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

在地球上，流经桑迪表面的气流会产生两种不同长度尺度的底形：波纹（10-1米）和沙丘（101米）。波长为100至101米的中间底形的稀缺性被称为“禁止波长间隙”。在火星上，情况是不同的米级风成底形（MSAB）是常见的，并对漫游者构成移动危险。最近的研究对地球和火星上的MSAB提出了截然不同的解释：一种是基于间接证据的风拖曳机制，另一种是基于陆地实地研究，强调一种涉及repton的机制，即大颗粒在较小颗粒的影响下跳跃短距离。这两种假设都可能是合理的，这意味着MSAB是通过不同的机制形成的;然而，这些假设是基于有限的实地数据和对关键过程的不完整理解，因此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的形成和演变。研究策略包括现场测量、实验和数值模拟的结合。研究活动将涉及三个相互关联的主题：（一）在陆地MSABs沉积档案，（二）沉积物输运和形态动力学，（三）元胞自动机建模。八名人力资源专业人员将领导这些主题内的项目，并将在MSAB占主导地位的两个国际地点开展实地工作：沿海秘鲁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攀登和穿越陡峭山坡的独特环境中检查MSAB。科学成果预计将产生一个改进的物理描述MSAB沉积学，地层学和年龄; MSAB粒度和密度，沉积物输运，形态动力学和风况之间的相互作用的更详细的机械理解;和一个新的三维建模框架，用于评估MSAB的整个生命周期，从形成到演变和消亡。结果将主要支持对地球上MSAB的理解，但也为解释火星上的MSAB提供了有价值的背景。由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破坏或加强传统智慧。

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.