In a dramatic new discovery, scientists have identified over 15,000 kilometers of ancient riverbeds on Mars, revealing that vast regions of the planet were once crisscrossed by flowing water.
These winding ridges, preserved in the Martian highlands, suggest that rainfall—not just glacial melt—once played a major role in shaping the Red Planet’s surface. The findings, mapped using high-resolution orbital data, challenge long-held views of Mars as cold and dry, pointing instead to a time when it may have been warm, wet, and far more Earth-like than we imagined.
Massive Network of Ancient Riverbeds on Mars
Scientists have uncovered over 15,000 kilometers of ancient riverbeds on Mars, offering strong evidence that the planet may have once been far wetter than previously believed.
The team examined features known as fluvial sinuous ridges (FSR), or inverted channels, located in Noachis Terra, a region in Mars’ southern highlands. These formations likely originated when river-deposited sediments hardened and were later left exposed as the surrounding landscape gradually eroded.
Similar ridge systems have been identified in other parts of Mars, but their widespread presence in Noachis Terra suggests that flowing water was once common there. Precipitation is considered the most likely source behind this extensive water activity.
This new research was led by Adam Losekoot, a PhD candidate at the Open University and funded by the UK Space Agency. He presented the findings at the 2025 National Astronomy Meeting of the Royal Astronomical Society, held in Durham.
Geological Stability During a Climate Shift
The findings indicate that surface water may have been stable in Noachis Terra during the Noachian-Hesperian transition, a period of geologic and climatic change around 3.7 billion years ago.
Noachis Terra has not been studied as extensively as other regions of Mars, in part because it contains few valley networks, which are branching erosional features that have traditionally been used to infer historical rainfall and runoff.
The study instead focuses on fluvial sinuous ridges as an alternate form of evidence for ancient surface water.
The Context Camera, called CTX, provides a big-picture, background view of the terrain around smaller rock and mineral targets that are studied by other cameras on Mars Reconnaissance Orbiter. CTX makes observations simultaneously with high-resolution images collected by HiRISE and data collected by the mineral-finding CRISM spectrometer.
Noachis Terra: A Martian Geological Time Capsule
“Studying Mars, particularly an underexplored region like Noachis Terra, is really exciting because it’s an environment that has been largely unchanged for billions of years. It’s a time capsule that records fundamental geological processes in a way that just isn’t possible here on Earth,” said Losekoot.
He and his team used data from three orbital instruments: the Context Camera (CTX), the Mars Orbiter Laser Altimeter (MOLA), and the High Resolution Imaging Science Experiment (HiRISE).
These datasets allowed the team to map the locations, lengths, and morphologies of ridge systems across a wide area.
The High Resolution Imaging Experiment is known as HiRISE. It takes pictures that cover vast areas of Martian terrain while being able to see features as small as a kitchen table, and has photographed hundreds of targeted swaths of Mars’ surface in unprecedented detail. The camera operates in visible wavelengths, the same as human eyes, but with a telescopic lens that produces images at resolutions never before seen in planetary exploration missions. These high-resolution images enable scientists to distinguish objects on Mars about 3 feet (1 meter) and to study the morphology (surface structure) in a much more comprehensive manner than ever before.
Ridge Systems Suggest Long-Term Water Flow
Many of the features appear as isolated ridge segments, while others form systems extending for hundreds of kilometers and rising tens of meters above the surrounding terrain.
The broad distribution and form of these ridges suggest that they likely formed over a geologically significant period under relatively stable surface conditions.
The spatial distribution and extent of the features indicate that the water source was precipitation.
“Our work is a new piece of evidence that suggests that Mars was once a much more complex and active planet than it is now, which is such an exciting thing to be involved in,” said Losekoot.
The Mars Orbiter Laser Altimeter (MOLA) was an instrument on the Mars Global Surveyor (MGS) spacecraft that mapped the topography of Mars using laser altimetry. It operated from September 1997 to June 2001, collecting data on the height of surface features. This data was used to create detailed topographic maps and study the planet’s geology and past climate.
Warm and Wet Mars? Challenging Old Views
The fact that the ridges form extensive interconnected systems suggests that the watery conditions must have been relatively long-lived, meaning Noachis Terra experienced warm and wet conditions for a geologically relevant period.
These findings challenge existing theories that Mars was generally cold and dry, with a few valleys formed by ice-sheet meltwater in sporadic, short periods of warming.
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5 Comments
and you know that how? you have water Detectors on mars? LOL!
The article explains that in 2nd and 3rd paragraphs.
Suggesting Mars was once warmer and wet. Was the Sun hotter? Or did Mars once have a dense, Earthlike atmosphere? Or was Mars in a different orbit, closer to the Sun? Many questions!
Mars used to have a thicker atmosphere.
More ”turf” for Musk and Co. to exploit and d’espoil?