Geologists Discover New Way of Estimating Size and Frequency of Meteorite Impacts

April 12, 2008
Geologists Discover New Way of Estimating Size and Frequency of Meteorite Impacts

Geologists have discovered a new way of estimating the size of impacts from meteorites. Credit: NASA

Scientists have developed a new way of determining the size and frequency of meteorites that have collided with Earth.

Their work shows that the size of the meteorite that likely plummeted to Earth at the time of the Cretaceous-Tertiary (K-T) boundary 65 million years ago was four to six kilometers in diameter. The meteorite was the trigger, scientists believe, for the mass extinction of dinosaurs and other life forms.

François Paquay, a geologist at the University of Hawaii at Manoa (UHM), used variations (isotopes) of the rare element osmium in sediments at the ocean bottom to estimate the size of these meteorites. The results are published in this week's issue of the journal Science.

When meteorites collide with Earth, they carry a different osmium isotope ratio than the levels normally seen throughout the oceans.

"The vaporization of meteorites carries a pulse of this rare element into the area where they landed," says Rodey Batiza of the National Science Foundation (NSF)'s Division of Ocean Sciences, which funded the research along with NSF's Division of Earth Sciences. "The osmium mixes throughout the ocean quickly. Records of these impact-induced changes in ocean chemistry are then preserved in deep-sea sediments."

Paquay analyzed samples from two sites, Ocean Drilling Program (ODP) site 1219 (located in the Equatorial Pacific), and ODP site 1090 (located off of the tip of South Africa) and measured osmium isotope levels during the late Eocene period, a time during which large meteorite impacts are known to have occurred.

"The record in marine sediments allowed us to discover how osmium changes in the ocean during and after an impact," says Paquay.

The scientists expect that this new approach to estimating impact size will become an important complement to a more well-known method based on iridium.

Paquay, along with co-author Gregory Ravizza of UHM and collaborators Tarun Dalai from the Indian Institute of Technology and Bernhard Peucker-Ehrenbrink from the Woods Hole Oceanographic Institution, also used this method to make estimates of impact size at the K-T boundary.

Even though these method works well for the K-T impact, it would break down for an event larger than that: the meteorite contribution of osmium to the oceans would overwhelm existing levels of the element, researchers believe, making it impossible to sort out the osmium's origin.

Under the assumption that all the osmium carried by meteorites is dissolved in seawater, the geologists were able to use their method to estimate the size of the K-T meteorite as four to six kilometers in diameter.

The potential for recognizing previously unknown impacts is an important outcome of this research, the scientists say.

"We know there were two big impacts, and can now give an interpretation of how the oceans behaved during these impacts," says Paquay. "Now we can look at other impact events, both large and small."

Source: National Science Foundation

4.2 /5 (39 votes)  

Filter


Move the slider to adjust rank threshold, so that you can hide some of the comments.


Display comments: newest first

Enthalpy
Apr 13, 2008

Rank: not rated yet
Really ? "The meteorite was the trigger, scientists believe, for the mass extinction of dinosaurs".

Newspapers have less room for doubt than scientists have...

The Chixulub impact is just one possible explanation among others, and it has some drawbacks.

But it is so pittoresque that newspapers just can't resist it.
Rank 4.2 /5 (39 votes)
Tags

Related Stories
Relevant PhysicsForums posts
  • Discrepancy between oxygen and carbon-dioxide levels
    created18 hours ago
  • where gems are found in the world
    created21 hours ago
  • Wind Waves in Reservoir ~ Wind run-up and Wind set-up
    createdFeb 08, 2012
  • Balance of oxygen in the atmosphere
    createdFeb 01, 2012
  • The case for a methanol-based economy
    createdJan 30, 2012
  • Weather in a rotating cylinder
    createdJan 25, 2012
  • More from Physics Forums - Earth

More news stories

Humans may have helped the decline of African rainforests 3000 years ago

(PhysOrg.com) -- Large areas of rainforests in Central Africa mysteriously disappeared over three thousand years ago, to be replaced by savannas. The prevailing theory has been that the cause was a change ...

Space & Earth / Environment

created 11 hours ago | popularity 5 / 5 (4) | comments 10 | with audio podcast report

Could Venus be shifting gear?

(PhysOrg.com) -- ESA’s Venus Express spacecraft has discovered that our cloud-covered neighbour spins a little slower than previously measured. Peering through the dense atmosphere in the infrared, the ...

Space & Earth / Space Exploration

created 7 hours ago | popularity 5 / 5 (5) | comments 7 | with audio podcast

Mars Science Laboratory computer issue resolved

(PhysOrg.com) -- Engineers have found the root cause of a computer reset that occurred two months ago on NASA's Mars Science Laboratory and have determined how to correct it.

Space & Earth / Space Exploration

created 8 hours ago | popularity 5 / 5 (5) | comments 3 | with audio podcast

Clam fields found at deep, low-temperature Mariana vents

(PhysOrg.com) -- Scientists have marveled at the unusual life forms thriving at high temperature hydrothermal vents of the deep ocean.

Space & Earth / Earth Sciences

created 7 hours ago | popularity not rated yet | comments 0 | with audio podcast

Two new moons for Jupiter

Advances in technology have lead to the discovery of new planets outside of our Solar System, and now even new moons in our own backyard.

Space & Earth / Space Exploration

created 7 hours ago | popularity not rated yet | comments 5


Complex wiring of the nervous system may rely on a just a handful of genes and proteins

Researchers at the Salk Institute have discovered a startling feature of early brain development that helps to explain how complex neuron wiring patterns are programmed using just a handful of critical genes. ...

CIA website offline, Anonymous takes credit

The website of the Central Intelligence Agency was unresponsive on Friday after the hacker group Anonymous claimed to have knocked it offline.

Q&A: Obama and the birth control controversy

(AP) -- What birth control debate? A half-century after the introduction of the pill, acceptance of birth control by American women is virtually universal.

The power of estrogen -- male snakes attract other males

A new study has shown that boosting the estrogen levels of male garter snakes causes them to secrete the same pheromones that females use to attract suitors, and turned the males into just about the sexiest ...

New error-correcting codes guarantee the fastest possible rate of data transmission

Error-correcting codes are one of the triumphs of the digital age. They’re a way of encoding information so that it can be transmitted across a communication channel — such as an optical fiber o ...

Both maternal and paternal age linked to autism

Older maternal and paternal age are jointly associated with having a child with autism, according to a recently published study led by researchers at The University of Texas Health Science Center at Houston (UTHealth).