Tutorial
Aeloin Features
Wind currently plays a powerful role in shaping the geologic landscape of Mars. By eroding, transporting, and shaping landforms, the wind on Mars creates a number of patterns and shapes called aeolian features. Examples include sand dunes, dust devil tracks, and wind streaks. Aeolian activity can operate on faster timescales than other geologic processes. Scientists have witnessed changes in the appearance of some aeolian features on Mars in images taken by the Mars Reconnaissance Orbiter currently orbiting Mars – this means that sediment deposition and transport by the wind is currently active on the Red Planet.
Sand Dunes
Sand dunes are hills shaped by the deposition of sand-sized grains that have been carried by wind. It is common to find many dunes in one place – this phenomenon is known as a dune field.
Practice identifying sand dunes
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Streamlined islands within a Martian channel in daytime IR
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Landslides in light-toned layered material in Valles Marineris
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Dark sand dunes in a crater in Arabia Terra
These are streamlined islands.
Streamlined islands are similar to sand dunes in that they can tell you something about flow direction—in the case of streamlined islands, the flow of water, and the flow of air in the case of sand dunes. The pointy end of the teardrop points in the direction of the flow of water. In this case, the water in this channel flowed roughly from south to north/northeast (bottom to upper right of the image).
These are dark landslide aprons.
While sand dunes on Mars are often dark-toned, the dark features in this image are aprons of material that have moved down a slope of light-toned layered material inside Valles Marineris, a 4000 km-long chasm on Mars—as long as the United States is wide!
Yes, these are sand dunes!
The dark features in this image are a type of sand dune called “barchan dunes.” These crescent-shaped dunes are very common on Earth and form in areas with one main wind direction. On Mars, these dunes are often found inside depressions such as craters or volcanic calderas. The dunes in this image are inside of Nili Patera, a large Martian volcano. The shape of the dunes shows that the wind here blows from northeast to southwest (upper right to lower left of the image).
Dust Devil Tracks
Mars' surface is regularly visited by spiral whirlwinds called dust devils. Dust devil tracks are linear features that mark the path that a dust devil has travelled. They can be straight or curvy. Typically they are dark in tone due to the removal of dust along its path, revealing the darker Martian surface beneath its coating of reddish dust.
Practice identifying a dust devil tracks
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Dust devil tracks on sand dunes
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Dark wind streaks on ancient lava flows
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Warrego Valles, a collection of dendritic channels (daytime IR view)
Yes, these are dust devil tracks!
Now this one is a bit of trick question—you might be thinking, "Wait, aren’t these sand dunes?" Yes, they are, but do you see the thin dark lines scribbled all over the top of the dunes? Those are the dust devil tracks! Many dust devils have moved across these dunes, blowing away fine-grained dust on the surface to reveal the darker dune material underneath.
These are wind steaks.
Dust devil tracks tend to be dark and squiggly, marking the paths of dust devils across the Martian surface. Wind streaks on the other hand form along the main wind direction and therefore tend to be very straight. These wind streaks on an ancient lava flow show that the wind here mainly blows from south to north (bottom to top of the image).
These are dendritic channels.
While they might look somewhat like the squiggly paths of dust devil tracks, these are actually channels carved into the Martian surface. These channels have a tree-like shape, connecting to a single major channel as they flow downhill over solid rock.
Wind Streaks
Where wind blows dust away around a topographic feature, wind streaks are formed. Craters, ridges, and cliffs can all have wind streaks wrap around them. Like dust devil tracks, wind streaks are often dark in tone due to the removal of dust. However, older or inactive wind streaks can appear light-toned as dust begins to cover them.
Practice identifying a wind streaks
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Dust devil tracks on sand dunes
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Dark wind streaks on ancient lava flows
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Warrego Valles, a collection of dendritic channels (daytime IR view)
These are sand dunes, not wind streaks.
These are linear sand dunes, formed from sand-sized grains transported and deposited by wind. Linear dunes can be tens of kilometres long and tend to form in areas where the wind mainly blows in a single direction, or in two slightly different directions. The lines of the dunes point parallel to the direction in which the wind blows.
These are sand dunes, not wind streaks.
Wind streaks tend to form off of features such as impact craters or mesas. Dust devil tracks on the other hand form along the paths of dust devils—small tornado-like storms that move across the Martian landscape. These thin dark lines are dust devil tracks on flat plains in the southern hemisphere of Mars.
Yes, these are wind streaks!
You are correct! The wind streak in this location has formed due to the presence of the small crater in this image. Winds here have swept away the fine-grained dust the covers much of the Martian surface, exposing darker underlying material along the edges of the wind streak. The lighter area of the streak behind the crater is an area where wind has deposited fine-grained dust. In this case, the wind blew from east to west (right to left in the image).