NASA's Perseverance rover has recorded signs that Mars' atmosphere may be far more dynamic than previously understood, capturing what scientists describe as small electrical discharges linked to the planet's swirling dust devils.
Researchers announced that the rover, which has been surveying Jezero Crater in Mars' northern hemisphere since 2021, detected the signals through audio and electromagnetic data collected by its SuperCam instrument. The findings include brief bursts of electrical activity — likened by one scientist to "miniature lightning" — produced as dust-filled whirlwinds move across the Martian landscape.
The discovery marks the first time electrical discharges have been documented in Mars' thin atmosphere. Scientists said the new evidence opens up fresh questions about how dust storms develop on the Red Planet and how these atmospheric processes might affect future robotic and human missions.
Planetary scientist Baptiste Chide of the Institute for Research in Astrophysics and Planetology in France, lead author of the study published on Wednesday, November 26, in the journal Nature, said, "These discharges represent a major discovery, with direct implications for Martian atmospheric chemistry, climate, habitability and the future of robotic and human exploration."
"The electrical charges required for these discharges are likely to influence dust transport on Mars, a process fundamental to the planet's climate and one that remains poorly understood. What's more, these electrostatic discharges could pose a risk to the electronic equipment of current robotic missions - and even a hazard for astronauts who one day will explore the Red Planet," Chide added.
A total of 55 electrical discharges—typically connected to dust devils and dust storm fronts—were found when the researchers examined 28 hours of microphone recordings that the rover had made over the course of two Martian years.
"We did not detect lightning by the common definition. It was a small spark, perhaps a few millimeters long, not really lightning. It sounded like a spark or whip-crack," said planetary scientist and study co-author Ralph Lorenz of the Johns Hopkins University Applied Physics Laboratory in Maryland.
During Perseverance's two near-misses with dust devils, sixteen electrical discharges were captured.
Dust devils are a common feature on dry and dusty Mars, according to another study published in October. Two spacecraft in orbit were able to detect wind speeds of up to 98 miles per hour (158 kph) in these whirlwinds that lift dust into the atmosphere.
The electrical discharges are caused by the internal dynamics of dust devils.
"I would call it 'mini-lightning,'" Chide said, adding, "The phenomena are caused by the friction of tiny dust grains rubbing against each other in the air, which builds up electrons and then releases their charge as electrical arcs just a few centimeters long, accompanied by audible shockwaves."
The phenomenon is known as triboelectricity.
"Think of a sunny, dry day when you walk on a rug or a rubber surface and bring your hand close to a door handle. The small spark you might generate, and thus experience, is the same kind of electrostatic discharge that we detected with SuperCam on Perseverance," said planetary scientist and study co-author Franck Montmessin of the French research agency CNRS and research laboratory LATMOS.
It had long been suspected that there was electrical activity in the Martian atmosphere.
"What we've observed is a result of having exceptionally sensitive instrumentation observing for a long period, so we can detect very small discharges, about the energy of an automobile ignition," Lorenz noted.
Mars is one of the planets with known atmospheric electrical activity, along with Earth, Saturn, and Jupiter. According to the researchers, other worlds in our solar system, such as the planets Venus and Uranus and Saturn's moon Titan, may also have this feature, though it hasn't been recorded yet.
"The Mars atmosphere was looking very favorable for electrification: full of dust, dry and turbulent," Chide said. "On terrestrial deserts on Earth, the electrification of dust and sand is well-documented, but it rarely results in actual electrical discharges. On Mars, however, the thin carbon dioxide atmosphere makes this phenomenon far more likely, as the amount of charge required to generate sparks is much lower than it is on Earth."
Shortly after Perseverance's landing in 2021, SuperCam had captured the first Martian sounds.
"Since then, it has been used daily to listen to the atmosphere, compiling a playlist of over 30 hours of sounds from the Red Planet: the howl of the wind, the whir of the (rover-deployed) helicopter Ingenuity's blades, and now, a new track: electrostatic discharges," Chide concluded.
