Investigating the asteroid that detonated over Chelyabinsk, Russia earlier this year, an international research team, including members of Western University’s Centre for Planetary Science and Exploration (CPSX), has discovered remarkable findings that will drastically change theoretical models about the frequency of such events and the potential damage that could be caused by them.

The results of the eight-month study were released today by Nature, the world’s most highly cited interdisciplinary science journal, in two corresponding papers. 

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The international team, which includes Western’s Peter Brown, Margaret Campbell-Brown, Paul Wiegert and David Clark, estimates the total energy of the event, which shattered thousands of windows in Chelyabinsk, to be equivalent to an explosion of around 500 kilotons of TNT. At peak brightness, the airburst appeared to be 30 times brighter than the sun. The authors show that existing models for estimating airburst damage for the circumstances of the Chelyabinsk impact do not match these observations. They suggest that the number of objects with diameters in the range of tens of metres that impact the Earth may be several times greater than previously thought. 

“Existing models predict events like the Chelyabinsk asteroid might hit every 120 or 150 years, but our data shows the frequency may be closer to every 30 or 40 years,” explains Brown, the Canada Research Chair in Meteor Science, who also serves as CPSX Director. “That’s a big surprise. When Chelyabinsk happened, I would have never expected to see an event big enough to cause damage on the ground. It’s totally outside the realm of what we thought likely in our lifetimes based on earlier statistics. Our statistics now suggest this type of event likely happens with more frequency.”

The Chelyabinsk asteroid impact occurred over a densely populated region of Russia and was observed globally by multiple instruments, including hundreds of amateur videos. Analyses of a selection of these videos reveal details about the journey taken by the roughly 19-metre-diameter asteroid (equivalent to a six-story building). 

According to the study, the orbit of the Chelyabinsk asteroid seems to be similar to another asteroid that has orbited close to Earth – the near-Earth asteroid 86039 (1999 NC43) – suggesting that the two were probably once part of the same object. The arrival times of secondary sonic booms heard on videos were also used to locate fragmentation points, and to calculate that the asteroid broke into small pieces between around 30 and 45 kilometres above the ground.

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