Russian Chelyabinsk meteor shockwave circled the Earth twice

The shock wave from an asteroid that burned up over Russia in February was so powerful that it travelled twice around the globe, scientists say.

They used a system of sensors set up to detect evidence of nuclear tests and said it was the most powerful event ever recorded by the network.

More than 1,000 people were injured when a 17m, 10,000-tonne space rock burned up above Chelyabinsk.

The study appears in the journal Geophysical Research Letters.

The researchers studied data from the International Monitoring System (IMS) network operated by the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO).

The detection stations look out for ultra-low frequency acoustic waves, known as infrasound, that could come from nuclear test explosions but the system can also detect large blasts from other sources, such as the Chelyabinsk fireball.

Alexis Le Pichon, from the Atomic Energy Commission in France and colleagues report that the explosive energy of the impact was equivalent to 460 kilotonnes of TNT.

This makes it the most energetic event reported since the 1908 Tunguska meteor in Siberia.