Surprise from the Skies: The Story of the Chelyabinsk Meteor

Chelyabinsk meteor as seen from a dash cam.
The fireball created as a superbolide flared over Chelyabinsk, Russia, on February 15, 2013. This was shot with a dashcam. Wikimedia Commons, CC-BY.

Every day, Earth is bombarded with tons of material from space. Most of it vaporizes in our atmosphere, while larger pieces fall to the ground as harmless meteorites. Sometimes we see swarms of these objects falling through the sky as meteor showers. What happens if a large rock — say one the size of a school bus — comes through the atmosphere? The residents of Chelyabinsk in Russia know the answer to that question all too well.

The Arrival of the Chelyabinsk Meteor

On the morning of February 15, 2013, people were going about their business when the skies suddenly lit up as a fireball flared across the sky. It was an incoming piece of space rock, a bolide moving more than 60,000 kilometers per hour (40,000 miles per hour). As the rock punched through the atmosphere, friction heated it up and it glowed more brightly than the Sun. It was so brilliant that people could see it from more than 100 kilometers in each direction along its path. This Chelyabinsk meteor was totally unexpected. It was very small, which meant that observing systems in place to detect incoming objects didn't see it, and the bolide's path happened to coincide with where the Sun was in the sky at the time.

Almost immediately after the blast, the Internet and Web were flooded with pictures and dash cam videos of the brilliant flare in the sky over Chelyabinsk caused by the bolide. It actually never hit the ground. Instead, the bolide disintegrated in an air burst about 30 kilometers above the city, with a blast energy the equivalent of a 400- to 500-kiloton nuclear weapon. Fortunately, most of that blast was absorbed by the atmosphere, but it still generated a shock wave that blew the windows in many buildings. Some 1,500 people were injured by flying glass. By some reports, nearly 8,000 buildings suffered damage from the blast, although none were hit directly by any pieces of the impactor.

What Was the Object?

The incoming meteor that blew up over Chelyabinsk was a piece of space rock that had a mass of more than 12,000 metric tons. Planetary scientists called it a near-Earth asteroid, and there are many of these orbiting in the space near our planet. After studying pieces of the rock that fell to Earth after the air burst, scientists figured out that this incoming piece of space rock was originally part of an asteroid that orbited out in the Asteroid Belt. The Chelyabinsk rock was a chunk that was broken from the parent rock early in solar system history. Its orbit gradually shifted over millions of years until it happened to cross the path of Earth's orbit and blast its way through the skies over Russia.

Recovering the Pieces

As soon as they could, people began searching for pieces of the impactor to study. For one thing, the small chunks would help scientists understand the origin of the parent body. For another, they are incredibly valuable to collectors. Mainly, however, impact fragments help scientists understand the origin and evolution of solar system bodies. The parent objects of incoming impactors are some of the oldest materials in the solar system, and they can tell a lot about conditions at the time they formed (some four and a half billion years ago).

The search area was quite large, mostly west of Chelyabinsk. Most of the rocks found were fairly small, the size of small pebbles. Some larger chunks were found in a nearby lake, and later studies revealed that at least one piece hit the lake at about 225 meters per second (not quite the speed of sound). Today, Chelyabinsk meteorites are found in many collections as well as in research institutes.

Impacts Always Pose a Threat to Earth

The impact danger for our planet is quite real, but large ones do not happen too frequently. Most people are aware of the giant impact of a rock called the Chixculub impactor, some 65 million years ago. It plunged into what is now the Yucatán Peninsula and is widely suspected to have contributed to the deaths of the dinosaurs. That meteor was about 15 kilometers wide and its impact raised a cloud of dust and aerosols that led to a global "winter". The aftermath of cooler temperatures, plant die-offs, and changed weather patterns killed off the dinosaurs as well as many other species. Such large impactors are fairly rare now, and if one were spotted on the approach, we'd likely have several years of warning.

Could another Chelyabinsk Happen?

Another Chelyabinsk will most definitely happen since there are many small impactors out there whose orbits can intersect Earth's. The idea of other smallish impactors plunging into Earth and causing damage led planetary scientists to devise searches for small projectiles. Finding large ones (like the Chixculub object) is fairly easy with current technology. However, the smaller ones can be quite deadly, too, as the Chelyabinsk meteor showed. Those are much harder to spot, even with dedicated survey cameras.

Thanks to our planet's atmosphere, which heated and weakened the structure of the incoming rock over Chelyabinsk in 2013, the impactor broke up high above the ground. However, not all impactors will do that. The potential for damage even from a school-bus sized object is quite high, particularly if it made it all the way to the ground in a highly populated area or close to a coastline. That's why there are projects such as SpaceWatch and others around the world dedicated to spotting these smaller impactors in time to warn people about possible collisions with Earth.

Luckily, for the people of Chelyabinsk, the meteor that lit up their skies didn't blast apart buildings or swamp the city in a tsunami. Their experience was a warning, however, that the solar system still has a few surprises to deliver to our planet.