Spectral reflectance of CO2-H2O Frosts

The spectral reflectance of CO2 and H2O frosts grown individually, simultaneously, and sequentially have been measured from 0.8 to 3.2 μ. Contamination and metamorphism were minimized by growing the frosts from high-purity gases in a cold vacuum chamber. CO2 frosts have generally high reflectance except for strong absorptions corresponding to those in the gas phase and several new absorptions unique to the solid. In contrast, H2O frosts have overlapping broad absorption bands shifted longward from the gas absorption wavelengths. Small fractional additions of H2O have pronounced effects on CO2 frost spectra, but the reverse is not true. The apparent composition of mixed frosts depends on textural scale. A few milligrams per square centimeter of H2O frost will mask an underlying thick CO2 deposit.