19. November 2020
Mission Mars Express

Chaos on Mars

True colour plan view of Pyrrhae Regio
True colour plan view of Pyrrhae Re­gio
Image 1/5, Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

True colour plan view of Pyrrhae Regio

Pyrrhae Re­gio, south-east of Eos Chas­ma, a side val­ley of the Valles Mariner­is, is a typ­i­cal three-to-four-bil­lion-year-old high­land plateau with nu­mer­ous craters, some of which are al­ready heav­i­ly erod­ed. In its north­ern part (right, in the im­age) an un­usu­al land­scape is no­tice­able. This is an area about 50 by 40 kilo­me­tres, con­sist­ing of in­ter­con­nect­ed de­pres­sions, ter­raced slopes on the sides, and in the far north seem­ing­ly ‘chaot­ic’ hills in a dense ar­range­ment. A long time ago, this ‘chaot­ic ter­rain’, a term used by ge­ol­o­gists re­search­ing Mars, was formed here af­ter ice thawed un­der the sur­face of the high­land plateau, flowed away and the re­sult­ing cav­i­ties col­lapsed. Just vis­i­ble are heav­i­ly erod­ed val­leys that flow in­to the de­pres­sions from the south, an in­di­ca­tion that there has al­so been an out­flow of wa­ter on the sur­face. The three old craters in the south, which are be­tween 20 and 50 kilo­me­tres in di­am­e­ter, are filled with sed­i­ment.
‘Chaos’ north of Pyrrhae Regio
‘Chaos’ north of Pyrrhae Re­gio
Image 2/5, Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

‘Chaos’ north of Pyrrhae Regio

This oblique per­spec­tive view from north­east to south­west over part of Pyrrhae Re­gio is spec­tac­u­lar. As with oth­er ‘chaot­ic ter­rain’ in the wider area east of the Valles Mariner­is, a land­scape re­veals it­self in which nu­mer­ous ‘chaot­i­cal­ly’ dis­tribut­ed mesas can be seen in a de­pres­sion. It was formed when wa­ter stored as ice un­der the plateau thawed and flowed north­wards in high-en­er­gy flash floods. What re­mained was an area in which the high­lands col­lapsed, and the edges slipped off in ter­races, there­by mas­sive­ly chang­ing the land­scape. The to­pog­ra­phy, which is not vis­i­ble from this per­spec­tive, is al­so im­pres­sive; from the high­land plateau in the back­ground to the low­est points of the chaot­ic area, the dif­fer­ence in al­ti­tude is more than 4000 me­tres.
Highlands near Pyrrhae Regio on Mars
High­lands near Pyrrhae Re­gio on Mars
Image 3/5, Credit: NASA/JPL/MOLA, FU Berlin

Highlands near Pyrrhae Regio on Mars

The most strik­ing land­scape fea­ture on Mars is the al­most 4000-kilo­me­tre-long Valles Mariner­is, just north of the equa­tor. In the east, at Eos Chas­ma, the up to ten-kilo­me­tre-deep canyon sys­tem merges in­to a net­work of wide out­flow chan­nels which ex­tend a fur­ther one-and-a-half thou­sand kilo­me­tres to the north and were cre­at­ed three to four bil­lion years ago by episod­ic, catas­troph­ic flash floods. The head­wa­ter re­gions of these val­leys of­ten con­tain ‘chaot­ic ar­eas’, which were formed when sub­sur­face ice thawed and flowed away. The re­sult­ing cav­i­ties col­lapsed, the en­er­gy-rich wa­ter mass­es took large amounts of erod­ed ma­te­ri­al with them, leav­ing be­hind a ‘chaot­ic’ pat­tern of mesas – the rem­nants of the orig­i­nal plateau. At Pyrrhae Re­gio, DLR’s HRSC in­stru­ment record­ed such a chaot­ic area dur­ing Mars Ex­press or­bit 20,972.
Topographic map of Pyrrhae Regio
To­po­graph­ic map of Pyrrhae Re­gio
Image 4/5, Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

