In February 2017 ESA, DLR and FU Berlin released fantastic images of the north polar ice cap of Mars acquired by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express Orbiter. The HRSC experiment is operated by the German Aerospace Center (DLR) since 2003. The Planetary Sciences and Remote Sensing group at Freie Universität Berlin now rendered a movie of the north polar ice cap of Mars. The systematic processing of the HRSC image data was carried out at DLR.
The north polar ice cap of Mars appears like a gigantic spiral out of ice and snow. Dark troughs in which wind-transported dust and deposits accumulated, alternate with white, ice-covered mounds. A particularly striking dark trough is Chasma Boreale, to be seen in the midterm of the movie. It is an up to 100 kilometer wide and 500 kilometer long canyon that cuts two kilometers deep into the north polar ice cap. Dark deposits on the bottom of Chasma Boreale are dunes made up of black sand that has been carried by wind into the canyon. The origin of Chasma Boreale is unclear: the structure could have been formed by non-uniform accumulation of ice and dust, by melting processes or by wind erosion.
The animated permanent ice cap has a diameter of about 1100 kilometers and stands up to three kilometers above the surroundings. It is also termed summer ice cap and is predominantly made up of water ice. Through the Martian winter an additional layer of carbon dioxide ice is deposited on top of the permanent water ice cap, because the atmospheric carbon dioxide turns into carbon dioxide ice at temperatures below -120°C. This carbon dioxide winter ice cap is only about one meter thick. Since carbon dioxide is the main component of the Martian atmosphere, the atmospheric pressure drops during Martian winter, when up to one third of the atmospheric carbon dioxide is deposited. The seasonal variations in atmospheric pressure induce major dust storms that distribute gas and dust over the whole surface of Mars.
Winter on Mars lasts twice as long as winter on Earth, since Mars is more far from the sun and takes nearly twice the time for an orbit. During winter season the north polar ice cap of Mars is typically covered by thick carbon dioxide clouds, which makes HRSC observations difficult. Therefore, the images on which the Mars-animation is based on where mainly acquired during the summer seasons.
Image processing and the HRSC experiment on Mars Express
The underlying HRSC mosaic consists of 32 orbit strips (1154, 1177, 1219, 1291, 1394, 1745, 3663, 3681, 3685, 3695, 5483, 5775, 5784, 5796, 5808, 5810, 5818, 5824, 5827, 5838, 5853, 5864, 5867, 5900, 5904, 5963, 6007, 6229, 8042, 8080, 8153, 8160) and covers a region 0°-360° East and approximately 78° to 90° North. The color mosaic was created using data from the nadir channel and the color channels of the HRSC. The mosaic image was combined with topography information from the Mars Orbiter Laser Altimeter (MOLA) experiment on board the NASA Mars Global Surveyor (MGS) mission to generate a three-dimensional landscape. The global Mars view is based on the Viking MDIM 2.1 colorized global mosaic.
Data: ESA/DLR/FU Berlin, NASA MGS MOLA Science Team, NASA AMES
Animation: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO
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The High Resolution Stereo Camera was developed at the German Aerospace Center (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 and 11 countries. The camera is operated by the DLR Institute of Planetary Research in Berlin-Adlershof.