| Mars is the most similar planet to Earth in the solar system,but its terrain,geology,climate,and other features differ significantly from Earth.The exploration and study of Mars are of great significance for humans to understand planetary formation,evolution,and the conditions for the existence of life.On May 15th,2021,the Tianwen-1 successfully landed on the Utopia Planitia in the southern part of Mars,and its rover,Zhurong,left the landing platform and began to explore the Martian surface seven days later.Martian dust devils are whirlwind-like air currents formed by sand or dust on the Martian surface under the action of wind,which can help clean the solar panels of the Mars rover and extend its scientific exploration life cycle.Small impact craters are the main surface features on all terrains of Mars.In addition,since there is no plate tectonics on the Martian surface,impacts are one of the main driving forces for the morphological evolution of Mars.Therefore,the shape and features of craters on Mars can reflect the process of the Martian surface operation,providing information for our understanding of the geological conditions,climate background,and structural evolution of the Martian surface.This thesis is based on the scientific research and application of China’s Mars mission Tianwen-1.Utilizing the remote sensing data from the High-Resolution Imaging Science Experiment and the Context Camera carried by Mars Reconnaissance Orbiter,the study focuses on the Tianwen-1 landing area and its surrounding areas.Starting from the morphology and statistical characteristics of Martian dust devils and small craters,the study focuses on issues such as the formation rate of dust devil tracks and the degradation law of craters.First,248 newly formed dust devil tracks were identified and digitized from 12 pairs of images around the Tianwen-1 landing area,and their features were analyzed,including width,length,and movement speed.In addition,the formation rate of newly formed dust devil tracks was calculated and analyzed,and it was found to be mainly affected by seasonal factors.Finally,the cleaning period of the solar panels of the Mars rover by dust devils was estimated,with a maximum value of around 980 Martian days and the minimum value of around 167000 Martian days among all image pairs.Due to the limited number of image pairs available and the poor detection efficiency of small-sized dust devil tracks in remote sensing images,this cleaning period is greatly underestimated and can only be regarded as an upper limit.Secondly,this thesis identified craters with diameters larger than 19 meters within an approximately 134 square kilometer area surrounding the Zhurong rover’s exploration zone and classified them into seven degradation classes using five morphological descriptors.The depth,rim height,and floor variability coefficient in the elevation of the craters were extracted using a semi-automatic process.Additionally,size-frequency distribution of each crater class was established to obtain their model ages,and the degradation and surface erosion rate of the craters were calculated based on the model ages.Finally,a temporal feature line of crater degradation was established using changes in crater depth and rim height as indicators.As time passes,the degradation process of craters is nonlinear.In the early stages of degradation,the degradation rate of newly formed craters in the study area can be as high as 0.2 m/Myr.The surface erosion rate in the study area is approximately 10-2 to 10-3 m/Myr,indicating that surface erosion on Mars has been primarily caused by wind erosion in arid environments since the Middle Amazonian period.Studying the morphology of Mars’ dust devils and small craters provides clues for understanding the near-surface stratigraphy,climate evolution,and degradation history of the Zhurong rover’s surroundings and broader areas,which is important for exploring Mars and studying its climate change,planetary formation history,and environment. |
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