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Short Sharp Science: A New Scientist blog

Alternative dino-killer theory lands with a thud

Jeff Hecht, contributor

Have we been missing the real killer of the dinosaurs? This week, Sankar Chatterjee of Texas Tech University told the Geological Society of America that the fatal blow was struck by a 40-kilometre object that blasted a 500-km hole into the continental shelf west of India, called the Shiva structure (see National Geographic News story). That would be by far the biggest impact known in the Earth's entire history, dwarfing the 300-km Vredfort crater formed 2.02 billion years ago in South Africa (see a gallery of the world's best impact craters).

"The dinosaurs were really unlucky," says Chatterjee. If he's right, that would be a major understatement. He dates the Shiva structure to the same time as two other cataclysms that also have been called dinosaur-killers: the impact of a 10-km asteroid that formed the 170-km Chicxulub crater along the Mexican coast, and the massive volcanic eruptions that formed the Deccan traps in India. Indeed, Chatterjee told geologists that the Shiva impact probably triggered some eruptions of the devastating Deccan flood lavas.

But his words didn't convince other geologists, who have traced Chicxulub debris around the world.

A recent review of crater ages in Earth and Planetary Science Letters listed Chicxulub as the biggest known in the last billion years.

More than 95 per cent of Earth scientists are convinced that the Chicxulub impact was the culprit for the mass extinctions, says Sean Gulick of the University of Texas at Austin in a story. And one of the few Chicxulub sceptics, Gerta Keller of Princeton University, called the Shiva idea "nonsense", saying Chatterjee's evidence for a crater does not point clearly to an impact. Steven D'Hondt of the University of Rhode Island told Discovery News that the effects of Chicxulub alone were enough to explain the mass extinction at the end of the Cretaceous.

Indeed, D'Hondt and others aren't even convinced the Shiva structure is a crater. It hasn't met the documentation standards needed to be listed in a database covering more than 170 terrestrial impact craters. That's not for lack of effort on Chatterjee's part; a Wikipedia article lists a conference paper he presented on the idea a dozen years ago. And he isn't giving up. A press release says he plans to examine rock cores drilled from the submerged crater, which he hopes will prove its nature.

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Disease from habitat change, seawalls giving way leaving water areas a desert. Food sources change but they eating habits don't. Higher predator birth. Over population changes food source. They could have ran out of breedability. Maybe their DNA died or wore out. A time limit on life and breeding. Humidity change, drier leaving skin more open to disease. New disease that were caused by anything. Their form of bubonic plague or flu. Pollution destroying eggs. Small amounts of poison like arsinic in enough areas could kill a whole heard of breeders, maybe causing bad eggs. They evolved into something besides dinosaurs. Cows, pigs, rhinosaurus, monkeys, wolves, lions and tigers and bears. Birds. They are all possibilities. Why think it was just one. Oh well maybe next planet.


objects which terminated the dinos could not have been the ones which produced the yucatan crater or the shiva structure (india subcontinent). a larger impact formation exists in australia. note the red colored glass which litters the australian desert.
however, australia may have been covered with polar ice when that event occured.


Sounds plausible.

Seems like we dont have positive proof of what the crater is, but some clues that it is an impact crater, and dated about right...


Whether the proximal cause for extinction (which by the way took tens of thousands of years, at least) may or may not be known. The discussion that this should start is about how all of these 'really bad things' occurred in a cluster. As the Solar System orbits the Milky Way, we move through some pretty bad neighborhoods apparently. As we near 2012 and the alignment, are there clusters of things in orbits that are going to ruin our day. Or is it possible there are conditions we haven't imagined yet. Gravitational lensing? Maybe something affects the Earth's orbit for a while. It wouldn't take much on the galactic scale to shake the dishes off the shelf.

The dinosaurs didn't die out.
They left.

After 150 millions years I suspect somebody back then developed a larger brain and opposable thumb just like us naked monkeys.
Whaddya think the Greys are, anyhow?

In 4 billion years, how many different ecosystems and dominant lifeforms could appear, thrive, and completely disappear. Given crustal subduction and all, even if they had a materialistic/technological civilization like ours, there would be no trace, except for odd, out of place artifacts that 'mainstream' science, i.e. 'patentable' science tries to suppress.


Obviously, the 10 and 40 kilometer size of the two asteroids or comets is based on a sphere. That means that the 40 kilometer object has 64 times the volume of the 10 kilometer object. It is probably assumed that the density is equal, or the article would have stated the approximate masses in tonnes.

What would a meteorite, roughly 64 times the mass of the Chixulub meteorite, and travelling the same speed, do to the Earth? Would the oceans boil? Would anything survive besides thermophile bacteria and subterranean nano-bacteria?


It would be more useful to give the approximate masses and velocities of the two meteorites. If the only information is that one was 10 km and the other 40 km, it must be based on a spheres of equal density. That means that the 40 km asteroid or comet was 64 times as massive.

If it was travelling the same speed what would it do to the planet? Would the oceans boil? Would anything survive besides subterranean thermophile bacteria and nano bacteria?


Obviously global melting is what killed off the dinosaurs. If they didn't melt then how come we have all that hot-sticky petroleum down in the ground? A lot of plants were melted too.


"That would be by far the biggest impact known in the Earth's entire history"

What about the impact that led to the formation of the moon? It was thought to be Mars-sized, which is a bit bigger than 40km!


What about a double hit ? A massive incoming object could have split into several smaller (relatively) bits with two still being exceptionally large, one hitting the Chicxulub and the other the Shiva Structure. Other components could also have hit but have left no immediately obvious traces. Such a double wammy event (with minor supporting ones too) would probably have been mre than sufficient to cause the extinctions.

The problem of the trace minerals etc around the world are a difficulty for this scenario but I suppose it could be possible that either the Chicxulub produced the relevent traces ecause of its particular impact site but also that the traces could have originated from both.


There is a third theory which seems linked to these. It postulates, as far as I recall, the mexican crater, but also that the impact ejected debris which spread out and fell down on the opposite side of the earth. Taking the earths' rotation into account, this would have made for a massive meteor bombardment in India.

There's a fourth theory less related to these, that says that a massive impact on one side of the planet could cause a massive earthquake on the exact opposite, with enormous lava flows as a result. Apparently there is one example of this on Mars.


Do 95% of Earth Scientists really support the Chicxulub-as-agent-of-extinction hypothesis? In the informal literature (i.e. society magazines etc.) and in talking to various geoscientists I would suggest that this is not true, at the very least I would say that most are equally open to chicxulub and the deccan traps as this agent for change.


"Indeed, D'Hondt and others aren't even convinced the Shiva structure is a crater."

I'm wondering what the shiva structure is, if it isn't an impact crater. Surely whatever it turns out to be, it is interesting, geologically speaking.


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