ON 15 FEBRUARY, early morning drivers around the Russian city of Chelyabinsk were startled by the biggest meteor strike in more than 100 years. Appearing literally out of the blue after sunrise, this cosmic missile became a fireball brighter than the Sun before exploding into thousands of fragments over the Urals. Since then, planetary scientists have been studying videos of the space rock’s final moments and analysing its remains.
The task of tracing the meteor’s final moments was made easier by a network of CCTV cameras in and around Chelyabinsk, plus footage of the brilliant fireball from the ‘dashcams’ commonly fitted to Russian cars to record accidents.
By analysing seven different videos, Dr Pavel Spurny and his team at the Ondrejov Observatory near Prague were able to triangulate key points in the rock’s path and from that, calculate the meteor’s orbit before it ran into our planet. Spurny says the rock orbited the Sun on an elliptical path that stretched from Venus to the centre of the asteroid belt between Mars and Jupiter.
“Our main contribution was to determine its atmospheric trajectory,” Spumy tells Us. “We proved that the main piece landed in Lake Chebarkul and that two or three large fragments and thousands of smaller, coin-size meteorites originated from the two biggest flares.” Spurnÿ’s analysis also shows the rock first became visible at a height of around 92km above ground before exploding at a height of 32km, 11 seconds later. The resulting shockwave damaged buildings and injured over 1,000 people. As it entered the atmosphere, the rock would have been about the size of a house and would have weighed in the region of 9,000 tonnes.
Many fragments of this behemoth have been found lying scattered around Lake Chebarkul. Prof Viktor Grokhovsky of Ural Federal University has collected more than 50 pieces himself, and found the asteroid was stony with a little iron, classifying it as a ‘chondrite’. The fragments contain glassy veins that would have been generated by collisions with other asteroid belt objects. This battering is likely to have led to weaknesses within the rock, which resulted in the spectacular explosion in our atmosphere. Rocks that were less flawed might have hit Earth’s surface intact.
Spurny is working to further refine his calculations of the rock’s orbit using more observations. The meteorite chunks will also be analysed in greater detail to reveal what they contain.