Dunes on Mars, shaped by the planet’s peculiar seasons. Image: NASA/JPL-Caltech/University of Arizona
Research led by Trinity College Dublin has helped us discover more about the seasons of Mars, and its winters have shown themselves to be powerful.
In our efforts to better understand Mars, researchers are analysing the planet’s thin atmosphere and weather to determine how its barren surface was formed.
One such effort is being led by Trinity College Dublin (TCD), which has unveiled new evidence for how contemporary features are formed on the Red Planet.
In a paper published to Scientific Reports, the team describes phenomena unlike anything seen on Earth, suggesting that the planet’s winter period is moulding its formations – in particular, CO2 sublimation.
The process – by which a substance changes from a solid to a gas without an intermediate liquid phase – is believed to be capable of morphing a planet’s surface with little to no water present.
Dendritic furrows on Martian dunes. The yellow arrows point to boulders, red arrows denote dark fans. Image: NASA/JPL/University of Arizona
During the winter, atmospheric CO2 – of which 95pc of the planet’s atmosphere is made – changes from a gas to a solid and is deposited onto the surface.
Then, in the Martian spring, this process is reversed as the ice sublimates. It is believed this may be integral to the planet’s geomorphological formations.
Several years ago, one of the researchers involved in this latest study, Dr Mary Bourke, discovered unique markings on the surface of Martian sand dunes, which she called ‘sand furrows’.
These elongated, shallow channels formed and disappeared with the seasons, and were unusual in that they appeared to trend both up and down the dune slopes, which ruled out liquid water as the cause.
Examples of the sand furrows discovered during experiments. Image: Lauren McKeown
Evidence of cryo-venting
With these new findings on sublimation, Bourke’s original theory of ‘cryo-venting’ now has more evidence to back it up.
Cryo-venting is a process whereby pressurised CO2 gas beneath the seasonal ice deposit erodes complex patterns on the dune surface when the ice fractures, and releases the gas in towering dust and gas geysers.
During experiments, CO2 blocks on the granular surface of a low humidity chamber showed they can form a range of furrow morphologies that are similar to those observed on Mars.
“The difference in temperature between the sandy surface and the CO2 block will generate a vapour layer beneath the block, allowing it to levitate and manoeuvre downslope, in a similar manner to how pucks glide on an ice-hockey table, carving a channel in its wake,” said Lauren McKeown, one of the researchers.
Her colleague Prof Jim McElwaine added that seeing it in person was “a really exciting moment” and is a process “unlike anything seen to occur naturally on Earth”.
The next step in their research will be to head to the Open University Mars Chamber to assess the influence of Martian atmospheric conditions on these new geomorphic processes, and test a numerical model developed by McElwaine.
