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

在地球上，经过沙质表面的风会形成两种不同长度的地形：波纹（10-1米）和沙丘（101米）。波长为100 ~ 101 m的中间床型的稀缺性被称为“禁波隙”。在火星上，不同的米尺度风成层（msab）很常见，对火星车的移动构成了威胁。最近的研究对地球和火星上的msab提出了截然不同的解释：一种是基于间接证据的风阻机制，另一种是基于陆地上的实地研究，并强调一种机制，涉及小颗粒撞击驱动的跳跃短距离的大颗粒。这两种假设可能都是合理的，这意味着msb的形成机制不同；然而，这些假设是基于有限的现场数据和对关键过程的不完整理解，因此有可能缺少细节或替代解释。******这个NSERC发现项目的目标是验证和加强假设和参数化，以解释地球和火星上msab的形成和演化。研究策略包括实地测量、实验和数值模拟相结合。研究活动将涉及三个相互关联的主题：(i)陆地msab的沉积档案；（ii）沉积物运输和形态动力学；（iii）细胞自动机建模。8个HQP将在这些主题内领导项目，并将在两个以msab为主的国际地点进行实地工作：秘鲁沿海和阿根廷西北部的安第斯山脉。最近在育空地区发现的第三个油田将用于在陡峭的山坡上攀登的独特环境中检查MSABs。预计科学成果将改进MSAB沉积学、地层学和年龄的物理描述；对MSAB粒度和密度、沉积物输运、形态动力学和风况之间相互作用的更详细的机制理解；以及用于评估mabs从形成到演变和消亡的全生命周期的新型3D建模框架。结果将主要支持对地球上MSABs的理解，但也为解释火星上的MSABs提供了有价值的背景。NSERC项目支持的HQP将在一个令人兴奋的研究领域获得新的技术和领导技能和经验，在这个领域，新的发现和贡献有可能颠覆或加强传统智慧。

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.