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Impromptu landing on an asteroid

NASA tries deep-space derring-do worthy of Captain Kirk

By Peter N. Spotts Staff writer of The Christian Science Monitor / February 9, 2001

For the past year, a tiny spacecraft nearly 200 million miles from home has orbited a space rock the size of southern California's Catalina Island, giving earthlings their first close look at debris from the dawn of the solar system.

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Now, as the craft's fuel gauge nudges "E" and time on NASA's deep-space communications network runs out, mission planners are racing to cement the craft's place in the history books.

On Monday, they will try to gently park the craft on potato-shaped Eros - performing the first-ever landing of a spacecraft on an asteroid.

Turning Eros into the craft's final resting place, instead of sending it off into space, caps a high point in what some planetary scientists call a renaissance for asteroid studies.

Climbing the social ladder

Since the first asteroid was discovered on Jan. 1, 1801, the objects once cast as the vermin of the solar system have risen to a place of respect.

Scientifically, asteroids have come to be recognized as key links to the solar system's past.

"We're seeing to the very beginnings of the solar system, when planets were being built," says Andrew Cheng, a planetary scientist at Johns Hopkins University's Applied Physics Laboratory and the mission's project scientist.

Beyond the science, however, lies a practical need to understand these lonely rocks. Close-up studies of these objects could help scientists devise strategies to deflect or destroy asteroids that have Earth in their cross hairs.

"These are objects that in the past have caused some bad days for some species on the earth," says Edward Weiler, associate administrator for space science at the National Aeronautics and Space Administration (NASA).

Although an entry in the record books is a plus, researchers are more interested in the close-up views of Eros they hope to get as the craft closes in on the surface. Those views could yield clues to some last-minute mysteries Eros has thrown their way.

In the year that the so-called NEAR craft has been waltzing with Eros, it has provided an intimate portrait of what once was a tiny point of light in a telescope. The mission has returned more than 160,000 images. It's tickled the surface with more than 11 million laser shots to build detailed maps of the asteroid. In all, it's beamed back 10 times more data than originally planned - covering everything from the varying strength of its gravity and the chemical composition of its surface to its solid but cracked interior.

Scientists have only scratched the surface of those data. Even so, a scant seven months after NEAR first began orbiting the asteroid, the team thought it had Eros pretty well figured out - at least in broad terms, says Joseph Veverka, a Cornell University astronomer who heads the NEAR imaging team. Last September, they published findings in a set of papers in the journal Science.

An unexpected puzzle

But in October, the team dropped the spacecraft into an orbit just 4 miles above the rock.

"We began to see things we never expected, things that really puzzle us," Dr. Veverka says. Layers of fine particles appeared to have collected in craters, while more fine-grained material appears to have slumped down the sides of crater walls.