A meteor that raced across the sky over central Russia early Friday, then exploded with a giant flash and massive boom, likely was unrelated to a known asteroid flyby on the same day, a Johns Hopkins asteroid expert said.
An asteroid the size of a 737 airliner, called 2012 DA14, was expected to pass within about 17,000 miles of Earth today, the closest pass of an object that size ever recorded. Andy Cheng, chief scientist of the Space Department at Johns Hopkins' Applied Physics Laboratory, said though it is "human nature" to assume a relationship between the asteroid and today's dramatic meteor entry, almost certainly there is none.
"It's most likely just a coincidence that it happened when it did," Cheng said. "These things happen all the time, in a cosmic sense.
"I suppose it's remotely possible that there's a connection, that a piece could have broken off," he added. "But that connection is not supported by science at this time."
NASA asteroid expert Dan Yeomans concurred, telling SPACE.com the object was likely an exploding fireball known as a bolide.
The shock wave from the meteor blast rocked buildings and shattered glass in Russia's Chelyabinsk region, in the Ural Mountains, shortly after 9 a.m. local time Friday. Nearly 1,000 people were hurt, though most of the injuries were not serious, the BBC reported on its website.
Numerous videos of the fireball racing across the sky and exploding, of the meteor's long white contrail, and of the sonic aftereffects of the explosion circulated on the Internet.
"This meteor event is an example of what we call an airburst, when an incoming body from space explodes in the atmosphere before it hits the ground," said K.T. Ramesh, professor of science and engineering at Johns Hopkins Whiting School of Engineering and founding director of the Hopkins Extreme Materials Institute. "This generally happens for relatively small, rocky asteroids, a few feet to tens of feet [in diameter]. Most of them come in at very high speeds, about 36,000-50,000 miles per hour. This means that everything happens very fast, in 10 seconds or so, once they enter the atmosphere."
The Russian meteor, estimated to weigh about 10 tons, entered Earth's atmosphere at a hypersonic speed of at least 33,000 miles per hours and shattered about 18 to 32 miles above the ground, scientists said. The precise size of the meteor was not known—it might have been a large meteor, but much smaller than 2012 DA14, Cheng said. The asteroid was expected to pass by Earth over Asia at about 2:25 p.m. EST. Live coverage is available online.
Richard Conn Henry, an astrophysicist in the Krieger School of Arts and Sciences, said the spectacular entry is the result the release of a tremendous amount of kinetic energy generated by the meteor's high speed.
"Thousands of meteors enter the atmosphere every day," he said. "Only rarely indeed do you get one as traumatizing as the one in Russia."
NASA's Near Earth Object Program and others track large asteroids like 2012 DA14, but its virtually impossible to identify and track all of the debris floating around in space. There are millions of meteors, most made up of silicate stone or iron, or occasionally a combination of the two.
"These are pieces of the earliest building blocks of all the planets, leftovers of the building process," said Bruce Marsh, a professor in the Department of Earth and Planetary Sciences at Johns Hopkins. "They are generally about 4.5 billion years old and come mainly from the belt of asteroids between Mars and Jupiter.
"Earth gets about 200 tons each day of meteoritic debris, most of which is small grains," Marsh added. "But larger chunks are always a possibility."