Scientists have discovered evidence that a series of comets smashed into earth in just a few hours 214 million years ago, devastating animal and plant life.

Watch this report by science correspondent James Wilkinson in Real Video

The impact left a straight line of enormous craters in the earth's crust, according to research published in the science journal Nature.

Experts say the impact would have plunged parts of the world into darkness for years, wiping out life forms.

The devastation caused by the fragments lends weight to the idea that a similar event probably made the dinosaurs extinct 65 million years ago.

Thousands of comets and asteroids routinely orbit the sun but occasionally one breaks up in space and fragments get too close for comfort.

Jupiter was left pockmarked when it was hit with fragments of a comet

The series of impacts were similar to what happened on Jupiter nearly four years ago.

Then, about 20 fragments of the Shoemaker-Levy comet hit Jupiter over several days leaving it pockmarked for months, each scar bigger than the earth.

Evidence of similar craters on earth dates from a time when the continents were joined together.

As the comet fragments came in, each several kilometres across, they impacted in a line.

The first one hit what is now southern France. The second fell in Quebec, in north east Canada and the third in western Canada.

One crater in Quebec remains visible

Today the remains of just one of those craters in Quebec is still visible. The others were found by scientific detective work.

Scientists say the asteroid or comet fragments arrived about the same time as many plants and animals became extinct.

Simon Kelly, of the Open University said: "They would have thrown up huge amounts of debris and rocks of all sizes.

"The power of the explosion would punch them right out into the stratosphere. They would be spread out and would cause darkness and terrible atmospheric effects probably for several years afterwards."

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