Research On Martian Sand Dunes

With the development of space exploration technology,Mars exploration has become the hot spot and focus of Earth-like planetary research,which has greatly promoted the development of many subjects.The aeolian landform process is the most common and most active landform process on modern Mars,and contains a wealth of information on Mars' surface processes,environment,and evolution history.This article focuses on the martian dune landforms,and attempts to systematically analyze its characteristics,types,distribution,pattern,and material composition under different environmental conditions to reveal the origin of dune landforms and their reflection on the environment.Using high-resolution remote sensing images covering the entire world of Mars,with the support of geographic information system software,analyze the distribution,morphology,and spectral characteristics of dune landforms on a global scale,and explore the relationship between regional environment and dune landforms to dig out the significance of aeolian geomorphology.The following main conclusions are initially drawn:(1)Morphological similarities between Mars and Earth's sand dunes.According to the dynamic-morphological principle adopted in the traditional dune classification system,two Mars dune levels and 15 types are divided.The first level looks at sand dune dynamics,including sand sheet,dome dune,transverse dune,linear dune,nail dune,dune network,star dune and obstacle dune.The second type focuses on the morphological characteristics of dunes,and further divides the transverse dune into barchan dune,barchaniod dune,and transverse ridge.Linear dunes are divided into linear ridge,seif linear dune,and raked linear dune.Dune networks are divided into square dune network,ladder dune,oblique dune network,and honeycomb dune.(2)The overall characteristics of the Martian dune distribution are small scale,scattered distribution,and significant spatial differences.The Latitudinal zonal distribution law of sand dunes is significant,mainly concentrated in the low plains,ice fields and highlands in the middle and high latitudes.The dunes in craters are mainly located in the plateau area south of 30°S,with less distribution in the northern hemisphere.The Olympia Undae has the highest dune density in Mars' Arctic,and the crater area is generally low.(3)The types of Martian dunes are simple,the scales are diverse,and the rules of spatial combination present multiformity and complexity.The morphological parameters of dunes have large dispersion,reflecting the differences in the size of dunes in different spatial ranges.The types and morphology of Mars dunes are simpler than the earth dunes,and the correlations with the morphological parameters of other planet dunes have good consistency.In the small-scale range,there are huge differences in the uniformity,spatial combination characteristics and the adaptability of the dunes to the terrain environment.In the mesoscale range,the sand dune pattern of each geographic unit has the characteristics of ring,discrete and stripe.Globally,the dune pattern is characterized by concentration and dispersion.(4)The mineral composition of the Martian dune sediments is relatively simple,mainly composed of iron-magnesia mineral pyroxene and olivine.Hydrated sulfate minerals are distributed in a limited area,and the clay mineral content is very small.The mineral type distribution of Mars dunes is uniform,but it is unique in some areas,reflecting the diversity and local characteristics of Mars sand sources.(5)In the dry and cold environment of Mars,the glacial landforms and dune landforms are in good agreement with the global spatial distribution of ice.The loose and broken material formed by freezing and thawing is likely to be the main source of sand dunes.Furthermore,a conceptual model of the origin of the Martian dune landforms was established:From the Hesperian to the early Amazonian periods,water scattered in different areas of the Martian surface gathered to the poles and high latitudes through evaporation,sublimation,atmospheric transport and condensation,forming polar ice caps and mid-high latitudes Shallow underground ice.In the long geological age,due to changes in climatic and meteorological conditions,freezing and thawing occurred on the surface,driving the weathering of rocks and sorting sediments,and shaping a lot of glacial landforms.Occasional gale events cause sand particles to jump and form a sand flow,which leads to further sorting and accumulation of sand particles.The terrain of the northern hemisphere is flat and wide,and large-scale circulation movements make the aeolian sediments gradually converge on the edge of the ice cap,forming a circular desert distributed along the latitude.Due to the terrain control,the aeolian sand deposits in craters and canyons cannot be migrated for a long distance,forming scattered flaky sandy lands.(6)The morphology of the linear ridges in the Qaidam Basin and the Mars Chasma Boreale is similar.The coexistence of transverse dune sand longitudinal dunes in a limited space is the result of the evolution from barchan dunes to linear ridges,reflecting the complex external environment.(7)The topographical features of Mars and Earth's sand dunes are similar,mainly in low-lying plains,craters and canyons.In the Arctic,the prevailing westerly winds from the mid-latitudes reduced wind speed after encountering huge topographic obstacles,forming a low wind energy environment at the edge of the ice sheet,providing favorable conditions for wind and sand deposition.The prosperity of the Arctic ice sheet is likely to have an important impact on local atmospheric circulation and dune patterns.The lack of large-scale sand dune landforms on Mars' largest impact basin indicates that the modern aeolian sedimentary process is not directly related to early water flow.Weak aeolian processes cannot transport sediments over long distances to form large-scale deserts.The dune deposits in the crater mainly come from the local area,and there is little material exchange between the craters.The sand dunes in different craters all have their own independent sedimentary history and formation age.There are huge differences between Mars and the earth's aeolian sand system,which are mainly manifested in the evolution of climatic environment,sources of aeolian sand sediment,erodibility of sediments,and ability of aeolian sand transport.Mars dune does not have significant wet and dry,and there is no difference between active and anchored,but the activity of the dunes is affected by seasonal frost.The richness of Mars sand sources in modern times is very low,due to slow weathering rates,weak sand transport capacity,and limited active time of sand.Ice-related surface processes caused by climate change will affect the formation and evolution of sand dunes.The content of this article can increase people's understanding of the martian landform features.In addition,it enriches the research content of planetary aeolian geomorphology,and it is conducive to the construction and improvement of the subject knowledge system.Discussion of the source of Martian sand will improve our understanding of the formation mechanism and migration mode of loose sediments in the dry and cold environments.Moreover,it provides clues for constructing sedimentary history of different geographic units of Mars.At the same time,field investigations and experimental simulations conducted by the Earth analogy research work will also enrich the research content of earth aeolian geomorphology.