Researchers from the University of Texas at Austin have identified 16 large drainage basins on ancient Mars, highlighting prime locations for evidence of past life. These basins, covering just 5% of the planet's ancient terrain, accounted for 42% of river erosion. The findings suggest these areas offered the most promising conditions for habitability when liquid water flowed.
Long before Mars turned into the cold, dry world observed today, its surface featured rain, rivers, and possibly vast oceans. Scientists believe these watery environments could have supported life, much like Earth's major river basins sustain diverse ecosystems today.
In a study published in the Proceedings of the National Academy of Sciences, a team led by postdoctoral researcher Abdallah S. Zaki analyzed existing data on Martian valley networks, lakes, and river features. By connecting these elements, they mapped 19 major groupings, with 16 forming interconnected watersheds each spanning at least 100,000 square kilometers—comparable to the minimum size for large drainage basins on Earth.
"We did the simplest thing that could be done. We just mapped them and pieced them together," Zaki said.
Co-author Timothy A. Goudge, an assistant professor at the UT Jackson School of Geosciences, noted the novelty of the work: "We've known for a long time that there were rivers on Mars, but we really didn't know the extent to which the rivers were organized in large drainage systems at the global scale."
Unlike Earth, which boasts 91 such basins—including the Amazon at 6.2 million square kilometers—Mars lacks active tectonics, resulting in fewer and smaller systems. Yet these Martian basins played a disproportionate role, eroding 42% of the planet's ancient river sediment despite occupying only 5% of the terrain.
Zaki emphasized their potential for astrobiology: "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."
Goudge added that the research informs future missions: "It's a really important thing to think about for future missions and where you might go to look for life."
The study, co-authored by David Mohrig, underscores how sediment from these basins could preserve biosignatures, making them key targets for exploration. While smaller drainage patches exist across Mars, the largest ones stand out for their scale and geological impact.