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Russian meteor largest in a century

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  • Romi Elnagar
    Russian meteor largest in a century Explosion rivalled nuclear blast, but rock was still too small for advance-warning networks to spot. * Geoff Brumfiel 15
    Message 1 of 1 , Feb 16, 2013
      Russian meteor largest in a century
      Explosion rivalled nuclear blast, but rock was still too small for advance-warning networks to spot.
      * Geoff Brumfiel
      15 February 2013 Corrected:
      1. 15 February 2013

      A meteor that exploded over Russia this morning was the
      largest recorded object to strike the Earth in more than a century,
      scientists say. Infrasound data collected by a network designed to watch for nuclear weapons testing suggests that today's blast released
      hundreds of kilotonnes of energy. That would make it far more powerful
      than the nuclear weapon tested by North Korea just days ago and the
      largest rock crashing onto the planet since a meteor broke up over
      Siberia's Tunguska river in 1908.
      "It was a very, very powerful event," says Margaret
      Campbell-Brown, an astronomer at the University of Western Ontario in
      London, Canada, who has studied data from two infrasound stations near
      the impact site. Her calculations show that the meteoroid was
      approximately 15 metres across when it entered the atmosphere, and put
      its mass at around 7,000 metric tonnes. "That would make it the biggest
      object recorded to hit the Earth since Tunguska," she says.
      Hidden approach
      The meteor appeared at around 9.25 a.m. local time over
      the region of Chelyabinsk, near the southern Ural Mountains. The
      fireball blinded drivers and a subsequent explosion blew out windows and damaged hundreds of buildings. So far, more than 700 people are
      reported to have been injured, mainly from broken glass, according to a statement from the Russian Emergency Ministry.

      The meteor contrail seen over Chelyabinsk, Russia, on 15 February. The
      object's explosion in the atmosphere is reported to have injured more
      than 700 people.
      Despite its massive size, the object went undetected until it hit the atmosphere. "I'm not aware of anyone who saw this coming,"
      says Heiner Klinkrad, head of the European Space Agency's space debris
      office at the European Space Operations Centre in Darmstadt, Germany.
      Although a network of telescopes watches for asteroids that might strike Earth, it is geared towards spotting larger objects — between 100
      metres and a kilometre in size.
      "Objects like that are nearly impossible to see until a
      day or two before impact," says Timothy Spahr, director of the Minor
      Planet Center in Cambridge, Massachusetts, which tracks asteroids and
      small bodies. So far as he knows, he says, his centre also failed to
      spot the approaching rock.
      The meteoroid itself was probably made of rock, but may
      have also contained nickel and iron. Campbell-Brown says that it was
      likely to have come from the asteroid belt, a region containing hundreds of thousands of rocky bodies and located between Mars and Jupiter. The
      European Space Agency does not think that the meteor is related to a
      much larger asteroid known as 2012 DA14, which will be passing within about 20,000 kilometres of Earth later
      today. Both the timing of the meteor's appearance and its location
      indicate that it came from a different direction, Klinkrad says.
      Campbell-Brown agrees: "We happened to have close approaches to two of
      them, and one of them got us," she says.
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      Although there are reports of fragments of the meteor, or meteorites, striking
      the ground, Klinkrad says that he believes the vast majority of damage
      in the region was caused by shockwaves of the explosion, as the rock
      broke up in the upper atmosphere. Campbell-Brown says that the
      infrasound data shows a very shallow angle of approach — a feature that
      funnelled much of the energy from the blast to the city below. Still,
      she adds, "It's lucky that there wasn't more damage."
      The infrasound stations belonged to the Comprehensive Test Ban Treaty Organization, an international body that is designed to watch the Earth for
      nuclear-weapons tests. It is unlikely to be the only source of data on
      the strike. Both the United States and Russia have satellites in
      geosynchronous orbit that watch for the heat signatures of missile
      launches and warhead re-entries. The US military has released data on meteor strikes in the past, but it is unclear whether they will do so for today's event.
      Klinkrad says it would have been hard to give warning of
      the blast. In addition to being relatively small in size, the rocky
      meteoroid was probably dark in colour, making it even harder to spot
      against the backdrop of space.  "We just have to live with it," he says.

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