Characterization and Analysis of Dune Fields on Sputnik Planitia

The New Horizons flyby of Pluto revealed widely varying ice composition and morphology in Sputnik Planitia, including dune features in its northwestern region (Telfer et al. 2018). A high-resolution image sequence with a 76 m/pix scale taken with the Long Range Reconnaissance Imager (LORRI) instrument was used to map over 1200 dunes for analysis and characterization on the surface of convection cells near the Al-Idrisi Montes (AIM). Their proximity to the adjacent mountain range led the primary focus of this investigation. The frequency of dunes decreases with distance from the AIM. This analysis further characterizes the environmental factors that lead to the development of dunes in this location.

Images and topography maps of the convective cells, wind streaks, and AIM provide evidence that the features are transverse and have an aeolian origin. The dunes are primarily concentrated near edges of convective cells where we observed the greatest amount of accumulated N₂-rich sediment. The orientations of dune crests are perpendicular to nearby wind streaks demonstrating correlation between aeolian forces and the features. The average orientation of wind streaks is 297° whereas nearby dune crests average 205° (counter-clockwise from north). Wind and crests are therefore within ~2° of perpendicular. Our findings are consistent with prior results (Telfer et al. 2018) indicating that these features are indeed transverse dunes that form orthogonally to wind direction in areas of accumulated sediment.

Other evidence supporting the interpretation of these features as dunes includes the proximity of valleys that exit the AIM near dune fields. The funneling of air through these trenches can be driven by gravity and pressure gradients accelerating winds to speeds necessary to initiate particle entrainment and subsequent saltation required for dune formation. Diurnal changes of near-surface temperatures are sensitive to N₂ ice sublimation from the surface of Sputnik Planitia (Bertrand et al. 2019) and can impact these gradients. Average orientation of local dune crests (189°) is also perpendicular to the average orientation of the canyons (282°), within ~3° of perpendicular, suggesting correlation between wind direction from valleys and formation of dunes.