Today's Image of Mars shows a partially exhumed crater in Evros Vallis.
What exactly is an 'exhumed' crater?
An exhumed crater is one that formed a long time ago, but was subsequently buried. It becomes re-exposed because the materials that originally filled and covered it start to erode. This is because oftentimes the materials that fill a crater are less wear resistant than the surrounding terrain, making them easier to erode.
In this image you can see many different dunes surrounding and even in the crater. Evros Vallis is full of these dunes. What do these dunes tell us?
Well if you look at this image you can see that not all the dunes have the same orientation. Since Martian dunes are created almost entirely from wind they are generally oriented the in the direction the wind was blowing. Because these dunes and others like them in Evros Vallis have different orientations we can tell that different 'wind regimes' were involved in the creation of the dunes. A 'wind regime' simply refers to the a pattern in the regularly flow and direction of the wind.
This image was taken by HiRISE. If you click on it you you will be taken to the original captioned image from them.