Formation and evolution of meter-scale granular bedforms on Earth and Mars

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On Earth, windflow over sandy surfaces produces bedforms in two distinct length scales: ripples (10-1 m) and dunes (=101 m). The scarcity of intermediate bedforms with wavelengths ~ 100 to 101 m has been called the `forbidden wavelength gap'. On Mars, the situation is different - meter-scale aeolian bedforms (MSABs) are common and pose a mobility hazard for rovers. Recent research has proposed vastly different explanations for MSABs on Earth and Mars: one implies a wind drag mechanism based on circumstantial evidence, the other draws on terrestrial field studies and emphasizes a mechanism involving reptons - large particles that hop short distances, driven by impacts from smaller particles. Both hypotheses may be plausible, implying that MSABs form by different mechanisms; however, the hypotheses are based on limited field data and an incomplete understanding of key processes, so it is possible there are missing details or alternative explanations. The objective of this NSERC Discovery project is to validate and strengthen hypotheses and parameterizations in order explain the formation and evolution of MSABs on Earth and Mars. The research strategy involves a combination of field measurements, experiments, and numerical modeling. Research activities will address three inter-related themes: (i) sedimentary archives in terrestrial MSABs, (ii) sediment transport and morphodynamics, and (iii) cellular automata modeling. Eight HQP will lead projects within these themes and will undertake field work at two international sites where MSABs dominate the landscape: coastal Peru and the Andes of NW Argentina. A third field site recently discovered in the Yukon Territory will be used to examine MSABs in a unique setting - climbing up and across steep mountain slopes. The scientific outcomes are expected to yield an improved physical description of MSAB sedimentology, stratigraphy, and age; a more detailed mechanistic understanding of the interplay between MSAB grain size and density, sediment transport, morphodynamics, and wind regime; and a novel 3D modeling framework for evaluating the full life cycle of MSABs, from formation to evolution and demise. Results will mainly support the understanding of MSABs on Earth, but also provide valuable context for interpreting MSABs on Mars. HQP supported by the NSERC project will gain new technical and leadership skills and experience in an exciting research area where new discoveries and contributions have potential to disrupt or reinforce conventional wisdom.