Subscribe free to our newsletters via your
. 24/7 Space News .




DEEP IMPACT
Absence Of Evidence For A Meteorite Impact Event 13,000 Years Ago
by Staff Writers
Manoa HI (SPX) Dec 09, 2009


The woolly mammoth was one of the large mammals that became extinct in North America at the onset of the Younger Dryas approx. 13,000 years ago. Wiki Commons Image.

An international team of scientists led by researchers at the University of Hawaii at Manoa have found no evidence supporting an extraterrestrial impact event at the onset of the Younger Dryas ~13000 years ago.

The Younger Dryas is an abrupt cooling event in Earth's history. It coincided with the extinction of many large mammals including the woolly mammoth, the saber toothed jaguar and many sloths. This cooling period is generally considered to be the result of the complex global climate system, possibly spurred on by a reduction or slowdown of the thermohaline circulation in North America.

This paradigm was challenged two years ago by a group of researchers that reported finding high iridium concentrations in terrestrial sediments dated during this time period, which led them to theorise that an impact event was instead the instigator of this climate shift.

A team led by Fran´┐Żois Paquay, a Doctoral graduate student in the Department of Geology and Geophysics at the University of Hawaii at Manoa (UHM) decided to also investigate this theory, to add more evidence to what they considered a conceptually appealing theory.

However, not only were they unable to replicate the results found by the other researchers, but additional lines of evidence failed to support an impact theory for the onset of the Younger Dryas. Their results will be published in the December 7th early online edition of the prestigious journal the Proceedings of the National Academy of Sciences.

The idea that an impact event may have been the instigator for this cooling period was appealing because of several alleged impact markers, especially the high iridium concentrations that the previous team reported. However, it is difficult for proponents of this theory to explain why no impact crater of this age is known.

"There is a black mat layer across North America which is correlated to the Younger Dryas climatic shift seen in Greenland ice cores dated at 13 thousand years ago by radio carbon," explains Paquay.

"Initially I thought this type of layer could be associated with an impact event because concentration in the proxies of widespread wildfires are sky high. That plus very high levels of iridium (which is one indicator used to indicate extraterrestrial impact events). So the theory was conceptually appealing, but because of the missing impact site, the idea of one or multiple airburst arose."

To corroborate the theory, Paquay and his colleagues decided to take a three-pronged approach. The first was to replicate the original researchers data, the second step was to look for other tracers, specifically osmium isotopes, of extraterrestrial matter in those rocks, and the third step was to look for these concentrations in other settings.

"Because there are so many aspects to the impact theory, we decided to just focus on geochemical evidence that was associated with it, like the concentration of iridium and other platinum group elements, and the osmium isotopes," says Paquay. "We also decided to look in very high resolution sediment cores across North America, and yet we could find nothing in our data to support their theory."

The team includes American, Belgian and Canadian researchers. Analysis of the sediments was done both at UHM and in Belgium, using the same sediments from the same interval and indepedently did the analysis work and got similar results. Both the marine and terrestrial sediment records do not indicate that an impact event was the trigger for the transition into the Younger Dryas cold period.

"The marine and terrestrial record both complement each other to support this finding," concludes Paquay. "That's what makes the beauty of this study."

.


Related Links
University of Hawaii at Manoa
Asteroid and Comet Impact Danger To Earth - News and Science






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








DEEP IMPACT
The 2009 Geminid Meteor Shower
Huntsville AL (SPX) Dec 09, 2009
Make hot cocoa. Bundle up. Tell your friends. The best meteor shower of 2009 is about to fall over North America on a long, cold December night. "It's the Geminid meteor shower," says Bill Cooke of NASA's Meteoroid Environment Office. "and it will peak on Dec. 13th and 14th under ideal viewing conditions." A new Moon will keep skies dark for a display that Cooke and others say could ... read more


DEEP IMPACT
Researcher Delighted That LCROSS Confirms Lunar Prospector Findings

Circumlunar Missions: The Missing Link

Partial Gravity And The Moon

Astronomy Question Of The Week: What Happens On The Moon During A Lunar Eclipse

DEEP IMPACT
Spirit remains trapped in Martian sand

Opportunity Investigates 'Marquette' And 'Islington Bay'

Spirit's Diagnostic Wheel Tests Continue

Orbiter Puts Itself Into Safe Standby

DEEP IMPACT
Japan's 'space beer' sparkles among drinkers

Branson unveils Virgin Galactic spaceliner

NASA to attend Copenhagen climate meeting

NASA to launch space education program for Arab youth

DEEP IMPACT
Chang'e-1 Has Blazed A New Trail In China's Deep Space Exploration

China To Launch Second Lunar Probe In 2010

China To Launch Research Satellite In Near Future

China's military making strides in space: US general

DEEP IMPACT
Russia To Launch MIM1 Module To ISS Next Year

Russia Plans To Send 10 Spacecraft To ISS Next Year

SpaceX Begins NASA Astronaut Training For Dragon Spacecraft COTS Program

Four "Butterflynauts" Emerge On ISS

DEEP IMPACT
Helios 2B Military Observation Platform Given "Go" For Launch

Arianespace Marks 30 Years Of Launch Services Excellence

WISE Spacecraft Ready For Launch Dec 9

Ariane 5 Getting Ready To Launch Helios 2B Reconn Satellite

DEEP IMPACT
Superior Super Earths

UCF Space Experiment To Fly On New Rocket Ship

SOFIA Seeks Secrets Of Planetary Birth

Hunting For Planets In The Dark

DEEP IMPACT
Cost-Effective Satellite Connectivity Brings Dispersed Businesses Together

Space Debris Removal Gets Visibility

Taiwan to invest 65 million dollars in e-book industry

New way to make single-crystal structures




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement