Planetary scientists have identified over 15,000 km of ancient riverbeds in the Noachis Terra region of Mars’ southern highlands, indicating that the planet may have been significantly wetter than previously believed.
This image depicts a flat upper eroded river wavy ridge above Mars, with dunes moving over it. Image credits: NASA/JPL/University of Arizona.
The nature of Mars’ climate during the Noatian-Hesperian transition, which occurred around 3.7 billion years ago, is still being debated. This period saw significant geological and climatic changes, as well as the formation of surface features like valley networks and lakes associated with liquid water.
There are two prevailing theories: the first suggests that a warm and wet environment followed early Mars, allowing liquid water to persist on the surface for an extended time. The second posits that Mars has generally been cold and dry, with flowing water created sporadically by melting ice during brief climate shifts.
In Noachis Terra, climate models predicting “warm and humid” conditions suggest significant precipitation levels.
A recent study led by Open University Ph.D. student Adam Losekoot and his team analyzed the region’s wavy ridges, also known as inverse channels.
“These formations likely resulted from sediments laid down by rivers that solidified, later exposed through the erosion of surrounding materials,” noted the lead researcher.
“Similar ridges have been identified in various Martian terrains.”
“Their presence implies that flowing water once traversed the area, with precipitation being the most probable source,” he added.
The team found that river-wave ridges are widespread throughout Noachis Terra, amounting to over 15,000 km in total length.
While many segments are isolated, some systems extend several hundred kilometers.
“Exploring Mars, particularly less altered regions like Noachis Terra, is thrilling because they have remained relatively unchanged for billions of years,” Losekoot commented.
“It acts as a time capsule that captures fundamental geological processes in ways that are impossible to observe on Earth.”
In their investigation, the researchers utilized data from three orbital devices: the Context Camera (CTX), the Mars Orbiter Laser Altimeter (MOLA), and the High-Resolution Imaging Science Experiment (HiRISE).
These datasets enabled them to map the locations, lengths, and forms of the ridge systems across various areas.
“Our findings present new evidence indicating that Mars was once a much more dynamic and complex planet than we suppose,” they stated.
“The size and interconnectivity of these ridges suggest that liquid water existed for an extended period, indicating that Noachis Terra experienced warm, wet conditions for a geologically significant time.
“These results challenge the conventional belief that Mars has been predominantly cold and dry, with valleys formed only by sporadic, short-term meltwater from ice sheets.”
The scientists presented their results on July 10th at the National Astronomical Conference of the Royal Astronomical Society 2025 in Durham, England.
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Adam Losekoot et al. The history of the rivers of Noachis Terra, Mars. NAM 2025
Source: www.sci.news
