Structure of Carbon Dioxide Crystals (Martian Frost)

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Earth and Mars are the only planets in our solar system having polar ice caps that expand and contract in response to changes in the seasons. On Earth, the polar caps are composed of water-ice (snow crystals). Whereas, on Mars, the extreme low temperatures at the polar cap regions result in the precipitation of carbon dioxide CO2 ice (Martian snow/frost) in addition to water-ice. Viking spacecraft have recorded various spectral data on this CO2 mantle and the transmission spectra for solid CO2 have been measured in the laboratory; however, little is known about the structural features of the crystals. Because previous studies have shown that low temperature SEM could be used to image structural variation of snow crystals and because data on the structure of CO2 crystals are needed to develop scattering and emission models of CO2 ice, we attempted to produce and image CO2 crystals. Low temperature SEM observations indicated that carbon dioxide crystals were relatively stable and could be successfully imaged with this technique. At high magnifications numerous 1 µm crystals were observed. These crystals consisted of polyhedrons; octahedrons were the most common shapes that were found. The results indicate that CO2 crystals can be imaged with a low temperature SEM and suggest that other gases, which precipitate at low temperatures and are of interest to interplanetary studies, may also be imaged using this technique.

Article from Agricultural Research/October 1998 on Martian Ice     get Acrobat pdf reader


carbon dioxide
carbon dioxide (CO2) ice/frost

carbon dioxide
carbon dioxide (CO2) ice/frost


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