One of the best ways to learn about a planet's history is to examine its geology, so one of the things scientists look for when sending rovers to Mars is areas on the planet's surface that allow access to multiple layers of diverse and interesting rock types.
The image featured up top was released yesterday by NASA's HiRISE project, and features a beautiful formation located in Mars' Nili Fossae region, which, according to HiRISE Principle Investigator Alfred McEwen, contains some of the planet's best exposures of ancient bedrock. Which, in turn, could teach us a lot about the history of the Red Planet:
Ancient bedrock can be tilted, folded, and generally complicated and difficult to understand, but the center of this image [13.2 Mb hi-res version available here] shows a stack of nearly horizontal layers. These layers might record how the environment on ancient Mars changed over time, and would be a good site for future exploration by a rover.
Read more at NASA HiRISE