Using Dunes to Interpret Wind on Mars
Boulder, Colo., USA: Dunes develop when wind-blown sand organizes into
patterns, most often in deserts and arid or semi-arid parts of the world.
Every continent on Earth has dune fields, but dunes and dune-like sand
patterns are also found across the solar system: on Mars, Venus, Titan,
Comet 67P, and Pluto. On Earth, weather stations measure the wind speed and
direction, allowing us to predict and understand airflow in the atmosphere.
On other planets and planetary bodies, we do not yet have weather stations
measuring the winds (with a few recent exceptions on Mars only). 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. Furthermore, by studying dunes across
planets, we can get a better understanding of how wind and sand behave in
general.
In this Geology paper, published today, Mackenzie Day of the
University of California Los Angeles focuses on what happens when two dunes
collide.
“On Earth, we know that dunes collide, combine, link, and merge all the
time,” says Day. This is what drives changes in dune-field patterns over
time. 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.”
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.
Whether or not these unusual features, sometimes called “transverse aeolian
ridges” or “megaripples,” are formed like dunes has been long debated.
“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.”
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. Banding occurring only on one side of the ridges suggests that
the banding formed as the ridges migrated. 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.
The pattern associated with dune-interactions only forms when two dunes
combine, therefore seeing it in these martian sand ridges demonstrates that
these enigmatic features (like those shown in the image attached) behave
like dunes on Earth. “Just like dunes on Earth, transvers aeolian ridges on
Mars migrate, combine, and develop complex patterns in response to the
wind.”
Transverse aeolian ridges are incredibly common on Mars, and the results of
this work allow us to better interpret the wind at the surface of Mars
using these dune-like features.
“Overall,” Day says, “this work leverages both knowledge of Mars and
knowledge of Earth to understand the other planet and opens the door to
improving how we interpret wind across planetary bodies further into the
solar system.”
FEATURED ARTICLE
Aeolian bedform-interaction strata exposed in migrating transverse
aeolian ridges on Mars
Mackenzie Day, daym@epss.ucla.edu, University of California Los Angeles,
Department of Earth, Planetary, and Space Sciences.
https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G49373.1/608087/Interaction-bounding-surfaces-exposed-in-migrating
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