Analyses of asteroids by spacecraft remote sensing

Solar X-rays impinge on an asteroid s surface, generating fluorescent spectra that can be measured using an X-ray fluorescence spectrometer. During times when the Sun is 

X-ray spectrum of (a) asteroid Itokawa, and (b) a standard, measured by the Hayabusa spacecraft. Locations of the Ka lines for magnesium, aluminum, and silicon are also shown. Modified from Okada et al. (2006). 

NEAR-Shoemaker also carried a gamma-ray spectrometer (Evans et al., 2001). Gamma-ray photons are emitted from the radioactive decay of long-lived radioisotopes and from other elements that are excited by cosmic-ray bombardment. The gamma rays are 

Another important chemical difference between chondrite groups is in their oxidation states. In Chapter 7, we learned that differences in chondrite compositions cannot be simply explained by fractionation of metallic iron, but also must involve oxidation or reduction of iron (see Fig. 7.14). 

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