What exploded over Russia? Space researchers explore, with infrasound sensors

The bizarre explosion in the skies over in Russia on Feb. 15, 2013 left scientists dumfounded. The asteroid 2012 DA14 was expected to pass some 17K miles over Indonesia, but the Russian impactor wasn't foreseen: it flew from the direction of the sun where telescopes couldn't see it, and surprised everyone hours before the more-publicized asteroid's flyby.

A NASA news item today explains how scientists are piecing together what happened, using 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.

Video above: Listen to the infrasound recording, sped up 135x into the range of human hearing. The video comes from the Comprehensive Test Ban Treaty Organization's YouTube channel.

Peter Brown, University of Western Ontario Professor of Physics, analyzed the data and determined that the asteroid was about 17 meters in diameter and weighed approximately 10,000 metric tons.

"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."

More: What Exploded over Russia? [NASA Science].


  1. Nice post and good information, but what’s up with the first sentence? The explosion wasn’t “bizarre,” and scientists (I’m one of them) weren’t “dumfounded.” An unusual and exciting event, sure, but just the sort of thing we expect to happen every once in a while. This lead-in seems to imply that there was something weird about the situation, which isn’t at all the case.

  2. My understanding is that we didn’t see this asteroid because it’s smaller than the type of asteroid we typically look for, also it came in from a bad angle.  There wasn’t anything particularly mysterious about it, just surprising.

    1. This.

      Plus it’s not even that rare. According to Wiki, megaton-range events happen around every 300 years. The last was the Tunguska-event in 1908 and this one weighed in at only ~.5 megatons.

  3. I have trouble visualizing the problems seeing objects that are closer to the sun than we are. If we stuck a survey telescope in orbit around venus, could it more easily catalog these objects? Would it help any to put the telescope in a trojan orbit around the sun from us?

    And in another track entirely: would there be any way of guessing how much mass we’d accounted for in all our cataloging? Junk in earth orbit, we have a pretty good object count. Solar orbit, not so much.

  4. I have been curious – but not curious enough to look into it more deeply – why it is presumed that the Russian event is not associated to the DA14 asteroid just because of the direction it entered the atmosphere.

    Would it be possible for smaller objects to be orbiting the larger asteroid – with elliptical orbits that could intersect earth orbit at any angle/direction as DA14 approached to the close fly-by?

    I just don’t see any reason why the direction of the russian object automatically rules out correlation to DA14 by itself.

    1.  Well, it came from the northeast, while DA14 was 230,000 miles south of Earth.  It would be a stretch to figure out how two objects coming at high velocities from opposite directions were originally associated.  I suppose we could go with some kind of “magic bullet” solution.

      1. “northeast”?   “south of earth”?  what does that mean in space?  If the smaller object was in orbit around DA14, they could easily approach earth from apparently different directions.  draw a picture of DA14 orbit approaching earth, then draw a eccentric ellipse around DA14 and you will see how it could be possible.

    1. That should be:  Somewhere in Seoul:  Whew! 

      If this had detonated over Pyongyang they might have mistaken it for a nuclear attack (in fact it was much more powerful than a nuclear attack) and retaliated with their own nukes, reducing the Nothern part of South Korea to a radioactive wasteland. 

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