It appears that the rocks at Meridiani were not just altered or modified by water,
they were actually formed in water, perhaps a shallow salty sea.
The Opportunity rover has sent back conclusive evidence of sedimentation on the surface of Meridiani Planum.
Sedimentation occurs when materials are deposited on the bottom of a body of moving water and create layered rocks.
Those rocks can then help geologists figure out what type of water was on the surface,
how much of it was there, and even how fast it was moving.
Scientists working on the rover project believe that Meridiani may have been the shoreline of a
large body of salt water that slowly formed the rocks found on this area of the martian surface.