Scientists have detected what they believe to be lightning on Mars by eavesdropping on the whirling wind recorded by NASA's Perseverance rover. The crackling of electrical discharges was captured by a microphone on the rover, a French-led team reported Wednesday. The researchers documented 55 instances of what they call "mini lightning" over two Martian years, the AP reports. Almost all occurred on the windiest Martian sols, or days, primarily during dust storms and dust devils. Just inches in size, the electrical arcs occurred within 6 feet of the microphone perched atop the rover's tall mast, part of a system for examining Martian rocks via camera and lasers.
Sparks from the electrical discharges—akin to static electricity here on Earth—are clearly audible amid the noisy wind gusts and dust particles smacking the microphone. Scientists have been looking for electrical activity and lightning on Mars for half a century, said the study's lead author Baptiste Chide, of the Institute for Research in Astrophysics and Planetology in Toulouse. "It opens a completely new field of investigation for Mars science," Chide said, citing the possible chemical effects from electrical discharges. "It's like finding a missing piece of the puzzle."
- The evidence is strong and persuasive, but it's based on a single instrument that was meant to record the rover zapping rocks with lasers, not lightning blasts, said Cardiff University's Daniel Mitchard, who was not involved in the study. What's more, he noted in an article accompanying the study in the journal Nature, the electrical discharges were heard—not seen. "It really is a chance discovery to hear something else going on nearby, and everything points to this being Martian lightning," Mitchard tells the AP. But until new instruments are sent to verify the findings, "I think there will still be a debate from some scientists as to whether this really was lightning."
Lightning has already been confirmed on Jupiter and Saturn, and Mars has long been suspected of having it too. To find it, Chide and his team analyzed 28 hours of Perseverance recordings, documenting episodes of "mini lightning" based on acoustic and electric signals. Electrical discharges generated by the fast-moving dust devils lasted just a few seconds, while those spawned by dust storms lingered as long as 30 minutes. "It's like a thunderstorm on Earth, but barely visible with a naked eye and with plenty of faint zaps," Chide said in an email. He noted that the thin, carbon dioxide-rich Martian atmosphere absorbs much of the sound, making some of the zaps barely perceptible.
Mars' atmosphere is more prone than Earth's to electrical discharging and sparking through contact among grains of dust and sand, according to Chide. "The current evidence suggests it is extremely unlikely that the first person to walk on Mars could, as they plant a flag on the surface, be struck down by a bolt of lightning," Mitchard wrote in Nature. But the "small and frequent static-like discharges could prove problematic for sensitive equipment."
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