The Aeolian Environment in Glen Torridon, Gale Crater, Mars

Abstract

The Mars Science Laboratory (MSL) rover spent a full martian year exploring the phyllosilicate‐bearing Glen Torridon trough on the flank of Aeolis Mons in Gale crater, enabling in‐depth assessment of aeolian processes. MSL encountered erosional and depositional features recording a long aeolian history. The trough has served as a long‐term conduit for sand transport, probably involving many cycles of sand accumulation and deflation. Rock abrasion textures indicate sand‐driving winds blowing W‐SW (opposite of abrasion textures on the Greenheugh Pediment above the trough floor). Indurated megaripple surfaces with 2–5 mm grains contrast with seasonally active ripples having finer maximum grain sizes, indicating more vigorous saltation in the past. Active ripples display a broad continuum of wavelengths, as well as coarser grains at crests than troughs, consistent with origins as impact ripples. Orientations of a wind streak extending from a large ripple field, and sandy wind tails behind obstacles, indicate sand is driven W‐SW in the current era, approximately along the trough axis. Erosion of drill tailings piles was strongly seasonal, enhanced during late spring and early summer (perihelion). Climate modeling suggests W‐SW sand transport can be attributed to seasonal enhancement of nighttime regional winds entering Gale crater from the N, combined with local katabatic winds flowing down the slopes of Aeolis Mons. However, it is unclear whether sand transport at Glen Torridon is primarily from these wind components combining and acting simultaneously, or occurring in serial at different times of night; field evidence supports both possibilities.

The Physical Properties and Geochemistry of Grains on Aeolian Bedforms at Gale Crater, Mars

“…These grains are more reddish on average than coarser grains due to greater abundances of ferric components (Johnson et al, 2017(Johnson et al, , 2018. Wheel scuffs and trenches into active aeolian deposits show that even where coarser grains are present on the surface (e.g., at crests of active large ripples), the underlying materials are still dominated by reddish <150 μm grains (e.g., Figure 9 of Sullivan et al (2022)). Wheel tracks and trenches into inactive bedforms, such as the Culbin Sands 2 megaripple, similarly reveal <150 μm grains dominating subsurface materials.…”

“…The long axis of each measured particle was chosen as proxy for grain size. This choice allows direct comparisons with some previous work (Banham et al., 2018; C. M. Weitz et al., 2018; Cousin et al., 2017; Ehlmann et al., 2017; Jerolmack et al., 2006), but results in small systematic differences with other work that includes or emphasizes measurements of different grain dimensions and/or utilizes different measurement techniques (e.g., Cabrol et al., 2014; Gough et al., 2021; Minitti et al., 2013; Sullivan & Kok, 2017, Sullivan et al., 2020, 2022). As pointed out by Gough et al.…”

“…(2022), Sullivan et al. (2022) interpreted Culbin Sands 2 as an ordinary megaripple from its morphologic characteristics and surface covered with very coarse, creep‐only grains (Figure 10b) and consequently we adopt the megaripple term here as well. The TAR‐like megaripple bedforms are oriented NW‐SE in HiRISE images with an inferred wind direction from the northeast, similar to other bright bedforms observed from orbit in the GT region (Figure 10c).…”

Active Ground Patterns Near Mars' Equator in the Glen Torridon Region of Gale Crater

“…They also differ clearly from rover tracks and from characteristic eolian sand ripples and dunes, which are discussed by Sullivan et al. (2022).…”

“…The collective motion of these splashed grains (the “reptation flux”) results in overall ripple migration. For example, the observed ripple crest migration over 45 sols during the windy season at the Mary Anning drill site (sols 2859–2904) implies a reptation flux, per unit distance transverse to the transport direction, of ∼2 × 10 −6 m 2 sol −1 (Sullivan et al., 2022), which is lower than the flux estimates at the Bagnold Dunes visited earlier in Curiosity's traverse (Baker, Lapotre, et al., 2018). Approximating the cross‐section of the axial trench at Upper Ollach as a triangle, 30 mm wide and 5 mm deep, based on the elevation profile (Figure 8), its cross‐sectional area is ∼10 −4 m 2 .…”