Ripple migration and dune activity on Mars: Evidence for dynamic wind processes

Abstract

[1] In this report we show evidence of widespread ripple migration over the stoss side of dark barchan dunes in Nili Patera on Mars. The measured average migration of ∼1.7 meters in less than 4 terrestrial months clearly indicates that active sand saltation is occurring in the study area. In addition, we document widespread changes in the dune base-ground surface contact and in the slip face structures, showing that not only the ripples, but the whole dunes are actually migrating in the present-day atmospheric setting. These results provide unequivocal evidence of recent aeolian activity and suggest that other dunes and ripples on Mars may also be active.

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.…”

“…Although the bulk of literature is devoted to dune mapping and inference of wind regimes, there has also been a recent shift towards quantitative methods in order to resolve spatial patterns and contemporary processes operating on the dunes (Fenton, 2006;Bishop, 2007;Bourke et al, 2008;Ewing et al, 2010;Silvestro et al, 2010). Thus, many of the same factors that propelled recent advances in research on terrestrial dunes (e.g., image resolution, software, and data availability) have also contributed to advances for other planetary bodies, especially Mars.…”

“…Similarly, shrinking and disappearing dome dunes in north polar region of Mars were interpreted as signs of active saltation by Bourke et al (2008). 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.…”

“…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.…”

Physical abrasion of mafic minerals and basalt grains: Application to martian aeolian deposits

“…The parameters that were used to derive thermal inertia included THEMIS IR band nine brightness temperatures, central dune field latitude and longitude, visible wavelength dust opacity, time of day, and Ls. Latitude and longitude values are used to extract elevation (atmospheric pressure) and albedo values from the Mars Orbiter Laser Altimeter (Smith et al, 2001) and the Thermal Emission Spectrometer data maps, respectively. IR dust opacities were converted to visible wavelength dust opacities for use in the KRC model by scaling the IR opacities by a factor of 2, according to the visible/9--μm extinction opacity ratio (Clancy et al, 1995;Wolff and Clancy, 2003 (Edwards et al, 2011) for each dune field location included in this study.…”