| As a typical wind erosion landform,yardang has always been the focus of researchers.However,compared with yardang on the earth,investigations on Extraterrestrial planets are very little.With the application of remote sensing technology and many similar landforms found on Mars,which has stimulated the interest of people on yardang landforms on Mars.However,the current research of yardang on Mars is relatively weak and few systematic research.Through the analysis of CTX and HiRISE images and morphological parameters,this paper mainly studied yardangs'classification,morphological parameters,distribution,formation reasons.This is of great significance for the future exploration on Mars,the understanding of the Mars environment,the expansion of the geomorphology theory and the enrichment of geomorphology knowledge.The conclusions of the paper are as follows:(1)The types of yardangs on Mars:Yardangs can be roughly divided into seven types.Streamlined yardang:whale-dorsal(teardrop-shaped)and oval-shaped yardangs are collectively called streamlined yardangs.Dome yardang:are dome-shaped.Curvilinear yardang:Ridges are more curved.Bidirectional yardang:Yardangs have two directions.V-shaped yardang:There is a v-shaped depression in front of yardang.Long-Ridge yardang:The ratio of length and width is larger.Bullet-shaped yardang:are bullet-shaped.(2)The external morphological characteristics of yardang landforms on Mars.Although the shape of streamlined yardangs is generally streamlined,there are differences between different regions.Some yardang bodies are oval-shaped and their surface has the signs of crack.Some yardang bodies are teardrop-shaped.Their tops are relatively flat,but the joints are obvious.Some yardang bodies have distinct layer structure.The range of l,w,R is 47?921m,23?385m,1:1?7:1,respectively.The directions of yardang bodies' long axis are different in different regions.The directions are NNW-SSE and N-S in the west of MFF.The directions are NNE-SSW and NE-SW in the middle of MFF.The directions of yardang bodies' long axis have large variation in Valles Marineris.Dome yardangs are roughly dome-shaped.Some yardangs have capping layer on the top and have gravel on the bottom.Some yardangs have distinct layered structure.The range of l,w,R is 62?1668m,40?1139m,1?3:1,respectively.The directions of yardang bodies' long axis are different in different regions.The directions are NW-SE and WNW-ESE in the west of MFF.The directions are NNE-SSW,N-S and NE-SW in the middle of MFF.The ridges of curvilinear yardang are curved.Some curvilinear yardangs' surface are relatively smooth and some are rough.Some curvilinear yardangs are accompanied by Bidirectional yardangs.Bidirectional yardang consist of three parts:front,rear and middle.Bidirectional yardang have two directions and have acute angle of intersection in the front and rear of yardangs.Long-ridge yardangs have different morphology in the different regions and same region.Some yardangs' tops are relatively flat.Some yardangs' tops are relatively cliffy.Some yardangs have good integrity.Some yardangs' morphology is similar to pea pods.Most of the long-ridged yardangs in Valles Marineris are formed on the slope where the layered sediments accumulate.The range of l,w,R is 78?44749m,21-2118m,1:1?61:1,respectively.The directions of yardang bodies' long axis are different in different regions.The directions are NW-SE,N-S,NNW-SSE and NNE-SSW in the west of MFF.The directions are N-S and NNW-SSE in the middle of MFF.The directions are NW-SE,NNW-SSE,NNE-SSW and SW-NE in Valles Marineris.The front of yardangs have v-shaped and u-shaped depression in which there are small bidirectional and streamlined yardangs along the wind.The top of v-shaped yardangs are bumpy and form a number of bidirectional yardangs which are perpendicular to wind.The directions of yardang bodies' long axis are different in the different regions and same region.(3)The distribution of yardangs on Mars:Yardangs on Mars are mainly distributed in low latitudes.They distribute in the plateau,canyons,craters and volcano.To be exact,the distribution of yardangs in the low latitudes is mainly in MFF which lies between the Tharsis and Elysium volcanic centers.The yardangs in the west of MFF distribute in Aeolis Planum,Zephyria Planum and between Aeolis Planum and Zephyria Planum.The yardangs in the centre of MFF distribute in southwest of Apollinaris Patera,north of Apollinaris Mons,south of Lucus Planum,north of Lucus Planum,east of Lucus Planum and centre of Lucus Planum.The yardangs in the west of MFF distribute in Eumenides Dorsum,between Eumenides Dorsum and Nicholson,between Amazonis Planitia and Eumenides Dorsum,Amazonis Mensa,Gordii Dorsum,between Eumenides Dorsum and Gordii Dorsum,south of Olympus Mons.Yardangs also exist in Valles Marineris,which is distributed in Tithonium Chasma,Ophir Chasma,Candor Chasma,MelaChasma,and Ganges Mensa.In addition,yardangs also distribute in Aeolis Mensae,Lycus Sulci.(4)The formation of yardang landforms on Mars:The formation of yardangs is mainly influenced by lithology,dynamics and environmental conditions.Some Yardangs have different degree of induration in vertical profile.Dynamics:wind is the main driving force in shaping yardang landforms on Mars.In addition,weathering,exfoliation,disintegration and collapse also affect the formation of yardang landforms. |
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