October 20, 2011
Scientists Model Chicxulub Meteorite Impact

When a massive meteorite hit the Earth 65 million years ago how big was its effects? Princeton researchers have developed a better model for simulating the effects of a large meteorite impact.

Seeking to better understand the level of death and destruction that would result from a large meteorite striking the Earth, Princeton University researchers have developed a new model that can not only more accurately simulate the seismic fallout of such an impact, but also help reveal new information about the surface and interior of planets based on past collisions.

Princeton researchers created the first model to take into account Earth's elliptical shape, surface features and ocean depths in simulations of how seismic waves generated by a meteorite collision would spread across and within the planet. Current projections rely on models of a featureless spherical world with nothing to disrupt the meteorite's impact, the researchers report in the October issue of Geophysical Journal International.

The researchers -- based in the laboratory of Jeroen Tromp, the Blair Professor of Geology in Princeton's Department of Geosciences -- simulated the meteorite strike that caused the Chicxulub crater in Mexico, an impact 2 million times more powerful than a hydrogen bomb that many scientists believe triggered the mass extinction of the dinosaurs 65 million years ago. The team's rendering of the planet showed that the impact's seismic waves would be scattered and unfocused, resulting in less severe ground displacement, tsunamis, and seismic and volcanic activity than previously theorized.

2 million times more powerful than a hydrogen bomb is pretty extreme.

On the bright side, the researchers do not think a Chicxulub-sized impact would unleash the scale of volcanic eruption that would basically wipe out huge numbers of species.

"Regarding the mass extinction, we saw from our measurements that a Chicxulub-sized impact alone would be too small to cause such a large volcanic eruption as what occurred at the Deccan Traps. Our model shows that the antipodal focusing of the seismic wave from such an impact was hugely overestimated in previous calculations, which used a spherical-Earth model.

"The Earth's maximum ground displacement at this point has been calculated to be 15 meters, which is extreme. The first outcome of our model was that this is reduced by a large amount to about three to five meters. On the spherical model, all the waves come together at exactly one point and, as a result, have a huge amplitude. We found the waves are disturbed by surface features and take on a more ragged structure, meaning less energy is concentrated at the antipode.

Still, surviving such an impact would not be easy. The ground movements and potentially huge ocean waves would combine with a big shock wave in the atmosphere and reduced sunlight afterward.

We need to find all the large objects that might strike the Earth and see if any will hit us any time this century. Then prepare accordingly.

Share |      Randall Parker, 2011 October 20 09:34 PM  Dangers Asteroids


Comments
Phillep Harding said at October 21, 2011 12:00 PM:

From what I've read and heard on the subject, the bone digger crowd does not agree. Seems there just aren't any dino bones in the layers close under the Chicxulub dust layer (K-T boundary), suggesting the die off occurred long before then.

Not that such an event would be good for us, it sure would not, just picking a nit. The people in the best position to know don't see the evidence.

egoist said at October 22, 2011 11:57 AM:

"Then prepare accordingly." I'm thinking gold & a gun ain't gonna help in this case.

Mike Giles said at October 22, 2011 12:06 PM:

As I understand it, it wasn't a case of their being fewer dinosaurs; but a lower diversity of dinosaurs. Instead of having a number of different types, there were huge numbers of fewer types. One of the reasons given is that as the continents came closer together, species were now able to interact. This allowed the spread of newer and more virulent (to some species) diseases. What we have toward the end of the Cretaceous, is the hardy survivors beginning to take over almost everywhere. Til the big rock got them, that is.

Sardondi said at October 22, 2011 12:06 PM:

Here's the unasked question which this study suggests (at least to me): if the Chiczulub strike wasn't violent enough to cause catastrophic worldwide vulcanism and a resulting titanic release of ash into the atmosphere, then was this the event that indeed signed the dinosaurs death warrant? Doesn't sound like it.

