Year of the Solar System, June 2011: Impacts!
Source: NASA
Excerpt: Collisions are at the core of solar system formation …and continue to be one of the most important processes throughout our solar system. ... the Earth-Moon system most likely formed by the impact of the early Earth with another planet half Earth's size ...NASA scientists have created their own impacts to study this important process -- on the Moon during the LCROSS mission and on comet Tempel 1 during the Deep Impact mission.
solarsystem.nasa.gov/yss/display.cfm
solarsystem.nasa.gov/yss/display.cfm