Scientists explain why we're just now learning about a giant meteor that exploded over Earth last year

A huge meteor exploded over the Bering Sea in December in the largest recorded event since a 2013 incident in Russia.

The explosion was recorded by government sensors on Dec. 18, according to a NASA tracker for fireballs. Fireballs are described by NASA as "exceptionally bright meteors that are spectacular enough to to be seen over a very wide area."

The blast generated energy roughly equivalent to 173 kilotons of TNT, the agency said. According to MIT Technology Review, that's about 10 times the energy generated by the atomic bomb used in Hiroshima in 1945.

"An event like this might occur two to three times a century," Lindley Johnson, a planetary defense officer at NASA, told USA TODAY.

Johnson said this is the second-largest event they've seen in the last 30 years.

Based on the amount of energy released, the meteor is estimated to be between 10 to 14 meters in size, said Kelly Fast, the program manager for Near-Earth Object Observations at NASA.

The last meteor of this magnitude to explode on Earth was in 2013, when a 20-meter meteor exploded in Russia's Chelyabinsk region, captured on video by security and dashboard cameras. Johnson said that meteor generated energy equal to 440 kilotons of TNT.

At the time of the 2013 meteor, NASA said it was the largest in more than 100 years, exploding with the force of 20 atomic bombs.

Johnson said NASA has an agreement with the U.S. Air Force to share data when natural events like the meteor explosion take place, which can sometimes take days or weeks to process.

Fast said more information on the meteor in December hasn't come out until now because the location of the explosion was in a remote location in the middle of the ocean.

"In the case of 2013, it happened over a populated area, lots of people could see it," she said.

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