NASA: What Exploded Over Russia, The Latest Results

 

“It was a meteor strike–the most powerful since the Tunguska event of 1908,” says Bill Cooke of NASA’s Meteoroid Environment Office.

In a coincidence that still has NASA experts shaking their heads, a small asteroid completely unrelated to 2012 DA14 struck Earth only hours before the publicized event. The impactor flew out of the blue, literally from the direction of the sun where no telescope could see it, and took everyone by surprise.

“These are rare events and it is incredible to see them happening on the same day,” says Paul Chodas of NASA’s near-Earth Object Program at JPL.

Researchers have since pieced together what happened. The most telling information came from a network of infrasound sensors operated by the Comprehensive Test Ban Treaty Organization (CTBTO). Their purpose is to monitor nuclear explosions.

Infrasound is a type of very low-frequency sound wave that only elephants and a few other animals can hear. It turns out that meteors entering Earth’s atmosphere cause ripples of infrasound to spread through the air of our planet. By analyzing infrasound records, it is possible to learn how long a meteor was in the air, which direction it traveled, and how much energy it unleashed.

The Russian meteor’s infrasound signal was was the strongest ever detected by the CTBTO network. The furthest station to record the sub-audible sound was 15,000km away in Antarctica.

Listen to the infrasound recording, sped up 135x into the range of human hearing. Play it

Western Ontario Professor of Physics Peter Brown analyzed the data: “The asteroid was about 17 meters in diameter and weighed approximately 10,000 metric tons,” he reports. “It struck Earth’s atmosphere at 40,000 mph and broke apart about 12 to 15 miles above Earth’s surface. The energy of the resulting explosion exceeded 470 kilotons of TNT.” For comparison, the first atomic bombs produced only 15 to 20 kilotons.

Based on the trajectory of the fireball, analysts have also plotted its orbit. “It came from the asteroid belt, about 2.5 times farther from the sun than Earth,” says Cooke.

Comparing the orbit of the Russian meteor to that of 2012 DA14, Cooke has shown that there is no connection between the two. “These are independent objects,” he says. “The fact that they reached Earth on the same day, one just a little closer than the other, appears to be a complete coincidence.”