Forget everything you thought you knew about Mars! The Red Planet, once a beacon of hope for finding signs of past life, is now revealing a surprising secret: its landscape is being sculpted, not by water, but by something far more unexpected – exploding dry ice.
Initially, scientists were captivated by the long, winding gullies etched into Martian sand dunes. They resembled formations created by flowing water, perhaps hinting at ancient rivers or even underground springs.
But here's where it gets controversial... the reality is far more unusual. Mars is a cold, dry world, with temperatures plummeting to a bone-chilling minus 190°F (minus 123°C) in some areas. Liquid water, as we know it, simply can't exist under these conditions for extended periods. So, what's responsible for carving these alien features?
The answer may lie in the behavior of carbon dioxide (CO₂) ice, also known as dry ice. The Martian atmosphere is primarily composed of CO₂, which freezes during winter, coating the surface like frost. As spring arrives, this ice rapidly warms. Unlike on Earth, where dry ice melts, on Mars, it undergoes a process called sublimation, transforming directly from a solid to a gas. And this is the part most people miss... this seemingly simple process is the key to understanding the gullies.
Recent lab experiments have shown that CO₂ ice blocks, some as large as 3 feet (0.9 meters) long, can actually dig into sand and slide downhill propelled by the escaping gas. As the bottom of the block sublimates, the gas has nowhere to go. Pressure builds up, and then… boom! The gas erupts, blasting sand in all directions.
Dr. Lonneke Roelofs, an Earth scientist from Utrecht University, described the phenomenon: "In our simulation, I saw how this high gas pressure blasts away the sand around the block in all directions." The escaping gas carves out a pit around the block, pushing sand aside and helping the block burrow deeper into the slope. As the block continues to sublimate, it pushes against the ground, slowly making its way down the slope, leaving behind a gully edged with ridges of sand – a perfect match for what we see on Mars.
To confirm these findings, Roelofs and master's student Simone Visschers recreated Martian conditions in a "Mars chamber" at the Open University in England. They experimented with different slope angles and dropped CO₂ ice blocks. After several attempts, the results were striking. Visschers commented, "After finding the right slope, we finally saw results. The CO₂ ice block began to dig into the slope and move downwards, just like a burrowing mole or the sandworms from Dune. It looked very strange!" This marked the first time anyone had observed dry ice behaving in this manner, a process not naturally occurring on Earth due to differing conditions.
So, where does this dry ice come from? During Martian winters, a thick layer of dry ice, up to 28 inches (70 centimeters) deep, blankets entire dune fields. As spring arrives, most of this ice sublimates. However, the last remaining patches, often on the shady sides of dunes, can break off and tumble down. Once these blocks hit the slope, the warmer sand triggers more sublimation, and the process begins, carving out the gullies we observe.
But why is this important? As Roelofs explains, "Mars is our nearest neighbour. It is the only rocky planet close to the 'green zone' of our solar system... which is a prerequisite for life." Studying Mars offers insights into the origins of life and the possibility of extraterrestrial life. Furthermore, researching the formation of landscapes on other planets allows us to challenge our understanding of Earth's processes, potentially leading to new discoveries.
For now, Martian gullies don't point to aliens or past water, but they do offer a fascinating glimpse into a unique geological process. One shaped by a type of ice we rarely consider, acting in ways we've never witnessed before.
What are your thoughts? Does this change your perspective on Mars? Do you think this dry ice process could be happening elsewhere in our solar system? Share your opinions in the comments below! The full study was published in the journal Geophysical Research Letters.
