Elemental composition of S-class asteroid Itokawa by XRS onboard Hayabusa and its meteorite connection

Abstract

We present the results of remote X-ray fluorescence spectrometry of a near-Earth asteroid 25143 Itokawa with the X-ray fluorescence spectrometer (XRS) onboard Hayabusa. As has been reported, major elemental ratios of Mg/Si and Al/Si indicate that the surface of asteroid is more like an ordinary chondrite meteorite, especially LL- or L-chondrite, although some kinds of primitive achondrite are not ruled out. In this study, compositions of heavier elements such as Ca/Si and Fe/Si are quantitatively analyzed as well as the upper limit of S/Si. These results also support that the surface of Itokawa is like an ordinary chondrite, but also suggest that the surface must have experienced a little bit of thermal alteration or micro-impact processes.