World / Science & Health

Asteroid passes close on heels of Russia strike

Flyby was expected; surprise small rock first to cause many injuries

The Washington Post, AP

It was a day when the Earth was caught in a cosmic crossfire. One rock, the size of an apartment building, came from the south and passed by very close. An unrelated object came from the east. It was slimmer but had better aim.

The larger asteroid missed by a bare 27,600 km, as expected — the closest pass ever for a sizable known object.

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. Russian emergency officials indicated about 3,000 buildings suffered damage

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 50-meter-wide 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 earlier 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 is when another meteor exploded over Siberia, leveling more than 2,000 sq. km 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 15 meters wide, weighed more than a nuclear-powered submarine and screamed in at 64,000 kph, said Campbell-Brown, who examined data from sonic sensors deployed by the Comprehensive Nuclear Test Ban Treaty Organization to detect nuclear detonations.

In its 30-second shallow-angle dive into the atmosphere, the meteor shed energy equivalent to more than 20 Hiroshima-size atomic bombs. Most of that energy was dissipated far above the surface. In a sense, the atmosphere saved the day, preventing catastrophic damage from a major surface impact.

Initial estimates from Russian authorities sketched a much smaller and weaker object, but meteor-tracking scientists say the nuclear-sensor network provides the best measure of a meteor’s size and power.

Intense heat and pressure shattered the object into dozens of large pieces during its descent. Russian officials said they believed they had identified meteorite fragments on the ground 80 km west of Chelyabinsk and had reports of pieces stretched out over another 120 km.

Occasional injuries from meteor strikes have been recorded, but the number hurt Friday is unprecedented, said Timothy McCoy, of the Smithsonian’s National Museum of Natural History. “I can’t think of a burst this size over a city before,” he said.

Scientists the world over, along with NASA, insisted the meteor had nothing to do with the asteroid, since they were traveling in opposite directions. The asteroid is a much more immense object and delighted astronomers who watched it zip harmlessly through the night sky.