Mars Express Images Shalbatana Vallis, a 1,300 km Equatorial Flood Channel That Burst From Mars 3.5 Billion Years Ago

Overview

The European Space Agency has released a new image of Shalbatana Vallis, a long winding valley near Mars’s equator that was carved when groundwater burst onto the surface roughly 3.5 billion years ago, according to ESA. The view, captured by the Mars Express orbiter’s High Resolution Stereo Camera (HRSC), is the latest in a series of Mars Express scenes that document how catastrophic floods reshaped the planet’s terrain in the deep past.

What We Know

Shalbatana Vallis weaves across Mars for some 1,300 kilometres, or roughly the length of Italy, as reported by Space.com. The main channel is about 10 kilometres wide and 500 metres deep, according to ESA. The valley sits near the equator, dividing the cratered southern highlands from the smoother northern lowlands.

ESA dates the formation to around 3.5 billion years ago, when “huge quantities of groundwater rose up to Mars’s surface,” the agency writes. “These catastrophic floodwaters cut into the rock and surged downhill, rapidly creating the winding, waterworn valleys we see here,” ESA adds in the same release.

The new HRSC image also captures a stretch of so-called chaotic terrain — a jumble of fractured rock blocks that appears where the surface has collapsed. ESA describes the process: “It’s thought to form as water ice trapped below the surface begins to melt, causing the ground above to shift and ultimately collapse,” the agency explains.

A distinctive dark blue-black deposit running along parts of the valley floor is thought to be volcanic ash that has been redistributed by Martian winds, ScienceDaily reports based on ESA’s release. Tech Times notes the same interpretation in its coverage, describing the dark material as ash redistributed across the surface over long timescales.

The Chryse Planitia Connection

Shalbatana Vallis empties toward Chryse Planitia, one of the lowest regions on Mars and the terminus of several major outflow channels. “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,” ScienceDaily writes. Space.com describes Chryse Planitia in similar terms, noting that “some researchers have proposed an ancient ocean may once have existed” there, in its summary of the ESA release.

What We Don’t Know

The ancient-ocean hypothesis is not settled. The ESA release frames the link between Shalbatana Vallis, Chryse Planitia and any standing body of water as a long-running open question rather than an established fact, and both Space.com and ScienceDaily attribute the ocean hypothesis to “some scientists” or “some researchers” rather than to a community consensus. Likewise, while the volcanic-ash interpretation of the dark deposits is consistent across the coverage, ESA’s wording — that the material is “volcanic ash blown about by martian winds” — leaves open how thick the layer is and over what period it accumulated.

The Mars Express HRSC scene also does not directly date the floods; the 3.5-billion-year figure is the agency’s reported estimate, not a measurement from this image. Higher-resolution follow-up from other orbiters and from in-situ missions will be needed to firm up the chronology and to test whether Chryse Planitia ever hosted a true ocean rather than transient flood lakes.

Why It Matters

Shalbatana Vallis is a small piece of a much larger story about whether early Mars supported persistent liquid water at the surface. Each new HRSC scene adds to a growing catalogue of channels, chaotic terrains and outflow basins that, taken together, constrain how much water flowed, when, and for how long — questions that bear directly on the habitability of early Mars and on where future missions should look for preserved evidence of past life.