21. February 2019
Mars Express mission

What the dev­il is leav­ing these trails on Mars?

Chalcoporos Rupes shown in contrast-enhanced colour
Chal­co­poros Ru­pes shown in con­trast-en­hanced colour
Image 1/5, Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

Chalcoporos Rupes shown in contrast-enhanced colour

The de­pict­ed re­gion re­veals very strong light and dark con­trasts. Against the Mar­tian land­scape, with its well-known ochre colour­ing, larg­er dark ar­eas can be seen in two craters that have been al­most lev­elled by ero­sion, as well as a pat­tern of fine dark lines spread over an area of over 2000 square kilo­me­tres. The large dark area in the north­ern crater (on the right-hand side of the im­age), around 35 kilo­me­tres across, is a dune field of dark sands blown by the wind. A small dune field can be seen on the floor of the south­ern crater (on the left-hand side of the pic­ture), this time con­sist­ing of ma­te­ri­al from the ex­posed dark lay­ers to­wards the top of the crater wall. The dark lines in the cen­tre of the im­age are ae­o­lian phe­nom­e­na, that is, they are caused by wind. These are the tracks of small whirl­winds, or ‘dust dev­ils’, which are the re­sult of at­mo­spher­ic tur­bu­lence. When a dust dev­il trav­els across the Mar­tian sur­face, it lifts a thin lay­er of light-coloured sand from the ground, ex­pos­ing the un­der­ly­ing dark­er ma­te­ri­al. The fine dark tracks mark the paths tak­en by dust dev­ils.
Perspective view of dust devil tracks in Chalcoporos Rupes
Per­spec­tive view of dust dev­il tracks in Chal­co­poros Ru­pes
Image 2/5, Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

Perspective view of dust devil tracks in Chalcoporos Rupes

This pat­tern of dark, nar­row, thread-like stripes was cre­at­ed by small whirl­winds, or dust dev­ils, which are caused by at­mo­spher­ic tur­bu­lence. When a dust dev­il trav­els across the Mar­tian sur­face, it lifts a thin lay­er of light-coloured sand from the ground, ex­pos­ing the dark­er ma­te­ri­al be­neath. The tracks mark the paths tak­en by the dust dev­ils. The trails left by dust dev­ils on the Mar­tian sur­face can be up to sev­er­al hun­dred me­tres wide and sev­er­al kilo­me­tres long. Their lifes­pan is rel­a­tive­ly short, as they tend to be cov­ered over again by light-coloured sand, es­pe­cial­ly af­ter dust storms, so that they dis­ap­pear with­in a mat­ter of days or months. The im­age shows an area ap­prox­i­mate­ly 50 kilo­me­tres across.
Topographical overview of the Chalcoporos Rupes region
To­po­graph­i­cal overview of the Chal­co­poros Ru­pes re­gion
Image 3/5, Credit: NASA/USGS (MOLA); FU Berlin

Topographical overview of the Chalcoporos Rupes region

The Chal­co­poros Ru­pes re­gion is lo­cat­ed in the south­ern Mar­tian high­lands, ap­prox­i­mate­ly 1000 kilo­me­tres to the west of the Hel­las im­pact basin and a few hun­dred kilo­me­tres south­west of the Neukum Crater (top right), which was named last year in hon­our of the ‘fa­ther’ of the High Res­o­lu­tion Stereo Cam­era (HRSC), Ger­hard Neukum, who worked at DLR and the Freie Uni­ver­sität Berlin. The re­gion is typ­i­cal of the Mar­tian high­lands, which lie in the plan­et’s south­ern hemi­sphere, with count­less im­pact craters, of which some of them are heav­i­ly weath­ered. This in­di­cates that the re­gion is very old – over three bil­lion years. The term ‘Ru­pes’ (mean­ing es­carp­ment) re­flects the fact that tec­ton­ic forces have stretched the Mar­tian crust here. This has re­sult­ed in elon­gat­ed frac­ture struc­tures that are clear­ly vis­i­ble on the re­gion­al overview, stretch­ing from south­west to north­east. The DLR-op­er­at­ed HRSC on board ESA’s Mars Ex­press or­biter im­aged the area on 3 Jan­uary 2019 from an al­ti­tude of ap­prox­i­mate­ly 300 kilo­me­tres, dur­ing or­bit 18,983. The im­age res­o­lu­tion is 13 me­tres per pix­el.
3D view of part of Chalcoporos Rupes
3D view of part of Chal­co­poros Ru­pes
Image 4/5, Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

