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NASA: Asteroid no cause for alarm when it buzzes Earth on FridayFeb 14, 2013 (Daily Press (Newport News - McClatchy-Tribune Information Services via COMTEX) -- An asteroid half the size of a football field is set to buzz Earth on Friday, careening much closer to us than the moon. Closer than some communication and weather satellites. Not to worry, experts say. "There's no possibility of hitting the Earth," said Dan Mazanek, Near-Earth Object (NEO) technical lead at NASA Langley Research Center in Hampton. In fact, said Mazanek, the gravity of our planet will "sling-shot" the asteroid into a different orbit, likely altering it enough to remove any threat to us in future, too. And that, says NASA, will leave only about 499,999 other asteroids of similar size out there in our solar system. That we know of. Scientists believe that for every such asteroid we know about, 99 others are yet to be discovered. "We live in a cosmic shooting gallery in our solar system," Mazanek said. "You can look up at the moon any time of night and see how pock-marked it is. And if (our planet) didn't have erosion, water and wind, we'd see the history of impacts." Earth's atmosphere, too, helps erase the traces by burning up bits of asteroids and comets before they can do real damage to the surface -- and the creatures living on it. "Every time you see a shooting star, that's some grain or pebble-size piece of debris coming through the atmosphere," Mazanek said. "We get hit by debris all the time and, luckily, space is a big place." Asteroid 2012 DA14 The asteroid zooming past on Friday wasn't even on the radar, so to speak, a year ago. While astronomers have been surveying asteroids for years, this one was first detected by a Spanish team only last February, when it was still 2.7 million miles away -- a flying boulder about 150 feet across, weighing some 130,000 metric tons. Its late detection is alarming to former astronaut Ed Lu, who told NPR last week it only "highlights the problem." Had the asteroid been on a collision course with Earth, Lu said, "there's no way we could have stopped this. Nothing we could have done. The only thing we could have done, if this was going to hit us, was to evacuate the area." Lu is head of the B612 Foundation, a nonprofit that plans to build and launch a space telescope to "find asteroids before they find us." When this asteroid was detected, it was named 2012 DA14 and reported to NASA's Minor Planet Center, which compiles comet and asteroid sightings in our solar system from observatories around the world. This is the first time they've spotted an object this large about to come so close, Mazanek said. At its closest, asteroid 2012 DA14 will rocket past at 17,450 mph about 17,200 miles above Sumatra in the eastern Indian Ocean, NASA says. It won't be visible to the naked eye. By comparison, satellites in farthest geostationary orbit are about 22,000 miles overhead, while the International Space Station orbits at an altitude of 240 miles. Even at its closest, the moon is a relatively remote 239,000 miles from Earth. According to NASA, asteroid 2012 DA14 will approach from below and shoot past in the relatively emptier space between the innermost and outermost constellations of satellites, with little likelihood of striking a satellite or spacecraft en route. Scientists estimate an asteroid of this size flies this close every 40 years on average, and actually hits Earth about every 1,200 years. Asteroid strikes The most recent strike was over a Siberian forest in 1908. Scientists call it the Tunguska Event, and still aren't sure if it was caused by an asteroid or a comet, Mazanek said. What is known is that an object about 160 feet across detonated above the forest and, "just like a nuclear air blast," leveled millions of trees over 750 square miles. "As far as I know, no people were injured or killed by it," Mazanek said. "If it had arrived some number of minutes or hours later, it would have been over populated Europe." If an object the size of asteroid 2012 DA14 were to hit Earth, NASA says, it would release about 2.5 megatons of energy in the atmosphere and cause "regional devastation." An asteroid twice its size could wipe out a major city. Larger asteroids are even more rare, but pack a far more explosive punch. An asteroid about 6 miles across hit the planet about 65 million years ago and is believed to have wiped out the dinosaurs. For years, NASA has conducted surveys to track and characterize 90 percent of all NEOs larger than a kilometer -- "the ones scientists believe could have devastating impact," Mazanek said. In 2009, NASA launched a space telescope called the Wide-field Infrared Survey Explorer, or WISE, to survey giant NEOs by taking representative samples. According to Mazanek, they've achieved that goal. Surveys also suggest there are fewer midsize asteroids -- those 330 feet to 3,300 feet wide -- flying around than earlier believed, NASA says. They'd expected to find evidence of about 35,000 midsize NEOs, but the study suggests there are less than 20,000. Most of those haven't been located yet. According to NASA, they detect and track asteroids using ground- and space-based telescopes in its Near Earth Object Observation (NEOO) Program. Called "Spaceguard," the program determines if an object could ever potentially threaten Earth. NASA is working on deflection technology to push or pull an asteroid over an extended period. But if there's only a short time to respond, said Mazanek, "your approaches are fairly limited." "You'd have to do something fairly explosive," Mazanek said. "Kinetic impact or a nuclear blast to stop something at that short of a time period." There's no such risk with asteroid 2012 DA14, he said, or with thousands of others already cataloged by the NEOO program. "But there's a lot of asteroids and comets out there that represent an impact risk," Mazanek said. "Especially these smaller ones. An object this size might not make it through the atmosphere, but it could." 'Synergy' Asteroids don't only present a potential impact risk -- they could also be golden opportunities, perhaps literally, for the precious metals and other natural resources that could one day be mined from them. Last year, a group of entrepreneurs announced plans to launch a spacecraft to an asteroid within two years for initial prospecting operations. The president of their new company is a former NASA engineer. And in 2010, President Barack Obama announced that a priority for space exploration beginning in 2025 is to send astronauts to an asteroid. A NASA mission launched in 2007 has now finished orbiting a giant asteroid named Vesta. In 2016, the agency plans to launch a spacecraft to map another asteroid, use a robotic arm to take samples, then, for the first time, return those samples to Earth in 2023. These missions could help explain how life and our solar system began. There's "synergy" between an asteroid's potential risks and benefits to humankind, said Mazanek. But first we must find, catalog and characterize them. "Right now, we have a limited number of Earth-based telescopes," he said. "There's a limited budget to detect and track these objects. There's been proposals to have space-based surveying characterization missions (but) they cost money, and it's a matter of what priorities we put on our spending. Personally, I think this should be a high priority." ___ (c)2013 the Daily Press (Newport News, Va.) Visit the Daily Press (Newport News, Va.) at www.dailypress.com Distributed by MCT Information Services |