NASA's Plan to Save Earth From Killer Asteroids

A 2013 meteor explosion above Chelyabinsk, Russia injured more than 1,700 people. It was completely unexpected — and it could happen again. Here’s what NASA’s doing to make sure we know how to act when (not if) the next one hits.

The Chelyabinsk meteor was a superbolide that entered Earth’s atmosphere over Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC). It was caused by an approximately 20 m (66 ft) near-Earth asteroid with a speed of 19.16 ± 0.15 kilometres per second (60,000[5]–69,000 km/h or 40,000[5]–42,900 mph).[6][7] It quickly became a brilliant superbolide meteor over the southern Ural region. The light from the meteor was brighter than the Sun, visible up to 100 km (62 mi) away. It was observed over a wide area of the region and in neighbouring republics. Some eyewitnesses also felt intense heat from the fireball.

Due to its high velocity and shallow angle of atmospheric entry, the object exploded in an air burst over Chelyabinsk Oblast, at a height of around 29.7 km (18.5 mi; 97,000 ft).[7][8] The explosion generated a bright flash, producing a hot cloud of dust and gas that penetrated to 26.2 km (16.3 mi), and many surviving small fragmentary meteorites, as well as a large shock wave. The bulk of the object’s energy was absorbed by the atmosphere, with a total kinetic energy before atmospheric impact estimated from infrasound and seismic measurements to be equivalent to the blast yield of 400–500 kilotons of TNT (about 1.4–1.8 PJ) range – 26 to 33 times as much energy as that released from the atomic bomb detonated at Hiroshima.[9]

The object was undetected before its atmospheric entry, in part because its radiant was close to the Sun. Its explosion created panic among local residents, and about 1,500 people were injured seriously enough to seek medical treatment. All of the injuries were due to indirect effects rather than the meteor itself, mainly from broken glass from windows that were blown in when the shock wave arrived, minutes after the superbolide’s flash. Some 7,200 buildings in six cities across the region were damaged by the explosion’s shock wave, and authorities scrambled to help repair the structures in sub-freezing temperatures.

With an estimated initial mass of about 12,000–13,000 tonnes[7][8][10] (13,000–14,000 short tons, heavier than the Eiffel Tower), and measuring about 20 m (66 ft) in diameter, it is the largest known natural object to have entered Earth’s atmosphere since the 1908 Tunguska event, which destroyed a wide, remote, forested, and very sparsely populated area of Siberia. The Chelyabinsk meteor is also the only meteor confirmed to have resulted in a large number of injuries. No deaths were reported.

The earlier-predicted and well-publicized close approach of a larger asteroid on the same day, the roughly 30 m (98 ft) 367943 Duende, occurred about 16 hours later; the very different orbits of the two objects showed they were unrelated to each other.