Apophis asteroid will miss us in 2036 but remains threat


FIRST THE good news – the Apophis asteroid will get very close but will not hit us in 2036. The bad news is the asteroid, almost 250 metres across, might hit us in 2068.

The latest calculations defining the orbit – and potential for Earth impact – of the asteroid were presented yesterday at a meeting of the American Astronomical Society in Puerto Rico.

Asteroid hunters have kept a close watch on Apophis since its discovery in 2004, their interest sparked by initial fears that it might slam into Earth.

Early calculations suggested there was a one in 37 chance it would strike us on April 13th, 2029, a Friday coincidentally for the superstitious.

There followed an immediate scramble to recalculate the asteroid’s orbit by examining telescope images of Apophis. This indicated we need not fear 2029 but rather 2036, when there was a one in 45,000 chance of an impact.

This might seem like long odds, but the consequences of even a tiny mistake are colossal, as previous Earth impactors show.

An incoming chunk of rock just tens of metres across flattened 2,150sq km (23,142sq ft) of Russian forest in 1908 in what is known as the Tunguska event. The rock exploded high up in the atmosphere, but still delivered a ground-level blast 1,000 times stronger than the A-bomb dropped on Hiroshima.

Then there is Meteor Crater, Arizona. A metallic asteroid about 50 metres across hit us travelling at an estimated 12.8km per second, punching a 1.2km-wide, 170m-deep hole in the ground.

This event took place about 50,000 years ago, probably before humans had even reached what is now North America.

But a Meteor Crater or Tunguska event occurring over any city today would leave nothing but rubble.

The very latest calculations by Dr David Tholen and colleagues of the University of Hawaii, and verified by Dr Steve Chesley and Dr Paul Chodas of Nasa’s Jet Propulsion Laboratory in California show, however, that we are safe in 2036.

Apophis will fly by at a shockingly close 32,000km – well inside the average lunar distance of 384,400km – but will miss us.

The focus now shifts to 2068, however, when Apophis will cosy up close once again.

The current figures suggest there is a three in a million chance of an impact, but we have to wait until it emerges from behind the sun in 2010 to get a better handle on its orbit.