Topographic map of Pyrrhae Regio

DLR’s High Res­o­lu­tion Stereo Cam­era (HRSC) on Mars Ex­press, with its nine sen­sors ar­ranged at right an­gles to the north-south flight di­rec­tion, records the sur­face of Mars at dif­fer­ent an­gles and in four colour chan­nels. From the four in­clined stereo chan­nels and the nadir chan­nel, which is di­rect­ed per­pen­dic­u­lar to the sur­face of Mars, sci­en­tists at the DLR In­sti­tute of Plan­e­tary Re­search and the Freie Uni­ver­sität Berlin com­pute dig­i­tal ter­rain mod­els, which as­sign el­e­va­tion in­for­ma­tion to each pix­el. The colour scale in the up­per right cor­ner shows that the Pyrrhae Re­gio high­land plain is al­most flat and ris­es on­ly slow­ly over the ejec­ta blan­kets to­wards the three large craters in the south (on the left of the im­age). How­ev­er, the craters them­selves are 2000 me­tres deep from the rim to their sed­i­ment-filled basins. The view from the edges of the in­ter­con­nect­ed de­pres­sions in the north (right) would be even more ex­treme. The out­flow of wa­ter ice stored in the sub­sur­face has cre­at­ed chasms that are more than 4000 me­tres deep, where the ero­sive force of the wa­ter has carved out a ‘chaot­ic ter­rain’.
3D view of Pyrrhae Regio
3D view of Pyrrhae Re­gio
Image 5/5, Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

3D view of Pyrrhae Regio

Anaglyph im­ages can be gen­er­at­ed us­ing da­ta ac­quired by the nadir chan­nel of DLR’s High Res­o­lu­tion Stereo Cam­era (HRSC) on ESA’s Mars Ex­press Or­biter and one of the four stereo chan­nels with an oblique view. When us­ing red-blue or red-green glass­es, these im­ages pro­vide a three-di­men­sion­al view of the land­scape. North is on the right of this im­age. Here the to­pog­ra­phy of the three large, promi­nent craters in the south of the scene (left in the im­age) is very clear­ly vis­i­ble. The al­ready heav­i­ly erod­ed crater rims show that the land­scape is very old and that the craters were prob­a­bly formed more than three bil­lion years ago. But the view in­to the more than 4000-me­tre-deep de­pres­sions in the north, whose sides are bor­dered by ter­races, is par­tic­u­lar­ly spec­tac­u­lar. In them, wa­ter has left be­hind a wild­ly rugged land­scape, re­ferred to as ‘chaot­ic ter­rain’, which is typ­i­cal of these re­gions on Mars.
  • These images, acquired by DLR’s HRSC instrument, show a ‘chaotic terrain’ located in Pyrrhae Regio in the southern highlands of Mars.
  • Numerous flood events have left traces behind.
  • HRSC has been mapping the Red Planet at unprecedented resolution, in three dimensions and in colour since 2004 as part of ESA’s Mars Express mission. Its data are an important resource for present and future Mars research.
  • Focus: Space, planetary research, Mars

These High Resolution Stereo Camera (HRSC) images show a fascinating landscape near the major canyon system of Valles Marineris on Mars. On a high plateau with numerous craters lies a geologically ‘disturbed’ aera, the technical term being ‘chaotic terrain’. Such terrain forms occur when underground ice reservoirs melt and large amounts of water are released from the subsurface. The heat necessary for such a process could have been emitted by nearby volcanoes or generated by asteroid impacts. After the water has drained away, the surface above the newly formed cavities collapses, and the overlying landscape falls in. What remains are numerous ‘chaotically’ scattered mesas.

HRSC was developed and is operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). HRSC has been mapping the Red Planet at unprecedented resolution, in three dimensions and in colour, since 2004 as part of ESA’s Mars Express mission. Its data are an important resource for present and future research on Mars. The findings acquired during the course of the mission have significantly changed our understanding of the Red Planet’s geological development.

Catastrophic floods have left their mark

South of Eos Chasma, or the ‘Gorge of Dawn’ – an eastern branch of the major Valles Marineris valley system – lies Pyrrhae Regio. It is situated on an ancient highland plateau covered with craters. These HRSC images show an impressive chaotic landscape at their right-hand edge.

