Much of the surface of Mars is covered by dunes, ripples, and other features formed by the blowing of sand by wind, known as saltation. In addition, saltation loads the atmosphere with dust aerosols, which dominate the Martian climate. We show here that saltation can be maintained on Mars by wind speeds an order of magnitude less than required to initiate it. We further show that this hysteresi...

Aeolian sand dunes originate from wind flow and sand bed interactions. According to wind properties and sand availability, they can adopt different shapes, ranging from huge motion-less star dunes to small and mobile barchan dunes. The latter are crescentic and emerge under a unidirectional wind, with a low sand supply. Here, a 3d model for barchan based on existing 2d model is proposed. After ...

Sand dunes have been observed throughout the surface of the planet Mars. Movement of these dunes has been theorized and inferred from the lack of craters on dunes. Dune movement has not yet been directly imaged, however. Understanding sand movement processes is vital to a correct Martian climate model, as well as the safety of future missions to Mars. Imagery from several Martian orbiters was a...

The occurrence of clonal growth of distylous Lithospermum caroliniense was investigated in a population in the Nebraska Sandhills, an area where sand dunes have been relatively stable for at least 1500-3000 yr, and compared to a population occurring at the Indiana Dunes, an area of active sand dune formation. Spatial autocorrelation analysis indicated the occurrence of significant clonal propag...

We investigated the variations in specific leaf area (SLA) and leaf dry matter content (LDMC) of 20 species (10 annuals and 10 perennials) that have different distributional patterns in the Kerqin Sandy Land in northern China. The main purpose of our study was to determine if SLA and/or LDMC could be used as indicators of plant resource-use strategy in sand dune environments. The selected speci...

Permian red beds of the De La Cuesta Formation in the Sierra de Narváez (Paganzo Basin, northwestern Argentina) are essentially composed of sandstones associated with mudstones and subordinate conglomerates. Facies distributions and stacking patterns indicate that these sediments resulted from the interaction between aeolian and ephemeral fluvial systems, and are represented by aeolian dune, dr...

Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009), we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was ...

Babolsar eastern coastal dunes have been developed along the southern coast of the Caspian Sea. The studied area is coordinated in N36°43' to N36°44' latitude and E52°44' to E52°52' longitude. The objectives of this research were to: Study mineralogy and geochemistry of sand dunes, to obtain chemical alteration index (CIA) and its relationship to climate and mineralogy, to de...

a r t i c l e i n f o Geologists, physicists, and mathematicians have studied ripples and dunes for more than a century, but despite considerable effort, no general model has been proposed to explain perhaps the most fundamental property of their morphology: why are some bedforms straight, continuous, parallel, and uniform in planform geometry (i.e. two-dimensional) whereas others are irregular...

Large dune fields can overrun for instance infrastructures lying in the way of their motion. Unidirectional wind fields and low sand availability give rise to single barchan dunes moving in the direction of wind. They can interact by directly exchanging their sand through collisions. This kind of interaction plays a crucial role in the evolution of barchan dune fields, for instance on the selec...