Furthermore, the dune-interaction pattern known from Earth can be seen in some ridges where the banding is truncated and then reconnects, just like two dunes touching and then combining downwind. Banding occurring only on one side of the ridges suggests that the banding formed as the ridges migrated.
In the Iapygia region of Mars, transverse aeolian ridges incorporated both light and dark sands, leading to light-dark banding in the upwind side of the ridges. "In this work, says Day, I show that these unusual wind-blown sand ridges sometimes show on their surfaces the pattern that forms when two dunes combine." Whether or not these unusual features, sometimes called "transverse aeolian ridges" or "megaripples," are formed like dunes has been long debated. On Mars, many dunes look and behave similar to dunes on Earth, but in addition Mars hosts patterns of organized sand that are dune-like but have some differences that have yet to be explained by the scientific community. When this happens, the dune-dune interaction leaves behind a particular pattern in the sand, but that pattern is usually covered by actively moving sand and difficult to see without special tools." This is what drives changes in dune-field patterns over time. "On Earth, we know that dunes collide, combine, link, and merge all the time," says Day. In this Geology paper, published today, Mackenzie Day of the University of California Los Angeles focuses on what happens when two dunes collide.
Furthermore, by studying dunes across planets, we can get a better understanding of how wind and sand behave in general. Without a way to directly measure wind on the surface of another planet, we can use the patterns in dunes to interpret what the wind must be doing, based on our knowledge of dunes on Earth. On other planets and planetary bodies, we do not yet have weather stations measuring the winds (with a few recent exceptions on Mars only).
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