NASA is to think over space shield

NASA has outlined what it could do, and in what time span, in case an asteroid named Apophis is on a course to slam into Earth in the year 2036. The timetable was released by the B612 Foundation, a group that is pressing NASA and other government agencies to do more to head off threats from near-Earth objects.

The plan runs like this: Eight years from now, if there's still a chance of a collision in 2036, NASA would start drawing up plans to put a probe on the space rock or in orbit around it in 2019.

If those readings still could not rule out a strike in 2036, NASA would try to deflect the asteroid into a non-threatening course in the 2024-2028 time frame by firing an impactor at it — using this year's Deep Impact comet-blasting probe as a model. Experts would start planning for the "Son of Deep Impact" mission even before they knew whether or not it was needed.

Apophis, also known as 2004 MN4, stirred up a flurry of concern last December when the risk of collision was raised temporarily to as high as 1 out of 40 for the year 2029. With an estimated diameter of 400 meters, the asteroid could destroy a city if it hit the wrong place on land, or raise a deadly tsunami if it plunged into the ocean.

Fortunately, more precise plotting ruled out a collision in 2029. However, Apophis will still make an extremely close pass — missing Earth by mere tens of thousands of miles. At that distance, Earth's gravitational pull could perturb Apophis' orbit enough to put it on a track to hit during another pass in 2036. Experts say that could happen if, during the 2029 close encounter, the asteroid passes through an outer-space "keyhole" that measures about 600 meters across.

Asteroid-watchers may be able to rule out a collision entirely as early as next year, when Apophis is in a good position for further observations. However, the key observations will come in 2013.

One way or another, NASA would try to push the comet out of a path leading to the 2029 keyhole.

Of course, chances are that the Apophis affair will turn out like previous asteroid alarms have — with more detailed observations eventually ruling out the threat.

Finally, it is said that the responsibility for protecting Earth from hazardous asteroids and comets should be officially assigned to a capable U.S. government agency. That agency might turn out to be NASA or the Department of Defense, NBC reports.

V.Y.