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A Happy Landing

Space: To end its mission, probe crashes on asteroid, achieving a space first and 'bonus science.'


A spacecraft touched down on the barren surface of the asteroid Eros on Monday, marking the first successful landing on a space rock.

The bus-sized probe sent signals back to Earth immediately, indicating that it had at least partially survived its soft crash-landing.

"I feel good," Jim Miller, a Jet Propulsion Laboratory engineer who helped lead the navigation team charged with sending the spacecraft toward the rock, said shortly after the noontime landing. "It was anybody's guess what would happen when it hit the surface."

The $223-million NEAR Shoemaker spacecraft has been on a five-year, 2-billion-mile mission to study the asteroid Eros. For the last year, the probe has been orbiting the asteroid, a 21-mile-long, Santa Catalina Island-sized rock about 196 million miles from Earth.

The spacecraft, without landing feet, a radar altimeter or shock absorbers, was not built to land safely. But because the craft was nearing the end of its run, mission director Bob Farquhar of Johns Hopkins University's Applied Physics Laboratory decided to "get a little bonus science" by attempting to land on the asteroid.

The Applied Physics Lab built the spacecraft and operates the mission for NASA. JPL engineers designed the trajectory of orbit and Monday's descent.

The primary goal was to obtain close-up photos of the potato-shaped rock as the spacecraft landed.

The last were beamed down just as the craft hit the surface. They are crisp, clear images of the asteroid's geology and show a smooth surface with few craters, a large layered rock and small rocks and rivulets as small as four inches across.

Farquhar said he was "absolutely amazed by the pictures," which are far more detailed than any captured in the last year.

The information will help scientists understand the physical makeup and history of the dense and primitive asteroid, which may be a mere chip off a much larger celestial block. The rock, likely to be a remnant from the formation of planets 4.5 billion years ago, may offer clues as to how the solar system formed.

Such asteroids are also studied because they can cause spectacularly damaging collisions with Earth. An object much smaller than Eros that hit Earth is largely believed responsible for wiping out the dinosaurs.

Beyond the scientific goals, Monday also offered NASA a chance to add to its technical prowess in landing on different types of objects. "This gives us a lot of practice," said Ed Weiler, NASA's associate administrator for space science. "We'll eventually want to land on comets because they hold the clues to beginnings."

This was the first time a spacecraft has landed on an object with so little gravity. The small object's gravitational field is so weak that the 1,100-pound spacecraft weighed just 1 pound on the asteroid.

Still, said Miller, the craft was descending with enough momentum that "had a Baltimore Ravens linebacker tried to catch it, he'd have been flattened."

About an hour before the noon landing, engineers slowed the spacecraft by firing its thrusters. It then began falling gently downward as the asteroid rotated underneath it.

Trying to safely land the craft was such a challenge that Miller, a 33-year JPL veteran, initially said "no way" to the project. "We were prepared with our excuses if it had crashed," he said. He credits much of Monday's success to two JPL engineers, Peter Antreasian and Steve Chesley, who "worked round the clock refining and recalculating the trajectory."

The craft was still emitting signals Monday afternoon. While no more images would be available, scientists said they may still be able to receive information on the object's magnetic field in the next few days.

In the future, near-earth asteroids may sport space colonies. When informed of the successful landing on Eros on Monday, spacewalker Thomas Jones, who is aboard the space shuttle Atlantis to help connect a new science laboratory to the International Space Station, said: "Fantastic. . . . I hope we'll have some astronauts following to the asteroid in a few years."


Asteroid Landing

The NEAR spacecraft touched down on the barren surface of the asteroid Eros on Monday, the first landing of a manmade object on an asteroid. The 21-mile-long rock may offer clues to how the solar system formed.



Size: 18 square feet at base

Cost: $223 million

Mission: 5-year, 2-billion-mile journey


Source and images: JPL/NASA

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