Thursday, 24 February 2011

Friday the 13th Might Be Pretty Frightening After All—in 2029

By Linda Orlando

Apophis was the name of the ancient Egyptian god of darkness and destruction. So there is no more appropriate moniker astronomers could have chosen to assign to a 25-million-ton, 820-ft. wide asteroid that is expected to slice across the orbit of the moon and hurtle toward Earth at more than 28,000 miles per hour on Friday the 13th of April, 2029, at 4:36 a.m. Greenwich Mean Time.

Scientists are 99.7% certain that Apophis, a huge pockmarked rock that carries the energy of 65,000 Hiroshima bombs, will pass the Earth at a distance of only 18,800 to 20,800 miles. That distance is shorter than a round-trip flight from Melbourne, Australia, to New York City, and well inside the orbits of many of the geosynchronous communications satellites that are now circling the Earth. Just after dusk on April 13, people in Europe, Africa, and parts of Asia will be able to see what looks like a star slowly making its way westward through the sky. Apophis will be the first asteroid in human history to be clearly visible to the naked eye.

The asteroid will be packing enough power to wipe out a small country or churn up an 800-ft. high tsunami. Current projections show the asteroid’s impact occurring somewhere along a 30-mile-wide path stretching from Russia across the Pacific Ocean into Central America and then across the Atlantic. Although San Jose, Costa Rica, Nicaragua, and Venezuela are all potential targets for total destruction, scientists believe the most likely target to be several thousand miles off the West Coast of the United States, where the impact would create a 5-mile wide crater in the ocean floor. The impact would trigger tsunamis that could pound the coast of California with 50-foot waves.

Scientists believe that if Apophis passes the Earth at a distance of exactly 18,893 miles, it will go through a "gravitational keyhole," where the Earth’s gravity could pull Apophis off track just enough to cause it to enter an orbit that is seven-sixths as long as the Earth’s orbit. If that happens, then exactly seven years later, as Apophis comes back around, the planet would be dead center in the path of the behemoth. Fortunately, current tracking estimates put the odds of that happening at about 45,000 to 1.

However, former astronaut Rusty Schweickart, now 71, who served on the Apollo 9 mission in 1969, feels that even a tiny risk cannot be ignored. Through his B612 Foundation, which he co-founded in 2001, Schweickart has been urging NASA to start now making preparations to do something about the asteroid. "We need to act," he said. "If we blow this, it’ll be criminal."

Despite Hollywood’s imaginative cinematic escapades, current technology does not provide any way for Apophis to be deflected by some 5000 miles to miss the Earth in 2036, if it does go through the gravitational keyhole and comes back around with our planet in its crosshairs. Not even Bruce Willis and his crew of roughnecks would be able to do a thing about it. Unless some revolutionary new technology emerges, there would be little scientists could do other than plotting the precise impact point and begin evacuating people.

In 2005, Schweickart began urging NASA administrator Michael Griffin to start planning a mission to land a radio transponder on Apophis, in an effort to track the asteroid’s path to confirm that it will not hit the gravitational keyhole. If that data shows that the path will bring it into the keyhole, there would still be time to do something about it and launch a deflection mission. Using current technology, we could nudge it slightly off course by hitting it with a simple 1-ton "kinetic energy impactor" spacecraft. An alternative solution would be to use a "gravity tractor" spacecraft to hover above the asteroid and gently pull it slightly off course using its own gravity.

For now, NASA has decided to wait and see what’s going to happen. According to an analysis by Steven Chesley of the Near Earth Object program at the Jet Propulsion Laboratory in Pasadena, CA, there is no cause for alarm yet. Apophis will be swinging by the Earth in 2013, when it will be in perfect position to be tracked by the 1000-ft. diameter radio telescope in Arecibo, Puerto Rico. The data obtained during that pass could rule out the asteroid hitting the keyhole in 2029. But if it isn’t able to rule out the possibility, there will still be enough time to launch a deflection mission. Schweickart estimates that such a mission could take as long as 12 years to complete. But for now, most scientists are content to wait until we get a better idea of exactly what the risks are.

"There’s no rush right now," says Chesley. "But if it’s still serious by 2014, we need to start designing real missions."