3D view of part of Chalcoporos Rupes

Anaglyph im­ages can be pro­duced from da­ta ac­quired by the nadir chan­nel (ori­ent­ed ver­ti­cal­ly on­to the sur­face of Mars) of the High Res­o­lu­tion Stereo Cam­era (HRSC) op­er­at­ed by the DLR on board the ESA Mars Ex­press or­biter and one of the four oblique-view stereo chan­nels. When viewed with red-blue or red-green glass­es, these im­ages give a re­al­is­tic, three-di­men­sion­al view of the land­scape. In the sec­tion shown, a plateau in the Chal­co­poros Ru­pes re­gion, shows lit­tle in the way of a to­po­graph­i­cal pro­file. How­ev­er, a few in­ter­est­ing land­scape phe­nom­e­na can be seen in the two large craters in the im­age. The south­ern (left-hand) half con­tains dark gul­lies where dark sand has trick­led down in­to the crater and been shaped in­to sand dunes by the wind. A field of dunes mea­sur­ing 10 by 15 kilo­me­tres is vis­i­ble in the large, heav­i­ly erod­ed crater to the north.
Topographical image map of Chalcoporos Rupes
To­po­graph­i­cal im­age map of Chal­co­poros Ru­pes
Image 5/5, Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

Topographical image map of Chalcoporos Rupes

The im­age strips cap­tured from dif­fer­ent an­gles by the High Res­o­lu­tion Stereo Cam­era (HRSC) on board Mars Ex­press were used to gen­er­ate dig­i­tal ter­rain mod­els of the Mar­tian sur­face. They con­tain height in­for­ma­tion for each record­ed pix­el. The ref­er­ence lev­el to which the al­ti­tude read­ings re­fer is an imag­i­nary sur­face that rep­re­sents the same grav­i­ta­tion­al pull as that at sea lev­el on Earth. Known as an equipo­ten­tial sur­face, this is shaped like a bi­ax­i­al el­lip­soid and is known as an Areoid, a name de­rived from Ares, the Greek name for Mars. In this im­age, north is to the right. The colour cod­ing of the dig­i­tal ter­rain mod­el (top right) in­di­cates the el­e­va­tion dif­fer­ences ef­fec­tive­ly: the to­po­graph­i­cal pro­file of the re­gion cov­ers rough­ly 1200 me­tres of el­e­va­tion and shows that the Mar­tian high­lands in this area form an ex­ten­sive plateau with­out any ma­jor dif­fer­ences in height, apart from the de­pres­sions of two large craters, whose en­tire pro­file has al­ready been sig­nif­i­cant­ly lev­elled by ero­sion. On the up­per (west­ern) rim of the larg­er crater is an­oth­er small­er crater whose cir­cu­lar ejec­ta blan­ket stands out strik­ing­ly against the to­po­graph­i­cal im­age map. Known as a ram­part crater, this is typ­i­cal of cer­tain re­gions on Mars where un­der­ground ice is (or once was) present. An as­ter­oid im­pact cre­ates this dis­tinc­tive ejec­ta blan­ket, which is formed by rock de­bris mixed with wa­ter.
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  • The Chalcoporos Rupes region is located in the southern Martian highlands approximately 1000 kilometres west of the Hellas impact basin.
  • The region is characterised by a heavy dust blanket and the activity of Martian winds. Here, narrow, dark lines that have been created by 'dust devils' – small whirlwinds – are striking.
  • From these, the wind directions in this region can be derived.
  • On Earth, dust devils are typically observed during summer in dry and desert landscapes, for example in the southwestern USA, Africa, Australia and China.
  • Focus: Spaceflight, planetary research, Mars

New images acquired by the High Resolution Stereo Camera (HRSC) operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) on board the European Space Agency's (ESA) Mars Express spacecraft in early 2019 show a region in the southern hemisphere of Mars that is defined by a thick blanket of dust and the activity of Martian winds. These aeolian forces – named after Aeolus, the god of the winds in Greek mythology – have left a striking pattern on the Martian surface, along with dark dunes. Particularly prominent are the numerous narrow dark lines left by dust devils, or small whirlwinds, on the ground. These allow scientists to deduce the direction of winds in this region.

Mars Express, the first planetary mission undertaken by ESA, has been orbiting Earth's neighbouring planet for more than 15 years and will soon have circled Mars 20,000 times. HRSC has imaged a section of the Martian surface on roughly every third to fourth orbit of Mars. Systematic processing of the camera data is carried out at the DLR Institute of Planetary Research in Berlin-Adlershof. From this data, staff specialising in planetology and remote sensing at the Freie Universität Berlin produced the views shown here. The Chalcoporos Rupes region is located in the southern Martian highlands, around 1000 kilometres to the west of the Hellas impact basin and a few hundred kilometres southwest of Neukum Crater, which was named last year in honour of the 'father' of the HRSC, Gerhard Neukum, who worked at DLR and the Freie Universität Berlin.

Small whirlwinds act like vacuum cleaners to expose the subsoil

The dark, narrow, thread-like stripes that can be seen in the images are the traces of small whirlwinds – known as dust devils – which are caused by atmospheric turbulence. Dust devils on Mars form in a similar way to their counterparts on Earth – as the Martian soil is warmed by sunlight during the day, the heated air rises, creating an updraught. Under certain conditions, this updraught then begins to rotate, causing a vertical vortex. Differences in atmospheric pressure create a suction effect, lifting any loose material from the surface. On Mars, this loose material is dust; on Earth it may also come in the form of sand or snow. When a dust devil moves across the Martian surface, it lifts a thin layer of light-coloured sand from the ground, exposing the darker underlying material. These narrow dark tracks mark the paths taken by dust devils.

