Comet May Have Exploded Over North America 13,000 Years Ago

Aug 15, 2007
Comet May Have Exploded Over North America 13,000 Years Ago
A "black mat" of algal growth in Arizona marks a line of extinction at 12,900 years ago; Clovis points and mammoth skeletons were found at the line but not above it. Credit: Allen West, UCSB

New scientific findings suggest that a large comet may have exploded over North America 12,900 years ago, explaining riddles that scientists have wrestled with for decades, including an abrupt cooling of much of the planet and the extinction of large mammals.

The discovery was made by scientists from the University of California at Santa Barbara and their colleagues. James Kennett, a paleoceanographer at the university, said that the discovery may explain some of the highly debated geologic controversies of recent decades.

The period in question is called the Younger Dryas, an interval of abrupt cooling that lasted for about 1,000 years and occurred at the beginning of an inter-glacial warm period. Evidence for the temperature change is recorded in marine sediments and ice cores.

According to the scientists, the comet before fragmentation must have been about four kilometers across, and either exploded in the atmosphere or had fragments hit the Laurentide ice sheet in the northeastern North America.

Wildfires across the continent would have resulted from the fiery impact, killing off vegetation that was the food supply of many of larger mammals like the woolly mammoths, causing them to go extinct.

Since the Clovis people of North America hunted the mammoths as a major source of their food, they too would have been affected by the impact. Their culture eventually died out.

The scientific team visited more than a dozen archaeological sites in North America, where they found high concentrations of iridium, an element that is rare on Earth, and is almost exclusively associated with extraterrestrial objects such as comets and meteorites.

They also found metallic microspherules in the comet fragments; these microspherules contained nano-diamonds. The comet also carried carbon molecules called fullerenes (buckyballs), with gases trapped inside that indicated an extraterrestrial origin.

The team concluded that the impact of the comet likely destabilized a large portion of the Laurentide ice sheet, causing a high volume of freshwater to flow into the north Atlantic and Arctic Oceans.

"This, in turn, would have caused a major disruption of the ocean's circulation, leading to a cooler atmosphere and the glaciation of the Younger Dryas period," said Kennett. "We found evidence of the impact as far west as the Santa Barbara Channel Islands."

Source: NSF

Explore further: Tree rings denote century-old weather patterns

Related Stories

5 things to watch at next week's Paris Air Show

Jun 12, 2015

Just eight miles from the center of Paris, the normally sleepy aerodrome in Le Bourget will undergo its biennial transformation into the center of the world's $700 billion aerospace and defense industry when ...

World's largest asteroid impact site could be in Australia

Apr 07, 2015

Not long ago, asteroid impacts weren't considered as a significant factor in the evolution of Earth. Following the Late Heavy Bombardment, which pummelled the inner solar system around 3.8 billion to 3.9 billion ye ...

Recommended for you

Satellite sees smoky skies over World Cup soccer

10 hours ago

Soccer fever gripped the U.S. at the same time as the smoke from Canadian wildfires gripped the skies over Vancouver, British Columbia. This was the site of the 2015 FIFA Women's World Cup Finals on July ...

NASA sees Nangka become a typhoon

17 hours ago

Tropical Storm Nangka strengthened to a typhoon in the Northwestern Pacific Ocean just after NASA's Aqua satellite passed overhead on July 6. Infrared data from the AIRS instrument showed very cold cloud ...

NASA's infrared look at strengthening Typhoon Chan-Hom

17 hours ago

During the early morning hours on July 6, Chan-Hom was a strong tropical storm. Infrared data from NASA's Aqua satellite showed very powerful thunderstorms that hinted at intensification, and later in the ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.