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'Stunning' images hint asteroid broke from a planet

Color Eros
Color composite image of Eros  

February 17, 2000
Web posted at: 3:58 PM EST (2058 GMT)

In this story:

Soccer field-sized boulders

A mysterious bright white spot

'We don't know what it all means'

LAUREL, Maryland (CNN) -- Poring over unprecedented close-up images of asteroid Eros, including the first one in color, NASA scientists on Thursday speculated that the space rock may have broken off from a small planet eons ago.

Only days into its yearlong orbit around Eros, the NASA robot ship has snapped asteroid pictures of unrivaled clarity, presenting a haunting panorama of boulders, bright spots and craters on the potato-shaped rock.

VideoCNN Science Correspondent Ann Kellan shows unprecedented close-up color photographs of an asteroid that indicate it may have broken off a planet eons ago.
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Collected by the Near Earth Rendezvous spacecraft, some of the images show signs of geological layering, which suggests that Eros was once part of a much larger celestial body, said Andrew Cheng, a NEAR project scientist.

"A plausible way that it (layering) happened is if Eros was once part of a larger body," Cheng said, "probably a planet-sized body that once broke up."

The parent object was most likely smaller than the Earth's moon, he said.

Soccer field-sized boulders

The preliminary images from NEAR offer a close-up look at the complex surface features, including six or seven boulders, some the size of soccer fields and one that seems to have rolled into a crater.

"I was stunned, speechless, by the beauty of this asteroidal landscape," project scientist Mark Robinson told reporters.

Gravity on Eros is only about one thousandth of that on Earth. A human could easily jump off the surface. Yet the gravity on the asteroid seems strong enough to make boulders roll downhill, NEAR scientists said.

The boulders "give us natural drill holes" that could enable future missions to answer questions about the interior of the asteroid, Robinson said.

A mysterious bright white spot

Other mysterious features include a white spot 25 times brighter than other parts of surface, which indicates it could have a different mineral composition than the rest of the asteroid.

Action Shots
In the first hours after NEAR's insertion into Eros orbit, the spacecraft's camera took these images from a range of 210 miles (330 km) above the surface

And the surface of a saddle-like feature is smooth, meaning it could be much younger than the rest of the asteroid. Most of Eros' surface is pockmarked by crater impacts.

The density of Eros is about the same as the Earth's crust. In contrast, Mathilde, an asteroid that NEAR zoomed by during its four-year trip from Earth, was hardly denser than water, said NEAR mission member Donald Yeomans.

The first color picture of the asteroid shows a slight butterscotch hue, consistent with the variety of minerals thought to compose Eros.

The first infrared images show an unusual concentration of colors in the two "noses" of the asteroid, now 160 million miles (250 kilometers) from Earth.

'We don't know what it all means'

"We're very excited by all this, but we don't know what it all means. What's coming over the next year, we can't even imagine," Robinson said.

NEAR began orbiting Eros from slightly more than 200 miles (300 kilometers) on Monday. But as the mission continues, it will move progressively closer to the asteroid and perhaps land briefly, project scientists said.

But orbiting Eros, which moves in an eccentric orbit like a tumbling potato, can be "very tricky," said Yeomans. NEAR could smack into asteroid or escape out into deep space if the craft experiences flight trouble, he said.

While Eros itself poses no threat to Earth, scientists hope the $224 million mission will determine the asteroid's origin and offer clues about how to protect Earth from catastrophic collisions with other large space rocks.

Built and managed by The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions.

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Near Earth Asteroid Rendezvous Mission
NASA Homepage
Asteroid Comet Impact Hazards
The Spacewatch Project
Smithsonian Astrophysical Observatory
Impact of an Asteroid off the New York Coast

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