The solitary rover Perseverance, working among the sands of , has finally answered an age-old question: if there are lightning strikes on the Red Planet, do they actually make sounds?
In recordings obtained by the rover, scientists have identified electrical discharges for the first time, captured during turbulent dust events on the , particularly during dust devils. And not just once, but 55 times over two Martian years of observation.
The dusty conditions in which these events occurred are essential for generating electricity in Mars’ thin, completely dry atmosphere. This had long been theorized but had never been demonstrated until now, according to Science Alert.
Typically, lightning occurs when turbulent conditions in the atmosphere collide particles, causing them to rub against each other and create a charge. Eventually, the charge builds up to the point where it needs to discharge, resulting in a lightning strike.
Lightning on Earth is a common phenomenon. It is closely associated with clouds of water vapor, but humidity is not a strict requirement. For instance, lightning discharges can occur in massive ash clouds ejected by volcanoes. Even sandstorms, whose dry silicate particles act as insulators rather than conductors, can generate enough charge to cause electrical discharges.
Researchers from suggested that such mechanisms could also operate on Mars, despite its atmosphere being primarily composed of carbon dioxide and being significantly thinner and drier than Earth’s.
Previously, lightning had been recorded on Jupiter and Saturn, and possibly detected on Neptune and Uranus. All these planets, like Mars, are fundamentally different from Earth.
By analyzing lightning data from other planets, scientists hypothesized that electrical discharges on Mars 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 of scientists 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 sound data and electromagnetic interference.
The scientists 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.
Initially, the device recorded a sudden electronic spike caused by electromagnetic interference when the electrical discharge tangled in the microphone wires. This spike was followed by a relaxation, or ringing, lasting about 8 milliseconds.
The seven events fully recorded by Perseverance concluded with an acoustic signature of a tiny rumble of thunder created by the electrical discharge heating and expanding the surrounding air.
To confirm that the recordings were indeed from miniature lightning discharges, researchers used a copy of SuperCam on Earth. They recorded electrical discharges that replicated the profile of the Martian recordings.
Interestingly, 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 on the Red Planet during the study period. Most of these 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 turned out to be 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 one billion joules. Thus, lightning on Mars is vastly different from that on Earth, but it still exists.
Now, planetary scientists can model chemical reactions in Mars’ atmosphere more accurately, driven by electrical discharges.
Photo: Unsplash
