We propose new 40Ar/39Ar analyses in Itokawa grains that the Hayabusa mission collected from asteroid 25143, Itokawa S(IV). The main purpose of this proposal is to constrain the time of Itokawa rubble pile formation. With microtomography and X-ray diffraction (XRD) using synchrotron radiation X-ray, we will obtain detailed mineral information for individual grains, accurate grain masses, and some information about shock. From the 40Ar/39Ar analyses, we expect to obtain an 40Ar/39Ar age for each grain. Also, depending on signal size, we may obtain information about the degree of solar wind exposure and the cosmic-ray exposure (age) on the Itokawa rubble pile surface from our research.
After irradiating the grains with neutrons, we do noble gas analyses by step-heating the grains with a laser to successively higher temperatures until fusion. We would be glad to return the remaining material (a quenched, radioactive glass) to JAXA, if required