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So, what is NASA doing about it?
Just last week they've launched the Near-Earth Object observation program to study the orbits of these potential threats. Right now, scientists can only track asteroids, which usually travel between 27,000 and 33,000 miles per hour, and warn the public of close calls. NASA has also started serveral basic research and technology demonstration projects to study asteroids and find ways to prevent them from striking Earth.
One of the possibilites reminds us of the movie, "Armegeden" with the use of nukes that could deflect a killer asteroid. Other methods to change an asteroid's course include hitting it with a heavy projectile traveling at high speed (tested by the Deep Impact mission which hit Comet Tempai 1 with an 850 pound copper slug), or using a gravity deflector from a spaceship near enough to slightly change its course. Other research being conducted now include improved Solar Electric Propulsion (SEP) systems that could push or pull an asteroid for an extended time, or the use of grappling mechanisms.
NASA has also built a 230-foot Goldstone antenna, near Barstow which is part of NASA's Deep Space network.
2012 DA14's route
The image above shows how close 2012 DA14 got as it passed by Earth. It orbits the Sun and takes 368 days to complete one full cycle. The encounter with Earth will speed its orbit up to 317 days. It will be at least three decades before 2012 DA14 could possibly come this close to Earth again.
In 2004, a newly discovered a 250-yard wide asteroid named Apophis, made a splash in the media when it was predicted that it had a 2.5 percent chance of striking Earth in 2029. New instruments and calculations, which are sixty times better than the ones used previously, show that there's virtually no chance of hitting Earth in 2029. And just last month it was determined that there's no chance of it hitting Earth in 2036 either. Apophis is circled above.
One of the biggest asteroid threats found so far is from 500-yard wide "1999 RQ36." It's estimated that it has a 1-in-2,400 chance of impacting Earth in the late 22nd century. NASA plans to send the OSIRIS-REx to land on the asteroid and take samples for further study. OSIRIS-REx is expected to launch in 2016, arrive in 2018, and work until 2021 before returning back to Earth with soil samples.