Crystallographic studies on interplanetary dust particles

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Interplanetary dust particles (IDPs) are considered to hold the information of an early stage of solar system. NASA/Johnson Space Center has collection of IDPs, and made preliminary investigation of them by the methods of electron prove micro analysis as well as observation through electron microscope. According to their size, X-ray diffraction method has not been applied on them. Therefore, crystallographic information are kept unknown.At the Photon Factory (PF), a system to analyze a sub micrometersized crystal has developed by using synchrotron radiation (SR) with Laue method. In order to obtain crystallographic information of IDPs, this system is applied to them. The colaborative study is performed by an aid of this International Scientific Research Program.Six IDPs were selected at NASA/JSC and then examined by SR at PF in this year are silicates, sulfides and alloys of which sizes are from eight to nineteen micrometers in diameter.Almost all samples give the complicated Laue patterns showing polycrystalline states with diffuse Laue spots or complete powder lines.As the first step of the crystallographic studies, the indices are assigned to Laue spots of the comparatively good sample ( (Fe, Ni) S) , and the structure refinement is now carried out based on Laue intensities.