WASHINGTON — It was a day when the Earth was caught in a cosmic crossfire. The big rock came from the south, the smaller one from the east. They were unrelated objects, with different orbits, one the size of an apartment building, the other slimmer but with better aim.
The larger asteroid missed by 17,000 miles, as expected, but the Russian meteor stole the show Friday, fireballing across the Ural Mountains in spectacular fashion and exploding into fragments, creating a powerful shock wave that blew out windows, collapsed roofs and injured 1,200 people, mostly from broken glass.
It was surely the most thoroughly documented meteor strike in human history — captured by countless crack-of-dawn Russian drivers who own dashboard cameras.
The spectacle capped an extraordinary day for the planet. The Russian meteor, which exploded over the industrial city of Chelyabinsk, was the largest such impact in more than a century and the first to cause significant human casualties, with at least 48 victims hospitalized.
The asteroid that was supposed to show up Friday, the much-hyped 2012 DA14, passed by harmlessly, just as the experts had promised it would.
But they had no way of seeing the other rock heading toward Russia. The explanation from NASA scientists, when asked why they hadn't spotted it, boiled down to two simple facts: It was small and the sun was in their eyes.
"This was the largest object observed to hit the Earth since 1908," said Margaret Campbell-Brown, an astronomer at the University of Western Ontario. That's when another meteor exploded over Siberia, leveling 800 square miles of forest in what became known as the Tunguska event.
On Friday, a global network of sensors recorded the space rock's descent and revealed its stunning power. The object measured about 50 feet wide, weighed more than a nuclear-powered submarine and screamed in at 40,000 miles per hour, said Campbell-Brown, who examined data from sonic sensors deployed by the Comprehensive Nuclear-Test-Ban Treaty Organization to detect nuclear detonations.