Perseverance has finally answered an age-old question: do lightning strikes on Mars make any sound?
In recordings obtained by the rover, scientists identified electrical discharges for the first time, captured during turbulent dust events on Mars, particularly during dust devils. And not just once — 55 times over two Martian years of observation.
Those dusty conditions help generate electricity in Mars’ thin, bone-dry atmosphere. Scientists had long theorized this, but it hadn’t been demonstrated until now, according to Science Alert.
Typically, lightning happens when turbulent conditions cause particles to collide and rub against each other, creating a charge. Eventually that charge builds up until it needs to discharge, producing a lightning strike.
Lightning on Earth is common and is closely associated with clouds of water vapor, but humidity isn’t strictly required. For example, lightning can occur in massive ash clouds from volcanic eruptions. Even sandstorms, whose dry silicate particles are more insulating than conductive, can generate enough charge to spark electrical discharges.
Researchers have suggested that the same mechanisms could operate on Mars, even though its atmosphere is mostly carbon dioxide and much thinner and drier than Earth’s.
Previously, lightning had been recorded on Jupiter and Saturn and possibly detected on Neptune and Uranus. All of these planets, like Mars, are fundamentally different from Earth.
By analyzing lightning data from other planets, scientists hypothesized that electrical discharges on Mars would most likely occur near the surface, where atmospheric pressure is highest. Fortunately, the Perseverance rover is equipped with a device capable of detecting signs of lightning.
What else have scientists learned?
A team led by planetary scientist Baptiste Chide from the University of Toulouse (France) analyzed data collected by the Perseverance rover’s SuperCam device. This instrument records audio and electromagnetic interference.
The team examined 28 hours of recordings, searching for signs of electrical discharges among the swirling dust on the planet. Ultimately, they identified 55 events, seven of which captured the distinctive signature of an electrical discharge.
At first, the device recorded a sudden electronic spike caused by electromagnetic interference when an electrical discharge affected the microphone wiring. This spike was followed by a ringing, or relaxation, that lasted about 8 milliseconds.
The seven events fully recorded by Perseverance ended with an acoustic signature — a tiny rumble of thunder produced when the electrical discharge heated and expanded the surrounding air.
To confirm that the recordings were indeed from miniature lightning discharges, researchers used a copy of SuperCam on Earth and recorded electrical discharges that replicated the profile of the Martian signals.
A high concentration of dust in the atmosphere alone was not sufficient to generate electricity.
The vast majority of events — 54 out of 55 — occurred during the 30 percent of the strongest winds recorded by Perseverance during the study period. Most of those events were associated with dust storm fronts.
Meanwhile, during two encounters with dust devils, 16 electrical discharges were recorded.
Based on six of the seven recorded thunder strikes, most discharges were tiny, ranging from 0.1 to 150 nanojoules. The seventh acoustic signal was the most powerful, with an energy of 40 millijoules. For comparison, on Earth the average energy of a lightning discharge between a cloud and the ground is about a billion joules. So Martian lightning is dramatically different from terrestrial lightning — but it exists.
Now planetary scientists can model chemical reactions in Mars’ atmosphere more accurately, taking into account the effects driven by electrical discharges.
Photo: Unsplash
