A powerful fireball exploded over the wilds of eastern Russia last December. Satellites captured the whole thing.

I was probably picking up a last-minute Christmas gift when it happened. Last December 18th at 11:48 a.m. local time, a meteoroid exploded with 10 times the force of the Hiroshima atomic bomb over the Bering Sea. It became the second most powerful meteor blast this century, after the Chelyabinsk explosion in 2013 that released the energy equivalent of 20 to 30 atomic bombs.

Had there been eyewitnesses, we'd have known about the Bering blast within minutes, but it happened beneath the cloud deck in a sparsely populated region off the east coast of Russia's Kamchatka Peninsula (58.6°N, 174.2°W). Military satellites designed to look for nuclear explosions picked up the blast, as did more than 16 infrasound detectors worldwide. Luckily for us, so did the Japanese Himawari 8 and U.S. Terra satellites, which took striking images of the evolving orange plume of meteoric dust and the shadow it cast on the clouds below during its atmospheric passage.

I originally thought the orange glow pictured in the images was part of the ionized trail left by the speeding meteoroid, but this can't be possible because traces of the color lingered for about 90 minutes, far too long. While trains can last for many minutes, the colorful, bright trail typically lasts only seconds.

The Sun stood about 11° at the time of impact and slowly declined thereafter, so the color likely comes in part from the low sun angle which tends to "warm" things up. Peter Brown, a meteor scientist and planetary astronomer at the University of Western Ontario, suggested in an e-mail communication the back-scattering properties of the meteoroid dust removed blue from the trail and further reddened its appearance.

Peter Brown first tweeted the news of the event on March 8th. Now it's making the rounds of the internet in various forms including being falsely reported on a few sites as occurring over Greenland. Based on the imagery and infrasound data, the asteroid responsible for all the fuss measured about 10 meters across, or a little larger than a two-story building. It packed the force of ~176 kilotons of TNT and would have made a spectacular sight. Perhaps ground video may yet surface.

Given the magnitude of the blast it's very possible that meteorites fell, likely in the Bering Sea. The Cuba meteorite fall on February 1st produced a far less powerful blast — only in the kiloton range — but made a memorable sonic boom and showered the region with many stony meteorites. Significant airbursts like the Kamchatka meteor occur about three to four times a century.



Fireball explosion over Pinar del Rio, Cuba, on February 1st. You can hear the explosion at the 55-second mark.

Astronomers have discovered more than 90% of near-Earth asteroids larger than a kilometer across — the ones that would have serious consequences in the event of a strike. But little ones, like Chelyabinsk or Tunguska? Nearly all are unannounced simply because they're so tiny, they escape our notice. Fortunately, the atmosphere serves as an excellent defense against objects up to several tens of meters.

You can always check on the most recent significant meteor blasts at NASA's Fireball and Bolide Data page, which also includes more details on the Bering Sea impact.

Much of a meteoroid's mass is shed as dust, some of which ultimately serves as nuclei for the formation of noctilucent clouds, pale blue clouds that glow just above the northern horizon at the end evening twilight in summer. In this way, such dramatic and potentially harmful events confirm Earth's cosmic connection every single day.