Hunting secrets of asteroid that wiped out dinosaurs

Scientists are travelling back more than 60 million years in history to drill deep under the ocean floor in search of clues about the event that wiped out the dinosaurs, and nearly extinguished life on earth.

Some 24km off the coast of Mexico's Yucatan Peninsula, on a platform above the crater left behind when a massive asteroid struck the earth, they are travelling back through 66 million years of the earth's history.

The area surrounding the crater, known as Chicxulub, is now characterised by serene seas and breathtaking sunsets. But it was once the site of a collision with the force of about 100 million atomic bombs.

Joanna Morgan, a professor of geophysics at Imperial College London and co-chief of the study at Chicxulub, describes the immediate aftermath of the asteroid's impact:

"The first thing you'd see would be thermal radiation, so it's very much like a nuclear explosion.

You get a great big, expanding vapour plume that then at a certain temperature turns red hot and radiates heat," she says, explaining that everything within 1000km - an area that on a current map includes Miami to the Northeast, Mexico City to the West and stretches down to Nicaragua to the South - would be incinerated.

That fireball was followed by hurricane-force winds, and a cloud of dust and sulphur that blocked out the sun.

"Within a few hours the whole of the earth would be dark," she says, "and it would immediately get cold, something like 5 to 10 degrees C colder than it would have been before the impact, and that lasts for many months, possibly a few years."

Dinosaurs had reigned for more than 150 million years, but in little more than an instant in geological terms they vanished from the earth.

While scientists generally agree that the crash landing Chicxulub was the primary factor precipitating the mass extinction, there is less consensus as to what symptom of the asteroid's impact - the blocking of photosynthesis, acidification of the ocean, or another cause entirely - was the most deadly.

That is one of many questions the team drilling into the crater hope to help answer.

Perhaps more importantly, they hope to determine how life returned after 75 per cent of the planet's living things were decimated.

"One of the interesting things we would like to do is to look at the way life comes back here in the ocean that re-formed over the crater" says Sean Gulick, a professor at the University of Texas and the project's other co-chief.

Discovering which species survived and why could provide a link between the age of the dinosaurs and our own, he explains.

"In some cases very few species of particular types made it through at all, and yet everything we have in the surface ocean now evolved from those few species."

The team of 12 scientists living on the platform and the additional 21 contributing to the project hope that the answers lie in the rocks they are bringing up to the surface each day.

Some are blackened with unmistakable evidence of the impact itself. Others contain fossils left by the survivors and their descendants.

Using shipping containers that have been re-purposed as laboratories, they are in the midst of what Gulick calls a "voyage of discovery" that will continue in Germany after the two months of drilling are complete.

The implications of those discoveries may be far reaching. Noting that large impact craters are far more common on many planets than on earth, Gulick says his team are looking for signs that they may be potential habitats for microscopic organisms.

Scientists of the future may therefore look to ground zero of one of the world's most deadly events for signs of life beyond the earth.

- Daily Telegraph UK

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