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17 Jun 2002
NASA spacecraft NEAR-Shoemaker has taken the first detailed mapping images of an asteroid.
In February 1996, NASA launched the Near Earth Asteroid Rendezvous (NEAR) Shoemaker. Loaded with scientific instruments including a multispectral imager, a laser rangefinder and near-infrared spectrometer, the spacecraft set off to image the surface of an asteroid called Eros.
After years of circling the asteroid, NEAR landed on Eros in February of this year to capture its last high-resolution images of the surface. Peter Thomas of US-based Cornell University and colleagues now report that the spacecraft was successful in making the first global mapping of an asteroid, (Nature 413 390-400).
NEAR's laser rangefinder used a solid-state pulsed Nd:YAG laser to measure the distance between the spacecraft and the surface of the asteroid. A series of high-resolution topographic profiles has allowed researchers to build a global model of Eros.
A multi-spectral imager provided visible and near-infrared images of the asteroid's surface features and mineral distributions, while a near-infrared spectrograph determined the distribution of surface minerals. Other instruments on board NEAR included an X-ray and Gamma-ray spectrometer and a magnetometer.
According to the researchers, the thousands of images taken by NEAR reveal debris strewn across the asteroid's 434 sq. mile surface. Certain that a single crater emitted the debris, the researchers are puzzled as to why other craters on Eros haven't behaved in a similar way.
"Either the rocks [from the other craters] have been buried, eroded or they weren't made in the first place," said Thomas. "[However] the observation is helping us to start answering questions about how things work on the surface of an asteroid."
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