Mars Express Unveils Shalbatana Vallis: A 3.5-Billion-Year Water-Worn Channel on Mars

In October 2025 the European Space Agency’s Mars Express orbiter used its High Resolution Stereo Camera (HRSC) to capture stereo images of Shalbatana Vallis, a winding channel near the Martian equator that stretches about 1 300 km from Xanthe Terra to Chryse Planitia. The valley reaches up to 10 km wide, 500 m deep and displays lava-filled floors, volcanic ash deposits, and chaotic terrain. The HRSC instrument was built and is run by the German Aerospace Center (DLR), and the image products were generated by DLR’s Institute of Space Research in collaboration with the Planetary Science and Remote Sensing group at Freie Universität Berlin.

European Space Agency

Scientists interpret the valley as the product of massive groundwater outbursts ~3.5 billion years ago. Rising water flooded the surface, eroding rock and carving the channel. Subsequent melting of subsurface ice caused collapse of blocks, forming the chaotic terrain observed alongside the valley, while later lava flows smoothed the floor and created wrinkle ridges.

European Space Agency

• Length: ~1 300 km (? 800 mi)

European Space Agency

• Width: ~10 km (? 6 mi)

European Space Agency

• Depth: ~500 m (? 0.3 mi)

European Space Agency

• Age of formation: ~3.5 Ga (billion years)

Strange, dark material spotted in an ancient channel on Mars, where water once flowed 3.5 billion years ago

• Identified chaotic terrains in the region: several, including Iani Chaos and Aram Chaos

European Space Agency

The valley’s proximity to Chryse Planitia, a basin that hosts many of Mars’s largest outflow channels, supports the hypothesis that the region once held a substantial standing body of water, possibly an ocean. These processes inform models of Mars’s climate history and past habitability.

European Space Agency

ESA officials describe the Shalbatana Vallis imagery as “a striking illustration of Mars’s dynamic early environment, where water, ice, and fire interacted on a planetary scale.” The mission team adds that the new 3-D visualizations “enhance our ability to interpret the stratigraphic relationships between fluvial, chaotic, and volcanic units.”

European Space Agency

The images confirm volcanic ash and lava-filled floors, yet the exact composition of the infill material remains still uncertain, because the sources state that the specific materials that filled the valley are not known.

Strange, dark material spotted in an ancient channel on Mars, where water once flowed 3.5 billion years ago

> “5 billion years ago, when huge quantities of groundwater rose up to Mars’s surface.” — ESA scientists, Mars Express mission

European Space Agency

> “Chaotic terrain can be seen here in the wider part of Shalbatana Vallis, near the dark layer of volcanic ash (see below).” — ESA scientists, Mars Express mission

European Space Agency

> “Overall, the terrain is relatively smooth, indicating that it has been flooded by lava; in places this lava crumpled and folded as it cooled and shrunk, forming irregular ‘wrinkle ridges’.” — ESA scientists, Mars Express mission

European Space Agency