Every Martian winter, strange patterns can be found snaking across the dunes of the Red Planet for thousands of feet. Now, scientists have unearthed the cause of these squiggling lines. No, it’s not extraterrestrial life, but it’s still pretty interesting.

Researchers from Trinity College Dublin and Durham University found these seasonal patterns are actually created by the freezing and melting of CO₂. More specifically, it’s caused by the sublimation of CO₂ gas, the process where a substance goes directly from a gas phase without passing through the intermediate liquid phase. Their study was recently published in the journal Scientific Reports.

"Several years ago I discovered unique markings on the surface of Martian sand dunes,” Dr Mary Bourke, study author, said in a statement. “I called them Sand Furrows as they were elongated shallow, networked features that formed and disappeared seasonally on Martian dunes. What was unusual about them was that they appeared to trend both up and down the dune slopes, which ruled out liquid water as the cause."

A million kilometers away from the surface of Mars, the researchers built a low-humidity chamber and placed CO₂ blocks on the granular surface in an attempt to mimic the scenario up there on Mars. What they found was “unlike anything seen to occur naturally on Earth,” according to Professor Jim McElwaine. Their experiments in this specially-designed chamber showed that sublimating CO₂ can form a range of odd, streaky patterns similar to those seen on Mars’ dunes, as seen in the image below.

"The difference in temperature between the sandy surface and the CO₂ block will generate a vapor layer beneath the block, allowing it to levitate and maneuver downslope, in a similar manner to how pucks glide on an ice-hockey table, carving a channel in its wake," Lauren Mc Keown, who also worked on the project, explained. "At the terminus, the block will sublimate and erode a pit. It will then disappear without a trace other than the roughly circular depression beneath it."

We know the atmosphere of Mars is composed of over 95 percent CO₂, but we still don't know how it interacts with the surface of the planet.

"Mars has seasons, just like Earth, which means that in winter, a lot of the CO₂ in the atmosphere changes state from a gas to a solid and is deposited onto the surface in that form," she added. "The process is then reversed in the spring, as the ice sublimates, and this seasonal interplay may be a really important geomorphic process."

So there you have it.