Dark volcanic ash has visibly reshaped Martian surface since 1976

Noticeable change on Mars often takes millions of years—but the European Space Agency's Mars Express has captured a blanket of dark ash creeping across the planet in just decades.

A new image from Mars Express's High Resolution Stereo Camera (HRSC), shows a scene of two halves, with Mars's bright tan-colored sands butting up against dark deposits of volcanic ash. When this part of Mars was seen by NASA's Viking orbiters in 1976, the ash was noticeably less widespread than it is today. Dark meets light So—what makes the dark part dark? Differing from the ochre-colored 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— Olympus Mons —which stands at more than double the height of the largest on Earth (Mauna Kea).

The volcanic material is rich in ' mafic ' minerals that form at high temperatures—olivine and pyroxene being key examples—and give the layer of ash its dark color. 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. 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—this is known as an " ejecta blanket ," 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.

Noticeable change on Mars can take millions of years – but ESA’s Mars Express has captured a blanket of dark ash creeping across the planet in just decades. The image shows a scene of two halves, with Mars’s typical bright tan-coloured sands butting up against dark deposits of volcanic ash. When this part of Mars was viewed by NASA’s Viking orbiters in 1976, the ash was noticeably less widespread than it is today. But this image shows far more than just colour differences. We’ve added labels to highlight features and regions of note. Credit: ESA/DLR/FU Berlin Read more

This view was generated from the digital terrain model and the nadir and colour channels of the High Resolution Stereo Camera on ESA’s Mars Express. It shows a bird’s-eye view of a large 15-km-across crater in Utopia Planitia, covered and surrounded by dark volcanic ash. Credit: ESA/DLR/FU Berlin Read more

A large dotted square highlights the area of Mars featured in new images from the High Resolution Stereo Camera (HRSC) aboard ESA’s Mars Express, released in April 2026. The two smaller boxes within mark the precise patch of surface shown in the images, captured by Mars Express on 9 November 2024 (orbit 26327). The elevation of the surface, shown by the bright colours marking the surface of Mars, is indicated by the scale to the bottom-right. Credit: NASA/USGS; ESA/DLR/FU Berlin Read more

A view from above: the sands of Utopia Planitia. Credit: ESA/DLR/FU Berlin Read more