Scientists are uncovering the mysteries of strange, winding gullies on Mars. New experiments show these formations aren’t made by water as once thought. Instead, they are carved by dry ice that sublimates and moves like a burrowing animal, clearing the sand in its path.
“It was like watching the sandworms from Dune,” says Lonneke Roelofs, an Earth scientist from Utrecht University.
These gullies have puzzled experts since they were first spotted in 1999. Initially, researchers thought they formed from seasonal water flows. However, ongoing studies revealed no evidence of liquid water on Mars, changing our understanding of these formations.
In 2013, scientists proposed another idea: the gullies could be created by carbon dioxide ice, or dry ice, sliding down the dunes. Early tests showed promise, but they didn’t replicate all the complex features we’d observed on Mars.
To dive deeper, Roelofs and her team returned to a specialized Mars chamber that simulates the planet’s cold, thin atmosphere. Here, they experimented with different slopes and sizes of sand grains, observing the effects of dry ice using high-speed cameras.
The results were fascinating. On steep slopes, the dry ice slid with little impact, but when they adjusted the slope to be less steep, the ice dug into the sand. As it sublimated, gas built up and expelled sand around it, creating the exact features seen in Martian gullies—curvy tracks and small levees.
Imagine a large block of dry ice quaking as it melts, creating a burst of sand. This doesn’t just happen anywhere; fine-grained slopes are crucial for this process. Roelofs notes, “We finally saw the right results when we got the slope just right.”
Interestingly, the Martian environment is rich in CO2. In winter, it can freeze into a layer of ice up to 70 centimeters thick over the mid-latitude dune fields. As the temperatures rise in spring, the ice sublimates and breaks off, leading to the characteristic gullies.
Roelofs emphasizes an exciting point: Mars is our closest rocky neighbor, situated in the “green zone” of our Solar System, where conditions might allow for liquid water—key for potential life. Understanding these processes on Mars might help us rethink how landscapes form on Earth.
This research contributes to a growing body of work that could reshape our knowledge about planetary geology, and it was published in Geophysical Research Letters.
As scientists continue to explore Martian features, the insights gained may not only explain the red planet’s landscape but also shed light on Earth’s processes, inviting us to consider broader questions about life beyond our planet.
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