You wait years for a space rock and then two come along at once. Just hours before an asteroid is due to almost graze Earth, a meteor has exploded over the Russian region of Chelyabinsk, injuring hundreds of people and damaging nearby buildings.
Studying the impact could give clues to future hits from rarer, bigger space rocks, which are bound to occur.
The impact occurred at 0320 GMT today, the very day that astronomers are anticipating the close fly-by of asteroid 2012 DA14, although there is thought to be no connection between the two events. "This is a remarkable coincidence," says Stephen Lowry, an astronomer at the University of Kent in Canterbury, UK.
Details of the strike are still emerging, but pictures and video shared on social media offer clues to the meteor's make-up and origin. "It's certainly smaller than 50 metres and larger than a metre," says Simon Green of the Open University in Milton Keynes, UK. It appears to have exploded as it entered the Earth's atmosphere, creating a shock wave that shattered windows, damaged buildings and apparently collapsed the roof and walls of zinc factory.
The Russian Academy of Sciences says the meteor weighed 10 tons and entered the atmosphere at a speed of at least 54,000 kilometres per hour, exploding between 30 to 50 kilometres above the ground. Reports from Russia also say that more than 900 hundred people have been injured, mostly by broken glass. Reports also suggest there are no fatalities, although two people are in intensive care.
Astronomers will want to recover any fragments of the meteorite that hit the ground. "You'll find them strewn over a large area. There may be some very large fragments but there will be many smaller ones spread over kilometres," says Green. "We can study the science of the bodies and learn more about the bigger ones, which are the real threat."
The much smaller Sutter's Mill meteorite that fell on California last year yielded many fragments that showed it was a very rare type of rock called a CM chondrite.
Strange coincidence
It is not unusual for meteors the size of the one that fell in Chelyabinsk to hit the Earth, though most end up falling into the sea unnoticed. "Depending on its size, it might be something that hits every few years or every few decades," says Green.
Although the odds of an unrelated meteor impacting on the same day as an asteroid fly-by seem astronomically high, experts seem sure the two objects are not linked, especially as the meteor hit over 12 hours before the expected fly-by. "2012 DA14 approaches from the south at quite a steep angle relative to the Earth's equatorial plane, so Russia being in the northern hemisphere makes [a link] extremely unlikely," says Lowry. "If this had been a southern hemisphere impact, serious questions would have been being asked."
One of the European Space Agency's satellites managed to spot the vapour trail of the meteor as it entered the atmosphere. The agency itself has also confirmed that there is no link with asteroid 2012 DA14, on course to fly past Earth at height of around 27,000 kilometres at 1925 GMT.
There are a large number of videos of the Russian meteor strike because it is common for Russian drivers to use dashboard-mounted cameras to prove liability in car accidents. The footage should allow astronomers to retrace the meteor's flight path and identify its origin, as well as any other space rocks that might be related. One possibility is that the meteor split off from a larger object. "It is possible that a collision could have happened further back in its orbit," says Lowry.
If the remnants remained on the same orbit, then they too could impact Earth, although that is unlikely as the planet has most likely moved out of the path of any potential secondary strike by now. "It is possible a parent fragment could hit Earth, but the probability decreases rapidly as time passes."
Read more: Meteorite hunters: Join the space rock rush
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