ESA – Waterworn chaos on Mars

Chalbatana Vallis is an impressive channel near the equator of Mars. This image, taken by Mars Express’s High Resolution Stereo Camera (HRSC), captures the northern part of the channel that winds its way across the surface of Mars for about 1300 km – around the length of Italy.

We visited this part of the red planet in October 2025, releasing a Mars Express video tour that follows this slowly rotating channel from its beginning (the highland region of Xanthe Terra) to its end (the smooth lowlands of Chryse Planitia).

Shalbatana Vallis was formed about 3.5 billion years ago, when massive amounts of groundwater rose to the surface of Mars. These destructive floodwaters cut through the rock and moved downwards, creating the sharply curving, waterlogged canyons we see here. The main valley, which originates at the bottom-left and extends from the frame to the right (north), is about 10 km wide and 500 m deep – something that is most clearly seen in the corresponding topographic view (Below).

rough meets smooth

Chalbatana Vallis was probably deeper in the past, but over time it has been filled with different materials. Although we don’t know exactly what material filled the valley, a distinct piece of recently deposited blue-black material can be seen in the most curved part of the channel: volcanic ash blown by Martian winds, as shown in the accompanying 3D perspective views (down, further down).

Shalbatana Valleys is one of many such valleys found in the region. This part of Mars divides the planet’s heavily cratered southern highlands (left) from the smoother northern lowlands (right). Just outside the frame is the above Crises Planitia, one of the lowest parts of the entire planet (see map below). Many of Mars’ largest outflow channels end on Crise Planitia, leading some to suggest that it may have been covered by a large ocean at some point in Mars’ warm, wet history.

chaos and pit

Many other interesting features can be seen here, all of which are labeled annotated view Of Shalbatana Wallis.

Outflow channels are usually found along chaotic terrain, something like a maze of raised blocks and rock piles. Here the chaotic terrain can be seen across a wide section of the Shalbatana Vallis, near a dark layer of volcanic ash (see below). It is believed to be formed when water ice trapped beneath the surface begins to melt, causing the ground above to slide and eventually collapse. This type of terrain is common on Mars, and has been captured before by Mars Express in areas such as Pyrrha Regio, Ioanni Chaos, Ariadne’s Colles, Aram Chaos and – as in the video – Hydrotes Chaos.

Many impact craters can also be seen here. Some are buried, some are eroded, and some are surrounded by a blanket of material ejected during the initial crater-forming impact. Overall, the terrain is relatively smooth, indicating that it has been flooded with lava; In some places this lava cooled and contracted, forming irregular ‘wrinkled streaks’. Isolated hills (‘mesas’) can also be seen (for example, at top right) – remnants of a once higher surface that has eroded over time.

Decades of Mars Exploration

This image comes courtesy of the HRSC camera, one of eight state-of-the-art instruments on Mars Express. Mars Express has been capturing and exploring many of Mars’ landscapes since its launch in 2003. The orbiter has mapped the planet’s surface in unprecedented resolution, color and three dimensions for more than two decades, returning insights that have fundamentally changed our understanding of our planetary neighbor (read more about Mars Express and its findings here).

The Mars Express HRSC was developed and operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). Systematic processing of the camera data took place at the DLR Institute for Space Research in Berlin-Adlershof. The Working Group on Planetary Science and Remote Sensing at the Freie Universität Berlin used the data to create the image products shown here.