What's carving active gullies on Mars? It's not water

Scientists were shocked when they received the first images of Martian gullies. They were even more shocked as those gullies appeared to change over time. The science-journalism coverage adds useful context, while the strongest evidential footing still comes from the underlying data, papers or institutional documentation.

This matters because Earth science becomes stronger when local observations can be placed inside a broader physical pattern that spans time and geography. The planet operates as a coupled system in which atmospheric, oceanic, cryospheric and solid-Earth processes interact across timescales from days to millions of years. A measurement that captures one variable at one location and one moment has limited interpretive value until it is embedded in the longer series and wider spatial coverage that allow natural variability to be separated from forced change. A new paper from Apolline Leclef of the Institut d'Astrophysique Spatiale at Université Paris-Saclay and her colleagues, available on the arXiv preprint server, shows how they are. Editors have highlighted the following attributes while ensuring the content's credibility: Add as preferred source Some of the "frosted" gullies as seen on Mars.

NASA/JPL-Caltech/University of Arizona Scientists were shocked when they received the first images of Martian gullies. Their similarities to gullies seen on Earth were uncanny, but all of Earth's gullies are formed by water runoff, and Mars is too cold and has too sparse an atmosphere to have.

To prove this idea, the authors turned to data from two of the longest-standing observers of Mars' environment, Mars Express and the Mars Reconnaissance Orbiter (MRO). They looked at data collected by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on MRO and the OMEGA spectrometer on Mars Express, but focused on a very specific.

On Earth, we think of geysers as jets of hot water spewing up from inside the Earth's surface. Eventually, after the pressure builds up enough, the ice ruptures and high-velocity jets of CO 2 gas erupt outward, bringing dark plumes of sand and soil with them.

The broader interest lies in linking the observation to climatic, geophysical or environmental dynamics that extend well beyond the immediate event or location. Earth science is unusual in that its most important questions operate on timescales that no single research career can observe directly, making the archival record, whether in ice, sediment, rock or satellite data, as important as any new measurement. Results that can be embedded in that record, and that either confirm or challenge the patterns it reveals, carry disproportionate scientific weight.

This results in the "dark spots" cameras on Mars Express and MRO have seen from orbit. The authors think a sublimation-driven process on Mars, known as CO 2 frost fluidization, does the same thing on a larger scale to the CO 2 ice sheets on Mars, causing the gullies.

Because this item comes through Phys. org Space as science journalism, it should be treated as contextual reporting rather than primary evidence. Good science reporting can identify why a result matters, connect it to the wider literature and make technical work readable, but the decisive evidence remains in the original paper, dataset, mission release or technical record. That distinction is especially important when a story is later repeated by aggregators, because repetition increases visibility, not evidential strength.

The next step is to place the result inside longer time series and to compare it with independent instruments and independent sites. Earth system observations gain most of their interpretive power from network density and temporal depth, not from any single measurement however precise. Model simulations that assimilate the new data will help clarify whether the observation fits comfortably within known natural variability or represents a shift that existing models do not reproduce.

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