On Dec. 18, 2018, one of the most powerful known explosions from a meteor in over a century rocked the atmosphere over the Bering Sea. According to estimates, the 32-foot-wide rock was traveling at speeds in excess of 71,000 miles per hour when it unleashed an explosion equivalent to 73 kilotons of TNT or more than 10 times the power of the Hiroshima atomic bomb.
Incredibly, due to both the altitude at which the explosion occurred (16 miles) and its remote location, astronomers who track meteors didn't learn of its existence until some three months later.
"It's an unusual event," said Peter Brown, a meteor expert and professor of physics and astronomy at Western University in Ontario, Canada, told the CBC. "We don't see things this big very often."
While no one below appears to have witnessed the massive fireball, NASA's Earth-watching Terra satellite had a front-row seat. According to the space agency, no less than five of the nine cameras on Terra's Multi-angle Imaging SpectroRadiometer (MISR) captured the meteor's fiery end.
"The shadow of the meteor's trail through Earth's atmosphere, cast on the cloud tops and elongated by the low sun angle, is to the northwest," they write. "The orange-tinted cloud that the fireball left behind by super-heating the air it passed through can be seen below and to the right of the GIF's center."
The MISR instrument, also on Terra 🛰, saw the large "fireball" — the term used for exceptionally bright meteors ☄️ that are visible over a wide area — as it exploded 💥 about 16 miles above the Bering Sea, far enough way to pose no threat. pic.twitter.com/lyjyZKBZOm— NASA Earth (@NASAEarth) March 22, 2019
A true color image, captured by Terra's Moderate Resolution Imaging SpectroRadiometer (MODIS) instrument, was also released showing the meteor's trail and subsequent explosion.
According to NASA, the explosion associated with this fireball is the largest observed since the Chelyabinsk event over Russia in 2013 and likely the third largest since the Tunguska event of 1908. Nonetheless, despite its unusual size, the agency reiterated that such celestial bombardments of Earth are not uncommon. Already in 2019, the National Meteor Foundation has recorded 154 fireball events.
"The public should not be concerned," Paul Chodas, manager of NASA's Center for Near-Earth Object Studies at JPL, told the CBC. "Because these events are normal. Asteroids impact Earth all the time, though it's usually much smaller than this size."