12. March 2015

The Cy­do­nia re­gion – was the north of Mars once cov­ered by an ocean?

Colour plan view of a region near Cydonia Mensae
Colour plan view of a re­gion near Cy­do­nia Men­sae
Image 1/5, Credit: ESA/DLR/FU Berlin – CC BY-SA 3.0 IGO.

Colour plan view of a region near Cydonia Mensae

This im­age was ac­quired us­ing the nadir and colour chan­nels of the High Res­o­lu­tion Stereo Cam­era (HRSC) op­er­at­ed by the Ger­man Aerospace Cen­ter (Deutsches Zen­trum für Luft- und Raum­fahrt; DLR) on board ESA's Mars Ex­press space­craft. The Cy­do­nia re­gion lies slight­ly to the north of the Mar­tian di­choto­my bound­ary, in the south of Aci­dalia Plani­tia. There are nu­mer­ous mesa-like struc­tures and small­er flat-topped moun­tains here – the re­mains of the erod­ed high­land that are spread over large ar­eas of this re­gion. Some plan­e­tary re­searchers be­lieve that parts of these north­ern low­land plains were once the bed of an ocean or of lakes, which were then cov­ered by lay­ers of la­va or sed­i­men­ta­ry de­posits sev­er­al hun­dreds of me­tres deep.
Oblique per­spec­tive view of two mesas in the Cy­do­nia re­gion
Image 2/5, Credit: ESA/DLR/FU Berlin – CC BY-SA 3.0 IGO.

Oblique perspective view of two mesas in the Cydonia region

Per­spec­tive views of the sur­face of Mars can be de­rived from dig­i­tal ter­rain mod­els cre­at­ed us­ing da­ta ac­quired by the High Res­o­lu­tion Stereo Cam­era (HRSC) op­er­at­ed by the Ger­man Aerospace Cen­ter (Deutsches Zen­trum für Luft- und Raum­fahrt; DLR) on board ESA’s Mars Ex­press space­craft. In the cen­tre of the im­age, two mesas can be seen, which are ap­prox­i­mate­ly 500 me­tres high and 20 kilo­me­tres long. The two moun­tains once formed a con­tigu­ous mas­sif but are now sep­a­rat­ed by an oval val­ley.
Anaglyph im­age of part of the Cy­do­nia re­gion
Image 3/5, Credit: ESA/DLR/FU Berlin – CC BY-SA 3.0 IGO.

Anaglyph image of part of the Cydonia region

The stereo ca­pa­bil­i­ty of the HRSC imag­ing sys­tem makes it pos­si­ble to cre­ate anaglyph im­ages from a com­bi­na­tion of the var­i­ous stereo im­age chan­nels, which are di­rect­ed oblique­ly to­wards the sur­face of Mars, and the nadir chan­nel that looks down ver­ti­cal­ly at Mars. View­ing the im­age us­ing red/green or red/blue coloured glass­es cre­ates a three-di­men­sion­al im­pres­sion of the land­scape. In the cen­tre of the im­age there are two large mesas around 500 me­tres high and some 20 kilo­me­tres in length, mak­ing them six times as large as the fa­mous 1000-me­tre-high Ta­ble Moun­tain near Cape Town in South Africa. The two moun­tains once formed a con­tigu­ous mas­sif but are now sep­a­rat­ed by an oval val­ley.
To­po­graph­i­cal im­age map of part of the Cy­do­nia re­gion
Image 4/5, Credit: ESA/DLR/FU Berlin – CC BY-SA 3.0 IGO.

Topographical image map of part of the Cydonia region

Dig­i­tal ter­rain mod­els can be de­rived from the HRSC imag­ing sys­tem’s stereo im­age da­ta, which al­lo­cates an al­ti­tude val­ue to each pix­el on the sur­face of Mars. The ref­er­ence lev­el for the al­ti­tude val­ues is an ‘areoid’ (named af­ter Ares, the Greek name for Mars), a no­tion­al plane of equal grav­i­ta­tion­al at­trac­tion that cor­re­sponds to sea lev­el on Earth. The dis­tri­bu­tion of al­ti­tude val­ues can be seen us­ing the colour scale in the up­per right of the im­age. In the cen­tre of the im­age there are two large mesas, around 500 me­tres high and some 20 kilo­me­tres in length, mak­ing them six times as large as the fa­mous 1000-me­tre-high Ta­ble Moun­tain near Cape Town in South Africa. The two moun­tains once formed a con­tigu­ous mas­sif but are now sep­a­rat­ed by an oval val­ley.
To­po­graph­i­cal con­text map of Cy­do­nia Men­sae
Image 5/5, Credit: NASA/JPL (MOLA); FU Berlin.

