Mars Express Reveals Dune Field and Water-Related Minerals in Kaiser Crater
New HRSC images of Kaiser Crater show dark dunes, clay minerals, and a dust devil, shedding light on Martian geology and past water activity.
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The European Space Agency's Mars Express orbiter has released new images of Kaiser Crater, captured by its High Resolution Stereo Camera (HRSC) on 5 October 2025 during orbit 27,461. The images reveal a large dark dune field on the crater floor, along with signs of clay minerals and a dust devil.
Kaiser Crater, located in the southern highlands of Mars, spans over 200 kilometres in diameter and is nearly two kilometres deep. It sits in Noachis Terra, one of the oldest regions on Mars, dating back to the Noachian Period roughly 4.1 to 3.7 billion years ago. The crater is named after Dutch astronomer Frederik Kaiser, who lived from 1808 to 1872.
The dune field consists of dark volcanic material. At its edges, crescent-shaped barchan dunes transition into barchanoid ridges and then into transverse dunes, whose crests run perpendicular to the prevailing westerly wind. Bright hoarfrost deposits on south-facing slopes give the dunes a metallic sheen. The images were taken during the second half of southern winter, when hoarfrost extends from the South Pole to mid-latitudes.
Wind erosion has exposed bright deposits that indicate clay minerals, formed by the weathering of basalt through contact with water. This suggests that liquid water was once present in the region. The HRSC also captured a small bright spot with a red-tinged edge, identified as a dust devil. Its shadow indicates a height of about two kilometres.
Narrow gullies on the inner walls of some craters are visible in the images. Their formation is not conclusively established; evidence points to dry landslides, though some may have involved meltwater or groundwater.
The HRSC camera, developed by the German Aerospace Center (DLR) with industry partners, has been sending images since January 2004. The images have a ground resolution of about 17 metres per pixel and are centred at approximately 48°S, 19°E.