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Fallout from the Russian fireball encircled Earth, research shows

The meteor that exploded near Chelyabinsk, Russia on February 15 created a mushroom cloud of microscopic dust grains that spread across the sky, encircling the planet within four days.

By Correspondent / August 19, 2013

This polar projection of Earth shows atmospheric particles encircling the globe a week after the February 15 blast over central Russia (white dot). Fast-moving particles (red) returned there within four days, and within seven days, they had 'lapped' the slow-moving particles (purple) to create a dust blanket around the globe. The rainbow colors represent altitude (and thus wind speed, since winds move faster at higher altitudes): Red is 27 miles above Earth's surface and dark purple is 21 miles up.

Courtesy of NASA/Goddard

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Six months ago, Russians watched a massive fireball streak across the sky. The sperm-whale-sized asteroid exploded before it hit the ground, shaking the air and land with as much force as a 440-kiloton nuclear bomb and shattering into countless rocks, shards, grains, and dust-sized particles. 

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The heaviest of these quickly fell to the ground, leaving a 60-mile-long swath of debris that fell along the meteor's trajectory. But the smaller and lighter fragments rose up, mushroom-cloud style, till they were caught by high-altitude winds that carried them around the world. According to a paper recently accepted by Geophysical Research Letters, microscopic meteorite grains were blown first across the Russian skies, then across the Pacific to Alaska and Canada, then over the Atlantic, ultimately encircling the globe with a ring of space debris.

"After the meteor exploded, like a fireball from a nuclear explosion, the material lifted very high," says Paul Newman, an atmospheric physicist with NASA. "And then the winds – what we call the Polar-Night Jet – carried that material around the northern hemisphere very quickly, forming this belt of particles." It reached Alaska by the next day, and looped the planet within four days.

What goes up ... doesn't always come down?

It's not unusual for fine material to stay aloft. "Imagine you took a handful of flour and threw it across the room. The bigger particles in flour will fall out quickly, and the smaller particles will continue to float in the air," says Dr. Newman, who is the chief scientist for atmospheric sciences at NASA's Goddard Space Flight Center. (See "Play along at home," below.) 

The particles from the Chelyabinsk blast, he says, are almost unimaginably small. "When the meteor exploded, it really pulverized the entire meteor," says Newman. "Literally, these particles were a thousand times smaller than the width of a human hair." And because they're so incredibly small, he explains, "they settle at a very, very, very slow rate."

The biggest of these microfine particles fell a few hundred feet per day, estimates Nick Gorkavyi, the lead scientist in the team, while the smallest fall less than 15 feet per day. 

Within hours, NASA's Ozone Mapping Profile Suite had spotted the plume – "over Siberia, a thousand miles from Chelyabinsk," says Dr. Gorkavyi, a programmer with NASA contractor Science Systems and Applications, Inc. "We were surprised: Why so far?" The initial atmospheric models had predicted a much slower spread across the sky.

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