Wherever there is sand and an atmosphere, prevailing winds may whip the undulating grains into shapes, pleasing to the eye with their calming repetition.
We've seen sand waves on other planets, but they're between ordinary beach ripples and full dunes in size, and are known as megaripples.
Grain size is a key characteristic of middle-ground ripples, and it is a surface of coarse grains over an interior of much finer material. The mix of grains is not the same as the winds that blow across the sand to create ripples.
Researchers have found a surprising mathematical feature of megaripples: Dividing the diameter of the coarsest grains in the mix with the diameter of the smallest grains always equals a similar number.
verse aeolian ridges are a type of megaripple. NASA, JPL-Caltech, and Univ. of Arizona are part of the same organization.
The number could be used to categorize different types of ripples and which grain transport processes formed them, according to the study authors.
The researchers found that the signature of grain-scale transport is in the grain-size distributions.
The data we have collected firmly establishes the accuracy and robustness of the theoretical prediction across a wide range of geographic locations and prevailing environmental conditions.
Megaripples are caused by fine grains kicking up coarser ones as winds whip across the sand. Coarse grains collect on the crests of the ripples while fine grains settle in the troughs.
In Israel, China, India, Israel, Jordan, Antarctica, and New Mexico, samples were studied. Observations made on Mars were added to the analysis.
The accuracy and robustness of this unexpected theoretical finding is supported by a comprehensive collection of terrestrial and extraterrestrial data.
Megaripples are more vulnerable to wind patterns than smaller sand ripples and larger dunes because they are more fragile and susceptible to wind patterns that get too strong.
The researchers suggest that their calculations could be used to predict when this will happen, and even to look back at past weather and climate conditions based on the debris left behind by previous megaripples.
The findings could help us understand how megaripples are created on planets such as Mars, and the sort of atmospheric conditions required to produce them rather than other types of sand waves.
"If we were able to explain the origin and migration of sand waves using prevailing atmospheric conditions, this would be an important step," says theoretical physicist Katharina Tholen.
It might 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.
The research has been published.
All Rights Reserved © 2024
