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

在地球上，沙地表面的风流产生了两种不同长度的河床：涟漪(10-1米)和沙丘(101米)。波长为100到101米的中间床的稀缺被称为禁止的波长间隙。在火星上，情况是不同的，米级的风沙床(MSAB)很常见，对火星车的行动构成了危险。最近的研究对地球和火星上的MSAB提出了截然不同的解释：一种解释是基于间接证据的风阻力机制，另一种解释是基于地面现场研究，并强调了一种机制，即Repton大粒子在较小粒子的撞击下短距离跳跃。这两种假说可能都是合理的，这意味着MSAB是由不同的机制形成的；然而，这些假说基于有限的现场数据和对关键过程的不完全理解，因此可能存在缺失的细节或替代解释。*NSERC发现项目的目标是验证和加强假说和参数化，以解释MSAB在地球和火星上的形成和演化。研究策略包括现场测量、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：(1)陆地MSAB中的沉积档案；(2)沉积物迁移和地貌动力学；(3)细胞自动机建模。Eight HQP将领导这些主题的项目，并将在两个MSAB占主导地位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实地地点将用于在独特的环境中检查攀登和跨越陡峭山坡的MSAB。预计科学成果将改进对MSAB沉积学、地层学和年龄的物理描述；更详细地从机理上理解MSAB颗粒尺寸和密度、沉积物迁移、地貌动力学和风况之间的相互作用；以及一个新的3D建模框架，用于评估MSAB从形成到演化和消亡的整个生命周期。结果将主要支持对地球上的MSAB的理解，但也为解释火星上的MSAB提供了有价值的背景。在NSERC项目的支持下，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.