Scientists Chart Mars’ Major Ancient River Systems in Landmark Study

Breakthrough Mapping Reveals 16 Large River Basins on the Red Planet

Scientists in the United States have produced the first comprehensive map of large river drainage systems on Mars, offering new insights into where life may once have existed and providing strategic guidance for future exploration missions.

Study Identifies Extensive Ancient Watersheds

The research, published in PNAS by a team at The University of Texas at Austin, identifies 16 major river basins that would have transported substantial volumes of water billions of years ago. These networks, which resemble the scale and organisation of large terrestrial watersheds, could have served as hubs of nutrient movement and potentially habitable environments during Mars’ wetter periods.

This is the first systematic effort to define large drainage systems across the Martian surface, consolidating fragmented datasets of valley networks, lakes and sediment deposits previously examined in isolation.

Researchers Map Planet-Wide Drainage Systems

Co-author Timothy A. Goudge, assistant professor in the Department of Earth and Planetary Sciences at the UT Jackson School of Geosciences, said scientists had long understood that rivers once flowed on Mars but did not fully appreciate how interconnected they were. “We’ve known for a long time that there were rivers on Mars,” he said. “But we really didn’t know the extent to which the rivers were organized in large drainage systems at the global scale.”

Goudge and postdoctoral researcher Abdallah S. Zaki compiled existing datasets to reconstruct an integrated map of the ancient networks. Their analysis revealed 19 clusters of valleys, channels, lakes and sedimentary features, 16 of which met the benchmark of 100,000 square kilometres used to classify large drainage basins on Earth.

“We did the simplest thing that could be done. We just mapped them and pieced them together,” Zaki said, emphasising the straightforward but high-impact nature of the work.

Comparisons with Earth’s Watersheds

Large watersheds are far more common on Earth, which has 91 systems exceeding 100,000 square kilometres. These include the Amazon basin—at 6.2 million square kilometres the largest in the world—and the Colorado River basin in Texas, which narrowly qualifies at 103,300 square kilometres.

Mars’ relative scarcity of large basins is linked to the absence of tectonic activity, which on Earth creates the varied topography necessary for extensive watershed formation.

Prime Targets for Habitability Studies

Despite covering only about 5 per cent of Mars’ ancient terrain, the large river basins account for approximately 42 per cent of all erosion attributed to flowing water. This suggests they played a central role in sediment transport, nutrient cycling and geological interactions that could support emerging life.

Zaki highlighted the importance of these areas in future astrobiological investigations. “The longer the distance, the more you have water interacting with rocks, so there’s a higher chance of chemical reactions that could be translated into signs of life,” he said.

Guiding Future Mars Missions

While Mars contains numerous smaller drainage systems—each potentially significant in its own right—the researchers argue the 16 large basins carry the greatest potential for uncovering evidence of past habitability. Their extensive networks and erosional influence make them strong candidates for preserving biosignatures or long-term water records.

“It’s a really important thing to think about for future missions and where you might go to look for life,” Goudge said, noting that mission planning increasingly relies on identifying the most promising scientific targets.

Institutional Response and Broader Impact

Danny Stockli, chair of the Department of Earth and Planetary Sciences at UT Austin, said the findings reinforce the university’s leadership in planetary sciences. “Tim Goudge and his team continue to be leaders in the field, making groundbreaking contributions to the understanding of Mars’ planetary surface and hydrologic processes,” he said.

The study was also co-authored by David Mohrig, professor in the same department.

As international interest in Mars exploration accelerates—supported by both government space agencies and private companies—the identification of large ancient watersheds provides a critical framework for selecting future landing sites and shaping scientific priorities. The research deepens the understanding of Mars’ early climate and reinforces growing evidence that the planet once hosted extensive and dynamic river systems.