In 2013, a massive meteorite exploded over Russia, injuring 1,500 people and damaging hundreds of buildings. Archival images are impressive, but also increasingly rare. Because of this, scientists are redoubling their efforts to predict these events.
Almost every day a piece of space rock falls to Earth after burning up in the sky as a fireball. These minor impacts are likely to be far more numerous than we think, as many of them occur in unpopulated areas and therefore are not necessarily detected. What doesn’t happen every day, however, is an impact like the one that literally shook Russia on February 15, 2013.
On that day, dashboard cameras and smartphone videos in and around the city of Chelyabinsk caught a massive daytime fireball accompanied by a violent shockwave that shattered windows in the city, home to more than a million people. Hundreds of buildings were damaged and many injured, but fortunately no one was killed.
The terrifying images that were filmed looked like war scenes, but the reason was not military. A large meteoroid, also known as a bolide, exploded across the sky shortly after entering the atmosphere at almost 60 times the speed of sound.
The explosion had a force 30 times that of the first atomic bomb test and occurred in the upper atmosphere, about three times the typical cruising altitude of an airliner.
What is believed to be the largest fragment of the supercar to reach the surface punched a 6-meter hole in the icy surface of the nearby lake and quickly sank. The three-quarter-ton meteorite was recovered and is now in the South Urals History Museum in Chelyabinsk.
A frozen lake is arguably the safest place for a meteorite to touch the surface of the planet other than the ocean. No damage has been reported from the impact of this meteor on the surface. Its collision with the atmosphere is another story.
More cosmic concerns
The piece, which is now the size of a clothes dryer in the museum, lost mass through friction as it moved through our atmosphere. At the time of its impact with the latter, it was an asteroid at least 19.8 meters in diameter and an estimated weight of about 12,000 tons.
The only modern event that really compares to the Chelyabinsk impact is the so-called Tunguska event in 1908. Another piece of asteroid or comet apparently exploded over Siberia. The resulting explosion flattened more than 80 million trees and may have played a role in three deaths.
A review of eyewitness accounts of the Tunguska event was published in 2019 by researchers who also studied the Chelyabinsk impact. They found that in the case of Tunguska, reports of broken glass occurred in an area four to five times larger than in Chelyabinsk. The damage done has little to do with the comparable size of the object, but more to do with the angle the Tunguska bolide took when it entered the atmosphere.
A 2014 analysis published in Physics Today concluded that “Damage [à Tcheliabinsk] could have been a lot worse.”
Better eyes for the sky
Since 2013, significant progress has been made in identifying and tracking near-Earth objects that could pose an impact risk. NASA and other space agencies continuously catalog and track thousands of asteroids.
Progress in that effort was evident this week when astronomers spotted a refrigerator-sized asteroid just hours before colliding with the atmosphere. Further observations were quickly made, and scientists were able to accurately predict when and where the meteor would turn into a fireball.
This ability is largely due to new sky surveys and observatories such as Meerkat in South Africa and Atlas in Hawaii that have been established over the past decade. Even more impressive is that NASA’s DART mission changed the direction of an asteroid in space last year.
But there are still many objects to be discovered, such as the Chelyabinsk racing car. In reality, we have a real blind spot when it comes to objects approaching us from the Sun. NASA’s NEO Surveyor mission could help solve this problem later this decade.
Chelyabinsk also gave us new reasons for concern. Research released later in 2013 suggests the supercar over Russia could be a fragment that broke off from a larger asteroid.
Another troubling paper published at the time suggests that we should expect such impacts to occur more frequently than once a century, perhaps even every two decades. No asteroids or other known objects currently pose an impact threat, but it’s always worth keeping as many eyes on the sky – and space – as possible.
Just worry, our vision of heaven tends to fade with global warming, as we recently told you:
CNET.com article adapted from CNET France