| Summary: | 碩士 === 國立中央大學 === 天文研究所 === 96 === Martian rampart craters are a special type of impact crater, which exist on Mars and some planetary satellites in the Solar System. They are located mostly in the mid- and low-latitude regions of the northern hemisphere of Mars. The formation of the plateau-like crater rims has been suggested to be caused by the mixing of the impact ejecta with water vapor during the impact explosion. Their distribution has therefore been used as indicators of potential sites of underground water or subsurface ice. In addition, their shapes and morphologies can provide important information about the erosion and sedimentary processes that occurred during the time when the northern hemisphere of Mars was probably partly covered by water. In this work, 88 craters in Chryse Planitia and 54 other craters located at latitudes between 65°and 80°N are examined using images obtained by instruments on-board various Mars-orbiting spacecraft including HRSC (Mars Express), MOC (Mars Orbiter Camera), THEMIS (Mars Odyssey) and HiRISE (Mars Reconnaissance Orbiter). Topographical data form MOLA (Mars Global Surveyor) and HRSC DTM measurements are used to characterize the physical properties. Here we discover that craters between 10 and 20 km in diameter have a diverse morphology. The relationship between morphology, diameter, and depth show us differences in the local geology. The different structures of different kinds of ramparts can be seen in cross-section. Some high latitude craters have ice caps inside the cavity, but the depth of the ice-rich layer may be very shallow.
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