Apophis -The Destroyer - (no longer) threatens the earth

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Apophis -The Destroyer - (no longer) threatens the earth

Two upcoming asteroid encounters are now regarded as no longer a threat to the Earth - see last post for update.

NASA is drawing up a shortlist of ideas to be unveiled early next year for diverting a 40m-ton asteroid that is on course to pass dangerously close to Earth.

The schemes will be presented and discussed at the annual meeting of the American Association for the Advancement of Science.

Fears that the planet may be in danger from asteroids were heightened by the discovery of one orbiting the sun that, on its present path, will pass within 22,000 miles- a hairs breadth in astronomical terms - in April 2029.

Nasa's idea is to engineer a minor shift in its trajectory that would make the asteroid miss Earth by a wider margin on this and all subsequent passes.

Under one possible plan, a robotic craft would be sent to the asteroid to attempt to alter its course. One option might be to install a propulsion system on the surface to nudge it onto a new course.

The studies follow the discovery of hundreds of small asteroids orbiting the sun that repeatedly cross Earth's orbit, raising the possibility of a devastating collision.

The one causing most concern is a rock of more than 1,000ft called Apophis, the Greek name for the Egyptian god Apep, known as -the Destroyer. It will come so close that it will pass under many satellites and may destroy some.

Astronomers fear that, although 2029 should pass without incident, coming so close to Earth might change Apophis's 323-day orbit around the sun during which it crosses the planets path twice creating an even bigger risk in the future. A second close encounter is predicted for 2036.

Since Apophis was discovered Nasa scientists have been drawing up proposals for diverting it or any other asteroid that might present a threat. Nasa estimates that if it hit Earth it would release energy equivalent to the detonation of 880 megatons of TNT. The 1883 eruption of Krakatoa was the equivalent of roughly 200 megatons.

One option, to be proposed by a former astronaut, Edward Lu, of Nasas Johnson Space Center in Houston, Texas, would involve building a heavy, nuclear-powered spacecraft to act as a gravitational tug. The spacecraft would hover over the surface of Apophis, using the asteroids gravitational pull to stay in orbit.

Lu calculates that a 20-ton craft gently firing its thrusters could safely deflect a typical 650ft asteroid in about a year, assuming there was 20 years of warning to launch and get into position.

Lu's approach is far more cautious than that proposed by Hollywood in films such as Deep Impact or Armageddon. In the latter, the character played by Bruce Willis dies leading a team of astronauts who drill into an Earth-bound asteroid to plant a nuclear weapon that destroy it, and him along with it.

Lu and others say that such an approach would increase the threat by turning a single piece of rock into smaller chunks that could bombard the planet.

Times-Online
By netchicken: posted on 25-12-2006

Another article, - Friday the 13th is the hit day...

Friday the 13th is supposed to be an unlucky day, the sort of day you trip on your shoe laces or lose your wallet or get bad news.

But maybe it's not so bad. Consider this: On April 13th--Friday the 13th--2029, millions of people are going to go outside, look up and marvel at their good luck. A point of light will be gliding across the sky, faster than many satellites, brighter than most stars.

What's so lucky about that? It's asteroid 2004 MN4 ... not hitting Earth.

For a while astronomers thought it might. On Christmas Eve 2004, Paul Chodas, Steve Chesley and Don Yeomans at NASA's Near Earth Object Program office calculated a 1-in-60 chance that 2004 MN4 would collide with Earth. Impact date: April 13, 2029.

The asteroid is about 320 meters wide. "That's big enough to punch through Earth's atmosphere," devastating a region the size of, say, Texas, if it hit land, or causing widespread tsunamis if it hit ocean, says Chodas. So much for holiday cheer.

More on the site
 http://science.nasa.gov/hea...
By netchicken: posted on 25-12-2006

Good news life on earth may not be extinguished in 20 odd years afterall.

NASA on Wednesday downgraded the odds of an 885-foot asteroid striking the planet in 2036.

Scientists initially believed there was a 1-in-45,000 chance that Apophis could hit the planet on April 13, 2036. But the threat was lowered to a 1-in-250,000 chance after researchers recalculated the asteroid's path.

"It wasn't anything to worry about before. Now it's even less so," said Steve Chesley, an astronomer with the Near Earth Object Program at NASA's Jet Propulsion Laboratory.

Chesley and his colleagues refined the asteroid's orbit after an astronomer in Hawaii analyzed previously unreleased images that gave scientists a better idea of Apophis' position.

Earth got a scare in 2004 when initial measurements suggested the newly discovered Apophis seemed to have a chance of hitting the planet in 2029. Further observations ruled out any possibility of an impact.

Scientists are tracking Apophis, which is slated to come within 18,300 miles above Earth's surface in 2029.

 http://news.yahoo.com/s/ap/...
By netchicken: posted on 8-10-2009








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