Martian winter wonderland – swirling snow in Ultimi Scopuli
December 22, 2022 | Mars Express mission
Martian winter wonderland – swirling snow in Ultimi Scopuli
Late winter landscape near the south pole of Mars
While those of us in Central Europe have to do without a snowy winter in many places almost every year, on Mars we can rely on frosty, white precipitation far into the temperate latitudes. In the Martian winter in the respective hemisphere, the planet is covered with carbon dioxide and water ice snow up to about the 50th parallel in the direction of the equator. When the Sun shines on the landscape again in spring, the snow cover evaporates and the orange-brown Martian surface reappears, as here in the Ultimi Scopuli region, where a ridge and large parts of a nearly 40-kilometre crater are already free of ice, allowing this aesthetic view, as if created by an artist.
Winter-white Mars: Ice and snow in the Ultimi Scopuli region
At least in higher northern and southern latitudes, Mars has a white Christmas every year. Like Earth, Mars, with its oblique axis of rotation, goes through seasons during its two-year orbit around the Sun. Then the polar regions are covered with carbon dioxide and water ice and snow up to several metres high. When they are exposed to solar radiation again at the beginning of spring and warm up, the ice and snow cover recedes to the permanent polar caps. This image shows a top view of Ultimi Scopuli, Latin for the 'last cliffs' (before the South Pole) at 75 degrees south latitude in early southern spring. It was taken by the DLR stereo camera HRSC at the end of May 2022.
So-called anaglyph images can be generated from the nadir channel of the DLR-operated HRSC camera system on board ESA's Mars Express spacecraft, which is directed perpendicularly to the surface of Mars, and one of the four oblique stereo channels. When used with red-blue or red-green glasses, they allow a three-dimensional view of the landscape and give the viewer a spatial idea of the differences in altitude. The two craters to the left and right of the centre of the image have diameters of 40 and 70 kilometres respectively and depths of up to 1500 metres.
Image data from the High Resolution Stereo Camera (HRSC) on board the Mars Express mission reveal layered deposits, frost, ice and dark dunes near the Martian South Pole.
The scenery resembles an abstract work of art with strongly contrasting shades of colour.
HRSC is a camera experiment developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) that has been relaying images of the Martian surface to Earth since January 2004.
Focus: Spaceflight
Christmas and winter spirit – also on Mars. Impact craters connected by a striped, coloured ribbon can be seen in the final and very wintry HRSC Mars image of this year. We wish all readers of our Martian image series, published together with the European Space Agency (ESA) and Freie Universität Berlin, happy holidays!
Image data from the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express mission reveal an exciting landscape of layered deposits, frost, ice, and dark dunes near the south polar region of Mars, known as Ultimi Scopuli (from the Latin for 'the final cliffs'). The High Resolution Stereo Camera (HRSC) was developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and has been sending images of the Martian surface to Earth since January 2004.
This amazing image shows a section of the landscape measuring approximately 215 by 65 kilometres and located 14 degrees north of the south pole. Many interesting landforms are visible – typical of regions that are permanently frozen but not covered by ice. Together with formations carved by the wind, known as aeolian landforms, and seasonal frost clouds, they complete the scenery.
The scenery appears very abstract with the strongly contrasting colour shades from the orange tones of the Martian soil and the white of water and carbon dioxide ice. Together with the curved landscape forms, it is not an easy landscape to make sense of at first glance. Nature seems to have acted as an expressionist artist on Mars too, giving the HRSC science team an aesthetic element to their processing of the colour stereo image data during the Christmas and New Year period.
These image data were acquired in the southern spring – the time when the ice retreats southward, leaving only a small ice cap at the south pole during summer in the southern hemisphere. During the seasonal cycle on Mars, carbon dioxide ice is deposited at the poles in winter. The amount of atmospheric gases trapped as ice at each pole in winter and then evaporating in spring is enormous, comprising over 10 percent of the atmosphere. This process leads to strong pressure changes in the Martian gas envelope and, as a result, to very high wind speeds. These occur primarily in the autumn and are caused by this difference in atmospheric pressure in the hemispheres.
