Six-kilometre-deep canyons in the 'Labyrinth of the Night'
January 28, 2016 | Mars Express mission
Six-kilometre-deep canyons in the 'Labyrinth of the Night'
Colour plan view of the northeast of Noctis Labyrinthus
Despite the almost monochromatic surface of Mars in Noctis Labyrinthus, the landscape features in the region are clearly highlighted by the various tones and the shadows cast by the uneven features in the terrain. The deeply cut side valleys in the mesa stand out especially. In many places, the remains of landslides can be seen at the foot of steep mountain flanks. Elsewhere, the slopes appear to be covered by massive wind deposits. The regular linear structures on the valley slopes on the left and right edges of the image can be interpreted as dune crests. In some places, sand has been transported down the slope, while in other places, uphill transportation of the dune sand has taken place, as can be deduced from the alignment of the crests.
Colour-coded topographic map showing the northeast of Noctis Labyrinthus
Digital terrain models of the Martian surface can be construed with a resolution of down to 10 metres per pixel with data acquired by the nadir channel, which is directed vertically onto the Martian surface and the oblique views obtained by the stereo channels of the High Resolution Stereo Camera (HRSC) on board Mars Express. In this colour-coded image, the absolute elevations above a reference level, the aeroid (derived from Ares, the Greek word for Mars), are well depicted. Using the colour scale in the upper right of the image, the enormous differences in elevation – up to 6000 metres – between the blue valley floors and the pink and brown elevated plateaus of the mesas are apparent.
At the transition between the gigantic Tharsis bulge in the Martian highlands to the Valles Marineris canyon system further to the east is the Noctis Labyrinthus region – a system of intersecting valleys and canyons up to six kilometres deep that is as impressive for its topography as for its size and geological structure. Extending 1200 kilometres east to west, it is approximately the same length as the River Rhine.
Directly to the west of the gigantic graben system of Valles Marineris on Mars, lies a no less impressive region called Noctis Labyrinthus – the Labyrinth of the Night. It consists of a labyrinth of intersecting valleys and canyons up to six kilometres deep. Extending over 1200 kilometres east to west, it is almost the same length as the River Rhine. The images shown here were acquired in July 2015 by the High Resolution Stereo Camera (HRSC) operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and show part of the northeast edge of the labyrinth.
Some smaller side valleys between deeply cut grabens can also be seen in images 1, 2 and 4. However, giant mesas, the plateaus of which represent the original surface level of the Martian highlands, dominate the whole region. With a width of approximately 30 kilometres, the valley in the right half of the image is one of the widest in the entire labyrinth. Elsewhere, the canyons narrow to a few kilometres. If an astronaut were to stand at the bottom of these valleys, the towering escarpments rising several kilometres on either side would be quite a spectacular scene.
The formation of this canyon system is linked to the uplifting of the surface in the Tharsis region, which lies further to the west. Intensive volcanism led to tectonic stress in the Martian crust, and with it, the fracturing of large areas of the surface. At the same time, parts of the surface sank between blocks of terrain that were pulled apart. The largest volcanoes on Mars are also found in the Tharsis-Region.
Upslope migration of dune crests
In many places, the steep valley slopes and the valley floor are covered with extensive landslides. Elsewhere, as can be seen well in these images on closer inspection, the slopes appear to be largely covered by massive wind deposits. The regular linear structures on the valley slopes visible on the left and right edges of the images can be interpreted as dune crests. From the alignment of the crests, it can be deduced that in some places, sand has been transported down the slope, while in other places, uphill transportation of the dune sand has taken place.
In every case, these surface structures created by the wind are no longer active. This is indicated not only by the consistent covering of red Martian dust (active dunes on Mars would be dark grey in appearance as they generally consist of old volcanic dust), but also by the presence of several small impact craters, visible in the lower right edge of the image, for example. In the event of a meteorite impact in an active dune, no crater would be left in the fine, loose material as the sand would trickle into the depression that was formed and immediately fill it back up again. Furthermore, any depression that was left would quickly be obliterated by sand moved by the wind. If the dunes are old and have hardened over the course of time, however, meteorites can leave small craters behind. The approximate age of the sand dunes can be determined If the crater sizes and frequencies are accurately measured. The small number and sizes of the craters found here indicates a relatively young age for the dunes.
Image processing
The HRSC system acquired these images on 15 July 2015 during Mars Express orbit number 14,632. The region is located at six degrees south and 265 degrees east. The image resolution is approximately 16 metres per pixel. The colour plan view (image 1) was produced by the nadir channel, which is directed vertically down onto the surface of Mars, along with the colour channels; the oblique perspective view (image 3) was calculated using data acquired by the HRSC stereo channels. The anaglyph image (image 4), which conveys a three-dimensional impression of the landscape when viewed through red-blue or red-green spectacles, was composed using data acquired by the nadir channel and one stereo channel. The colour-coded plan view (image 2) is based on a digital model of the regional terrain, from which the landscape topography can be derived.
The HRSC experiment
The High Resolution Stereo Camera (HRSC) was developed at DLR and built in collaboration with industrial partners (EADS Astrium, Lewicki Microelectronic GmbH and Jena-Optronik GmbH). The science team, which is headed by Principal Investigator (PI) Ralf Jaumann, consists of 52 co-investigators from 34 institutions in 11 countries. The camera is operated by the DLR Institute of Planetary Research in Berlin-Adlershof.
