Geologists from the University of Colorado Boulder have made a groundbreaking discovery about ancient Mars. Using landscape evolution models and topographic data from NASA missions, they found that extensive valley networks on Mars were likely formed by widespread precipitation, challenging previous theories that attributed their formation to runoff from melting ice caps.
The researchers analyzed a large region of Mars’ southern highlands, focusing on the locations and elevations of valley heads within dendritic valley networks. They used two different models: one driven by widespread precipitation (rain or snow) and another by runoff from melting ice caps. The precipitation model predicted valley heads forming across a broad elevation range, closely matching the observed distribution on Mars.
In contrast, the ice-driven simulation failed to replicate the widespread and elevation-diverse valley head patterns observed. The simulations showed that ice-cap runoff would create valleys in a narrow elevation band, limiting their distribution.
The team’s findings suggest that precipitation was a huge contributor to valley formation during the Noachian epoch. They adapted a computer model originally developed for Earth studies, creating synthetic Martian terrain resembling the equatorial highlands. In simulations, water from precipitation or ice melt flowed for tens to hundreds of thousands of years, carving valleys and headwaters.
The research also considered geological evidence from NASA’s Perseverance rover, which is exploring Jezero Crater, a former lakebed fed by a river delta. The presence of large boulders and sandstone deposits in the crater shows powerful water flows, consistent with precipitation-driven runoff. The findings indicate that Mars’ ancient climate supported an active hydrological cycle, unlike the cold, dry conditions of today.
The discovery supports the idea of a climate warm enough to sustain rain or snow across Mars’ surface. It also highlights the importance of considering alternative explanations for geological features on other planets and moons in our solar system.
Source: https://watchers.news/2025/04/26/evidence-rain-snow-ancient-mars