Constraints on the Aphelion Cloud Belt Phase Function with Mars Science Laboratory (MSL) and Mars Color Imager (MARCI)

We constrained the phase function of Martian water ice clouds (WICs) in the aphelion cloud belt season using data from both Mars Science Laboratory (MSL), and the Mars Color Imager (MARCI). The modeled ice crystal phase functions which best fit our derived results were aggregates (with p-values ranging from 0.908-0.940 for MARCI, and 0.60 for MSL), closely followed by bullet rosettes and columns, while the least likely were spheres (0.399-0.454 for MARCI and 0.2 for MSL). Additionally, this work probed the opposition surge to examine the Martian atmospheres relationship between ice water content and extinction, and found it to be less than was previously proposed for particles at the Phoenix landing site by a factor of 2, with a large dependence upon particle radius. Half-width-half-maximums of the 180 peak in five MARCI images were analyzed and compared to models for WICs and found to agree better than those for dust.