| On May 15,2021,China’s first Mars exploration mission Tianwen-1,successfully landed in the south of Utopia Planitia.The research area of this thesis includes the Tianwen-1 landing area and its surrounding area,using the optical camera,thermal infrared and digital elevation data on the Mars satellite,and the VOC2012 and MP2022 datasets trained by neural network:(1)Based on the efficient sub-pixel convolutional neural network,the super-resolution reconstruction model for Mars image is trained,and the super-resolution image is reconstructed from the Mars CTX image,which significantly improves the feature details of the landform objects in the study area,and analyzes the fluctuation of the evaluation factors in the superresolution process.(2)Ten typical geomorphic features in the study area,including 9666 landform objects,were identified and extracted based on super-resolution images,and their morphological parameters and spatial location information were obtained.(3)On the basis of the characteristics and spatial distribution of geomorphic features,6 geomorphic units(i.e.,Isidis unit,volcanic units 1 and 2,transitional unit,Vastitas Borealis Formation unit and sedimentary unit)were divided in the study area and the geomorphologic map of the study area was drawn.(4)The crater sample area is selected in each geomorphic unit,and the absolute model age of the geomorphic unit is calculated by the crater size-frequency distribution method(CSFD).(5)On the grounds of the geomorphic units’ ages,the possible causes of typical geomorphic features and the geological background of Utopian Planitia,the formation mechanism of Polygonal Trough and Thumbprint Terrain are analyzed.In addition,the possible water/ice environment and geological evolution process in the study area are discussed.The main conclusions of this thesis include:(1)The polygonal troughs in the study area may be related to large-scale water/ice activities.Polygonal troughs are concentrated in the northeastern part of the study area and the central area of the Utopian Planitia,and their formation may be the result of compaction of large water bodies or flood sediments.(2)The formation of thumbprint terrain has a variety of hypotheses(such as mud volcanoes,glacial mounds,moraine,etc.).After analyzing the morphology and spatial distribution characteristics of thumbprint terrain,this thesis is more inclined to the moraine hypothesis to explain its unique concentric circle/parallel spatial arrangement.(3)The formation of polygon troughs and thumbprint terrain requires the participation of water or ice,revealing that the study area may have a water/ice environment in the early stage.(4)The dating results show that the geological age of the study area ranges from～3.20 Ga(Late Hesperian)to～1.13 Ga(early Amazonian).(5)Through the analysis of the dating results,this study found that the coverage of the Vastitas Borealis materials may be between～3.17 Ga and～2.68 Ga;during the period from～2.68 Ga to～1.68 Ga,the Vastitas Borealis material experienced a long-term surface remodeling event,forming a granular upwardly refined stratigraphic sequence at a depth of 10 m to 80 m underground;from the formation of VB unit to～1.96 Ga,the formation pressure of the Vastitas Borealis Formation may gradually increase,and the surface pressure reaches the threshold at～1.96 Ga to produce polygonal troughs. |
PDF Full Text Request