Dust on Mars – Københavns Universitet

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Dust on Mars

The surface of Mars is covered in a thin layer of reddish dust, and the atmosphere also contains a significant amount of dust. Both the dust on the surface and in the atmosphere is magnetic in the sense that it sticks to permanent magnets. The magnetic properties are due to the content of magnetite, or possibly titanomagnetite, in the dust.

Magnetization of the dust

On average the dust can be shown to have a saturation magnetization of less than 2 Am2/kg, however some grains are significantly more magnetic, and sub-populations have been seen to have magnetizations of more than 7.2 Am2/kg.

Shape and size of the dust particles

The average radius of the airborne dust particles has been estimated to be 1.0 ± 0.3 μm. This result comes from the Imager for Mars Pathfinder (IMP) camera, which observed the distribution of brightness in the Martian sky at wavelengths from 444 to 965 nm at various times of day and at various locations relative to the Sun throughout its roughly three months of operation on the surface of Mars. From these observations the size of the dust particles can be estimated. The shape of the atmospheric particles is unknown.

Dust storms

Dust storms and dust devils are the main parameters in the transport and mixing of dust on Mars. Dust storms can be local, but global dust storms covering the entire planet are not uncommon. The figure shows Mars before and after the onset of a global dust storm. Dust absorbs sunlight, and atmospheric dust can therefore heat the dry, thin atmosphere of Mars, and this heat fuels the winds.

Since Mars is a global desert, the storms can reign unstopped over the entire planet. Dust particles of sizes around 1μm can be lifted approximately 10-20 km vertically by a dust storm. It takes several days for such a particle to fall one kilometer, which means that the dust lingers in the atmosphere for several months after a storm. The dust on Mars is believed to be globally mixed because of the storms.