Topographical context map of Cydonia Mensae

The Cy­do­nia re­gion lies slight­ly to the north of the Mar­tian di­choto­my bound­ary, in the south of Aci­dalia Plani­tia. There are nu­mer­ous mesa-like struc­tures and small­er flat-topped moun­tains here – the re­mains of the erod­ed high­land spread over large ar­eas of this re­gion. Some plan­e­tary re­searchers be­lieve that parts of these north­ern low­land plains were once the bed of an ocean or of lakes, which were then cov­ered by lay­ers of la­va or sed­i­men­ta­ry de­posits sev­er­al hun­dreds of me­tres deep.

These images, acquired by the High Resolution Stereo Camera (HRSC) operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) on board ESA’s Mars Express spacecraft, show a region close to Cydonia Mensae in the northern hemisphere of Mars. Some of the geological formations suggest the existence of standing water, lakes or even an ocean here for an extended period of time.

A planet of two halves – still puzzling researchers

One of the most striking features of Mars is its topographical dichotomy, with a northern region of lowland plains and a higher southern upland with numerous impact craters. The processes that have led to this are still not fully understood. One theory suggests that the northern hemisphere of Mars was struck by a planetoid over four billion years ago, which blasted away the young crust that had recently solidified and part of the underlying mantle.

The transition from the highlands to the lowlands follows a narrow, geologically varied zone referred to as the 'dichotomy boundary'. Here, erosion caused by flowing water, wind, ice and ground water has created a striking landscape of rugged escarpment outliers, deeply cut valleys and smaller hills. The Cydonia region lies slightly to the north of the dichotomy boundary, in the south of Acidalia Planitia. There are numerous mesa-like structures and smaller flat-topped mountains here – the remains of an eroded highland are distributed over large parts of this region. Some planetary researchers believe that parts of these northern lowland plains were once the bed of an ocean or of lakes, which were then covered by layers of lava or sedimentary deposits several hundreds of metres deep. This layer was subsequently removed by erosion. Water again played a role in this.

Evidence of standing water

Today, many examples of the remains of the layer can be seen in this region; the mountains and hills have flattened summits topped with hard, erosion-resistant layers. In the majority of cases, these topmost layers have a higher density of impact craters, indicating that they are older than the less cratered plains that surround them, and so were once part of a huge, continuous southern upland region. It is also possible that the underlying layers were compacted by an earlier, large asteroid impact on this plain and so resisted erosion for longer.

The topographical view (image 4) clearly shows the difference in altitude between the southern highlands (left in the image) and the northern lowlands (right). In the centre of the image there are two large mesas around 500 metres high and some 20 kilometres long, making them six times as large as the famous 1000-metre-high Table Mountain near Cape Town in South Africa. The two mountains once formed a contiguous massif but are now separated by an oval valley. The surface of the mesas differs greatly from their surroundings, indicating that the uppermost layer covering the mountains consists of a different material. In addition, on the southern side of the left-hand mesa, there is a small outflow channel.

Slightly below the centre of the image is a 15-kilometre-wide crater surrounded by a very typical double layer of material, which was formed as a result of the impact. The inner layer of crater ejecta is covered over by the larger layer that stretches out much further. This shape is particularly interesting, as it is suspected that this special type of ejecta blanket is only caused by impacts into water- or ice-rich material. In these HRSC images, it looks as if the impact might have blasted away parts of the formerly contiguous mesa.

The supposed 'face on Mars'

The Cydonia region achieved fame because of an image acquired by the Viking 1 probe on 25 July 1976 while looking for a suitable site for its lander. It showed a mountain massif that looks like a three-kilometre-long face due to a series of terrain features and the specific angle of the shadows at the time the image was acquired. All of the Mars researchers at the time believed it was an optical illusion. The HRSC camera captured the face on Orbit 3253, and the images were published in September 2006. In these images it is easy to see that the mountain massif no longer looks like a face with eyes and a mouth when imaged from a different angle and under different lighting conditions, but is actually an eroded mesa, of which there are hundreds in this area.

  • The HRSC experiment

    The HRSC was developed at 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.

  • Image processing

    The images were acquired by the HRSC on 19 November 2014 during Mars Express orbit 13,816, at 353 degrees east and 38 degrees north. The image resolution is approximately 21 metres per pixel. The colour plan view (image 1) was acquired using the nadir channel of HRSC, which is directed vertically down onto the surface of Mars; the oblique perspective view (image 2) was computed from data acquired by 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 data acquired by the nadir channel and one stereo channel. The colour-coded plan view (image 4) is based on a digital terrain model of the region, from which the topography of the landscape can be derived.

Contact
  • Elke Heinemann
    Ger­man Aerospace Cen­ter (DLR)

    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 2203 601-2867
    Linder Höhe
    51147 Cologne
    Contact
  • 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
    Contact
  • Ulrich Köhler
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Rutherfordstraße 2
    12489 Berlin
    Contact
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