ESA assesses Russian meteor explosion
The European Space Agency (ESA) is assessing information about the Chelyabinsk meteor that exploded last week over Russia in the hope of improving the space agency’s asteroid-hunting program. Calculations by Peter Brown at Canada's University of Western Ontario based on the analysis of extremely low-frequency sound waves detected by a global network, was combined with videos, satellite images and eyewitness accounts to allow ESA to construct a more complete and accurate account of the event.
On February 15, a large fireball was reported over Chelyabinsk, Russia flying northeast to southwest at an angle of 20 degrees above the horizontal at a speed of about 18 km/s (64,800 km/h, 40,000 mph). Seen by thousands of eyewitnesses and recorded on car dashboard cameras, the 17-meter (56-ft) meteor with an estimated mass of between 7,000 and 10,000 tonnes exploded at 03:20:26 GMT over 55° 10' N, 61° 25' E at an altitude of 15 to 20 kilometers (9.3 to 12.4 miles) with a force of 500 kilotons – the equivalent of 30 Hiroshima atomic bombs.
In an interview with Nicolas Bobrinsky, Detlef Koschny – who is responsible for ESA’s Space Situational Awareness (SSA) program’s Near-Earth Object operations – outlined some of the findings and their importance in detecting similar meteors before they hit.
One point that was easy to determine was that the Chelyabinsk meteor is completely unrelated to asteroid 2012 DA14, which passed remarkably close to Earth the same day. Despite the timing, the orbits of the two objects don’t match and therefore the events of Friday were merely coincidental.
In regard to the damage caused by the Chelyabinsk meteor sonic boom and explosion, the meteor traveled on a shallow trajectory and the explosion sent out a cylindrical shock wave directly over the town of Chelyabinsk. This caused an over-pressure of up to 20 times normal atmospheric pressure, which damaged walls and blew in windows.
No reports were made of anyone harmed by meteorite fragments (that is, bits of a meteor that has survived the trip through the atmosphere), though many were caused by flying glass. Some meteorite pieces have claimed to have been found in Lake Chebarkul along the meteor’s flight path, but the Russian authorities have yet to confirm this.
ESA’s main concern is with the 600,000 known asteroids in our Solar System and particularly the 9,000 that pass close to the Earth. The agency is working with NASA and European national space agencies to develop an early warning system to detect similar meteors in the future.
Koschny described a 2008 meteor that was detected by accident 20 hours before it hit in the Sudan. If the Chelyabinsk meteor had enjoyed a similar heads up, people in the region would have had sufficient warning to prepare for the blast and stay clear of windows or weakened structures.
As part of its effort to provide such a warning, ESA’s SSA program is working to carry out an extensive sky survey using up to six automated 1-meter (39.4-in) telescopes to photograph the entire sky. By comparing images taken at various points and times, it would be possible to detect any new objects orbiting the Sun by their shifting in the images. From these shifts, the trajectory of the objects can be calculated and the threat, if any, they pose to Earth can be assessed. According to ESA, such a survey – along with space-based observations – would be able to detect an object the size of the Chelyabinsk meteor several days before impact.