Deserts may seem dead and inert, yet they are alive and thriving. Sand dunes, in particular, develop and move, and they breathe humid air, according to a decades-long scientific endeavor.
The discoveries reveal for the first time how water vapor penetrates powders and grains, and they might have far-reaching implications beyond the desert, including medicinal research, agricultural and food processing, and planetary exploration.
The study by the researchers was published in the Journal of Geophysical Research-Earth Surface.
To measure matter with greater sensitivity, lead author Michel Louge, a professor of mechanical and aerospace engineering at Cornell University, created capacitance probes, which use multiple sensors to record everything from solid concentration to velocity to water content with unprecedented spatial resolution.
In the early 2000s, Louge began working with Ahmed Ould el-Moctar of the University of Nantes in France to use the probes to study the moisture content in sand dunes in order to better understand the process by which agricultural lands become desert – an interest that has only grown more pressing with the rise of global climate change.
The probe finally demonstrated how porous sand is, with just a trace of air passing through it. Previous study suggested that this form of seepage occurred in sand dunes, but no one could confirm it until now.
“The wind blows across the dune, causing pressure imbalances that physically drive air into and out of the sand. So the sand is breathing, just as an organism does “Louge said.
This “breathing” is what permits bacteria to survive deep into hyper-arid sand dunes despite the high temperatures. For the last decade, Louge has worked with Anthony Hay, an associate professor of microbiology at Cornell, to investigate how bacteria might help stabilize dunes and keep them from encroaching on roadways and infrastructure.
Louge and his colleagues also discovered that desert surfaces exchange less moisture with the atmosphere than previously thought, and that water evaporation from individual sand grains works like a sluggish chemical process.
The majority of their data was collected in 2011, but it took Louge and his colleagues another decade to make sense of some of the discoveries, such as discovering surface disturbances that induce evanescent, or nonlinear, waves of humidity to travel downward into the dunes extremely fast.
The researchers hope that their probe will be used for a variety of purposes, including researching how soils absorb or drain water in agriculture, calibrating satellite data over deserts, and exploring alien habitats that may contain minute quantities of water. It wouldn’t be the first time Louge’s study ended up in orbit.
The detection of moisture contamination in medicines is arguably the most urgent use. Since 2018, Louge has been working with Merck to employ the probes in continuous production, which is thought to be a quicker, more efficient, and less costly technique than batch manufacturing.
The Qatar Foundation provided funding for the study.