Four Mars Years of ACB Phase Function Observations from the Mars Science Laboratory Show Low Interannual and Diurnal Variability and Suggest Irregular Water–ice Crystal Geometry

We extend previous work examining the water–ice cloud phase function to four years (Mars years 34-37) using observations taken during the Aphelion Cloud Belt season by the Mars Science Laboratory. From these phase functions, we continue to see little interannual or diurnal variability in Mars years 35-37, but potential diurnal variability in p=MY 34, which is not well understood. We use our derived phase functions to comment upon possible ice-crystal geometry by fitting a two-term Henyey–Greenstein function and comparing our results with those of modeled water–ice crystals and dust. These results suggest that cloud particles on Mars could have irregular geometry. • Water–ice cloud phase function is examined through four Mars years at Gale crater. • Little interannual or diurnal variability is present. • Water–ice cloud particles at Gale crater could have irregular geometry.