We haven't heard much lately about the Japanese Hayabasa probe which had the mission to rendevous with asteroid Itokawa back in 2005. It studied various factors of the asteroid and collected samples duly brought back to Earth. The smaples consist of very small grains, microscopic in size, but a lot has been hypthesized from them. It seems they have different patterns on the surface which have been divided into different causes or reasons for their presence. Crystallisation by extreme heat, evidence of impact shatter, and exposure to the solar wind. The team has concluded Itokawa originally had a much different shape and form – an size (when it was first formed billions of years ago). It was over 40 times larger it is being suggested. In contrast we might point out if this asteroid was a former comet and then it may have lost large amounts of mass as it orbited around the Sun.
In assuming it was a much larger object it is required that an impact shattered it into several pieces. One of these fragments is Itokawa. See http://phys.org/print386322516.html