Department of Earth Sciences

The image shows an area of the equatorial region of Mars covering approximately 28.000 km², which is almost the size of Belgium. The region exhibits several kilometer long linear structures with interspersed channels. The entire area shows impressive examples for the erosional force of wind on Mars. Although Mars‘ atmosphere is rather thin compared to the Earth’s atmosphere - just 0.75% of the mean surface pressure, which corresponds to an altitude of about 35 Kilometers above earth’s surface - it can be very dynamic and plays a major role in shaping the red planet‘s landscape over a long period of time.

The region is dominated by so-called “Yardangs“, which cover most of the pictured area. Yardangs are features in sedimentary rock originating from the erosional force of wind. The wind is transporting loose material like sand grains and acts like a sand-blast unit. It erodes the soft sedimentary rock along already existing structures like gaps, fault lines or incisions and removes the material. A preferential direction of these features can develop if the wind direction is always alike. In the area pictured, most of the Yardangs are oriented in a northwest-southeast direction.

The flat area to the east of the scene at first glance seems to be featureless but after strong contrast enhancement of the annotation image so called platy flows become discernable. Here, the surface of a lava flow – possibly from close Olympus Mons - cooled and solidified, while liquid lava beneath kept flowing. The continued flow broke apart the solid surface and moved the pieces like rafts.

Apart from the large fresh looking impact crater with its clearly noticeable fluidized ejecta blanket (formed when impact debris mixed with subsurface water or ice), small ancient craters are visible in the southeast of the scene. These have been emplaced before yardang formation but withstood wind erosion better than the surrounding area due to ground compaction during the impact process.

Stunningly, crater ejecta, platy lava flow and yardangs encounter each other south (left) of the large impact crater where the yardang field becomes visible. As yardangs are placed on top of the platy lava flows, they are younger than the latter. Only very few yardangs are within the ejecta zone around the crater so at least these few should be younger than the impact event as they are uncovered by ejecta. Finally it seems that the impact ejecta have covered the platy lava field, meaning that it is younger, but this is not entirely clear. Beyond that one has to keep in mind, that morphologic processes can be repetitive. Thus the analysis of the time sequence remains challenging.

Neigboring areas of Eumenides Dorsum from HRSC orbit 5114 are shown in earlier Press Releases from 2008 and in Medusae Fossae from 2022 (HRSC orbit 21948).