Argon isotope analyses provide three kinds of information when applied to extraterrestrial material: 1) they allow establishing the impact history of a sample down to the single grain level, 2) they yield cosmic ray exposure ages showing the burial history of individual grains and 3) they provide the 38Ar/36Ar composition of the solar wind implanted at the surface of each grain. In this study, we propose to apply the argon- argon technique to four grains recovered from Itokawa’s surface with the following goals:
1) The rubble pile structure of Itokawa indicates that the later has been formed by the catastrophic disruption of a significantly larger parent body. 40Ar/39Ar ages will enable us to date the disruption event and hence the formation age of Itokawa. This age will be then compared with the age database of LL chondrites.
2) 38Arc exposure ages calculate with the cosmochron approach allow a complete decoupling between the different argon reservoirs. The new exposure ages will be used to refine the asteroid erosion hypothesis based on Ne isotopes and the model of fine particle migrations within the regolith.
3) 38Ar/36Ar intercept ratios measured using the cosmochron approach will provide us with the argon isotopic composition of the solar wind implanted within Itokawa grains. Comparison between Genesis measurements and Itokawa and lunar samples will allow a better understanding of the interaction between solar wind and bodies exposed to the vacuum of space.