NASA says rotor blades might start to glow in Mars' dry atmosphere
Whirring rotors of helicopters or drones may cause tiny electric currents in the extremely dry Mars atmosphere, and if said currents are large enough, it can make the air around the aerial craft glow, a NASA release announced.
The same process also occurs naturally on Earth, sometimes seen on aircraft or ships in electric storms, known as Saint Elmo’s Fire. The phenomenon, named after the Christian patron saint of sailors, happens when the electrical field around a pointed object is charged to a critical point, and ionizes the surrounding air — turning it into plasma.
"The electric currents generated by the fast-rotating blades on drones are too small to be a threat to the craft or the Martian environment, but they offer an opportunity to do some additional science to improve our understanding of an accumulation of electric charge called ‘triboelectric charging," explains William Farrell of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of a paper on the research.
Triboelectric charging happens when friction transfers electric charge between objects, like when a person rubs a balloon against their hair or sweater. The electrified balloon will attract the person’s hair causing it to lift toward the balloon– which indicates that the balloon has developed a large electric field from the triboelectric charging process.
The faint glow would be most visible during evening hours when the background sky is darker,” said Farrel, and added, "NASA’s experimental Ingenuity helicopter does not fly during this time, but future drones could be cleared for evening flight and look for this glow."
The research team used computer modeling and applied laboratory measurements to study how electric charge might build up on rotor blades. As charge build-up happens especially in dusty environments, the team also used interpretations and modeling of helicopters on Earth.
The study suggests that, as the rotor spins, especially when the craft is at low altitudes, it runs into tiny grains of dust in the air and they transfer the charge to dust grains, thus building up electricity and creating an electric field surrounding the blades, a process known as "atmospheric breakdown".
The team found that breakdown begins as an invisible “electron avalanche”. The atmosphere of Mars is extremely thin and the atmospheric pressure on the red planet is a tenth of Earth’s, which makes the breakdown more likely.
This means that if we fly drones that are large enough to start an electron avalanche, the craft would possibly glow in blue-purple color.
So if the day comes, raves at Mars would be rad under those glowing drones.