Moon's craters give new clues to early solar system bombardment

http://news.brown.edu/pressreleases/2010/09/moon

In this article, "Moon's craters give new clues to early solar system bombardment", a research team led by Brown University had identified about 5,200 craters on the moon, which confirms the theory that there was a time in history where comets, asteroids, and other space matters had bombarded the moon and other bodies of the solar system. Using the Lunar Orbiter Laser Altimeter, an instrument from NASA's Lunar Reconnaissance Orbiter, they have determined that the moon's oldest regions are in the southern near side and the north-central far side of the moon. Although scientists had believed in the "size-frequency distribution", a group led by University of Arizona hypothesized that the ratio of objects hitting the moon had been difference since the moon was formed. They later found that the older surfaces had a greater ratio of larger projectiles, which brings to question what was going on in the solar system before the Orientale Basin was formed. They think that the rate of the bombardments of asteroids had been completely different before three and a half billion years, and a different force, probably from the gravitational pull of larger planets, like Jupiter and Saturn, had changed the rate of the hurdling asteroids from the asteroid belt.