The results of initial analysis for mineralogy and petrology (Nakamura et al., 2011, Science) indicate that the majority of Itokawa surface particles suffered long-term thermal annealing at approximately 800°C and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid. This suggests that Itokawa parent asteroid suffered a catastrophic impact responsible for disruption. Although some of the Itokawa particles show shock-induced deformation and melting, the nature of the catastrophic impact event remained to be clarified. In this research proposal, we aim to uncover temperature, intensity, and timing of the catastrophic impact. For this purpose, we only need Itokawa particles that experienced heavy impact and show heavy deformation and localized melting. In the course of initial analysis, such heavily impacted particles are found, but the abundance is very low (only one particle among five to ten particles). Therefore, we first investigate allocated particles in an undestructive way using synchrotron X-ray radiation such as CT and XRD, in order to identify heavily shocked particles. Further analyses will be done only on the shocked particles and the remainder will be returned to JAXA. If we find such shocked particles, then we obtain detailed mineralogical and compositional signatures using scanning and transmission electron microscopy and compare the results with those obtained during initial analysis. If the shock-induced properties found in this study and those in the initial analysis are similar, we can conclude that one intense, catastrophic impact is responsible for the widespread shock-induced features. Finally we will measure U-Pb absolute ages of the impact-melting portions in order to determine the timing of the impact.