The `crumb' that could have exterminated the dinosaurs

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The Independent Online
An object like this may have brought an end to the reign of the dinosaurs 65 million years ago.

It is an interplanetary crumb, dating back to the formation of the solar system, which was never baked into the recipe of the rest of the planets; an asteroid, 33 miles across, whose surface reflects so little light that it is twice as dark as charcoal - meaning that only computer enhancement makes it visible.

The US space agency Nasa released the pictures, which were captured during a flypast of Asteroid 253 - or "Mathilde" as it is better known. The images were taken by the Near Earth Asteroid Rendezvous (Near) spacecraft, 186 million miles from the sun - beyond the orbit of Mars. The Near spacecraft passed just 750 miles from Mathilde.

Its irregular shape includes many impact craters - some almost half as wide as its diameter - and show that Mathilde has "a very tortured past," according to Donald Yeomans of Nasa's Jet Propulsion Laboratory, who heads the radio science team observing the object.

The Nasa scientists have been surprised by the size and depth of the craters in the asteroid. The fact that it has not broken apart, despite the apparent signs of damage, suggests that it is less dense, yet also more uniform, than a solid piece of rock.

The team have determined that it must be made of carbon-rich material, and that it formed early in the creation of the solar system, but was not pulled in to any of the processes that formed the planets between 4 and 5 billion years ago.

Those would melt and mix the materials of any object, making them increasingly reflective - that is, raising their albedo. The Earth, for example, reflects 33 per cent of the sun's light, meaning its albedo is 0.37. Mathilde rates just 0.03.

Mathilde lies, like millions of other asteroids, in the gap between Mars and Jupiter.

Occasionally some asteroids fall out of those orbits towards the planets; hundreds are believed to be scattered throughout the solar system, some close enough to pose a threat to Earth.

Many scientists believe one such asteroid crashed into the Gulf of Mexico and caused drastic climate changes which killed off the dinosaurs.

The data gathered in the latest fly-by may help scientists to detect them in future, and even to decide how best to deflect them from hitting Earth, if that becomes necessary.

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