This time we saw coming towards us in February 2012, astronomers were able to detect it before its passage. Asteroid 2012 DA14 discovered in February 2012, has a small size of 45 meters and a mass of 135 000 tons. It will come near the Earth, February 15, 2013 at 7:24 p.m. (UTC). Since the beginning of the program to detect near-Earth asteroids, this asteroid is the largest object brushing as close to Earth. The distance this time yet large enough to pose no risk of collision, astronomers reported. It will pass closer to Earth at 27,700 km, which represents a very small distance across the solar system, the Moon is 360,000 km.
Many small rocky bodies called asteroids are present in the solar system, an important part of them circulate in a ring between the orbits of Mars and Jupiter between 2 and 4 AU, in what astronomers call the asteroid belt, otherwise known main belt. It marks the boundary between the terrestrial planets and the gas giants. An asteroid is a celestial object is not observable to the naked eye because of its small size which varies from a few tens of meters to several hundred kilometers in diameter and is part of our solar system. Objects less than 50 m in diameter, as the asteroid 2012 DA14 are called meteorites.
"On average, an asteroid this size will approach as close to the Earth every forty years and is likely to collide with our planet every 1200 years," said Donald Yeomans, manager of the Office of Near Earth Object (NEO) of the Jet Propulsion Laboratory of NASA.
An asteroid 45 meters in diameter that enters the atmosphere with a very low incidence angle (a few degrees), fails to pass through the atmosphere and causes no damage. It simply bounce on the atmospheric layer of the Earth and walk away in space. This happened August 10, 1972 in the Montana sky in the northern United States. But if it fall vertically its size is sufficient to make damage at the level of a department. An object 50 meters in diameter makes a huge crater like the famous Meteor Crater in Arizona. By comparison, a meteorite crater 1 km provoke a diameter of 20 km and kill 2-3 billion people in the tsunami triggered across a terrestrial hemisphere. The probability that this happens is once every 150,000 years.
nota: (symbol: AU) The average distance Earth to the Sun. One AU is 149 597 871 km. It is a unit often used for distances in the solar system, or the distance between two stars in a binary system.
The meteorite responsible for the extinction of dinosaurs 66 million years ago, measured 10 kilometers in diameter, it fell into the Gulf of Mexico (see the trace on the image opposite). An asteroid is classified as near-Earth object if its size is greater than 152 meters and it distance is inferior to 7.5 million kilometers from Earth. NASA has already identified 9500 potentially hazardous small bodies or one tenth of the total.
Image: Known asteroids larger (above).
nota: Lincoln Near-Earth Asteroid Research (LINEAR) is a joint research project of the U.S. Air Force, NASA and MIT Lincoln Laboratory. LINEAR robotic telescopes have detected 15 September 2011, 231082 asteroids, 2432 comets and 279 objects cruisers.
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Image: The Chicxulub impact crater in Mexico is aged ≈ 65 million years, it has an average diameter of 200 km, the estimated diameter of the meteorite responsible for the cataclysm is 10 km. Source: MIAC website Gravimetry