15 October 2004
It is now early summer in the northern hemisphere on Mars, and this means that the ices of the north polar cap are in full retreat. Exposed from beneath seasonal frost are the eroded layers of what Mars scientists suspect are composed of a mixture of dust and ice (and in some layers, sand). This October 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the north polar layers exposed on a moderately-dipping slope. The bright material at the top of the image is water ice frost; the triangular features are thought to be caused by wind erosion of the frost. This image is located near 87.1°N, 267.4°W, and covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.