Drones flying over Mars could cause Saint Elmo’s fire, NASA says
A team of NASA scientists conducted research to investigate how electricity could build up on the rotor blades of drones, causing the Martian air to glow. This phenomenon is known as Saint Elmo’s fire and could help scientists learn more about electric charges.
The accumulation of electric charge known as ‘triboelectric charging’ is a result of friction which transfers the charge between different objects. This can occur, for example, by rubbing your hair against a balloon.
Using laboratory measurements and computer modeling, the scientists found that the spinning drone’s blades would run into tiny grains of dust in the Martian air, which causes an electric field.
“As the blades impact the grains, charge is transferred, building up on the blades and creating an electric field. As charge builds to high levels, the atmosphere starts to conduct electricity, a process known as ‘atmospheric breakdown’, creating a population of electrons that form an enhanced electric current that acts to dissipate or offset the charge build-up on the rotorcraft,” NASA explained.
‘Atmospheric breakdown’ is more likely on Mars than on Earth because the Martian atmosphere is much thinner – the molecules which form it are very widely spaced, so free electrons can accelerate easier. Although the currents generated by a drone are small, they might be large enough to cause the air around the blades and other parts of the craft to “glow a blue-purple color.” This conclusion is just a prediction, NASA says, as “sometimes nature has other plans.”
“The faint glow would be most visible during evening hours when the background sky is darker. 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.” said William Farrell of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the lead author of the research, published in Planetary Science Journal last year.
He added that the electric currents generated by drones would not pose any threat to 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.’”