Martian ice cloud distribution obtained from SPICAM nadir UV measurements
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The Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument on board Mars Express has successfully performed one Martian year of measurements. Nadir UV (200-310 nm) measurements allowed it to build maps of ice cloud optical depth distribution for all seasons. The development and decay of the aphelion cloud belt (ACB) and polar hoods were observed. The characteristic values of the cloud optical thickness were 0.1-0.3 at the early stage of the ACB formation in the solar longitude range Ls = 20-60°. After Ls = 93°, the well-developed ACB showed cloud optical thicknesses varying between 0.3 and 0.8. The ACB quickly decayed after Ls = 140°. Both polar hoods were observed during their development and decay stages, showing cloud optical thicknesses of about 0.35. The north polar hood started to develop at Ls = 160° and the south one at Ls = 330°. Estimates of water content in the ice clouds gave values of 0.35-1.8 gm-2 for ACB and 0.4 gm-2 for the polar hoods. A comparison with water vapor abundance showed that only a small fraction (10-20% for ACB and 30% for the polar hoods) of total water content in the atmosphere was accumulated in clouds. The Martian surface albedo at the wavelength 300 nm appeared very low (0.004-0.018) and exhibited anticorrelation with the visual albedo consistent with optical properties of iron oxides abundant in Martian soils. The investigation of a regional dust storm allowed the estimation of dust optical parameters at the wavelength 300 nm (asymmetry factor gd = 0.8 and single scattering albedo σd = 0.6).
CitationMateshvili, N.; Fussen, D.; Vanhellemont, F.; Bingen, C.; Dodion, J.; Montmessin, F.; Perrier, S.; Dimarellis, E.; Bertaux, J.-L. (2007). Martian ice cloud distribution obtained from SPICAM nadir UV measurements. , Journal of Geophysical Research E: Planets, Vol. 112, Issue 7, E07004, DOI: 10.1029/2006JE002827.