On February 15, 2013 an huge fireball exploded over Chelyabinsk, Russia. Astronomers have been able to observe this asteroid impact event from over 400 different angles due to videos that Russian citizens posted on YouTube. The video documentation, combined with information collected from Russian seismologists, has allowed scientists to gain a better understanding of the how the fireball came to be.
The incredible number of available videos is largely thanks to dash cams, which nearly every Russian motorist has in order to provide credible eyewitness testimony for traffic incidents and theft. Mobile phones and security cameras also provided scientists with the information needed to determine speed, size, and force of the fireball’s shockwave. Previously, scientists had to speculate about impact events through modeling. The video footage from the Chelyabinsk event has revolutionized scientist’s knowledge of asteroid impacts and nine countries have already established a new modeling system based on this information.
Several videos were recreated at night, so scientists could use the position of the stars in the background as a guide to calculate the speed. It was determined that the asteroid was traveling at about 42,500 miles per hour (19 kilometers per second) at impact. As it traveled through our atmosphere, the amount of drag generated heat and caused the asteroid to ignite, creating a massive fireball that was brighter than the sun. The blast broke thousands of windows, sending glass shards flying. Scientists used the shards to determine that the fireball exploded with a force of at least seven times that of Little Boy, the atomic bomb dropped on Hiroshima, Japan at the end of World War II.
Before the explosion, the asteroid was estimated to be about 56-66 feet (17-20 meters) long. While most of it was incinerated by the blast, approximately 9,000-13,000 pounds (4,000-6,000 kilograms) made contact with the surface as meteorites. The largest recovered meteorite from the impact event weighed in at about 1,400 pounds (650 kilograms) and was discovered in Lake Chebarkul, about 59 miles (95 kilometers) away from Chelyabinsk just a few weeks ago.
The scientists analyzed the fracture lines in the meteorites, known as shock veins. Grains of iron in the breaks had cooled into layers after impact, making the shock veins particularly brittle. Astronomers say that these veins could have formed 4.4 billion years ago, shortly after the formation of the solar system. These physical characteristics helped determine the asteroid’s behavior as it became a fireball. The data also suggests that these events may be more common than previously thought. Previously, impacts of this size were thought to happen every few thousand years, but they could actually occur every 100-200 years.
Information collected from the Chelyabinsk event will be incorporated into current research involving other near-Earth objects (NEO). Earlier this year, NASA announced a new mission to obtain and redirect an asteroid to orbit Earth, allowing astronauts to visit it for study. Asteroids may give clues about the origin of the solar system, how Earth got water, and potentially even explain the origin of molecular precursors for life. Understanding NEOs may also allow scientists to better predict their movements and more precisely calculate the odds of an impact event.
Correction: The speed should have read 19 kilometers per second, not meters per second.
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