The trails left by dust devils on the Martian surface can be up to several hundred metres wide and several kilometres long. They tend to form in the afternoon on warm spring and summer days, when the surface is illuminated by sunlight for a longer time, and thus heats up more. Nevertheless, dust devils have also been observed during the winter months. Dust devil tracks may run straight or follow curved or winding paths, as well as intersecting or overlapping with one another. Their lifespan is relatively short, as they tend to be covered over again by light-coloured sand that is whipped up by dust storms, so that they disappear within a matter of days or months.

Dust devil traces can be found almost everywhere on Mars. They are particularly well documented on the plains of Amazonis Planitia and Argyre Planitia, as well as on Hellas Planitia, the lowland plain in Hellas, the largest impact basin on Mars. However, they can also be seen in the Proctor and Russell impact craters near the area shown here, as well as in many other regions of Mars. NASA's Mars rovers have observed dust devils in action by chance, and they have even more frequently been captured in satellite images of the Martian surface. If such images are taken in quick succession, the speed of the dust devils can be determined and their movement replicated in short animations. A particularly striking example is the series of 21 images acquired by the Mars exploration rover Spirit on 15 May 2005 near its landing site in Gusev Crater, showing a dust devil one kilometre away over a period of almost 10 minutes, which were compiled by NASA to create a 'flip book'.

Measurements showed that this dust devil was travelling at a speed of approximately 17 kilometres per hour, and was 35 metres in diameter. According to measurements taken from orbit, dust devils on Mars move much more rapidly than those on Earth. Although first-hand sightings of dust devils are far more common on our planet, they leave few recorded traces. They are typically observed in summer in dry desert landscapes, such as in the southwestern United States, Africa, Australia and China.

Large temperature differences due to intense warming during the day mean that the dust devils on Mars can be much bigger than those on Earth. On Mars, they can reach a height of eight kilometres, effectively carrying dust into the Martian atmosphere. Estimates suggest that overall, dust devils on Mars can lift as much material as a global dust storm, thus contributing significantly to an increased amount of dust in the atmosphere.

The dark deposits in the two impact craters shown in the north and south in Image 1 (right and left) are dune fields. On Mars, these mainly consist of old volcanic ash – hence their dark hue. In this contrast-enhanced image they have a slightly blue tinge, but in reality they range from black to grey. Dark dune fields are abundant on Mars and are often located on the floor of impact craters. Contrary to initial assumptions, the dust is not swept into the craters, becoming trapped there, but rather forms within the crater itself. It often originates from dark layers of buried volcanic ash that have been re-exposed by the impact crater. One good example is the southern (left-hand) crater in Image 1, where the crater wall reveals dark gullies. The dark dust trickles out of a layer in the crater wall and is transported down the gullies and into the interior of the crater, where the wind finally shapes it into dunes.

The colour of the dunes is very similar to the colour of the Martian soil exposed by the tracks of the dust devils. This is because almost the entire Martian surface consists of volcanic rock, which has a high iron and magnesium content and is very dark – just like the volcanic ash in the dunes. The lighter dust that covers large swathes of the Martian surface ranges from ochre to reddish in colour, as it has 'rusted' through the process of oxidation, whereby the once-dark iron in the dust reacted with the scarce oxygen in the Martian atmosphere to form iron oxide, turning it a shade of red. Most dunes on Mars are not covered in dust, as their material is constantly shifting, affording no opportunity for a layer of dust to settle.

  • Image processing
    The High Resolution Stereo Camera (HRSC) acquired the data from which these images were created on 3 January 2019 during Mars Express orbit 18,983. The image resolution is 13 metres per pixel. The centre of the imaged area is at approximately 23 degrees east and 53 degrees south. The colour image was generated using data from the HRSC nadir channel, the field of view of which is directed perpendicular to the surface of Mars, and the colour channels. The perspective oblique view was computed from terrain model data and data from the nadir and colour channels of HRSC. The anaglyph image, which gives 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 the stereo channels. The colour-coded topographic image is derived from a digital terrain model (DTM) of the region from which the topography of the landscape can be computed. The reference body for the HRSC DTM is a Martian equipotential surface (Areoid).
  • HRSC on Mars Express
    The High Resolution Stereo Camera 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 51 co-investigators from 35 institutions in 11 countries. The camera is operated by the DLR Institute of Planetary Research in Berlin-Adlershof.
Contact
  • Elke Heinemann
    Ger­man Aerospace Cen­ter (DLR)
    Pub­lic Af­fairs and Com­mu­ni­ca­tions
    Telephone: +49 2203 601-2867
    Fax: +49 2203 601-3249

    Contact
  • Ulrich Köhler
    Pub­lic re­la­tions co­or­di­na­tor
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Rutherfordstraße 2
    12489 Berlin
    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
  • Daniela Tirsch
    Ger­man Aerospace Cen­ter (DLR)

    In­sti­tute of Plan­e­tary Re­search
    Telephone: +49 30 67055-488
    Fax: +49 30 67055-402
    Linder Höhe
    51147 Köln
    Contact

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