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It was an asteroid out of nowhere, and it was big. Really big.

In mid-May, scientists at the U.S. Air Force telescope near White Sands, N.M., unexpectedly spotted a massive asteroid passing relatively near Earth. Two months later, astronomers with NASA's Jet Propulsion Laboratory got the best look ever at one of the 1,000 to 2,000 large asteroids that occasionally pass within 30 million miles of our planet.

The asteroid, JM8, turned out to measure an average of 2 miles across, more than enough for what Scott Hudson, a Washington State University electrical engineer, calls "the Armageddon factor" of total human annihilation in the unlikely event it actually hit Earth.

Astronomers have logged about 10 percent of the large asteroids, which measure about a half-mile or more across. NASA hopes to have all the large asteroids recorded within 10 years.

More immediately, the JM8 project showed how far scientists have come during the past decade in documenting asteroids in striking detail.

"It's basically the best one we've ever looked at," said Lance Benner, leader of the team analyzing JM8 using radar-imaging telescopes.

By examining asteroids, JPL scientists figure they can unravel solar system mysteries with far less risk and expense than a trip to Mars or the moon. They can analyze the basic building blocks of the solar system, including amino acids and other organic compounds key to the formation of life. They can use asteroids as space way stations, or as sources of building materials or water.

"If ever there was an example of something that is faster, better and cheaper -- which is one of NASA's objectives -- this is it," Benner said. As it happens, the asteroid radar-imaging work, part of NASA's Deep Space Network, risks deep cuts as Congress considers the space agency's budget for next year.

JM8 is one of the largest near-Earth asteroids ever seen. Its imaging comes a year after the same researchers recorded images of KY26, the smallest object in the solar system ever studied in detail.

KY26 is no wider than a baseball diamond and spins faster than any object seen in the solar system. Its day lasts about five minutes. JM8 tumbles slowly and erratically, like a badly thrown football. Its rotation lasts about a week. The JPL team is unsure why it has not settled into a regular rotation, but the wobbly motion could give an indication of how and when JM8 was thrown toward Earth from the asteroid belt between Mars and Jupiter.

Such research is possible because of sensitive radar-imaging telescopes that paint their objects with radio signals the way flashbulbs bathe an image in light. Returning signals are then analyzed to create digital photographs and, with the help of super-computing pioneered by WSU's Hudson, three-dimensional images.

The JM8 researchers used the 240-foot Goldstone Solar System Radar and Puerto Rico's 1,000-foot-wide Arecibo Observatory dish, which was seen in the movie "Contact." The images were clear enough to detect features on the asteroid 100 yards long.

"You can't even think of doing that with an optical telescope," said Steven Ostro, a JPL scientist who made the first radio images in 1989. "You would need a telescope with a mirror hundreds of meters across."

"This asteroid was 5.3 million miles away, and we could see things the size of a football field," said Benner. "That's part of why this is so incredible."

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