\t\t\t\t\t\t15\/04\/2026<\/span> Noticeable change on Mars often takes millions of years \u2013 but the European Space Agency\u2019s Mars Express has captured a blanket of dark ash creeping across the planet in just decades.<\/p>\n<\/div>\n A new image from\u00a0Mars Express’s High Resolution Stereo Camera (HRSC), shows a scene of two halves, with Mars\u2019s bright tan-coloured sands butting up against dark deposits of volcanic ash.<\/p>\n When this part of Mars was seen by NASA\u2019s Viking orbiters in 1976, the ash was noticeably less widespread than it is today (see comparison below).<\/p>\n<\/p><\/div>\n \t\t\t\t<\/p>\n <\/figcaption><\/figure>\n<\/p><\/div>\n So \u2013 what makes the dark part dark? Differing from the ochre-coloured dust and broken up rock that covers most of Mars, this dark material is thought to have been made and distributed by volcanoes. Mars has a known history of volcanic activity; it even hosts the largest volcano in the Solar System \u2013 Olympus Mons \u2013 which stands at more than double the height of the largest on Earth (Mauna Kea).<\/p>\n The volcanic material is rich in \u2018mafic\u2019 minerals that form at high temperatures \u2013 olivine and pyroxene being key examples \u2013 and give the layer of ash its dark colour. The spread of the ash over the last 50 years has two possible explanations: either it has been picked up and moved about by martian winds, or the ochre dust that previously covered the dark ash has been blown away.<\/p>\n A large crater can be seen within this blanket of ash (see image below). It is surrounded by a striking ring of material that is lighter than the surrounding landscape \u2013 this is known as an \u2018ejecta blanket\u2019, and is made up of material thrown out by the impact that formed the crater itself. This crater is about 15 km across and has interesting squiggly lines within it, marking where icy material has crept about within the crater.<\/p>\n<\/p><\/div>\n Mars has a few colossal impact basins, all initially formed as large rocks collided with the planet. This scene lies in one of them: Utopia Planitia, an ancient basin with a diameter of around 3300 km (just under twice the north-south size of Earth\u2019s Sahara Desert).<\/p>\n Once upon a time, Utopia Planitia is thought to have hosted a body of water, possibly a lake or even an ocean. It\u2019s now filled with rock and sand, but still holds a lot of water beneath its surface in the form of ice. Many features across the landscape still show signs that water once flowed here.<\/p>\n<\/p><\/div>\n Some such signs can be seen to the lower right of the main image, in the dark blanket of ash. Here, we can see vaguely rounded pits with wavy edges. Known fittingly as \u2018scalloped depressions\u2019, these features are very common in this part of Mars, and indicate that the region is periglacial (on the fringes of glaciers or in cold-climate landscapes, undergoing cycles of freezing and thawing, typically featuring lots of buried ice).<\/p>\n Scalloped depressions form as ice below the surface melts or escapes to the air, causing the covering ground to become unstable and collapse. They don\u2019t occur in isolation but rather merge to form larger areas, providing a perfect example of how Mars\u2019s surface is constantly changing.<\/p>\n It may not command our attention in the same way as the dark ash, but the left half of this two-toned scene is just as fascinating.<\/p>\n Far on the left lies\u00a0a curious feature seen often across Utopia Planitia: a series of shadowy ditches around 20 km long and 2 km wide stretching out across the surface, meeting to form a giant shape (see close-up below).<\/p>\n<\/p><\/div>\n These ditches \u2013 also known as grabens \u2013 are formed when the surface cracks, either because layers of wet sediments form weak points or because of tectonic activity.\u00a0The grabens of Utopia Planitia are also featured in a 2016 image release by Freie Universit\u00e4t Berlin\u00a0(where the working group behind these new images is based).<\/p>\n<\/p><\/div>\n This image was captured by HRSC, one of eight state-of-the-art instruments aboard Mars Express.<\/p>\n Mars Express has been capturing and exploring Mars\u2019s many landscapes since it launched in 2003. The orbiter has mapped the planet\u2019s surface at unprecedented resolution, in colour, and in three dimensions for over two decades now, returning insights that have drastically changed our understanding of our planetary neighbour (read more about Mars Express and its findings\u00a0here).<\/p>\n<\/p><\/div>\n The Mars Express High Resolution Stereo Camera (HRSC) was developed and is operated by the German Aerospace Center (Deutsches Zentrum f\u00fcr Luft- und Raumfahrt; DLR). The systematic processing of the camera data took place at the DLR Institute of Space Research in Berlin-Adlershof. The working group of Planetary Science and Remote Sensing at Freie Universit\u00e4t Berlin used the data to create the image products shown here.<\/i><\/p>\n<\/p><\/div>\n
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\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nDark meets light<\/h3>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nConstant change<\/h3>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nA labyrinth of fractures<\/h3>\n
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\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nDecades of Mars exploration<\/h3>\n