Eros 410 days apart
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Eros 410 days apart

October 22, 2009
On February 6, the Multispectral Imager on NEAR acquired the two right-hand views of the asteroid Eros as it closed to within 4200 miles (6800 km). This distance is just greater than the distance at which NEAR imaged Eros during a flyby of the asteroid on Dec. 23, 1998 (images on left).

The differences in Eros's appearance at the two times result from seasonal variations in solar illumination and from NEAR's viewing angle when the two sets of images were taken. Last year NEAR approached from the north when the asteroid was experiencing southern hemisphere summer and thus the north pole was in shadow, resulting in a mostly shadowed, crescent asteroid. Now, nearly 14 months later, Eros is experiencing northern summer. Now the spacecraft is again over northern latitudes, but because of the difference in illumination it views a mostly sunlit, gibbous Eros.

Images of Eros taken with different illumination and viewing are needed to piece together a global view of the asteroid's geology. For example, in the flyby views at left, the shading accentuates a low linear feature that runs the length of the asteroid. The recent approach images at right show northern hemisphere features not visible during the flyby. By combining images taken with very different viewpoints a complete history of the asteroid's surface can be compiled. In order to build up this complete view, at very high resolution, NEAR will orbit the asteroid for about one Earth year.

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