Live on Mars

In this image, we can see that the north pole is surrounded by a vast .sea. of basaltic sand dunes. In northern winter a seasonal polar cap composed of carbon dioxide ice (dry ice) forms and the surrounding dunes become covered with frost. In the spring, the ice sublimates (evaporates directly from ice to gas) loosening and moving tiny dust particles.

The bright portions of the dunes in this image are areas still covered with seasonal frost while dark spots are areas where the frost is gone or dark dust has cascaded down the sides of the dune.

The dunes imaged here are similar to barchan dunes that are commonly found in desert regions on Earth. Barchan dunes are generally crescent-shaped with a steep slip face bordered by horns oriented in the downwind direction. Barchan dunes form by winds blowing mainly in one direction and thus are good indicators of the dominant wind direction when the dunes formed.

Seen here are gullies in a northern hemisphere crater. The crater is well-preserved as indicated by its sharp rim and steep walls. Gullies are rarer in the northern hemisphere, possibly because there are fewer slopes for them to form on compared to the heavily cratered southern highlands.

This image captures a range of gully morphologies. The gullies on the north wall (south facing) are more abundant and evenly-spaced than those on the east and south walls, and they extend up to the crater rim on the northern side. These differences might occur because of differences in sunlight exposure and temperature variations.

The crater floor has a linear texture suggestive of flow. Ice-rich material might have moved off the crater walls, driven by gravity, and flowed towards the crater center.

This image shows a large gully in the wall of a crater in the southern hemisphere. Such gullies are among the most recent landforms on Mars, and were probably carved by liquid water.

The source of the water is still unknown; it could have been groundwater from a shallow aquifer or melted snow or ground ice from a different climate.

This gully is not particularly fresh, but it is among the largest observed; several sub-channels merge in the alcove on the upper slope, in the north part of the image. Numerous faint troughs and lineations are visible downslope, likely indicating old channels that have been buried or reworked. The upper alcove exposes a dense cluster of boulders not seen on the adjacent slope. This could indicate that smaller material has been removed by the gullies, exposing the boulders without transporting them far.

This image covers a portion of Eberswalde Crater, which has an ancient deltaic depositional setting. Eberswalde is an approximately 65 kilometer diameter, closed basin crater. This image was targeted in the landing ellipse as a possible site for the 2009 Mars Science Laboratory mission. The image shows resistant mounds and knobs as well as a scoured surface.

The CRISM instrument on board the Mars Reconnaissance Orbiter has detected phyllosilicates (clays) in the bright layers in the crater. One of the ways clays form on Earth is when water erodes rock and makes fine particles which settle out of water; this often occurs in river deltas and lake beds. The delta and meandering channels in Eberswalde Crater (to the west of the landing ellipse) and the detection of phyllosilicates provides evidence for possible persistent aqueous activity on Mars.