Analysis of Steins Cratering History Using the OSIRIS/ROSETTA Images

We present a preliminary analysis of the craters on the asteroid Steins images obtained by OSIRIS, the imaging system on board the ESA mission ROSETTA, during the flyby on 5th September 2008. Steins has been observed at the closest distance of about 800 km achieving the maximum resolution of 80 m/px. Several small-to-medium craters have been identified, in addition to few very large craters: one of them is nearly 2 km across. The images show also the superposition of small craters on larger ones, and some structure that may represent the remnant of old degraded craters. A structure of chain-like craters has also been identified. All the craters have been counted in order to get the cumulative number per square km. Then we have applied our model to estimate the collisional age of Steins using the most recent modeling of the current population of the Main Belt asteroids (Bottke et al., 2005) to define the impactor flux. The model uses the scaling law of Holsapple and Housen (2007) to determine the crater diameter as a function of the impactor radius.