Asteroids Created the Oldest Craters on the Moon
Four billion years ago, the solar system went through an epoch of collisions that left craters throughout the inner solar system, including Earth, the Moon and other rocky bodies. A study by astronomers from the University of Arizona and the National Astronomical Observatory of the Japan shows that the size distribution of objects in the asteroid belt match the size distribution of these craters for sizes ranging from a few hundred meters to tens of kilometers. Subaru contributed to the measurement of the size distribution of asteroids, and NAOJ's simulation computers calculated the size of objects that created the craters.
More info: Subaru telescope web page