Metallic waves on historical Mars

This month’s snapshot of Mars, taken by the Excessive Decision Stereo Digital camera (HRSC) aboard ESA’s Mars orbiter, captures one of many oldest elements of the Crimson Planet: Noachis Terra. Located in Mars’s historical southern highlands, Noachis Terra has been closely bombarded with rocks from area over the previous 4 billion years – and the scars from these collisions are clear to see.

This picture is filled with influence craters. The suitable half of the picture is dominated by a part of the ground of the large Kaiser Crater, a big basin that measures about 180 km throughout and a few kilometres deep. The outstanding ridge working down the center of the picture marks a part of the crater’s southern rim.

To the left facet is a large scattering of smaller craters, some with crisp edges and others which have been step by step worn away over time. The distinction in elevation between the left and proper sides of this picture – a results of Kaiser Crater’s formation – is marked and engaging, and finest seen within the related topographic map under.

Numerous notable craters additionally lie close by however out of body (see context map under), together with Greeley, Le Verrier, and Neukum Craters. All of those craters have been the main target of earlier Mars Categorical releases, and the final is called after Gerhard Neukum: one of many planetary scientists that based the Mars Categorical mission itself and led the event of the spacecraft’s HRSC.

Sandy waves formed by water and wind

A lot of the ground of Kaiser Crater is roofed by distinctive, darkish, nearly shiny waves that look nearly as in the event that they’re carved out of metallic. These ridges are sand dunes which have been moulded by martian winds – they’ll tower greater than 100 m above the encompassing floor. Some are extra solitary and remoted, whereas others merge to kind a steady dune subject that extends for a number of kilometres. Their shiny, barely metallic look is brought on by brilliant frost deposits on their south-facing slopes.

This dune field comprises a mix of ‘transverse’ and ‘barchan’ dunes. Barchan dunes are sickle-shaped; they are the most common type of dune found on Mars and also prevalent in Earth’s deserts (such as Africa’s Sahara and Namib deserts). Also seen on our planet, transverse dunes are instead more elongated and parallel in their distribution, and can evolve as barchans accumulate more and more sand. Both types of dune are formed by sand building up and being swept about by winds blowing from the same direction.

The winds in this part of Mars blow predominantly from the west (top), pushing and moving sand around to form these distinctive wave crests. The sand itself is fine and basaltic in nature – meaning that it’s rich in minerals such as pyroxene and olivine, which are formed by volcanoes – and is constantly in motion, causing these dynamic landforms to slowly change and evolve over time.

There are also signs of water-related activity here. Martian winds have stripped away the upper layers of the planet’s surface in places, revealing light-toned clay rock that likely formed in the presence of water. There are also little gullies and narrow channels lining the steeper walls of some of the craters here – while these were likely formed by dry landslides slipping down unstable slopes, some of the older gullies may have formed as ice reserves melted, or buried groundwater reservoirs caused the ground above to shift.

Decades of Mars exploration

This image comes courtesy of the HRSC camera, one of eight instruments aboard Mars Express.

Mars Express has been capturing and exploring Mars’s many landscapes since it launched in 2003. The orbiter has mapped the planet’s surface at unprecedented resolution, in colour, and in three dimensions for over two decades now, returning insights that have drastically changed our understanding of our planetary neighbour (read more about Mars Express and its findings here).

The Mars Express HRSC was developed and is operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). The systematic processing of the camera data took place at the DLR Institute of Space Research in Berlin-Adlershof. The working group of Planetary Science and Remote Sensing at Freie Universität Berlin used the data to create the image products shown here.