Field analog studies of the distribution of windblown sediments at Amboy Crater, California, with application to Mars

Many shallow craters in the Spirit Mars Exploration Rover site contain asymmetric distributions of windblown sediments, which could indicate the predominant local wind direction at the time of their deposition or redistribution. Terrestrial analog field work at the Amboy lava field, Mojave Desert, California, included real-time wind measurements and assessments of active sediment deposition in four small (<100 m) craters. Preliminary results indicate that reverse flow or stagnant wind flow likely occurs in craters with depth-to-diameter (d/D) ratios of ≥0.05. Measurements taken within a crater of d/D of ∼0.02 do not indicate reverse flow; therefore, reverse flow is expected to cease within a d/D ranging from 0.02 to 0.05, resulting in wind movement directly over the crater floor in the downwind direction. Craters with asymmetric eolian deposits near the Mars Spirit landing site have d/D from 0.034 to 0.076, suggesting that reverse flow occurs in these craters. Thus, the position of windblown sediments in the small craters on the northwest part of the floor would indicate prevailing winds from the northwest to the southeast at the time of deposition or redistribution.