Ed Zeppelin said at October 22, 2011 12:23 PM:

When the next big impact comes, I hope to get some good photos

crosspatch said at October 22, 2011 12:28 PM:

"We need to find all the large objects that might strike the Earth and see if any will hit us any time this century"

If you look at craters on the Moon, Mars, Mercury and other places, you will note that there are a significant number of impacts from outside the ecliptic. Notice the craters at the poles. We are currently limiting our search for large potential impacting objects to the ecliptic. One arriving from due North or due South is likely to arrive without much notice.

StephenB said at October 22, 2011 12:42 PM:

The NEOWISE program surveyed the entire sky. They also found less asteroids than previously assumed. http://neo.jpl.nasa.gov/programs/neowise.html

John Burgess said at October 22, 2011 2:21 PM:

Why, oh why, is the graphic used at the Princeton site using a contemporary map of the world?

The continents had not yet settled down into their current configuration. South America and North America were not yet connected; India was floating around in the Indian Ocean. Australia, Antarctica, and South America were still connected. North America was still connected to Eurasia; the Arabian Peninsula was still connected to Africa; there was no Italian Peninsula yet.

So that puts Chiczulub exactly where? And was it's actual location used in the study's map? The graphic would suggest otherwise.

GaryP said at October 22, 2011 3:04 PM:

From my old "MO Board" problems in the Navy: If you are going to collide with something (or it with you) when you are both in motion, it exhibits "constant bearing, decreasing range." Can't see objects that are going to collide with Earth with any simple technique I know of; the object will just gradually get brighter and larger (as it gets closer). That is really hard to spot against the background of the "fixed" stars. An object coming directly at Earth will NOT produce a streak on a photograph as objects that are going to miss the Earth do. Unless the object is going to miss us this orbit of the sun and hit us next time (or the time after that) looking for objects that will hit the Earth is a waste of effort. The really dangerous stuff (i.e. things on a collision course) will be on us before we see it. Mostly this issue is just the "astronomer's full employment act" justification.

David said at October 22, 2011 3:58 PM:

How nice that are astronomical budget for all of the NSF is about to be cut 20%......weeeeeee......

Earl Harding said at October 22, 2011 4:00 PM:

GaryP,

Your Navy MO board problems only dealt with objects moving in a straight line.

Stuff in solar orbit move in elliptical orbits. In this case both bearing and range change. This is also incidentally true when dealing with intercepting incoming ballistic missles.

Typically a naval bridge doesn't have to deal with curvature of the earth or elliptical orbits.

In fact if you have 2 boats changing both velocity and heading they can collide with much changing of bearing and range. This is the same situation as elliptical orbits. The rate of bearing change will reduce the closer to impact you get, but detect it far enough out and you will see it streaking.

Tom the Redhunter said at October 22, 2011 7:11 PM:

"2 million times more powerful than a hydrogen bomb"

Which tells you very little. It's like saying something is "2 million times more powerful than a bullet" Are you talking about a .22 long Rifle or a Weatherby .460? Depending on the exact bullet, the former comes in at between 104 and 204 ft lbs of energy, and the latter 7,072 to 7,504.

It's the same as with hydrogen bombs. They can be made as small as a dozen kilotons, or as big as 50 to 100 megatons. There's no more an "average" hydrogen bomb than theyre is an "average" bullet.

Where you end up with the multiplication depends on where you start.

Richard said at October 22, 2011 11:11 PM:

I was shown by God three Visions about an asteroid strike. Of course no one believes it. God's remark after showing me our damaged Earth was " Enjoy it while it Lasts ". The Strike will be a 1000 miles across land locked hole centered on greece.Sorry, visions don't come with calendars.

PacRim Jim said at October 23, 2011 12:05 PM:

Gold & gun might not work.
But a gold gun against the temple will.
Sometimes a problem is over-thought.

NerdSlapper said at October 24, 2011 6:35 AM:

God killed off the dinosaurs so that they wouldn't eat Adam & Eve.

Kudzu Bob said at October 24, 2011 9:49 PM:

The Strike will be a 1000 miles across land locked hole centered on greece.

The destruction of Greece by a giant meteor would be redundant.

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