Seasonal Erosion and Restoration of Mars’ Northern Polar Dunes

Abstract

Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars' CO(2) seasonal polar caps. Numerous dunes in Mars' north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter. Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars' current climate.

Remote sensing and spatial analysis of aeolian sand dunes: A review and outlook

“…Thus, signs of contemporary dune mobility on Martian dunes are required to validate their use as indicators of present-day wind direction, but only if the activity is consistent with the morphological interpretation of wind direction. Indeed, many signs of isolated present-day aeolian transport are apparent on Mars (Bridges et al, 2007;Sullivan et al, 2008;Reiss et al, 2010;Silvestro et al, 2010;Hansen et al, 2011). However, evidence of widespread, present-day dune activity and migration is thus far limited.…”

“…Silvestro et al (2010) showed evidence of ripple migration on the surface of dunes in the Nili Patera and inferred dune migration from changes in the dune base-ground surface contact and in the development of streaks representing grainflows on the slipface. More recently, Hansen et al (2011) showed that the morphology of northern polar dunes on Mars is modified by seasonal sublimation of CO 2 and aeolian sediment transport. Collectively, the evidence suggests aeolian saltation is occurring; however, there remains some uncertainty as to whether the dunes are actively modified by aeolian erosion and deposition, or if the observed changes are simply an effect of sediment bypassing over indurated (crusted) dunes (cf.…”

“…However, recent advances in the spatial resolution of image data from Mars, mainly from the High Resolution Imaging Science Experiment (HiRISE), have prompted several important contributions inferring both past and contemporary processes. Several studies have recently applied HiRISE images to document contemporary activity of gullies on dune lee slopes (Diniega et al, 2010;Gardin et al, 2010;Reiss et al, 2010;Hansen et al, 2011). These features are indicative of secondary processes responsible for denuding dune lee slopes and, in some locations, are argued to be evidence for recent liquid water flow on the surface of Mars.…”

“…Progress in quantifying dune field dynamics in three-dimensions has also enabled improved understanding of dune form evolution and morphodynamic feedbacks (Vermeesch and Drake, 2008;Reitz et al, 2010). Moreover, contemporary processes operating on the lee slopes of dunes on Mars have been revealed using free imagery from the High Resolution Imaging Science Experiment (HiRISE) (e.g., Reiss et al, 2010;Silvestro et al, 2010;Hansen et al, 2011). In all four examples the improved spectral or spatial resolution provided new insight that would be difficult, if not impossible, to obtain with any other method.…”

“…Similarly, free images and digital terrain models are available for Mars (Table 1, Fig. 2), thus accelerating research and discoveries about contemporary dune dynamics that would not be otherwise possible (e.g., Hansen et al, 2011). Areas that are relatively inaccessible can now be investigated remotely, beginning with a few clicks of a mouse button, an Internet connection, and applicable software.…”