Earth scientist Lonneke Roelofs from Utrecht University has been at the forefront of unraveling decades-long Mars mysteries posed by the bizarre sand gullies. Roelofs made the journey to Milton Keynes to learn about the processes that forge the Martian landscape. There, he worked hand in hand with master student Simone Visschers. Here’s what recent research published in the Geophysical Research Letters tells us that’s so cool. It’s the sublimation of CO₂ ice that’s most responsible for the creation of these mysterious shapes.
Roelofs and Visschers were the first to start looking into the gullies. Their goal was to recreate Martian conditions in order to observe the effects of CO₂ ice on dune formation. In preparation for their field work, they ran a series of experiments on Mars inside the Chamber. Their mission: crack the puzzle of these enigmatic sand formations that have baffled science for generations.
Investigating Martian Landscape Formation
In particular, Roelofs was interested in the conditions under which blocks of CO₂ ice could start to carve out gullies on Martian dunes. During the severe winter months on Mars, temperatures can reach minus 120 degrees Celsius. That intense cold results in the thick CO₂ ice layer covering the entire dune field. This layer can be up to 70 centimeters thick.
With the arrival of spring, the westward dune slopes become more receptive to the sun’s rays. This heat leads to immense blocks of frozen CO₂ breaking off, with some over a meter long! Roelofs likens this process to a real-life, burrowing mole, or to the imagined, giant sandworms of the movie Dune.
“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.” – Lonneke Roelofs
In addition to changing the size of the dune, their experiments accounted for different angles of dune slopes. They then watched how a large block of solid CO₂ interacted when it started moving down the slopes. This opened up opportunities for them to study the unusual phenomena produced by the blocks.
The Role of Sublimation in Gully Formation
The study underscores how crucial sublimation is. This process, known as sublimation — the process by which solid CO₂ becomes a gas — is an important driver of the creation of these gullies. As chunks of glacial ice flow down the mountains, they bore depressions in the millions of sand grains since the glacial ice sublimates and eventually vaporizes.
“The last remnants of this ice are located on the shaded side of the dune tops, and that is where the blocks break off from once the temperature is high enough. Once the blocks reach the bottom of the slope and stop moving, the ice continues to sublimate until all the CO₂ has evaporated. What remains is a hollow in the sand at the bottom of the dune.” – Lonneke Roelofs
This discovery confirms that blocks of CO₂ ice are a key component in the formation of gullies. They produce xenogeological structures, which are environments and landforms that do not exist on Earth. In particular, Roelofs emphasizes that doing research on extraterrestrial landscapes can provide a valuable perspective on geological processes happening on Earth.
“Also, conducting research into the formation of landscape structures of other planets is a way of stepping outside the frameworks used to think about Earth. This allows you to pose slightly different questions, which in turn can deliver new insights for processes here on our planet.” – Lonneke Roelofs
Implications for Extraterrestrial Life
Roelofs believes that when researchers study these landscapes on Mars, it would help to answer questions related to where life beyond Earth first originated as well. Mars, being Earth’s nearest neighbor in the solar system, lies within the ‘green zone’ where liquid water may exist—a key requirement for life.
“Mars is our nearest neighbor. It is the only rocky planet close to the ‘green zone’ of our solar system. This zone lies exactly far enough from the sun to make the presence of liquid water possible, which is a prerequisite for life. Questions about the origin of life, and possible extraterrestrial life, could therefore be solved here,” – Lonneke Roelofs
With every new bit of research into Martian geology, Roelofs is optimistic. Scannapieco encourages scientists to continue studying how these processes can enhance understanding of life’s potential elsewhere in the universe. Her recent work on CO₂ ice and its effects on Martian dunes provides an exciting pathway of future exploration, as well.