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NASA unplugs NEAR

The last and closest image of asteroid Eros as the NEAR spacecraft touched down. The streaky lines at the bottom indicate loss of signal as the spacecraft touched down on the asteroid during transmission of this image.  

(CNN) -- A NASA probe on the surface of a deep space asteroid was cut off from contact with Earth on Wednesday, following a brief reprieve in which scientists squeezed out additional data from an onboard instrument.

The NEAR-Shoemaker spacecraft became the first to land on an asteroid two weeks ago, despite having no landing gear. The NEAR (Near Earth Asteroid Rendezvous) had just completed a yearlong orbit of the space rock Eros when it made its improbable touch down on the surface.

NASA planned to pull the plug on the $200 million mission on February 14, but extended it so NEAR scientists could peer into the interior of the oddly shaped asteroid using a gamma-ray spectrometer that survived the soft landing.

NASA's Deep Space Network antennas pulled down their last NEAR mission data Wednesday evening, bringing to a close the first mission to extensively study an asteroid, NEAR mission scientists said.

Mission researchers determined that the readings beamed back and received by the Deep Space Network are good, but they will need some time to sort out the data.

Check out NASA's movie simulation of NEAR-Shoemaker's risky descent to Eros

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"They will have to wade through it for months to get specific readings," Johns Hopkins University Applied Physics Laboratory spokesman Michael Buckley said on Wednesday. The Laurel, Maryland, lab manages the NEAR mission for NASA.

Based on the probe's observations, scientists have already made several important findings. They determined that Eros likely broke off from a larger planet-like body, and that it shares the same elemental composition of the earliest rocky building blocks of the solar system.

But NEAR-Shoemaker has also uncovered mysteries about the 21-mile-long (34 km) asteroid. Unexplained erosion processes unlike anything in the solar system have modified craters and boulders. And scientists detected no magnetic field.

"They think it's unusual they didn't find one," Buckley said.

NEAR researchers will need months or years to make sense of the all the information collected by NEAR-Shoemaker, which beamed back 160,000 images and an exhausting amount of data during a yearlong orbit around Eros, an oddly shaped asteroid likened to a kidney bean or peanut.

The automobile-sized probe traveled about 2 billion miles (3.2 billion km) during an odyssey that lasted five years. Its fuel supply and budget exhausted, NEAR-Shoemaker was commanded to land and take pictures during the descent.

Despite astronomical odds, it managed to survive and stay in radio contact with Earth. It snapped the closest image of the surface from only 394 feet (120 meters).

The change of the seasons on Eros will seal the fate of NEAR-Shoemaker. Its solar panels will receive increasingly smaller amounts of sunlight beginning next month when the summer ends in the south where it landed. Spring sunlight arrives in November but mission scientists give little chance for the lander to survive the three months of total winter darkness.

Considering that the craft has far exceeded expectations, however, NEAR engineers were discussing the possibility of attempting to revive it in a year or two during a southern Eros summer.

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Near Earth Asteroid Rendezvous Mission
Johns Hopkins University Applied Physics Laboratory
Near Earth Object Program

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