![]() ![]() “We have an upper bound on the time that it takes for a given dune to adjust to changes in environmental conditions, and that is the time it takes for a dune to migrate by a distance of one dune length,” Marvin said. There, the dunes react to that change until they have migrated far enough into these new conditions for their pattern to have once again matured, decreasing the number of dune interactions. But further downwind, the winds become more variable and frost locally makes it harder for grains to be blown away. There, the migrating dunes have settled into their current conditions – they’re well spaced, they look the same, they’re the same size – and because of that, they interact very little with one another. They also found that pattern to be true on Mars, where a big dune field occurs around the north pole. This trend is exactly what we expected to see.” “They move into the portion outside the valley and they again readjust to their unconfined conditions, and we see a drop in the number of interactions. “As both sand and winds get funneled into the valley, the dunes feel a change in their boundary conditions, and their pattern needs to adjust,” said lead study author Colin Marvin, a PhD student in Earth and planetary sciences. They found that dunes outside the valley displayed few defects in their patterns, but as they migrated through the valley – which starts very wide, then narrows, then becomes wide again – dunes interacted more with each other. Next, they investigated dunes migrating through a valley in the Namib Desert to see how changes in the wind conditions, triggered by topography, impacted dune patterns. “When the dunes and their patterns were not in equilibrium with their current conditions, the interaction density was high, and through time we could see it decreased consistently, as is expected from our hypothesis,” Lapôtre said. (Image credit: NASA/JPL/MSSS/The Murray Lab) The study authors analyzed satellite images of the dune field from 2016 to 2022 to see how it grew from a flat bed to large dunes in equilibrium with their environment.Ĭrescentic dunes in Nili Patera on Mars, primarily composed of basaltic sand. In a part of China’s Tengger Desert, researchers once flattened a dune field to have a baseline for understanding its subsequent reformation. To test their hypothesis, they used data from Earth and Mars to verify how known changes in environmental conditions, such as wind direction or the amount of sand available, affected dune interactions in the dune fields. ![]() Thus, the researchers hypothesized that a high number of interactions, in turn, must signal recent or local changes in those boundary conditions. Through such interactions, dunes evolve toward a pattern that is free of defects, reflecting a state of equilibrium with local conditions. Physically, dune interactions manifest themselves as locations where the crestlines of two dunes get very close to each other. The scientists analyzed satellite images of 46 dune fields on Earth and Mars and studied how the dunes interact, or exchange sand. “These findings offer a really exciting new tool to decipher the environmental history of these other planets where we have no data.” You don’t have access to the surface,” said senior study author Mathieu Lapôtre, an assistant professor of Earth and planetary sciences in the Stanford Doerr School of Sustainability. “When you look at other planets, all you have is pictures taken from hundreds to thousands of kilometers away from the surface. 1, can be used as a new tool for understanding environmental changes on any planetary body that harbors dunes, including Venus, Earth, Mars, Titan, Io, and Pluto. Now, Stanford researchers have found a way to interpret the meaning of these patterns. For decades, scientists have puzzled over why they form different patterns. Dunes, the mounds of sand formed by the wind that vary from ripples on the beach to towering behemoths in the desert, are incarnations of surface processes, climate change, and the surrounding atmosphere. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |