Dust and Dust Devil Tracks
Large portions of the martian surface are blanketed with bright reddish-ochre dust. The dust particles are typically less than 40 micrometres in size and are composed of iron oxide minerals. Data from the Thermal Emission Spectrometer (TES) on the Mars Global Surveyor spacecraft has allowed planetary scientists to estimate the amount of dust cover for broad swaths of the planet. In general, the Diacria quadrangle is extremely dusty, particularly in Arcadia Planitia and the region around the flank of Alba Mons and the Olympus Mons aureole in the southeastern portion of the quadrangle. A few large patches of relatively low dust cover occur in Amazonis Planitia and in the northwest corner of the quadrangle.
Many areas on Mars, including the Diacria quadrangle, experience the passage of giant dust devils. When a dust devil goes by it blows away the coating of dust and exposes the underlying dark surface. Dust devils have been seen from the ground and high overhead from orbit. They have even blown the dust off of the solar panels of the two Rovers on Mars, thereby greatly extending their lives. The twin Rovers were designed to last for 3 months, instead they both lasted more than six years, and one is still going. The pattern of the tracks have been shown to change every few months.
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Milankovic Crater central area, as seen by HiRISE. Click on image to see more details: dark dunes, beautiful dust devil tracks, and boulders (small bright dots).
Read more about this topic: Diacria Quadrangle
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