather. 

This effect is known as a plume and is similar to that which was seen when
comet Shoemaker Levy 9 hit Jupiter in 1995.

Historical references from this period of history - known as the Dark Ages
- are sparse, but what records there are, tell of crop failures and summer
frosts. 
...
The surprising result of the new work is just how small a comet is needed
to cause such dramatic effects. The scientists calculate that a comet not
much more than half a kilometre across could cause a global nuclear winter
effect. This is significantly smaller than was previously thought.

Dr Ward Thompson said: "One of the exciting aspects of this work is that
we have re classified the size of comet that represents a global threat.
This work shows that even a comet of only half a kilometre in size could
have global consequences. Previously nothing less than a kilometre across
was counted as a global threat. If such an event happened again today,
then once again a large fraction of the earth's population could face
starvation."

The comet impact caused crop failures and wide spread starvation among the
sixth century population. The timing coincides with the Justinian Plague,
widely believed to be the first appearance of the Black Death in Europe.
It is possible that the plague was so rampant and took hold so quickly
because the population was already weakened by starvation. 
...