The surface of Mars consists of a thick layer of oxidised iron dust and rocks of the same color which turns Mars into the ”Red Planet”. The crust, beneath the layer of dust which is fine like talcum powder, has the abundance of volcanic basalt rock. Similar to tornadoes on Earth, the dust from the planet’s surface is frequently disturbed by giant ”dust devils”. So the atmosphere can become dusty also. The Martian soil holds nutrients such as pottassium, sodium, magnesium and chloride. The atmosphere of Mars holds 95% of CO2 and is too thin to easily support life. The entire Martian surface is apparently sterile at present due to process called photocatalytic oxidation, the destruction of any organic molecules by free oxygen radicals.
From our childhood we all are familiar with the magic- a plastic comb, after rubbing through hair, can attract small pieces of paper. Can you believe that the same ”magic” makes the Martian dust storms to glow! The Science behind the above mentioned phenomena are Triboelectric charging. The electrification through frictional and collisional interactions is called triboelctric charging. So the familiarised everyday static electricity is triboelectric.
There is no direct evidence of electric sparkles of dust storms in the low-pressure atmosphere of Mars. Different experiments were conducted by recreating the Red Planet atmosphere in labs to check the presence of glowing dust storms. Artificial dust storms were created inside low-pressure containers by agitating the grains of volcanic rock and resulted in ”sparkles”. Joshua M´endez Harper, a geologist from the University of Oregon pointed out that the insights provided by the laboratory studies summarized above are invaluable. M´endez Harper explained that the particles in the storms were allowed to come in contact with the materials which are not expected to be present on the Martian surface and this can direct to misleading results.
M´endez Harper and his colleagues studied the dust storms with the more accurate design of the artificial Martian atmosphere. Before going through their experiment and result let us discuss why M´endez Harper pointed out the ”misleading results” of previous studies. The collision with the container wall, the vanes of stirrer, or between the different composition particles can also give a significant contribution to the overall electrification by two mechanisms:
- The interaction between two chemically dissimilar materials can produce more intense charging than the interaction between chemically identical materials. So the collision of dust particles with the container walls and the vane of the stirrer can also add electrification to result sparks.
- Many experiments have shown that when two surfaces interact repeatedly, the larger surface acquires a positive charge and the smaller one becomes negatively charged. So, when the interacting surfaces are of particles made up of incomparable in size, the segregation and accumulation of charge will be more efficient. Even if the container wall and the grains have the same chemical composition the container wall may acquire a positive charge compared to that of the agitated small particle. This size-dependent triboelectric charge may have set up an electric field inside the experimental apparatus so that it can even result the breakdown condition of CO2.
”However, because the electrification observe in many previous studies arose from experimental artifacts, the results of those works cannot be applied to understanding charging in natural Martian systems”, M´endez Harper added. M´endez Harper and his colleagues tried a replica of the Martian atmosphere by eliminating the above-mentioned faults. They selected the tiny grains of volcanic basalt which has a resemblance to rock detected in the Red Planet. In order to avoid the interaction of dust with the wall of the container, they maintained a distance between the dust and the wall. Also, CO2 was used as a stirrer. These artificially-made Martian storms allowed the flurries to spark!
The low atmospheric pressure condition in Mars hinders the formation of long lightning filament similar to that happens on Earth. So spark would discharge easily in the Martian atmosphere and make the thick, violent clouds glow purple – ’Corona Glow’!
The origin of interest in characterizing the study of tribocharging is from an hypothesis which explains that, like on Earth, triboelectric charging on Mars may have the ability to modulate a vast range of phenomena. This can include the photochemical destruction and production of species with the indication for the presence of organics and methane.
Reference:
- https://ui.adsabs.harvard.edu/abs/2021Icar..35714268M/abstract
- https://www.space.com/16895-what-is-mars-made-of.html
- https://www.space.com/15175-mars-dust-devil-photo.html
- https://www.jpl.nasa.gov/news/martian-soil
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