Free Astronomy Magazine November-December 2026

36 NOVEMBER-DECEMBER 2026 ASTRO PUBLISHING A t the top: ESA’s Mars Express has imaged beautiful swirls of pur- ple, pink and red near Mars’s south pole. These ridges of colour form Thyles Rupes: one of the most promi- nent cliff-faces in Mars’s ancient southern highlands. In the center: A color topographic image of Thyles Rupes. At the bottom: A stereoscopic image of Thyles Rupes, generated from data captured by the High Res- olution Stereo Camera on ESA’s Mars Express orbiter on 17 February 2026 (orbit 27925). The anaglyph offers a three-dimensional view when viewed using red-green or red-blue glasses. [ESA/DLR/FU Berlin] ing it to contract and deforming the planet’s crust above. Some blocks of Mars’s surface would have been pushed upwards via this process, forming steep cliffs – as seen here. Unlike Earth, present-day Mars lacks active tectonics. While we see the evidence today, the processes once at play here occurred billions of years ago. Thyles Rupes is found in the region near Mars’s south pole, in the planet’s southern highlands. It ex- tends for hundreds of kilometres, slicing across terrain that’s heavily covered in impact craters. While some of these craters are cut through by the cliffs, indicating that they formed first and that Thyles Rupes came after, others lie on top, indicating the opposite. Different kinds of sand dunes can also be seen here, most prominently in the rippled patches of white visi- ble to the lower-right of centre. Winds blowing from all directions have picked up and carried sand across the martian surface, forming dunes of various shapes and types (including longitudinal and trans- verse dunes – long, parallel scratches that form parallel to or at right an- gles to the wind direction, respec- tively – and sickle-shaped barcha- noid ridges). not, try flipping the image upside down, and this may help you visu- alise the topography correctly. The rocky cliffs of Thyles Rupes can reach towering heights of over 1 km tall in some places. They are thought to be tectonic in nature, meaning that the cliffs formed as two parts of Mars’s crust were pushed together, causing one to rise up above the other. This likely happened as the in- terior of Mars began to cool, caus- !