It was the biggest asteroid to strike Earth in more than a century, yet no one saw the Chelyabinsk meteor coming.
When the space rock smashed into western Russia in February 2013 it generated a shockwave as strong as 35 Hiroshima atomic bombs, leaving more than 1,600 people injured.
But how come no one detected the 60ft (19 metres)-wide meteor heading straight for us? The answer, experts say, is that it was hidden by the glare of our sun.
Worst still, it will not be the only one, as they warn that an ‘unknown’ number of space rocks could be heading for Earth undetected.
‘Asteroids the size of the Chelyabinsk meteor strike Earth roughly every 50-100 years,’ warned Richard Moissl, the European Space Agency’s head of planetary defence.
Read more: Invisible asteroids could strike Earth at any MINUTE: Scientists warn an ‘unknown number’ of space rocks could be heading for Earth, hidden in the glare of our sun