This research is shared jointly with the Arizona State University newsroom.

The surface and atmosphere of Mars have seen many changes over its 4.5-billion-year history. While the planet's current atmosphere is very thin (about 0.6% of Earth's), it was once thick enough to sustain liquid water.

According to new research published in Communications Earth & Environment, these atmospheric changes could play a key role in how we interpret sediment deposits on the planet.

“We found that the changing pressure resulting from atmospheric changes would have produced sediment-rich water flows with varying shapes over time,” says co-author and Georgia Tech Assistant Professor Frances Rivera-Hernández, adding that since Mars’ present-day atmosphere is very thin, the associated low pressures would produce behaviors not seen on Earth. 

“Earth’s thicker atmosphere means that there are higher pressures on our planet, which produce very different behaviors,” she explains. “This means that Earth analogs may not be reliable for interpreting some Martian sedimentary landscapes.”

“At low present-day pressures, Mars mud would boil and levitate if the surface temperature was warm, or freeze and flow more like lava if the temperature was cold,” adds study lead Jacob Adler, who began working on the project while a postdoctoral researcher in Rivera-Hernández’s PLANETAS Lab at Georgia Tech, and continued the study in his current role as an assistant research professor in Arizona State University's School of Earth and Space Exploration. 

The team also included Georgia Tech Ph.D. student and current PLANETAS Lab member Sharissa Thompson, along with researchers from the Open University and Czech Academy of Sciences.

“This study adds a critical layer of nuance to analogue research,” says Rivera-Hernández. “By comparing our lab results to real Martian landforms, we can better reconstruct Mars’ past climate — leading to increasingly successful research in the future.”

Making Martian mud

In order to recreate past conditions on the red planet, the team conducted over 70 experiments in a Mars simulation chamber, testing how flowing water-sediment mixtures would be affected by the varying pressures and temperatures throughout the planet’s history.

Thompson, who specializes in understanding these types of mixtures, played a key role in interpreting the results. “As part of my Ph.D. work at Georgia Tech, I uncover how and why flow shapes evolve as pressure changes, which helped us understand how these flows could have shifted with changing pressures on Mars over time,” she says. “I’m thrilled to have contributed to the innovative flow experiments this study conducted.”

The experiments revealed that at higher atmospheric pressures, water and mud would have similar flow physics (rheology) as on Earth, indicating that some of the oldest sedimentary features on the surface should appear similar to Earth environments. In these scenarios, surface conditions may also have been more habitable for life.

On the other hand, as Mars started to lose most of its atmosphere, the dominant physics in sediment flow experiments changed to freezing and boiling. The team found that at the lower pressures Mars has experienced after the Noachian, the rheology and deposit shapes (morphology) were not at all Earth-like.

“When we mapped out where on Mars, we would expect this different behavior, we found that this opposite behavior could happen at the same time at different locations on the planet,” Adler shares. “The small-scale climate variations across Mars’ topography are enough to see these opposing effects.”

Decoding Mars' past

The research suggests that studying the specific shapes of features like sediment flows, debris flows and mudflows could help scientists better estimate climate conditions. It also highlights how laboratory experiments are a critical part of planetary science activities, as they can help scientists better interpret remote sensing and modeling results.

"By finding matching morphologies of what we see on Mars and what we see in these lab experiments, we might be able to better time-stamp the paleoclimate record,” Adler explains.

"We’ve sent rover missions to Mars largely because we find compelling remote sensing evidence of deposits formed by water or mud that could indicate a habitable environment,” he adds. “We are often eager to compare what we find to Earth analogs, but these are not always suitable for comparison. This study shows there is still much we can learn about Mars by conducting experiments under Mars conditions.”

Funding: NASA

DOI: https://doi.org/10.1038/s43247-025-02879-w