The Weather of Martian Dust Devils: Dust Devil Variability Across Different Timescales at Gusev Crater, Mars

Mars Exploration Rover - A (MER-A) Spirit landed in Gusev Crater, Mars on January 4, 2004 collecting data through imaging, remote sensing, spectroscopy, soil observations, and more until final communications on March 22, 2010. In order to characterize the current weather, dust devil "movies", compositions of 21 consecutive images at varying time intervals at a single location, were recorded over the three Martian years MER-A Spirit took data in Gusev Crater. Although several researchers have used this data in regards to understanding the role dust devils play in the Martian dust cycle, many issues remain. A complete database of observed dust devils has not been published; derived information from previous observations has omitted some key climatological information such as short-timescale temporal variability. Creating time-resolved Martian dust devil archives will lead to more accurate models. In order to accomplish this, all dust devil movies observed by MER-A Spirit must be tracked and analyzed for dust devil frequency, size, and vertical velocities. This paper analyzes seasonal, diurnal and hourly frequency trends for 41 Martian days between sols 455 and 541. Dust devils were identified, tracked, and outlined using codes in Interactive Data Language (IDL). Over the span of 86 sols, the average number of dust devils shows no sol-to-sol trends. Hourly, the data follows an average peak in dust devil frequency per frame at noon, but reveals small time scale variability. Further, within single movies, this much variability leads to unpredictable quantities per frame after about three minutes. Wide variability of dust devil frequency at different time scales proves dust devils are weather phenomena, therefore climatological graphs of mean dust devil frequencies provide inaccurate dust loading models.