Posted on 04/10/2008 8:18:52 PM PDT by blam
"Dino Killer" Asteroid Was Half the Size Predicted?
Ker Than
for National Geographic News
April 10, 2008
The meteorite that wiped out the dinosaurs might have been less than half the size of what previous models predicted.
That's the finding of a new technique being developed to estimate the size of ancient impactors that left little or no remaining physical evidence of themselves after they collided with Earth.
Scientists working on the technique used chemical signatures in seawater and ocean sediments to study the dino-killing impact that occurred at the end of the Cretaceous period, about 65 million years ago.
They also looked at two impact events at the end of the Eocene epoch, roughly 33.9 million years ago.
In what could be a major scientific puzzle, the team's new size estimate for the dino-killing meteorite is a mere 2.5 to 3.7 miles (4 to 6 kilometers) across.
The most recent computer models predicted a size of 9 to 12 miles (15 to 19 kilometers) across.
The team notes that their findings could also mean that the makeup of the impactor is different from what scientists commonly assume.
"We are hoping this will lead to further work," said study leader Gregory Ravizza of the University of Hawaii in Honolulu.
Impact Fingerprints
The fiery passage of asteroids and comets through Earth's atmosphere leaves chemical traces in the land, sea, and air.
The most common types of meteorites to hit Earth are chondrites, stony objects that originate in the asteroid belt.
Chondrites contain two different versions, or isotopes, of the naturally occurring element osmium: osmium 187 and osmium 188.
Seawater and sediments also contain the two osmium isotopes, but the ratio of osmium 187 to osmium 188 is usually much larger in the ocean than it is in chondrites.
When a small- to medium-size meteorite enters Earth's atmosphere, much of the object is vaporized and the osmium ratio in seawater around the world is temporarily decreased.
Over time, this osmium imprint is transferred to sediments at the ocean bottom, creating a more enduring record of the impact.
The new technique therefore looks for osmium spikes in ocean sediments and analyzes the isotope ratio. Scientists can then predict when an impact event occurred and the size of the projectile.
The research is detailed in tomorrow's issue of the journal Science.
Dramatic Upheaval
In addition to the smaller Cretaceous impact, the team estimates that two known meteorites from the late Eocene were smaller than previously believed.
Boris Ivanov, an impact modeler at the Russian Academy of Sciences, said that if the new size estimates prove correct, they would create a "dramatic controversy" within the impact physics community.
"Most numerical modeling specialists believe the current modeling gives us fidelity of a factor of a few times the mass of a projectile with assumed average impact velocity," Ivanov said.
Study co-author Francois Paquay, also at the University of Hawaii, said that more work needs to be done to confirm the latest estimates.
"We think the discrepancy is important and it will need to be addressed in future [scientific] meetings," Paquay said.
Jay Melosh, a planetary scientist at Arizona State University who was not involved in the study, called the new method a "potentially powerful" technique for filling gaps in the geologic impact record.
"It's a very valuable contribution to the tool kit of ways we have of estimating the presence of impacts in the geologic record," Melosh said.
I lost the URL for a great Japanese animation of a planet-killer striking the earth. Very high quality and, somehow, calming. If the Big One hits, I won’t even feel a thing.
Who was it the PREDICTED the size of the asteroid which killed the dinosaurs? That must have been some trick.
Chemostratigraphic Evidence of Deccan Volcanism from the Marine Osmium Isotope Record
Science 21 November 2003:
Vol. 302. no. 5649, pp. 1392 - 1395
DOI: 10.1126/science.1089209
Continental flood basalt (CFB) volcanism is hypothesized to have played a causative role in global climate change and mass extinctions. Uncertainties associated with radiometric dating preclude a clear chronological assessment of the environmental consequences of CFB volcanism. Our results document a 25% decline in the marine 187Os/188Os record that predates the Cretaceous-Tertiary boundary (KTB) and coincides with late Maastrichtian warming. We argue that this decline provides a chemostratigraphic marker of Deccan volcanism and thus constitutes compelling evidence that the main environmental consequence of Deccan volcanism was a transient global warming event of 3° to 5°C that is fully resolved from the KTB mass extinction.
1 Department of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822–2225, USA.
2 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution (WHOI), Woods Hole, MA 02543, USA.
So this asteroid caused Osmium levels to decrease thousands/millions of years before it actually hit??