Layered deposits of water ice and fine dust
The two most eye-catching features of this image are two large impact craters that appear to be connected by a striped band. The band and craters exhibit an intense reddish-brown hue that contrasts with the grey and white of the surrounding landscape. In addition, alternating layers can be seen in the crater rims and band – especially when you zoom in. These layers are successive layers of dust and sand that have been deposited continuously and approximately horizontally on the terrain features. They consist primarily of water ice and approximately 10 percent of fine sediments.
The individual layers differ from each other in their albedo (the reflectivity of sunlight), their colour, thickness and their degree of weathering. These deposits are formed by dust and water ice dissolving from the atmosphere and sinking to the surface, and by direct frost condensation on the ground. The orange regions in the image clearly show the layered nature of these deposits.
Some regions in the image appear hazy. Clouds have formed over the scene and can be detected, particularly in the centre, above the band. Clouds in the south polar region contain not only water droplets frozen into ice crystals, but often needles of carbon dioxide ice given the extremely low temperatures of well below minus 100 degrees Celsius. Their trajectory as they sink to the ground is partly influenced by the landforms on the surface. In some regions of the image, extensive evaporation structures can be seen, making the surface appear levelled and resembling the water level of terrestrial lakes.
Mysterious dark material
Dark dunes and dune fields can be identified in numerous places, often covered by a thin layer of frost. Where they have been strung into thin lines by the wind, they resemble a formation of elongated rock ridges and wind alleys pointing in the same direction, known as yardangs. From their orientation one can read the prevailing wind direction, which can vary greatly on a local scale and is strongly influenced by the terrain formations.
There are still open questions about the origin of the dark material on Mars. It is assumed that it originates from old, buried layers of volcanic ash as well as from weathered lava. Deposits of this type are found in almost every region on Mars. While the dark dunes on the innumerable crater floors often unite to form large complex dune fields, the dunes at the north and south poles are often still present in their individual form, as can be seen here in the innumerable black dots. Presumably, in the polar regions, the frost covering prevents the material transport, which is already a rare phenomenon on Mars, and thus the mobility and ‘unification’ of the dunes.
In addition, the image presented here also shows individual, small dark spots from which narrow lines that resemble spider legs emerge in different directions. These may be indicative of another distribution process of dark material typical of polar latitudes on Mars: carbon dioxide jets formed by heating dark material under an ice sheet, leading to a direct transition of ice from the solid to the gaseous state, which is then ejected at high pressure in fountains mixed with dark sand. Continuous observation of these phenomena help us to understand processes that are constantly changing the surface appearance in the polar regions on Mars.
Image processing
The images were acquired by the High Resolution Stereo Camera (HRSC) on 19 May 2022, during Mars Express orbit 23 219. The ground resolution is approximately 18 meters per pixel. The image is centred at approximately 185 degrees East and 76 degrees South.
This colour image was created from data from the nadir channel, the field of view oriented perpendicular to the surface of Mars, and the HRSC colour channels.
HRSC is a camera experiment developed and operated by the German Aerospace Center (DLR). The systematic processing of the camera data was carried out at the DLR Institute of Planetary Research. Personnel in the Department of Planetary Sciences and Remote Sensing at the Freie Universität Berlin used these data to create the image products shown here.
The High Resolution Stereo Camera (HRSC) was developed at the German Aerospace Center (DLR) and built in cooperation with industrial partners (EADS Astrium, Lewicki Microelectronic GmbH and Jena-Optronik GmbH). The science team, led by Principal Investigator (PI) Dr Thomas Roatsch of the DLR Institute of Planetary Research, consists of 52 co-investigators from 34 institutions and 11 nations. The camera is operated by the DLR Institute of Planetary Research in Berlin-Adlershof.
