A Car-Sized Robot Whirling on Mars Has Detected Unusual Sounds That Resemble Lightning

What is there when there is nothing except an empty atmosphere? A NASA scientist would likely say this as the answer. Hundreds of millions of miles away, where there is nothing but an empty world of red rock, a lonely car-sized robot has recently heard a crackling sound. When the rover pointed its cameras at the ground, it observed striking N-shaped wave signatures materializing in the Martian soil. NASA’s favorite robot, named Perseverance Rover, was trundling across the muted terrains of the Red Planet, investigating its dusty winds, when one of its SuperCam microphones detected this sound. Back in the laboratory, scientists are overjoyed to explore this unfathomable dimension that Perseverance has opened up for them to investigate, as they documented in Nature.  

Perseverance is one of the topmost trailblazing robots NASA engineers have constructed in the last few decades. Jangling with a jewellery of seven scientific instruments, 19 cameras, and two microphones, the rover has accomplished what humans wouldn’t be able to do by themselves. In the last few years, it has conducted an array of experiments, communicating an enormous data archive to the scientists below, who are excited more than ever to unravel the planet’s greatest mysteries. Two months ago, NASA’s JPL shared footage of Perseverance as it explored the Jezero crater. A 210-foot-wide dust devil erupted in the atmosphere, as large as an airliner’s wingspan.

In another experiment, researchers put volcanic sand into a flask and pumped it down to Martian atmospheric pressure. Swirling the sand in the flask emitted a glow that was visible in the dark, scientist Ralph Lorenz shared with NPR. They found that the glow was coming from electrical charges triggered by friction between particles of sand.

Currently, Perseverance is exploring the planet’s Witch Hazel Hill. But just a short while ago, it recorded 55 instances of what researchers are calling “mini lightning.” The latest recording documented a lightning episode unfolding in the “eye of the vortex” with N-shaped wave signatures emerging in the red soil, recorded by SuperCam. Scientists believe that these N-shaped acoustic signatures are shock waves caused by point source explosions such as electric spark discharges.

The zaps, the crackles, the subtle thunderclaps; the gusty recording captured an entire musical concert playing out in the bone-dry atmosphere of Mars. While lightning has already been detected on Jupiter and Saturn, this is the first time Mars has shown a hint of this phenomenon. Lightning is usually triggered when atmospheric conditions are turbulent, and particles are colliding with each other, creating electrical charges. When these charges accumulate into clouds, they have to discharge them somewhere. On Earth, deserts can become electrified with charges. In the US, southerly winds travelling towards the north can build up these charges.

But on Earth, the primary triggers for lightning come from clouds of water vapor, moisture-laden droplets, or volcanic ashfalls, per Weather.com. Since Mars doesn’t have water, the idea of lightning is interesting. Scientists detected 55 events, seven of which recorded a distinctive electrical discharge signature with an electronic “blip” sound. Due to some tangled wires, the sound was recorded with an interference, but every blip was followed by a relaxation, a ringdown, lasting about 8 milliseconds.

Baptiste Chide, the study’s lead author, described to ABC News that it’s like a “thunderstorm on Earth, but barely visible with a naked eye and with plenty of faint zaps.” Perseverance recorded this sound with a camera and lasers, just 6 inches in size, with a microphone perched atop the rover’s tall mast. Scientists, however, are not sure whether this sound really was lightning, as Daniel Mitchard told the news outlet.

Perseverance has detected signs of microbial life in Martian soil, the traces of an old river, the clues of past volcanic eruptions, and now this. This, Chide said, is like finding a missing piece of the puzzle. If some trigger can evoke lightning on Mars, it means the same trigger could nudge a collection of biological ingredients necessary for the emergence of life. This sound has opened up a fresh doorway into this seductive investigation.

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