Today's Image of Mars was taken on Jan 14 2004 and was one of the first returned from the European Space Agency's Mars Express orbiter. The image shows a stretch of Valles Marineris, considered to be the Grand Canyon of Mars.
The raised surfaces seen in this image are likely inverted riverbeds formed when the sediment deposited by rivers is harder than the surrounding terrain. Over billions of years erosion wore down the surrounding terrain, but because the riverbeds were more resistant to erosion they were reduced much less, thus creating the inverted features you see in the image below.
Clicking on this image will take you to the original high resolution image from Mars Express. [See the ESA article on this image]