Confirm antiripple observation in Venus wind tunnel experiments

Ascertain whether upwind-propagating impact ripples (antiripples with negative propagation speed c < 0) were observed in the Venus wind-tunnel experiments of Greeley, Marshall, and Leach (1984) by determining the ripple propagation speeds under their experimental conditions and establishing the sign of c.

Background

The paper develops an analytical and numerical framework in which impact ripple wavelengths are selected by a granular impact–ejection lag length rather than by a transport hoplength scale. A key prediction is the existence of antiripples—impact ripples that propagate upwind (negative propagation speed)—under conditions where the average hoplength is small compared to the selected wavelength, such as in high-density atmospheres (e.g., Venus) or with sufficiently large grains on Earth.

To compare predictions with observations, the authors reference prior Venus wind-tunnel experiments (Greeley et al., 1984). These experiments reported ripple wavelengths but did not include measurements of propagation speed. Consequently, it remains unresolved whether antiripples occurred in those tests, which is important for validating the model’s prediction of upwind-propagating ripples under Venus-like conditions.