LOL! These Asteroid people with their computer models and evidence cherry picking are almost as bad as the Global Warming Religionist
Ya know, I disagree with the theory that the dinosaurs were wiped out in one cataclysm.
What would seem more likely, according to the evidence we keep finding, is that it happened in chunks and pieces over time.
That may be why there are drawings found of giant reptiles and mammals in action. Real-life experience or tribal legend.
Maybe man walked with the dinosaurs. But there were darn few of them and only in certain climates.
How convenient, theoretical "impactors" that conveniently vanish leaving no trace they ever hit the earth, and killed all those dinosaurs.Must be true however, because they said so.
Scientists working on the technique used chemical signatures in seawater and ocean sediments to study the dino-killing impact that occurred at the end of the Cretaceous period, about 65 million years ago.
Great. This ones even better. Chemical signatures from things that may or may not have existed, but left no evidence of being there so one can't say either way. But somehow, the KNOW just what chemical signatures they lefty behind, even though they can't tell you what it was made of, snow, rock, frozen methane?
One thing we know,(because they say so) these impacts made all the dinosaurs fall into what are now the saudi oil fields and other large oil fields arounfd the earth.
500 billion of them fell in just in ONE Saudi oil field. There sure were a lot of dinosaurs on the earth when that invisible meteor hit. Zillions of them.
This is what really killed the dinosaurs.
It must have been a dinosaur that forgot to do his metric conversions.
Probably an ancestor of one of our political pollsters.
Now some dinosaurs undoubtedly did become oil deposits too, but not enough to matter. There simply weren't enough of them.
Dima, Baby Mammoth. In 1977, the first of two complete baby mammoths was found—a 6–12-month-old male named “Dima.” His flattened, emaciated, but well-preserved body was enclosed in a lens of ice, 6 feet below the surface of a gentle mountainous slope. “Portions of the ice were clear and others quite brownish yellow with mineral and organic particles.” Silt, clay, and small particles of gravel were found throughout his digestive and respiratory tracts (trachea, bronchi, and lungs). These details are important clues in understanding frozen mammoths.
There things are 4-6 thousand years old. Not 65 million. They didn't die then get buried by snow, otherwize their flesh would have suffered cellular degradation from slow cooling, and would have completely decayed with contact to warm earth. They were frozen instantly, flash frozen, with the tropical vegetation still in their mouths and stomachs.
These make the global warming alarmists really mad, because these are proof the arctic was not frozen a mere 4-6 thousand years ago. It was a warm tropical place.
The Siberians are using the tons of ivory they find, perfectly preserved, for carving. That wouldn't be possible if they were millions of years old. Ivory unless well cared for, becomes useless for carving after only being left exposed to the elements for less than a year.
They are also using timber which is being released by the melting ice they were frozen in for those few thousand years, as if it were cut down yesterday. Tropical furs and cedars that no longer exist there today.
Dig a little deeper and you will see the clay under it, and the limestone under that. and then the granite. I own plenty of peat bog land. No chance of it ever becoming oil wells no matter how many billion years you give it. It simply breaks down into soil after all the vegetation completely decays. What makes pete bogs is lowlaying grasslands, swamp grass and reeds that die off every year and pile up. eventually the soil builds up raising that low land and the process stops. No oilwell, sorry. just nice black dirt.
The dead se animals etc doesn't wash either. it simply doesn't add up. Plus, most of that turns to methane and decays completely long before it becomes buried.
Oil is found much deeper than that, were there are no dinosaur bones, no sign of any organic life whatsoever. It's very difficult to explain how all this stuff got under the earths crust- 5 miles think and more in places. Oh they try, but there is no evidence to back up that theory.
Oil must really go through some amazing process, because there are no organic markers found in oil, only what is present as a contaminant which gets into it as it is brought up through the sedimentry layers.
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Apparently craterless, but it still dragged along a powerful local shockwave.
“This is what really killed the dinosaurs. “
I’m with you. Gorzirra was tough, but those Zeros were tougher.
It's the same technique using the same kind of extrapolations and guess work that Al Gore and his buddies used to estimate Global Warming.
All these are computer models. Computer models invariably validate the prejudices of those that design them.
Supposedly, fossils revealed enough to determine that a good number died from ash suffocation, and those that didn't, died from starvation, that is the ash either covered "food", or was so thick, the animals couldn't move to scavenge.
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