A lower-than-expected saltation threshold at Martian pressure and below
| Autor: | Jonathan Merrison, Philippe Claudin, Bruno Andreotti, Keld Rømer Rasmussen, J. J. Iversen |
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| Rok vydání: | 2021 |
| Předmět: |
Bedform
010504 meteorology & atmospheric sciences Mars FOS: Physical sciences Impact ripples Condensed Matter - Soft Condensed Matter 010502 geochemistry & geophysics 01 natural sciences Wind speed Physics::Geophysics Physics - Geophysics Saltation (geology) 0105 earth and related environmental sciences Wind tunnel Martian Multidisciplinary Fluid Dynamics (physics.flu-dyn) Physics - Fluid Dynamics Mars Exploration Program Mechanics Geophysics (physics.geo-ph) Physical Sciences Saltation at low pressure Sediment transport threshold Aeolian processes Soft Condensed Matter (cond-mat.soft) Sediment transport Geology |
| Zdroj: | Proc Natl Acad Sci U S A Proceedings of the National Academy of Sciences Andreotti, B, Claudin, P, Iversen, J J, Merrison, J P & Rasmussen, K R 2021, ' A lower-than-expected saltation threshold at Martian pressure and below ', Proceedings of the National Academy of Sciences of the United States of America, vol. 118, no. 5, e2012386118 . https://doi.org/10.1073/pnas.2012386118 |
| DOI: | 10.48550/arxiv.2104.05341 |
| Popis: | Aeolian sediment transport is observed to occur on Mars as well as other extraterrestrial environments, generating ripples and dunes as on Earth. The search for terrestrial analogues of planetary bedforms, as well as environmental simulation experiments able to reproduce their formation in planetary conditions, are powerful ways to question our understanding of geomorphological processes towards unusual environmental conditions. Here, we perform sediment transport laboratory experiments in a closed-circuit wind tunnel placed in a vacuum chamber and operated at extremely low pressures to show that Martian conditions belong to a previously unexplored saltation regime. The threshold wind speed required to initiate saltation is only quantitatively predicted by state-of-the art models up to a density ratio between grain and air of $4 \times 10^5$, but unexpectedly falls to much lower values for higher density ratios. In contrast, impact ripples, whose emergence is continuously observed on the granular bed over the whole pressure range investigated, display a characteristic wavelength and propagation velocity essentially independent of pressure. A comparison of these findings with existing models suggests that sediment transport at low Reynolds number but high grain-to-fluid density ratio may be dominated by collective effects associated with grain inertia in the granular collisional layer. Comment: 38 pages, 21 figures |
| Databáze: | OpenAIRE |
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