These latest findings from the Mars Global Surveyor show that we will need more study both from orbit and on the surface to really learn the truth about the history of water on Mars, according to Dr. Jim Garvin, a scientist with the Mars Exploration Program at NASA Headquarters. He said that the plan will be to follow up on the visual signs of water, then do studies on the surface, and finally use actual rock, soil, air and other samples to gain more knowledge about these discoveries. But these new photos of Mars' sedimentary rocks are showing us lots of places to look for answers. When sand or dust grains are laid down under water, or by wind or even by glaciers, they settle in layers. These materials are called sediment.
Sediments build up at the bottom of oceans, lakes and rivers.
The layers are pressed down by their own weight, or by the weight of water or ice, and they get very dense and hard. Over thousands or millions of years, the layers become rock. There are three kinds of sedimentary rock. The first is called mechanical sedimentary rock, because it is made of tiny bits of other rocks and minerals that are moved from their original place before being deposited by water, wind or ice. This type of sedimentary rock includes sandstone, shale and conglomerates.