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March 2014 brings small risk of huge disaster

Tim Radford, science editor
Wednesday September 3, 2003
The Guardian

The world can breathe again. Probably. Asteroid 2003 QQ47, a lump of rock the size of Ben Nevis, could hit Earth at a speed of about 13 miles a second on March 21 2014, to cause the kind of destruction expected in thermonuclear war, experts warned yesterday.
But they gave the 2,600m tonne monster a danger rating of just one on the Torino scale. That means its chances of actually slamming into Earth are 909,000 to 1 against.

The Torino scale goes up to 10, at which point collision is a certainty. That the object rates as a danger at all is because earthlings know so little about their nearer neighbours. At present astronomers have counted 523 potentially hazardous objects - bits of rubble left over from the building of the solar system 4.5bn years ago - that may be on collision course with Earth. Asteroid 2003 QQ47, three-quarters of a mile in diameter, first spotted on August 24 and observed so far only 51 times, could be another.

"The near-Earth object will be observable from Earth for the next two months, and astronomers will continue to track it over this period," said Alan Fitzsimmons, of Queen's University, Belfast.

Kevin Yates, manager of the UK near-Earth object information centre, based at the National Space Centre in Leicester, said: "As additional observations are made, and uncertainties decrease, asteroid 2003 QQ47 is likely to drop down the Torino scale."

Earth's nearest neighbour, the moon, is pockmarked by aeons of cosmic collisions. There have been many impacts on Earth during geological history, but for the most part the dents have been smeared away by wind, rain and plant growth.

The last epic impact was probably 65m years ago, at the close of the Cretaceous period, when an asteroid or comet may have wiped out the dinosaurs and most other life on Earth. But there have been many smaller impacts, including the equivalent of a powerful atomic bomb over the Tungus region of Siberia in 1908.

The cosmos, astronomers warn, remains a potentially dangerous place. Amateur astronomers at a BBC "star party" 10 days ago, to celebrate national astronomy week, may have identified 20 more potential killers.

The planet is showered by small objects every day - many of them burn up harmlessly as shooting stars - but larger lumps of rock hit the ground as meteorites.

The bigger fragments have the potential to wipe out whole cities. One of them sped harmlessly past Earth on August 16, missing it by about 2.4m miles. Others have come to within almost the distance of the moon.

Goodbye, cruel world

Astronomers and Earth scientists have proposed a number of potential endpoints for humanity

· The runaway greenhouse effect. Could Earth end up like Venus, with ground temperatures at the melting point of lead?

· Snowball Earth, or at least the return of the ice age, with vast glaciers ploughing as far south as Middlesex. The last ice age ended only 10,000 years ago

· The swelling of the sun. In about 5bn years, the sun will expand to red giant stage, incinerating all the rocky inner planets, and any life on them

· Cosmic collapse: a random quantum fluctuation in space could destroy mass and trigger a bubble of destruction that would advance at the speed of light