The overview map (Image 3) shows a larger part of the surrounding landscape. In the northeast (outside the marked rectangular HRSC image section) branching river channels, called the Osuga Valles, flow into this chaotic region. Scientific investigations of the collapse structures in Eos Chasma, in the southwest and Pyrrhae Regio, and the outflow channel system of the Osuga Valles, which lies between the two, revealed that at least two opposite outflow events occurred here. First, there was an outflow from Pyrrhae Regio in Eos Chasma, and later an outflow in the opposite direction.

After water and sediment flowed out of Pyrrhae Regio, rugged blocks remained in the depression where ice was once hidden in subsurface cavities and thus protected from sublimation (vaporisation under the low atmospheric pressure of Mars). Presumably, in addition to meltwater, groundwater leakage also occurred. The escaping groundwater then led to landslides and collapses at the outer edges of the small chaotic area. The concentric structures at the edges of the terrain bear striking witness to how the slopes slid down into the interior of the depression. The difference in altitude here is four thousand metres. The amount of material released and removed was therefore enormous.

Sapping valleys

On the southern side (left in Images 1, 4 and 5) two large and one small impact crater can be seen, the latter measuring approximately 20 kilometres in diameter. The largest crater shows some linear fracture structures on the crater floor. They were probably formed when lava, which escaped into the crater interior after the impact, cooled down rapidly and contracted. Between the crater and the chaos area two valleys can be seen. Both are two kilometres wide. These valleys, especially the upper one, show great similarity to sapping valleys. In this form of erosion, groundwater emerges directly at the edge of the terrain or slightly below it as if from a trickling spring. This erodes and hollows out the slope. As a result of material slipping along the top edge of the terrain, the erosion edge migrates further and further back as material is carried away by flowing water. This creates steep, U-shaped valley structures.

Some background on mythology

The region was named after Pyrrha, daughter of Pandora and Epimetheus. She was the wife of Deucalion, who in Greek mythology has the same role as Noah in the Old Testament. He was asked by his father Prometheus to build an ark to save himself and his wife from the great flood that Zeus had summoned to destroy humankind. Pyrrha and Deucalion were the only ones to survive the catastrophe. They re-created humanity by throwing rocks over their shoulders, from which human beings emerged.

All images in high resolution and more images acquired by the HRSC instrument can be found in the Mars Express image gallery on flickr.

  • Image processing

    These images were acquired by the High Resolution Stereo Camera (HRSC) on 3 August 2020 during Mars Express orbit 20,972. The resolution is approximately 16 metres per pixel. The centre of the images is located at approximately 322 degrees east and 16 degrees south. The perpendicular colour view was generated using data acquired by the nadir channel, the field of view which is aligned perpendicular to the surface of Mars, and the colour channels of HRSC. The oblique perspective view was computed using a Digital Terrain Model (DTM) and data acquired by the nadir and colour channels of HRSC. The anaglyph, which provides a three-dimensional view of the landscape when viewed using red-green or red-blue glasses, was derived from data acquired by the nadir channel and the stereo channels. The colour-coded topographic view is based on a DTM of the region, from which the topography of the landscape can be derived. The reference body for the HRSC DTM is a Mars equipotential surface (Areoid).

    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 was performed at the DLR Institute of Planetary Research in Berlin-Adlershof. Personnel in the Department of Planetary Sciences and Remote Sensing at Freie Universität Berlin used these data to create the image products shown here.

  • The HRSC experiment on Mars Express
    The High Resolution Stereo Camera (HRSC) was developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and built in collaboration with partners in industry (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.
  • Elke Heinemann
    Ger­man Aerospace Cen­ter (DLR)
    Pub­lic Af­fairs and Com­mu­ni­ca­tions
    Telephone: +49 2203 601-2867
    Fax: +49 2203 601-3249

  • Daniela Tirsch
    Ger­man Aerospace Cen­ter (DLR)

    In­sti­tute of Plan­e­tary Re­search
    Telephone: +49 30 67055-488
    Fax: +49 30 67055-402
    Linder Höhe
    51147 Köln
  • Ulrich Köhler
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Rutherfordstraße 2
    12489 Berlin
  • Prof.Dr. Ralf Jaumann
    Freie Uni­ver­sität Berlin
    In­sti­tute of Ge­o­log­i­cal Sci­ences
    Plan­e­tary Sci­ences and Re­mote Sens­ing
    Telephone: +49-172-2355864
    Malteserstr. 74-100
    12249 Berlin
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