22-EPN3-076: Aeolian Ripples Development under Martian Atmospheric Conditions

Visit by Simone Silvestro and Giuseppe Mongelluzzo of INAF (Italy), to TA2.4 Planetary Environment Facilities (PEF), AU (Denmark)
Dates of visit: 16-20 October 2023

Report summary: In our experiments in the Planetary Environment Facility in Aarhus we obtained, two superimposed ripple patterns on monodisperse (90-150) glass beads in CO₂ air. The presence of two distinct sets of aeolian sand ripples in unimodal sand suggests two formational mechanisms, impact for the cm-scale ripples and hydrodynamic for the decimetre scale set. We also run the experiment for natural 125µm-sand for terrestrial and Martian pressures (and below). Two patterns might be visible, but not very clearly, suggesting that the shape of the grains is playing a role in the formation of the hydrodynamic pattern. We also found a potential inverse relationship between impact ripple wavelength and pressure that we are currently investigating.

**Fig. 1:** Ripple pattern obtained in the wind tunnel. a) two ripple sets formed in glass beads at 1031 mb. b) ripples in natural 125µm-sand at 250 mb. Two patterns might be distinguished but they are not as evident as in the glass beads. c) ripples at 4 mb in natural sand. Only one pattern can be distinguished. Credit: Silvestro et al.

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