CAP CANAVERAL, FLORIDA, USA - A large meteor exploded over Earth, Nasa has revealed.

It said the massive fireball was the second largest blast of its kind for 30 years, and yet it went mostly undetected.

The meteor exploded with ten times the energy of the Hiroshima atomic bomb.

t blew up over the Bering Sea, off Russia's Kamchatka Peninsula, in December, Nasa said.

The asteroid came through the Earth's atmosphere at a speed of 32km/s on December 18, on a steep trajectory of seven degrees, BBC News reported.

Lindley Johnson, planetary defence officer at Nasa, told the BBC that a fireball of its size is only expected two or three times every century.

It measured several metres and exploded 25.6km above the Earth's surface, with an impact energy of 173 kilotonnes.

It was the largest fireball since one exploded over Chelyabinsk in Russia six years ago.

Dr Kelly Fast, near-Earth objects observations programme manager at Nasa, said: "That was 40% the energy release of Chelyabinsk, but it was over the Bering Sea so it didn't have the same type of effect or show up in the news.

"That's another thing we have in our defence, there's plenty of water on the planet."

She gave details of the blast at the 50th Lunar and Planetary Science Conference near Houston, Texas.

Nasa was notified of the explosion by the US Air Force after it was picked up by military satellites.

Dr Johnson said the meteor came in over an area not far from routes used by commercial planes flying between North America and Asia.

Nasa is checking with airlines to see if there were any reported sightings.