Southern Meridiani is on a smooth Martian plain. Not far away, the Opportunity rover found evidence of flowing water in the past. Scientists now know that the plains have a complex story to tell. Their history involves flowing water, groundwater, lakes, and wind. The area also spans two major eras of Martian history. The Mars Science Laboratory rover would trace that history further back than ever before. Later in the mission, the rover would cross onto older crust of the Noachian era. There, the rover would study clay minerals and evidence for past flowing water observed from orbit. The rover would use its on-board science lab to study the environment of early Mars and whether it could have been friendly for life.