Using dunes to interpret wind on Mars

Date:
October 1, 2021
Source:
Geological Society of America
Summary:
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.



FULL STORY ========================================================================== 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." ========================================================================== Story Source: Materials provided by Geological_Society_of_America. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Mackenzie Day. Interaction bounding surfaces exposed in migrating
transverse aeolian ridges on Mars. Geology, 2021; DOI:
10.1130/G49373.1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211001082627.htm

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