If experiments performed in small bottles in a University of Oregon lab are accurate, the friction of colliding Martian dust particles is unlikely to generate large electrical storms or threaten newly arrived exploration vehicles. or, possibly, human visitors.
For 50 years since Viking landers and subsequent orbiters detected silt, clays, windblown bedforms and dust devils on Mars, scientists have worried about the potential for large lightning storms and the possibility that static electricity generated by basalt rock particles on the planet could damage vehicles or human protective equipment.
In the newspaper Icarus, a UO team reports that the friction caused by dust particles in contact with each other can indeed produce electric shocks on the planet’s surface and atmosphere, but the resulting sparks are likely small.
Such concerns had resurfaced in connection with NASA’s new Mars mission, which successfully put the Perseverance rover and the Ingenuity robotic helicopter on the Red Planet on February 18.
In the laboratory of volcanologist Josef Dufek, researchers used a vertical glass tube comparable in size to a water bottle measuring about 4 inches in diameter and 8 inches in length. Inside, they swirled volcanic ash to replace Martian dust in a series of experiments that allowed them to avoid traps that had hampered previous research.
They determined that the electric shocks would likely be weak, given the weak electric fields, around 20,000 volts per meter, supported by Mars’ atmosphere.
Earth’s atmosphere, by comparison, can withstand electric fields of up to 3 megavolts per meter, producing spectacular lightning storms common and sometimes fatal in the southeastern United States, said Joshua Méndez Harper, research engineer at the United States. Oregon Center for Volcanology of the Department of Earth Sciences. .
“Our experiences, and those of others before us, suggest that on Mars it is easy to get sparks when you stir up sand or dust,” Méndez Harper said. “However, it can be difficult, even in large dust storms or dust devils, to get very large discharges or conventional lightning because the Martian atmosphere is bad for storing charge.”
These rubbing processes are experienced on Earth in a much simpler way – by touching a doorknob after the socks have slipped on a carpet or by sticking a balloon on a window after rubbing it on human hair.
Martian dust demons, Méndez Harper said, can appear to twinkle, crackle, or lightly glow in dark conditions as they roll through the parched landscape of Mars. However, the discharges can be so weak that they can only be detected by using the radio waves they emit at close range.
Previous experiments were inconclusive because the particles were swirled so as to bring them into contact with the walls of the test chambers. Some experiments have used particles of material not found on Mars. Such contacts may have produced a charge not characteristic of a Martian dust storm.
Méndez Harper, Dufek and George McDonald, postdoctoral researcher at Rutgers University, bypassed the wall exposure limitation by using the glass tube. They created a frictional charge by striking particles of basalt ash from the Xitle volcanic eruption in Mexico about 2,000 years ago.
The collisions in the sealed tubes occurred at speeds expected in a light Martian breeze, with particles far away from the outer walls and under a pressurized atmospheric pressure of 8 millibars of carbon dioxide, similar to that of the Martian surface.
The volcanic rock used in the project is similar to Martian basalt, as detected by rovers in the Pathfinder and Mars Exploration Rover missions and dust analogues developed by NASA’s Jet Propulsion Laboratory.
For comparison, the researchers also allowed particles to come in contact with surfaces alien to the conditions predicted on Mars. It created sparks but with a different polarity than the new experiences.
“We were interested in continuing this work because of the number of new missions to Mars and the potential for compelling observations,” said Dufek, OU president Gwen and Charles Lillis and director of the Oregon Center for Volcanology.
“The quantification of charge and discharge behavior affects the transport of dust in the atmosphere and has long been studied in relation to the modulation of chemical reactions, including the synthesis of organic compounds,” he said. declared.
The low discharge energy on Mars, as indicated by the new experiments, means these effects are unlikely to impact mechanical operations, Dufek said.
Nonetheless, Jezero Crater seems to experience regular dust storms in the fall and winter. This, McDonald said, may provide opportunities for rudimentary observations of electrostatic phenomena by the newly deployed rover.
One of the objectives of its mission is to assess past environmental conditions. Evidence of a more substantial atmosphere in the past would affect the electrical environment of the planet and how it changes over time.
“The big advantage of this study is that Mars can be an electrically active place, albeit quite differently from Earth,” Dufek said. “The fact that analog Mars dust easily charges to the point of discharge even when the grains aren’t rubbing against other surfaces suggests that future settlers might find a world altered by static electricity in subtle ways.
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