Cambridge, England — Recent discoveries on Mars have unveiled the existence of expansive ancient riverbeds, indicating that the planet may have once been significantly more water-rich than previously believed. An extensive analysis of high-resolution images captured by orbiting spacecraft has shown geological evidence of nearly 10,000 miles of waterways dating back more than three billion years.

The research suggests that these river systems, which vary in length and structure, typically span over 100 miles in some areas. Experts hypothesize that these waterways were likely sustained by consistent rainfall or snowfall in the region.

Adam Losekoot, a doctoral student at the Open University, emphasized that while signs of water have been identified on Mars before, this finding is notable for its confirmation in a region long considered dry. “We discovered that this area did indeed support water, and it was widely distributed. The extent of the rivers suggests a major source of precipitation was required to maintain such a system,” Losekoot explained.

Mars features numerous valley networks and canyons, which are believed to be the result of water erosion. However, certain areas, such as Noachis Terra—one of the planet’s oldest landscapes—had posed questions for scientists due to a lack of visible riverbeds or valleys.

To reconcile these inconsistencies, Losekoot and his team analyzed high-resolution images from NASA’s Mars Reconnaissance Orbiter and Mars Global Surveyor, exploring nearly 4 million square miles of Mars’ southern highlands. Their observations led to the identification of numerous geological formations known as fluvial sinuous ridges, or inverted channels, which form when sediments from ancient rivers harden and become exposed as surrounding material erodes.

Some of these ridges are modestly sized, while others exceed a mile in width. The images revealed a complex network of tributaries and features that indicate where ancient riverbanks once collapsed. One particularly telling image displays a pair of rivers spilling into a crater, likely filling it before breaching the opposite side.

The findings, which will be shared at the Royal Astronomical Society’s national meeting in Durham, imply that surface water was present in significant amounts in the Noachis Terra region approximately 3.7 billion years ago. This challenges earlier assumptions about the planet’s climatic history.

Mars’ transformation from a warmer and wetter world to the arid landscape observed today is believed to have been influenced by the weakening of its magnetic field, which allowed solar winds to strip away its atmosphere and consequently deplete surface water. Nevertheless, it is possible that reservoirs of water still exist beneath the Martian surface, as suggested by a recent report indicating a large water reserve hidden below.

These new insights may reshape our understanding of Mars’ environmental evolution and its potential for past life, fueling ongoing research into the planet’s history.