In a study published in the December 8 issue of the journal Science, the authors report signs of sedimentary layers in Martian basins and craters. The sediments often appear in visible layers. The MGS pictures show hundreds of identically thick layers, which suggest that water carried the sediments into the depressions. There could be other causes for the appearance of sedimentary layering, such as high atomic pressure, but the possibility that layered rocks formed on Mars just as they do on Earth remains an exciting one. You can look at more MGS pictures at the Malin Space Science Systems site.
Water is one of the basic ingredients for life.
A good starting point in a search for life is the search for water sources. Scientists have long accepted as fact the existence of frozen water on Mars' surface and in its atmosphere. But scientists believe that the northern cap also contains a large deposit of frozen water. This process is called sublimation. Icy fogs and frost form during the cold nights and disappear during the day.