ESA’s Mars Express mission is spotlighting Shalbatana Vallis this month, an enormous Martian valley marked by evidence of ancient water, volcanic activity, impact craters, and collapsed terrain.
Located near the equator of Mars, Shalbatana Vallis stretches across the planet for roughly 1,300 kilometers, about the length of Italy. The latest image from the spacecraft’s High Resolution Stereo Camera (HRSC) focuses on the northern section of the valley as it winds across the Martian landscape.
In October 2025, Mars Express also released a video tour of this remarkable region, tracing the valley’s path from its source in the highlands of Xanthe Terra to its endpoint in the smoother terrain of Chryse Planitia.
Ancient Floods Shaped Shalbatana Vallis
Scientists believe Shalbatana Vallis formed around 3.5 billion years ago after vast amounts of groundwater burst onto the surface. The resulting floods tore through the landscape, carving deep channels as the water rushed downhill.
The main valley visible in the image enters from the lower left and exits toward the north on the right side of the frame. It measures roughly 10 kilometers wide and reaches depths of around 500 meters, features that are especially clear in the accompanying topographic view.
Researchers think the valley was once even deeper than it appears today. Over billions of years, various materials gradually filled parts of the channel. One especially noticeable blue-black patch in the rougher section of the valley is believed to be volcanic ash that was later redistributed by Martian winds, as seen in the accompanying 3D perspective views.
Evidence of Water, Lava, and a Possible Ancient Ocean
Shalbatana Vallis is one of many outflow channels found in this part of Mars. The region marks the transition between the heavily cratered southern highlands (to the left) and the smoother northern lowlands (right).
Nearby lies Chryse Planitia, one of the lowest regions on Mars (see map). Many of the planet’s major outflow channels end there, leading some scientists to suggest that the area may once have contained a large ocean during a warmer and wetter period in Mars’s history.
Chaotic Terrain and Impact Craters
The area surrounding Shalbatana Vallis contains many additional geological features, all labeled in the annotated image of the region.
Outflow channels on Mars are often associated with so-called chaotic terrain, landscapes filled with broken blocks, ridges, and irregular mounds of rock. In this image, chaotic terrain appears in the broader section of the valley near the dark volcanic ash deposits (see image at the top of this article).
Scientists think this type of terrain formed when underground ice began melting. As the ice disappeared, the ground above it shifted and collapsed. Similar chaotic landscapes have been observed by Mars Express in areas including Pyrrhae Regio, Iani Chaos, Ariadnes Colles, Aram Chaos, and Hydraotes Chaos.
Numerous impact craters are also visible throughout the region. Some remain sharply defined, while others have been partially buried or eroded away over time. Several are surrounded by ejecta blankets, debris blasted outward during the original impacts.
The smoother appearance of much of the terrain suggests that lava once flowed across the region. As the lava cooled and contracted, it folded and crumpled, producing uneven features known as ‘wrinkle ridges’. Isolated hills called ‘mesas’ are also visible (to the upper right, for example). These are remnants of older elevated surfaces that have slowly eroded over time.
More Than Two Decades of Mars Exploration
The image was captured by the HRSC camera, one of eight scientific instruments aboard Mars Express. Since launching in 2003, the spacecraft has spent more than 20 years studying the Red Planet and mapping its surface in color and in three dimensions at unprecedented detail.
Data collected by Mars Express has significantly expanded scientists’ understanding of Mars and its geological history.
The Mars Express HRSC was developed and is operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). Camera data processing was carried out at the DLR Institute of Space Research in Berlin-Adlershof. Researchers in the Planetary Science and Remote Sensing group at Freie Universität Berlin used the data to create the image products shown here.