2023 CSDMS meeting-101

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Impact Ripple Emergence and Scaling Across Planetary Environments

Conner Lester, (He/Him),Duke University Durham North Carolina, United States. Conner.lester@duke.edu

Orencio Duran, Texas A&M University College Station Texas, United States. oduranvinent@tamu.edu

Brad Murray, Duke University Durham North Carolina, United States. abmurray@duke.edu

Sediment transport is a universal phenomenon responsible for the self-organization of bedforms and dunes seen on the surfaces of many planetary bodies. The smallest of these patterns are wind, or impact ripples. Encoded in the sizes and propagation speeds of impact ripples is direct information about the local transport and environmental conditions: sediment fluxes, wind speeds, grain size, etc. However, to get at this information we must understand the processes that govern ripples dynamics. Because of the complexity of sediment transport, our current understanding of ripples is almost purely empirical, and the parameter space of the system has barely been explored. To aid at the process of understanding impact ripple dynamics in arbitrary environments we turn to a discrete element model (DEM) of sediment transport. Simulated ripples sizes from the DEM quantitatively agree with wind-tunnel and field data and therefore the DEM can be used as an experimental tool to explore the state space of the system. Preliminary experiments suggest that ripple wavelengths scale with the average hoplength of eroded grains, but only above a threshold. Below this threshold wavelengths stagnate and ripples begin to propagate upwind. These “antiripples” have not previously been predicted or observed. Yet simulations suggest that they are persistent for many planetary conditions such as those on Venus and even Earth (for large enough grain sizes). We present additional findings for a range of environmental conditions found in our solar system and beyond, and thus map out a more complete space of possible states for ripple formation in the Universe.

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An example of a ripple simulation for Earth-like conditions close to transport threshold wind speed and sand grains of around 100 microns. Sand grains are shown as black spheres with time lagged white tails and the background color shows the wind speed profile. Flow is from left to right.