Wind creates bumps on Mars

Shots of the stereo camera HRSC show the power of wind erosion

Perspective view of a section in the Eumenides Dorsum area © ESA / DLR / FU Berlin (G. Neukum)
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New images of the space probe Mars Express impressively demonstrate the powerful forces of wind erosion on the red planet: the area "Eumenides Dorsum" is almost entirely crossed by very narrow, linear structures with narrow valleys in between, the so - called "Yardangs" can be up to 50 kilometers long.

These structures are very similar to desert structures in Central Asia, which the Swedish explorer Sven Hedin discovered some 100 years ago on his travels.

The Eumenides Dorsum area is a north-south elevation on Mars, west of the Tharsis volcanic region. It has about five times the size of the Saarland and is part of the Medusae Fossae region. Probably the area consists of so-called pyroclastic deposits, which arise when ignited by volcanoes, red hot rocks and ashes to more or less strongly solidified rock such as tuff or pumice solidify and therefore relatively easily attacked by erosion. In Eumenides Dorsum impressive examples of the erosive force that the wind can exert on the surface of the Red Planet can be seen.

Wind as a formative force of the Martian surface

The atmosphere of Mars, which consists mainly of carbon dioxide, is very thin: The surface pressure on the Red Planet at zero level is only about 0.75 percent of the Earth's air pressure at sea level. It thus corresponds to the pressure at a height of about 35 kilometers above the earth's surface. Despite the very thin Martian atmosphere, winds can develop amazing dynamics. They are involved in the creation of impressive surface shapes over long periods of time.

The new images of the German Aerospace Center (DLR) -based HRSC on board Mars Express show a 12, 000 square kilometer section of Eumenides Dorsum, a ridge named after the goddesses of the gods (Furies) of Greek mythology at two degrees to the south Latitude and 206 degrees east longitude. The recordings were taken on December 26, 2007 from a height of 260 kilometers. display

Topographic HRSC image map of the Eumenides Dorsum region ESA / DLR / FU Berlin (G. Neukum)

Wind erosion leads to similar structures on Earth and Mars

The region is dominated by narrow, steep sand dunes, called "yardangs" or "wind hoppers" that stretch across much of the area. Yardangs are landforms in sediments created by the erosive action of wind. The wind carries grains of sand along with them, which erode and carry away material similar to a sandblast blower along already existing structures such as lines, gutters or bumps.

The unusual sounding name Yardang goes back to the Swedish geographer and explorer Sven Hedin (1865-1952), who on one of his three long journeys through Central Asia in 1902 by the desert Lop Nor came and there steep mountains, prepared by the wind from the sedimentary rocks, discovered, which were called by the native Uighurs with the word Yar . Yardangs have been observed by Mars Express in many places.

Even smaller, bumpy elevations were eroded by the wind and show a striking, pyramid-like shape. If the wind always blows from a certain direction, structures with a preferred direction are created. In the case of the Eumenides Dorsum region, it can be clearly seen that the Yardangs are all oriented in the north S d direction. The smooth areas also appear to be made of material that could better withstand erosion. According to the DLR, this could be rocks of magmatic origin. These rocks are generally harder and are much less attacked by wind blow, the so-called Korrasion.

Creased ridges in southern part - origin still unclear

Also noteworthy is a structure in the southern part of the landscape covered by yardangs, in which several arcuate ridge segments are arranged concentrically and transversely to the predominant, parallel north-south orientation of the wind humps, As the straight yardangs pass over these curved backs, they are younger than the latter.

Perspective view from the southeast to the area Eumenides Dorsum ESA / DLR / FU Berlin (G. Neukum)

About the origin of the curved ridges can only be speculated, according to the DLR. Presumably, the effect of the wind exposed an older structure, at times covered by volcanic deposits, which can now only be recognized in its outlines. These could be former flowing fronts of frozen lava flows or endmor nen, which a previously existing glacier pushed forward and pushed together on its front which have remained behind after its melting.

However, it could also be that the upper part of a magmatic body, which had dripped into the crust, was exposed by the erosion, which in itself is not homogeneous but stratified and therefore resistant to erosion to varying degrees was, so that the bowl-shaped structure of the body still pervades the landscape.

(German Aerospace Center (DLR), 01.12.2008 - DLO)