A Hubble Space Telescope picture shows a comet breaking apart on April 18, 2006.
Image courtesy NASA, ESA, H. Weaver (APL/JHU), M. Mutchler, and Z. Levay (STScI)
Published April 7, 2010
The comet that created the annual Taurid meteor shower was also responsible for snuffing out large mammals in North America 13,000 years ago, a controversial new study says.
The geologic record shows that global temperatures plummeted by as much as 14 degrees Fahrenheit (8 degrees Celsius) just as Earth was thawing out from the last ice age.
This cold snap probably led to the extinction in North America of large animals such as saber-toothed cats and wooly mammoths. But scientists have been unsure what triggered the abrupt change.
For more than 15 years, astrobiologists Bill Napier and Victor Clube have argued that the culprit was a 30- to 60-mile-wide (50- to 100-kilometer-wide) comet that entered the inner solar system—the region between the sun and the asteroid belt, just past Mars's orbit—20,000 to 30,000 years ago.
In the new study, Napier, of Cardiff University in the U.K., suggests that the huge comet settled into a new, faster orbit around the sun and began to break apart, creating fragments that pummeled Earth about 13,000 years ago.
His model suggests that those pieces might still be visible today as the Taurid complex, a debris cloud that sends tiny meteors streaming through Earth's atmosphere in late October and early November. (See pictures of the Perseid meteor shower.)
The study, according to Napier, further bolsters the comet-impact theory, which many astronomers continue to dismiss.
"We are looking at this as an actual, reasonable, astrophysical mechanism," said Napier, whose paper is now online at arXiv.org and will appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society.
Taurid Link No More Than "Window Dressing"?
Napier made the connection between the Taurids and the mammal extinctions after hearing about evidence for microscopic nanodiamonds at Ice Age sites across North America. Such tiny diamonds are thought to form only during extraterrestrial impacts.
"When we see the evidence of nanodiamonds on the ground, it clicks," Napier said.
Also, a barrage of fiery comet fragments would explain the evidence for ancient wildfires found at many North American sites from this time period.
But many astronomers say the idea is improbable, because space rocks big enough to cause such a catastrophe aren't known to orbit so close to the sun.
"So this would be something pretty unusual," said Jay Melosh, an impact expert at Purdue University in Indiana, who remains unconvinced by the new study.
What's more, if an existing debris cloud did cause the ancient extinctions, there should still be threatening chunks in the inner solar system, argued Alan Harris, a senior researcher at the Space Science Institute in Colorado who studies impact hazards.
"An abrupt comet [or asteroid] shower is bit like, say, a stove fire that can fill the kitchen with smoke in a few seconds but takes many minutes to hours to clear out," Harris said in an email.
Surveys for such comet chunks show that "they simply aren't there in the numbers needed [to account for a giant, disintegrating comet]," Harris said.
"And what we do see are not in coherent or clustered orbits that could possibly have come from a single body" within the last 20,000 to 30,000 years.
According to Harris, the claim that the Taurid complex is linked to the North American extinctions "is just the most current window dressing for a broad hypothesis that has not yet been proven."
Most Popular News
-
Black Hole Seen Eating Asteroids?
An ongoing rocky buffet would explain bright x-ray flares seen around our galaxy's supermassive black hole since 1999, astronomers say.
-
Zebra Stripes Are Bug Repellant?
Stripes may do more than help zebras hide in tall grass—the pattern may scramble the vision of bloodsucking horseflies
-
Lake Vostok Breached
Russian scientists have confirmed that they have breached the subglacial Lake Vostok in Antarctica—a first.
Advertisement
From the Web
-
From Huffington Post: Wolf Fosters Kitten
Adorable footage shows a pet wolf looking after a tiny kitty.
-
From Huffington Post: Rare Albino Hummingbird Spotted
The tiny bird was seen visiting a backyard in Virginia.
News Blogs
-
Texas Moves to Save Critical Groundwater
Ogallala Aquifer has dropped as much as 150 feet.
-
Good News, Bad News on U.S. Energy Outlook
The "all of the above" energy approach Obama championed in his State of the Union speech is at odds with U.S. climate goals.
-
Uranus Easy to Find This Week
Thanks to a close encounter with Venus, sky-watchers will have the chance the next few nights to easily glimpse the "green giant" Uranus.
ScienceBlogs Picks
Connect With Nat Geo
Got Something to Share?
Special Ad Section
Great Energy Challenge Blog
Green Living Hot Topics
-
Organic Air Fresheners
Avoid toxic chemicals and create a calming space.
-
Surprising Recyclable Household Items
With a little know-how, you can recycle more than you think.
-
Side Effects of Vegetarianism
Find out how to stay healthy and eat lower on the food chain.
