It's official: An asteroid wiped out the dinosaurs

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http://news.yahoo.com/s/nm/20100304/sc_ ... s_asteroid

LONDON (Reuters) – A giant asteroid smashing into Earth is the only plausible explanation for the extinction of the dinosaurs, a global scientific team said on Thursday, hoping to settle a row that has divided experts for decades.

A panel of 41 scientists from across the world reviewed 20 years' worth of research to try to confirm the cause of the so-called Cretaceous-Tertiary (KT) extinction, which created a "hellish environment" around 65 million years ago and wiped out more than half of all species on the planet.

Scientific opinion was split over whether the extinction was caused by an asteroid or by volcanic activity in the Deccan Traps in what is now India, where there were a series of super volcanic eruptions that lasted around 1.5 million years.

The new study, conducted by scientists from Europe, the United States, Mexico, Canada and Japan and published in the journal Science, found that a 15-kilometre (9 miles) wide asteroid slamming into Earth at Chicxulub in what is now Mexico was the culprit.

"We now have great confidence that an asteroid was the cause of the KT extinction. This triggered large-scale fires, earthquakes measuring more than 10 on the Richter scale, and continental landslides, which created tsunamis," said Joanna Morgan of Imperial College London, a co-author of the review.

The asteroid is thought to have hit Earth with a force a billion times more powerful than the atomic bomb at Hiroshima.

Morgan said the "final nail in the coffin for the dinosaurs" came when blasted material flew into the atmosphere, shrouding the planet in darkness, causing a global winter and "killing off many species that couldn't adapt to this hellish environment."

Scientists working on the study analyzed the work of paleontologists, geochemists, climate modelers, geophysicists and sedimentologists who have been collecting evidence about the KT extinction over the last 20 years.

Geological records show the event that triggered the dinosaurs' demise rapidly destroyed marine and land ecosystems, they said, and the asteroid hit "is the only plausible explanation for this."

Peter Schulte of the University of Erlangen in Germany, a lead author on the study, said fossil records clearly show a mass extinction about 65.5 million years ago -- a time now known as the K-Pg boundary.

Despite evidence of active volcanism in India, marine and land ecosystems only showed minor changes in the 500,000 years before the K-Pg boundary, suggesting the extinction did not come earlier and was not prompted by eruptions.

The Deccan volcano theory is also thrown into doubt by models of atmospheric chemistry, the team said, which show the asteroid impact would have released much larger amounts of sulphur, dust and soot in a much shorter time than the volcanic eruptions could have, causing extreme darkening and cooling.

Gareth Collins, another co-author from Imperial College, said the asteroid impact created a "hellish day" that signaled the end of the 160-million-year reign of the dinosaurs, but also turned out to be a great day for mammals.

"The KT extinction was a pivotal moment in Earth's history, which ultimately paved the way for humans to become the dominant species on Earth," he wrote in a commentary on the study.

(Collins has created a website at http://impact.ese.ic.ac.uk/ImpactEffects/Chicxulub.html which allows readers to see the effects of the asteroid impact.)

And to think if it weren't for that asteroid we wouldn't even be here.

"And then there was the next impact, which, as we all know, lead to us giant cockroaches ruling the Earth."

Actually, I do wonder if (err, I mean when) that happens again what species will end up taking the position that humans are now. (I'm thinking intelligent tool-making, system-building, civilization-building beings of some sort.) Or will that just not happen again? The "big animals/plants" era had it's day, but it looks like that is permanently over. Is intelligent life inevitable? or not?

They say the impact was on land so it kicked up enough dust to create a "nuclear winter"

But.... if it had landed in the ocean then it would have caused huge tidal waves but most of the planet would not have been affected.

So a few minutes difference in the impact time and the world would be ruled by cold blooded lizards.

(Just as it is now)

Did they ever think to try and rule out the whole time travel wiping out the dinosaurs from the old "Dinosaur Attacks" topps card series? Until I see that disproven, the jury is still out for me.

For the uninitiated!

from what I've seen on this...the likeliest crater is partially in the Gulf of Mexico...so maybe it did hit water...

Correct. We are an Accident.

ruveyn

But depending on the sea level at the time the Gulf of Mexico might have been dry land.

Neil Degrasse Tyson, notable PhD (from NOVA on public television), claimed that the iron in that asteroid matches the iron in our blood. Gives me the chills...but I like it!

Actually, with the asteroidal impact described, it wouldn't make any difference whether it hit land or water - it would blast away the water and the ground underneath anyway, throwing seafloor into the sky in exactly the same fashion as dry land...

I once saw a documentary on Discovery Channel I thought was super-cool. It was about a so called "antipodal" theory that an asteroid hitting the earth would cause a vulcano to appear at the other side of the Earth. That was due to the shock waves that were transmited through the core of the Earth that would hit the other side of the Earth (the researchers said they proposed this theory studying head injuries where the exact same phenomenon happened (hit in the front and damage at the back)). They said that the period that the asteroid hit the Earth was accompanied by increased vulcanic activity. Well I´m not a scientist and also I don´t study this subject so I can´t know if that is true, but I thought that the theory was very cool.

If we were an accident, why are we still here. I think it was inevitable that intelligent life rise. It's the only thing that can adapt better than simplicity (bacteria.)

Of course it does, iron is iron.

The water in our bodies is also from Space. Where is my PhD?

It should be noted that it only took 55,000,000 years for something like us to appear, and like us only 125,000 years ago. Very like us 40,000 years ago.

Liking the background of a story, we move up and down through the Galactic Plane, up, then down, then back up, which is happening now, and also happened at the time of this story. It is roughly 35,000,000 years, and two back, Bang! It also fits the pattern of the eight extinctions before then.

We do have a good supply of rodents that are just waiting to evolve. It should be quicker this time.

Racoons have the hands, they are well on the way, smart, adaptive.

He might've meant that the isotopic composition of the iron is different than that of terrestrial iron.