Today's Image of Mars shows colorful springtime layered deposits in the North Polar Region of Mars, as taken by HiRISE. Scientists study layered deposits because it lets them determine the past environment on Mars by studying the chemical makeup of the different layers. The oldest layers are buried beneath billions of years of sediment and dust deposits.
When exposed, these layers tell us a lot about the past Martian climate including what the environment on Mars was when the layer was deposited, the length of time Mars experienced a certain climate, and the approximate time of environmental change. In short, studying layered deposits will help scientists determine when water was abundant on Mars and approximately when and how long it took for the planet to reach its current barren state. If we know when and how long it took for the water to disappear we can use that information to discover where the water on Mars went.
Clicking on the image below will take you to the original high resolution image from HiRISE. [See their caption for the image]