Today's Image of Mars shows a potential landing site for future missions to Mars in Ismenius Cavus. Ismenius Cavus is a 600m deep basin that was once a lake, located north of Arabia Terra. The basin has six distinct valleys that run into it, lending credence the idea that the basin once contained a large lake.
Further evidence that water was abundant in Ismenius Cavus is found in the minerals. Iron and magnesium phyllosilicates, as well as clays have been discovered in the area, which are only ever formed in the presence of water.
The outline below indicated the candidate landing site for the Mars Science Laboratory. It was beaten out by Gale Crater, but will most definitely remain at the top of the list of potential landing sites for future missions to Mars!
Clicking on this image will take you to the original high resolution image. [See a separate article from the Lunar Planetary Institute on Ismenius Cavus]