What's Carving Active Gullies on Mars? It's Not Water

Scientists were shocked when they received the first images of Martian gullies. The gullies appeared to change over time and were similar to Earth's gullies, but they couldn't have been formed by water. A new paper from Apolline Leclef and her colleagues suggests that the gullies are caused by CO2 frost turning into a fluid. The authors used data from Mars Express and MRO to support their claim. The gullies are located near the polar ice cap, but they are not in the temperate latitudes where most gullies form. The study discredits the idea that liquid water is responsible for the gullies. The researchers also rule out geysers as the cause, because the timing doesn't match. The third theory, called the Air Hockey Effect, suggests that CO2 frost fluidization causes the gullies. This process doesn't require liquid water and is based on the freeze-thaw cycle of the Martian atmosphere. The findings challenge the notion that Earth-like features always require Earth-like physics. The study shows that the gullies on Mars are formed without liquid water, and instead rely on the freeze-thaw cycle of the Martian atmosphere.

AI-generated summary of the original article — see the source for the full story.