Scientist: Asteroid May Hit Earth in 2029

LOS ANGELES - There's a 1-in-300 chance that a recently discovered asteroid, believed to be about 1,300 feet long, could hit Earth in 2029, a NASA (news - web sites) scientist said Thursday, but he added that the perceived risk probably will be eliminated once astronomers get more detail about its orbit.

There have been only a limited number of sightings of Asteroid 2004 MN4, which has been given an initial rating of 2 on the 10-point Torino Impact Hazard Scale used by astronomers to predict asteroid or comet impacts, said Donald Yeomans, manager of the Near Earth Object Program at NASA's Jet Propulsion Laboratory in Pasadena.

On Friday, April 13, 2029, "we can't yet rule out an Earth impact," Yeomans said. "But the impact probability, as we call it, is 300-to-1 against an impact."

"This is not a problem for anyone and it shouldn't be a concern to anyone, but whenever we post one of these things and ... somebody gets ahold of it, it just gets crazy," he said.

"In the unlikely event that it did hit, it would be quite serious. We're talking either a tsunami if it hit in the ocean, which would be likely, or significant ground damage," Yeomans said.

Its estimated size has been inferred from its brightness, which assumes that its reflectivity is similar to other asteroids that have been observed. At about 1,320 feet in length, it would have about 1,600 megatons of energy, Yeomans said.

Asteroid 2004 MN4 takes less than a year to go all the way around the sun and on each orbit it passes by Earth's orbit twice, Yeomans said. It is also nearly on the same plane as Earth's orbit.

The asteroid will be visible for the next several months and the NEO program has alerted its network of ground-based observers to include 2004 MN4 in their searches.

Yeomans said there have now been about 40 observations, first from the observatory at Kitt Peak, near Tucson, Ariz., and this month from Australia and New Zealand.

I still like this story from earlier this year.

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Senior Science Writer
posted: 08:03 am ET
18 March 2004

Update: This story was originally posted at 7:08 a.m. EST

An asteroid will pass closer to Earth than ever recorded at 5:08 p.m. EST (2208 GMT) today, NASA scientists announced. The planet is not at risk, they said.

The space rock is about 100 feet (30 meters) wide.

It will pass just 26,500 miles (43,000 kilometers) over the southern Atlantic Ocean. That's about 3.4 times the Earth's diameter. It's also just beyond geostationary weather satellites, which orbit at an altitude of 22,300 miles.

Scientist said experienced backyard stargazers should be able to see it with binoculars or small telescopes from much of Asia, Europe and the Southern Hemisphere if skies are clear.

The object, named 2004 FH, was detected Monday.
"It's a guaranteed miss," astronomer Paul Chodas, of the Near Earth Object Program office at NASA's Jet Propulsion Laboratory, said Wednesday.

As it flies past Earth, the path of 2004 FH will be bent about 15 degrees by Earth's gravity. It will zoom from one side of the Moon's orbit to the other in 31 hours. Astronomers are swinging telescopes toward the newfound object in what they consider an unprecedented opportunity to study a space rock up close.

An object of this size, where it to take direct aim, would likely break apart or explode in the atmosphere, astronomers say. The result could cause local damage. Something just slightly larger could survive to the surface and destroy a city.

Out there

Most asteroids reside in a belt between Mars and Jupiter, orbiting the Sun for eons without leaving that general region. But gravitational interactions kick some inward. It is not uncommon for asteroids to pass near the Earth. It is uncommon to spot them.

Prior to this event, the closest known asteroid flyby was on Sept. 27 last year, when another smallish rock named 2003 SQ222 came within 54,700 miles (88,000 kilometers) of Earth. It was not detected until after it hurtled by. Experts say other similarly sized space rocks pass close about once every two years but go undetected.

Smaller boulders routinely plunge into the atmosphere and vaporize or explode, sometimes dropping fragments to the surface and igniting fires and fears.

Earlier this month, astronomers gathered to pondered the risk of small space rocks that typically are not spotted until they are within hours of possible impacts. Asteroid detections have skyrocketed in recent years, meanwhile, as new electronic cameras increase sensitivity and automated telescopes scan the skies for anything that moves in relation to background stars. Researchers say significant new spending would be required to purposely find and track asteroids smaller than 0.6 miles (1 kilometer).

Meanwhile, asteroid hunters have for the past decade or so focused on finding the larger asteroids, those that could cause global damage. They are not set up to spot all of the smaller objects that inhabit the same general space as Earth. There could be millions. Those that are found involve serendipity.

Lucky find

"The important thing is not that it's happening, but that we detected it," JPL astronomer Steve Chesley said of today's flyby.

The newfound asteroid was detected late Monday by the NASA-funded LINEAR asteroid survey in New Mexico. Follow-up observations were made on Tuesday to confirm the course.

The asteroid circles the Sun every 9 months, according to calculations by Gareth Williams of the Minor Planet Center in Cambridge, Mass. It swings inside the orbit of Venus and ranges just beyond Earth, moving in roughly the same plane in space through which the planets travel.

Astronomers can't say whether the asteroid might encounter Earth in the future as it continues to orbit the Sun.

Spotting 2004 FH will be difficult for most observers. Owing to its proximity, the asteroid's location in the sky will vary greatly depending on a person's exact location on the ground, explains Joe Rao, SPACE.com's Night Sky columnist. Seasoned skywatchers can find detailed position information, or ephemeris, at the Minor Planet Center's web site.

Asteroids aren't the only wanderers to frequent the inner solar system. This spring, two recently found comets are expected to become visible to the naked eye for observers around the world. Meanwhile, casual skywatchers can see all five naked-eye planets right now in the evening sky.

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