This was just released on January 2, 2009 and has been mentioned in another thread here already but I thought it worth a mention in this section as well...........

From ScienceDaily.com
QUOTE
Abundant tiny particles of diamond dust exist in sediments dating to 12,900 years ago at six North American sites, adding strong evidence for Earth's impact with a rare swarm of carbon-and-water-rich comets or carbonaceous chondrites, reports a nine-member scientific team.


Also of note........this may be proven to be the climate change factor that killed over 35 large mamal species and the Clovis native americans around 12,900 years ago and could have changed the weather globally for over a mellium!

For the full story check the ScienceDaily.com website