MEASUREMENT OF MULTIYEAR RIPPLE AND WHOLE-DUNE SAND FLUXES AT ACTIVE DUNES AT NILI PATERA, MARS

Aeolian sand dunes are observed across Mars’s surface. The arrival of the HiRISE camera at Mars in 2007 enabled detection of modern-day movement of dunes and meter-scale ripple features in high-resolution satellite images for the first time. Since 2007, the HiRISE camera has remained in orbit around Mars and collected long timeseries of repeat imagery at various dune fields. We apply this long timeseries of imagery to study the movement and dynamics of dunes and meter-scale ripples at the Nili Patera barchan dune field in equatorial Mars over 5 Mars years.

We present measurements of whole-dune sand flux at Nili Patera extracted via manual tracking of dune crestlines and slipfaces in optical HiRISE imagery. Additionally, we present a multiyear timeseries of ripple flux measurements extracted using automatic correlation of ripple features in optical imagery performed using COSI-Corr algorithms. An ICA (independent component analysis) technique is used to filter out noise signals and maximize the accuracy of ripple-displacement measurements.

Ripple sand fluxes are found to vary seasonally with a maximum in northern-hemisphere autumn and spring on Mars, in agreement with the pattern found by previous work using more limited timeseries. Whole-dune fluxes are measured across the dune field and found to be much larger than ripple-only fluxes. Additionally, we present comparisons of our ripple flux measurements to ripple wavelength, derived from analysis of optical images, at various sites across the dune field.