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S. M. Metzger, J. R. Carr (Geological Sciences, Univ. NV, Reno), J. R. Johnson (USGS Flagstaff), M. T. Lemmon (LPL, Univ. AZ), T. J. Parker (JPL)
We report the first direct evidence by a surface lander of a dust entrainment mechanism at work on Mars. Wind-blown transport of fine particulates is the dominant geomorphic process on Mars, creating a pronounced haze due to the amount of dust suspended in the lower Martian atmosphere. Because of spectral similarity with this haze, conventional image processing methods do not readily reveal dust devils in IMP images. Alternatively, iterative spectral differencing, wherein a 440 nm (visible blue) image is subtracted from a 670 nm (visible red) image, identifies several dust devil features in images acquired near midday. Preliminary analysis of thermal vortex encounters with Pathfinder's meteorology mast suggests that the unstable atmospheric conditions which spawn dust devils are a daily phenomena that develops between 9 am until at least 4 pm. On average, at least one vortex crossed the MPF lander every 2 days. Pressure structures for several vortices were recorded by the ASI Met mast instruments and are compared favorably to similar attributes of terrestrial dust vortices directly sampled in southern Nevada. Dust devils are tracked through consecutive IMP images to obtain measures of size and velocity. Based on interpretations of their distance from the lander, the dust columns ranged from 15 m to 80 m in width, 46 m to over 350 m in height, and traveled across the landscape at from 0.5 m/s to over 4.5 m/s. MPF and Mars Global Surveyor data are being used to estimate spatial and temporal distributions. Such characteristics are consistent with studies of terrestrial dust devils and this knowledge is used to infer geologic and meteorologic surface conditions on Mars conducive to the generation of wind vortices and the susceptibility of the landscape to erosion.
The author(s) of this abstract have provided an email address for comments about the abstract: metzger@scs.unr.edu