An hour long hailstorm from space may have changed the climate of the Earth

A comet may well have caused the earth to freeze for over 1,000 years.

A new theory put forward by according to Professor Bill Napier, from the Cardiff  University Astrobiology Centre suggests it occurred when the Earth strayed into a dense trail of fragments shed by a large comet.

Thousands of chunks of material from the comet would have rained down on Earth, each one releasing the energy of a one megaton nuclear bomb.

The catastrophe, caused by a disintegrating comet, wiped out large numbers of animal species and disrupted human cultures.

The impacts would have triggered wildfires covering whole continents, filling the atmosphere with smoke and soot and blotting out the Sun.

What caused a sudden cooling of up to 8C just as the Earth was warming at the end of the last ice age has puzzled scientists.

The change caused glaciers to re-advance and coincided with the rapid extinction of 35 families of North American mammals.

Evidence exists of an extraterrestrial event, such as an asteroid or comet impact.

Experts have found a ”black mat” of soot a few centimetres thick thought to be left by continental-scale wildfires.

Microscopic ”nanodiamonds” produced by massive shocks and only found in meteorites or impact craters have also been discovered dating back to the disaster.

These findings led to suggestions that an object from space four kilometres across smashed into the Laurentide ice sheet, which at the time covered what is now Canada and the northern US.

But the likelihood of the Earth being struck by such a large object only 13,000 years ago are a thousand to one against.

Also, a single impact cannot explain the occurrence of such widespread fires.

The fragmenting comet theory is more plausible, according to Professor Bill Napier, from the Cardiff  University Astrobiology Centre.

He believes there is ”compelling evidence” to indicate that such a comet entered the inner solar system between 20,000 and 30,000 years ago and has been breaking apart ever since.

The destruction of the comet has given rise to a number of closely related meteor streams known as the Taurid Complex.

”A large comet has been disintegrating in the near-Earth environment for the past 20,000 to 30,000 years and running into thousands of fragments from this comet is a much more likely event than a single collision,” said Prof Napier.

His model, published in the journal Monthly Notices of the Royal Astronomical Society, suggests that the ”hailstorm” would have only lasted about an hour.

One recent impact that may have come from the comet is known as the Tagish Lake meteorite, said Prof Napier.

The object fell on Yukon Territory in Canada in January 2000. It contained the largest amount of nanodiamonds of any meteorite studied so far.

It would have caused thousands of impacts, generating global fires and depositing nanodiamonds at the ”extinction boundary” marking the point in time when many species died out.

Steve Peat the most successful Downhill competitor

Sheffield-born Steve stopped off north of the border to show off the world-class skills that have led to him being crowned the most successful Downhill competitor ever, (with more than 50 podium results in World Cups and World Championships) and helped to kick-off ticket sales for the 9th annual World Cup.

Downhill mountain biking’s most successful competitor and reigning World Champion Steve Peat rolled into Scotland today (Monday 22nd March) to mark the official launch of the UCI Fort William Mountain Bike World Cup 2010.

He and hundreds of other professional mountain bikers will return to the scenic Scottish Highlands on 5 – 6th June 2010, for the multi award-winning event – an adrenaline-packed weekend of world-class Downhill and 4-Cross action which this year features a new Downhill Rock & Roll theme.

As he prepares to head off around the globe on the competitive mountain bike circuit, Steve said he can’t wait to get back to Fort William: “Scotland has some of the best biking terrain in the world, and there’s a real enthusiasm for the sport here which always makes for a brilliant atmosphere. It always helps to have a vocal UK crowd – especially when I’m going to be defending my title!”

Mike Jardine of organisers Rare Management said the World Cup is much more than a sporting event: “Steve’s such a hero in the mountain biking community we’re sure the crowds will be even bigger as they come to cheer him on as reigning World Champion. It’s all shaping up for a really entertaining and exciting two days, both for fans of the sport and those who’re simply after an action-packed day out or weekend away.”

Last year’s event attracted more than 18,500 fans to Fort William, and generated an estimated £2.5 million for the local economy.