Visible albedo of Marsʹ south polar cap: 2003 HST observations

The martian south polar cap was observed with the High Resolution Camera on Hubble Space Telescope near the very favorable 2003 opposition. Well calibrated images taken at a number of wavelengths in visible and UV were used to measure the apparent Lambert albedos of two bright polar areas. These were corrected for the effects of atmospheric dust to obtain wavelength-dependent surface albedos, which are diagnostic for the purity and grain size of the CO2 deposits. The bolometric albedo estimated from these data may be sufficiently large to be consistent with stability of the perennial CO2 in the residual cap.