CNN.com wrote:LOS ANGELES, California (AP) -- There's a 1-in-300 [.33%] chance that a recently discovered asteroid, believed to be about 1,300 feet long, could hit Earth in 2029, a NASA 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.
No previously observed asteroid has been graded higher than 1.
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."
The asteroid was discovered in June and rediscovered this month.
"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, Arizona, and this month from Australia and New Zealand.
For those of you interested, 1,600 megatons is approximately 96,746 times the amount of energy released by the Hiroshima nuclear bomb.