| Mars is the most similar planet to earth in the solar system,which is a crucial target of China's deep space exploration.China's first Mars exploration mission(Tianwen-1),launched on July 23,2020 with the goal of "orbiting,landing,and roving" and its tentative landing areas are Chryse Planitia(Tentative landing area 1)and the southern Utopia Planitia(Tentative landing area 2).Dust storm is a typical activity on Mars,which is formed by the intense atmospheric movement of the dust on the Martian surface.It occurs in all seasons,which is one of the essential atmospheric activities on Mars,and poses many threats to the exploration mission.The ability to analyze the temporal and spatial distribution of Mars dust storm is one of the critical technologies that need to be studied in advance.This technology is related to the success of the landing mission and affects the landing accuracy,as well as the regular operation of the probe.Based on the repeatability,seasonality,and regularity of Martian atmospheric activities,we made the following research:(1)Based on Mars Orbiter Camera(MOC)and Mars Color Imager(MARCI)Daily Global Maps(MDGMs)from Mars Years 24-32,we identified 882 dust storms within the 2000 km radius monitor circle of the Southern Utopia Planitia(17° N,107° E).Then we extracted the shape,area and location parameters of these dust storm objects;(2)The temporal probability of dust storm activity in the 2000km radius circle was calculated to be 0-14.13%based on dust storm occurrence frequency,a weighted average of coverage area percentage,and recurrence probability.The dust storms temporal probability in the northern spring and summer is much lower than that in autumn and winter.There are two active period of dust storm activity(Ls=176-225° and Ls=302-355°)in the 2000 km radius circle;(3)The 2000 km radius circle is divided into 0.5°×0.5° regular grid,and the temporal probability of dust storm activity is calculated which ranged from 0 to 11.87%.It is found that the spatial probability distribution of dust storm is affected by terrain,dust storm origin area and moving path;(4)Comparing the dust storm activity probability in Tentative landing area 1 and 2 of Tianwen-1,the temporal and spatial security of dust storm activity is evaluated,and the safe landing period is selected as Ls=20-41°;(5)A total of 4661 dust storms with area>105 km2 between 60° S-60° N were identified.The temporal and spatial distribution of dust storms in the non-polar region of Mars was studied.It was found that there are two active periods of dust storm activity in Mars non-polar region(Ls=150-240° and Ls=300-360°).The number of dust storms increases with latitude,and the dust storms are most concentrated near the two poles.During the whole Martian year,there are two active periods of dust storms in the nonpolar region:Ls=1 50-240° and Ls=300-360°.The minimum dust storm temporal probability occurs during Ls=93-116°. |
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