The risk of large asteroids hitting Earth is ten times larger than we previously thought, according to a new study.
Three extensive studies of the asteroid which exploded above the Russian town of Chelyabinsk in February, resulting in injuries to 1,000 people, shows that it was not as extraordinary as previously thought.
Hundreds of cameras captured the moment when the meteor blasted through the blue Russian sky. It was hard to miss - it shined 30 times brighter than the Sun and exploded with the force of 500 kilotons of TNT.
Those videos initially proved viral fodder for social media networks - and the HuffPost. But using those clips scientists made an analysis of the rock's flight path and trajectory.
Their findings show that the rock was an "ordinary" chrondrite from the asteroid belt between Mars and Jupiter, about twice as large as previously thought (about 12,000 tonnes). The two studies in Nature and one study in Science - all published simultaneously - so it was travelling at 19 km/s and exploded at about 27,000 metres above the surface.
And of the millions of objects of similar size and mass in the solar system, only 500 have ever been mapped accurately.
Peter Brown, a planetary scientist at the University of Western Ontario, says that while the estimated rate of similar impacts is about once in 150 years, the observed rate is orders of magnitude higher.
In his study, Brown and his team show that number of impacts over 1 kiloton of TNT could be up to ten times higher than previously thought.
So while the potential for a world-ending asteroid hitting Earth seems low, at least for the next couple of centuries, it could be that we're only now grasping just how often we're set to be pummelled by smaller rocks from the asteroid belt.
And next time it could be much worse.
"Luckily, most of the kinetic energy was absorbed by the atmosphere," Jiří Borovička, an asteroid researcher at the Astronomical Institute, near Prague, told Nature.
"A more solid rock that might have blasted closer to the ground would have caused considerably more damage."
Several efforts are ongoing by ESA, NASA and others to catalogue and track potentially dangerous asteroids. But the sheer scale of the task for small rocks is so vast, that none are anywhere near comprehensive. And - as we're not obliged to point out in articles such as these, Nasa's chief recently said that our best defense remains, unsettlingly, "prayer".