Hidden order in windswept sand
Researchers make new discoveries about 'megaripple' grain composition


Date:
January 11, 2022
Source:
Universita"t Leipzig
Summary:
Researchers have analyzed an extensive collection of sand samples
from so-called megaripple fields around the world and gained new
insights into the composition of these sand waves. These could
help settle debates about the mechanistic origin of some recently
discovered enigmatic extraterrestrial sand structures and improve
our ability to infer information about past weather and climate
events from sediment records.



FULL STORY ========================================================================== Researchers have analyzed an extensive collection of sand samples from so- called megaripple fields around the world and gained new insights into the composition of these sand waves. These could help settle debates about the mechanistic origin of some recently discovered enigmatic extraterrestrial
sand structures and improve our ability to infer information about past
weather and climate events from sediment records.


========================================================================== Megaripples are sand waves with wavelengths in the metre range, between ordinary beach ripples (centimetres) and dunes (ten to 100 metres). They
are commonly found on earth and Mars. Their sand consists of a unique
mixture of coarse and fine grains. "This mixture always looks similar, but
is never identical because of the turbulent winds," explained Professor Klaus-Dieter Kroy of the Institute of Theoretical Physics at Leipzig University, one of the study's leaders.

Among this diversity, the interdisciplinary team of geomorphologists
and physicists from three universities in Germany, Israel and China has
now discovered an unexpectedly uniform characteristic of the underlying
sand transport process, one that had previously eluded decades of field studies. In their analysis of sand sample data from around the world,
the researchers compared the frequencies of all sizes of shifting grains
and divided the diameter of the coarsest grains and of the rarest fine
grains for each sample.

A surprisingly consistent number emerged, as Kroy pointed out. That number
can now be used to decide more reliably which category newly discovered
sand ripples belong to -- as predicted by the team's theoretical
calculations -- and by which physical transport process they were formed.

The international team also hopes that its discovery could help in
the future to better explain the formation of some mysterious new sand
waves recently observed on Mars. Katharina Tholen, a doctoral researcher
at Leipzig University and lead author of the study, said: "If we were
able to use prevailing atmospheric conditions to explain the origin and migration of terrestrial and extraterrestrial sand waves, this would be an important step. It might then be possible to evaluate the sand structures
we are currently observing, for example on Mars or in fossils and remote locations on earth, as complex archives of past climatic conditions." ========================================================================== Story Source: Materials provided by Universita"t_Leipzig. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
* Megaripples ========================================================================== Journal Reference:
1. Katharina Tholen, Thomas Pa"htz, Hezi Yizhaq, Itzhak Katra,
Klaus Kroy.

Megaripple mechanics: bimodal transport ingrained in bimodal sands.

Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-021-26985-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220111100019.htm

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