Meteroids are small pieces of space debris — usually parts of comets or asteroids — that are on a collision course with the Earth. They become meteors when they enter the Earth’s atmosphere. Most meteors burn up in the atmosphere, but if they survive the frictional heating and strike the surface of the Earth they are called meteorites.
NASA said the Russian fireball was the largest reported since 1908, when a meteor hit Tunguska, Siberia, and flattened an estimated 80 million trees. Chelyabinsk is about 3,000 miles west of Tunguska. The Tunguska blast, attributed to a comet or asteroid fragment, is generally estimated to have been about 10 megatons.
Scientists believe that a far larger meteorite strike on what today is Mexico’s Yucatan Peninsula may have been responsible for the extinction of the dinosaurs about 66 million years ago. According to that theory, the impact would have thrown up vast amounts of dust that blanketed the sky for decades and altered the climate on Earth.
Paul Chodas, research scientist at the Near Earth Object Program Office at the Jet Propulsion Laboratory, said that ground telescopes would have needed to point in the right direction at the right time to spot yesterday’s incoming meteor.
“It would be very faint and difficult to detect, not impossible, but difficult,” Chodas said.
The 150-foot space rock that safely hurtled past Earth at 2:25 p.m. EST yesterday was dubbed Asteroid 2012 DA14 and was discovered a year ago. It came closer than many communication and weather satellites that orbit 22,300 miles up.
The asteroid was invisible to astronomers in the United States at the time of its closest approach on the opposite of the world. But in Australia, astronomers used binoculars and telescopes to watch the point of light speed across the clear night sky.
Jim Green, NASA’s director of planetary science, called the back-to-back celestial events an amazing display.