NEAR-Shoemaker spacecraft

The only in situ chemical data for asteroids are from the NEAR Shoemaker spacecraft, which orbited 433 Eros in 2000-1, and from the Japanese Hayabusa spacecraft, which visited 25143 Itokawa in 2003. NEAR obtained numerous measurements of the surface composition using X-ray fluorescence and gamma-ray spectrometers, and Hayabusa carried an XRF. The magnesium/silicon and aluminum/siUcon ratios for both asteroids are consistent with the compositions of chondrites. However, sulfur is depleted in Eros relative to chondritic compositions, possibly due to devolatilization by impacts or small degrees of melting. 

Composite view of asteroids visited by the Galileo and NEAR Shoemaker spacecraft, as well as the asteroid-sized moons of Mars. All are shown approximately at the same scale. Clockwise from upper left are Phobos, Eros, Ida, tiny Dactyl, Mathilde (the largest object), and Deimos, with Gaspra in the center of the figure. After Sullivan et al. (2002), with permission. 

In February 2000, asteroid studies took a remarkable jump forward when the Near Earth Asteroid Rendezvous (NEAR)-Shoemaker spacecraft, first of NASA s Discovery series of relatively low-cost space probes, went into orbit around the asteroid 433 Eros, an S-class asteroid about 8 X 8 X 21 mi (13 X 13 X 33 km) in size. NEAR-Shoemaker, the first spacecraft ever to orbit an asteroid, had already flown by the C-class, main-belt asteroid 253 Mathilde in 1997, taking high-resolution... 

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