Eros, asteroid

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. 

Nittler, L. R. and 15 coauthors (2001) X-ray fluorescence measurements of the surface elemental composition of asteroid 433 Eros. Meteoritics and Planetary Science, 36, 1673-1695. 

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... 

Analysis of X rays emitted by Eros during a solar flare and observed by NEAR-Shoemaker showed that the asteroid s composition closely resembled that of the chondritic meteorites, which are considered remnants of the early solar system. This has bolstered the theory that the asteroids, too, are primordial leftovers that have never been part of any planet. 

For example, an Nd YAG laser was used by the Near Earth Asteroid Rendezvous (NEAR) spacecraft in 2000 to map the surface of the asteroid Eros. Light beams sent out by the laser measured with a high degree of accuracy the elevation of various parts of the asteroid, providing one of the best topographical maps of an asteroid surface ever obtained. 

Yeomans, D. K. (1999). Imaging of Asteroid 433 Eros During NEAR s flyby reconnaissance. Science, 285, 562-4. 

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