NASA’s Mars Reconnaissance Orbiter and Mars Global Surveyor have revealed thousands of miles of ancient riverbeds on Mars, challenging scientists’ previous understanding that the planet was arid for most of its history.
Researchers found nearly 10,000 miles (16,000km) of geological traces believed to be over 3 billion years old, indicating a wetter world than previously thought. The networked rivers were probably replenished by regular rain or snowfall in the region, and their widespread presence suggests a significant source of water.
The discovery was made possible by high-resolution images of the rugged landscape captured by Mars orbiters. Fluvial sinuous ridges, formed when ancient river tracks hardened over time, are visible in these images. These features provide evidence of ancient rivers that flowed across the terrain, carving out valleys and canyons.
One region, Noachis Terra, was particularly puzzling to scientists due to its expected rain or snowfall patterns. However, high-resolution images revealed a network of meandering tributaries and spots where ancient riverbanks burst. This suggests an enduring presence of surface water in the Noachis Terra region about 3.7 billion years ago.
The findings contradict previous assumptions that Mars was arid for most of its history. Instead, scientists now believe that the planet held vast bodies of water in its warmer, wetter past. The discovery highlights the importance of continued exploration and research into Mars’ history, which may reveal more about this enigmatic planet’s past.
Source: https://www.theguardian.com/science/2025/jul/10/mars-once-wetter-than-thought-surprise-discovery-10000-miles-ancient-riverbeds