Itokawa particles are the first regolith samples from “rubble-pile” asteroid that clearly witness multiple processes over a 4.6 billion year period. A series of elaborate studies [e.g. Nakamura et al. 2011; Noguchi et al. 2011; Tsuchiyama et al. 2011] revealed that Itokawa had suffered from complex history such as (1) intense thermal metamorphism around the 800-900 degree, (2) catastrophic collision and disaggregation, (3) reaccretion onto rubble-pile asteroid, and (4) space weathering. However, the chronology of Itokawa and its parent body is not well understood.
In order to decipher the history recorded in Itokawa particles, here, we propose the investigation of U-Pb systematics of phosphates in Itokawa particles using NanoSIMS. It is well established that this method has a great advantage of constraining on not only the thermal metamorphism age, but also the impact age by assessment of both 238U and 235U decay series, if U-Pb systematics is disturbed by secondary event (See the main text). This new insight would shed light on the impact history of near earth asteroids. Here, we request two polished sections that include appropriate apatite grains (> three micron) for this study.