Hi -
The dust veil that caused a climate collapse at 536 CE was known. The debate was whether it was caused by volcanic eruption, which was argued by David Keys, or by Comet Encke's debris stream hitting the Earth's atmosphere, which was argued by Mike Baillie.
That debate just got settled:
http://www.newscientist.com/article/mg2 ... nline-news
The impacts themselves which were associated with this interception were minor and appear to have occurred about 50 years later, and the dust did not come from them, but rather from the debris stream of fine particles.
E.P. Grondine
Man and Impact in the Americas
What finished the Hopewell Hopewell
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