Today's Image of Mars shows layered deposits on the rim of a crater close to Argyre Basin, as imaged by HiRISE. The sun struck the crater at a low enough angle that it cast the interior into deep shadow, while illuminating the distinct layers on the crater rim.
Layered deposits are important to scientists because they provide insight about the past environment on Mars. Transitioning layers imply that the environment on Mars was changing during that time period; how much and how often depends on the variance and size of the layers.
Clicking on this image will take you to the original high resolution image from HiRISE. [See their caption for the image]