Dunes on Earth behave in a similar way to dunes of Mars. Mackenzie Day compares dunes on Earth and Mars to understand the movement of sand in wind in the featured Geology article. Credit: Mackenzie Day.
Wind-blown sand forms dunes when it is exposed to wind. This happens most often in deserts or areas that are semi-arid. Dunes can be found on every continent of the Earth, as well as in the solar system, including Mars, Venus and Titan. Weather stations on Earth measure wind speed and direction. This allows us to predict and understand the airflow in the atmosphere.
We don't have weather stations that measure the wind on other planets or planetary bodies. There are a few exceptions to this rule, such as one on Mars. We can interpret the patterns of the dunes, which are based on Earth's knowledge, to determine what the wind is doing. However, there is no way to measure wind directly on another planet. We can also study dunes on other planets to gain a better understanding about how wind and sand behave.
Mackenzie Day, University of California Los Angeles Geologist, discusses what happens when two dunes collide in a Geology paper.
Day says, "On Earth, it is known that dunes collide and combine, link, merge, and merge all of the time." This is what drives the evolution of dune-field patterns. This is when dune-dune interactions leave behind a specific pattern in the sand. However, this pattern is often covered by actively moving sand making it difficult to see without special tools.
Many dunes on Mars look and behave like dunes on Earth. However, Mars also has patterns of organized sand that look dune-like, but with some differences that remain to be understood by the scientific community. It has been debated for years whether these strange features, also known as "transverse Aeolian Ridges" or "megaripples," can be formed like dunes.
As seen in this satellite photo taken from the Iapygia Quadrangle on Mars, sand on Mars creates dunes and dunelike features. These dune-like features are moving toward the lower left of the image, while the wind blows from the upper left. Banding was visible on their backs. Credit: NASA/U of A. HiRISE camera image EP_020782_1610.
Day says, "In this work," Day says, "I show how these wind-blown sandridges can sometimes show on their surface the pattern formed when two dunes combine."
Transverse aeolian transverse ridges in Mars' Iapygia area included both light and darker sands. This led to light-dark banding on the upwind side. The banding only appearing on one side suggests that the banding formed when the ridges moved. The dune-interaction pattern, as it is known from Earth, can be seen in some of the ridges where the banding becomes truncated then reconnects. It's like two dunes touching each other and then merging downwind.
Dunes can only combine to form the pattern that is associated with dune interactions. This is why you can see it in the Martian sandridges. Transverse aeolian and ridges of Mars are similar to dunes on Earth. They combine with wind to form complex patterns.
The transverse aeolian and ridges of Mars are extremely common. These dune-like features allow us to better understand the wind at Mars' surface.
Day stated that "Overall," Day said, "this work leverages both Earth and Mars knowledge to understand the other planet. It opens the door for improving wind interpretation across planetary bodies further into our solar system."
Further exploration of the colourful dunes found on Mars' windswept surface
Mackenzie Day, Interaction bounding surface exposed in migrating transversely aeolian-ridges on Mars, Geoology (2021). Information from the Journal: Geology Mackenzie Day. Interaction bounding surfaces in migrating transverse Aeolian Ridges on Mars. (2021). DOI: 10.130/G49373.1
