摘要：We have studied the collisional process on the nucleus of Comet 9/P Tempel 1 (T1) and estimated the mass loss of surface materials due to the impacts of asteroidal objects.The mass loss rate is around ∼2×105 kg yr-1, which is smaller than that of water sublimation of ∼6×109 kg yr-1.We then estimated the number density of craters formed by asteroid impacts to infer the collisional history of T1.We found that the time necessary to accumulate the crater population on T1 is as long as ∼ a few 104 years, suggesting that T1 crossed the asteroid belt region more than ∼ a few 104 years ago, though this estimated time may be reduced to several thousands of years by taking into account the influence of the sublimation process on the crater size.Alternatively, the total period of the recent orbit, in which the perihelion distance is small enough to cause significant sublimation by erasing a large number of small craters, may be less than ∼2×103 years.
