Collisional process on Comet 9/P Tempel 1: mass loss of its dust and ice by impacts of asteroidal objects and its collisional history

We have studied the collisional process oil the nucleus of Comet 9/P Tempel I (T1) and estimated the mass loss Of Surface materials due to the impacts of asteroidal objects. The mass loss rate is around similar to 2 x 10(5) kg yr(-1). which is smaller than that of water Sublimation of similar to 6 x 10(9) 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 T I is as long as similar to a few 10(4) years, suggesting that T1 crossed the asteroid belt region more than similar to a few 10(4) years ago, though this estimated time may be reduced to several thousands of years by taking into account the influence of the sublimation process oil 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 similar to 2 x 10(3) years.