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Correlations of atmospheric water ice and dust in the Martian Polar regions

We report on the interannual variability of the atmospheric ice/dust cycle in the Martian polar regions for Mars Years 28-30. We used CRISM emission phase function measurements to derive atmospheric dust optical depths and data from the MARCI instrument to derive atmospheric water ice optical depths. We have used autocorrelation and cross correlation functions in order to quantify the degree to which dust and ice are correlated throughout both polar regions during Mars Years 28-29. We find that in the south polar region, dust has the tendency to "self clear", demonstrated by negative autocorrelation around the central peak. This does not occur in the north polar region. In the south polar region, dust and ice are temporally and spatially anti correlated. In the north polar region, this relationship is reversed, however temporal correlation of northern dust and ice clouds is weak - 6 times weaker than the anticorrelation in the south polar region. Our latitudinal autocorrelation functions allow us to put average spatial sizes of event cores and halos. Dust events in the south are largest, affecting almost the entire pole, whereas dust storms are smaller in the north. Ice clouds in north are similar in latitudinal extent to those in the south (both have halos < 10°). Using cross-correlation functions of water ice and dust, we find that dust events temporally lag ice events by 35-80 degrees of solar longitude in the north and south poles, which is likely due to seasonality of dust and ice events.