Aurorae Chaos – the transition from Valles Marineris to the large outflow channel systems
November 19, 2015
Aurorae Chaos – the transition from Valles Marineris to the large outflow channel systems
A vertical plan view of the western runout of Aurorae Chaos
Numerous interesting landscape features can be identified in this true colour plan view of Aurorae Chaos, which represents an area of about 180 north to south by 100 kilometres east to west (north is on the right). The centre of the image is dominated by the enclosed basin of Aurorae Chaos, which is situated more than three thousand metres lower than the surrounding area. Illustrative examples of a typical 'chaotic terrain' that can be found on Mars are visible on the left half of the image. It is believed that chaotic regions are formed when subsurface ice reservoirs melt due to heat and are suddenly released. If the water drains away, the surface falls over the newly created cavities and the landscape collapses into itself. Aurorae Chaos continues another several hundred kilometres further to the east. Enormous quantities of water must once have flowed towards the northern lowlands through Aurorae Chaos and over the adjacent regions of Hydraotes Chaos and Chryse Chaos.
In the north, the Aurorae Chaos region is bound by a wall more than 3000 metres high. Along this steep – and unstable in places – surface feature, large rock masses break loose repeatedly, forming huge alluvial fan deposits. Semicircular indentations are left behind in the terrain edge. The landslides were most likely 'lubricated' by water, which existed as ice within hollow spaces under the plateau and suddenly melted. This would explain the alluvial fans extending into the Aurorae basin as well as the occasional flow structures.
Topographic map of the eastern runout of the Valles Marineris
The topographic map shows the large enclosed basin of Aurorae Chaos, which is several thousand meters deep, nestled between four blocks of the Martian highlands to about 10 degrees south. The valleys of Capri and Eos Chasma in Aurorae Chaos open up from the south-west; Eos Chasma – the 'Valley of the Dawn' – forms the eastern continuation of the rift valley system of the nearly 4000 kilometre-long Valles Marineris. The images presented in this article were acquired by the HRSC camera system in Orbit 14635 in the area of the small rectangle marked in this image.
The latest images acquired by the High Resolution Stereo Camera (HRSC – High Resolution Stereo Camera), operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) on board the European Space Agency (ESA) Mars Express spacecraft, show a runout of the Aurorae Chaos region – an eastern continuation of the massive Valles Marineris graben system on Mars.
Aurorae Chaos is a very extensive ‘chaotic terrain’ that extends several hundred kilometres further to the east. Chaotic terrain refers to regions with dozens – or up to several hundred – small peaks and mesas. They may sometimes constitute a random pattern over many thousands of square kilometres on Mars – or just have a 'chaotic' arrangement. Aurorae Chaos lies northeast of the point at which the Capri Chasma and Eos Chasma valleys meet, and covers an area of roughly 700 by 400 kilometres, connecting the grabens of Valles Marineris with Ganges Chasma in an area a little more than half the size of Germany. Enormous quantities of water must once have flowed towards the northern lowlands through here and over the adjacent regions of Hydraotes Chaos and Chryse Chaos.
Landscape features indicate great masses of water in Mars' past
The transition of the collapsed regions to the south (left on Images 2, 3 and 4) towards the smoother area in the centre of the images – a part of the Ganges Chasma valley – is clearly visible in the images. The fan-shaped deposits along the slopes suggest the occurrence of mass movements down these slopes, which carried sediment and subsequently deposited it there. A little further north (right in the image) is a steep slope that is adjacent to a cratered plateau – a part of the highlands region Xanthe Terra. 4800 metres separate the valley floor and the plateau – this height difference is strikingly noticeable in the 3D view and also stands out clearly in the topographical image. This is the altitude of Mont Blanc – however, when it is measured from sea level, these are dimensions on an enormous scale.
The region portrayed in the image shows numerous interesting landscape features that point to large amounts of water flowing across the Martian surface in the past. Chaotic terrains are believed to have developed by collapse, triggered by the sudden release of water when giant subterranean ice reservoirs melted. The source of the heat could be nearby volcanoes or an asteroid impact. When the water drains away, the surface falls over the newly formed cavities and the landscape collapses onto itself. A close look at the topographic map reveals that the high plateaus to the north and south of Aurorae Chaos are approximately the same height. The southern plateau (top left in the plan views) shows a field of mountains with rounded peaks, a small, chaotic terrain located several thousand metres up as well as numerous buttes smaller than those in the valley and that have not been worn by erosion. The northern plateau does not show traces of an eroded landscape. Some smaller branching channels can be seen on the surface. Therefore, water was possible present in the subsoil in the south but not in the north.
In the centre of the image, a group of remnant buttes in the midst of the low-lying valley shows a stepped morphology, as do some of the fan-shaped deposits in the north. This could be an indication that different water or ice levels once existed in this area. Also notable are the two faults that cut through a collapsed block (visible in the top centre of the image). Referring again to the topographical map, the faults appear to cut through the southern plateau (top left corner of the image). They could be the result of a later occurring tectonic event or have simple subsidence.
Image processing
The images were acquired by the HRSC (High Resolution Stereo Camera) on 16 July 2015 during Orbit 14,653 of the Mars Express spacecraft, at 320 degrees east and 8 degrees south. The image resolution is approximately 17 metres per pixel. The colour image (image 1) was acquired using the nadir channel of the HRSC, which is directed vertically down onto the surface of Mars; the perspective oblique view (image 2) was computed from the HRSC stereo channels. The anaglyph image (image 3), which creates a three-dimensional impression of the landscape when viewed with red/blue or red/green glasses, was derived from the nadir channel and one stereo channel. The aerial view encoded in rainbow colours (image 4) is based on a digital terrain model of the region, from which the topography of the landscape 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.
