Today's Image of Mars shows the landing site for Mars Science Laboratory Curiosity at the foot of Mount Sharp, the 5km high central mound in Gale Crater. The turquoise line shows the expected path of MSL after it lands and begins navigating its way up Mount Sharp. The black oval measures about 20km by 25km and is the area in which MSL Curiosity has a 99% probability of landing.
The lowest portion of Mount Sharp is comprised of clays and sulfates, materials which are formed in the presence of water. The overlying layers contain sulfates, but very little clay, indicative of an environment in which water was evaporating and Mars was becoming drier. Scientists hope that studying Mount Sharp's layers can provide insights into the past Martian climate and give them a better idea as to whether Mars was once, or may still be habitable.
This image combines data from the High Resolution Stereo Camera on the European Space Agency's Mars Express orbiter, with data from the Context Camera on NASA's Mars Reconnaissance Orbiter, and color information from the Viking Orbiter. Clicking on this image will take you to the original higher resolution image from NASA. [See the NASA article on Mount Sharp]