Cratering records in the inner solar system in relation to the lunar reference system

The well investigated size-frequency distributions (SFD) for lunar craters is used to estimate the SFD for projectiles which formed craters on terrest rial planets and on asteroids. The result shows the relative stability of t hese distributions during the past 4 Gyr. The derived projectile size-frequ ency distribution is found to be very close to the size-frequency distribut ion of Main-Belt asteroids as compared with the recent Spacewatch asteroid data and astronomical observations (Palomar-Leiden survey, IRAS data) as we ll as data from close-up imagery by space missions. It means that asteroids (or, more generally, collisionally evolved bodies) are the main component of the impactor family. Lunar crater chronology models of the authors publi shed elsewhere are reviewed and refined by making use of refinements in the interpretation of radiometric ages and the improved lunar SFD. In this way , a unified cratering chronology model is established which can be used as a safe basis for modeling the impact chronology of other terrestrial planet s, especially Mars.