Today's Image of Mars shows an inverted, winding, riverbed surrounded by features called yardangs.
Yardangs are created when the primary form of erosion is wind. They are easy to identify as they have multiple sharp ridges that are oriented in a similar way: a result of wind erosion over millions of years.
But why is the riverbed raised? Shouldn't it be carved into the surface?
When the river was flowing it deposited layer after layer of sediments, which were harder than the surrounding terrain. Since the river dried up the whole area has spent millions of years being eroded by wind. Because the sediments deposited by the river bed were harder than the surrounding terrain they were eroded much less than the rest of the surface, thus the reason the river bed is inverted.
Today's image was taken by HiRISE. Clicking on the image will take you to the original captioned image from them!