Observations of near-surface fog at the Phoenix Mars landing site

The Surface Stereo Imager (SSI) on the Phoenix Mars Lander was able to complement the operations of the LIDAR on four occasions during the mission by observing the laser beam while the LIDAR laser was transmitting. These SSI observations permitted measurement of the scatter from atmospheric aerosols below 200 m where the LIDAR emitter and receiver do not overlap fully. The observed laser scattering was used to estimate the ice‐water content (IWC) of near surface fog. Values of IWC up to 1.7 ± 1.0 mg m−3 were observed. Compared to air aloft, fog formation was inhibited near the surface which had accumulated at least 30 ± 24 mg m−2 (0.030 pr‐μm) on sol 113. Microphysical modeling shows that when precipitation is included, up to 0.48 pr‐μm of water may be present on the surface at the time of measurement. Integrated over the entire night, this represents up to 2.5 pr‐μm of water taken up diurnally by the surface, or 6% of the total water column.