NASA rover detects electrical sparks in Mars’ dust devils and storms

Perseverance has confirmed a long-suspected phenomenon in which electrical discharges and their associated shock waves can arise within the Red Planet’s mini-torpedoes.

NASA’s Perseverance Mars rover recorded the sounds of electrical discharges – sparks – and mini sonic booms in dust devils on Mars. Long theorized, the phenomenon is now confirmed thanks to audio and electromagnetic recordings captured by the rover’s SuperCam microphone. The discovery, published Nov. 26 in the journal Nature, has implications for Mars’ atmospheric chemistry, climate and habitability, and could help inform the design of future robotic and human missions to Mars.

A common phenomenon on the Red Planet, dust devils form from rising and rotating columns of hot air. Air near the planet’s surface heats upon contact with the warmer ground and rises through the denser, cooler air above. As air moves along the surface to replace the rising warmer air, it begins to rotate. As the incoming air rises in the column, it gains speed like ice skaters bringing their arms closer to their body. The air rushing through also picks up dust and a dust devil is born.

SuperCam recorded 55 separate electrical events during the mission, starting on the mission’s 215th Martian day, or sol, in 2021. Sixteen were recorded when dust devils passed directly above the rover.

Decades before Perseverance landed, scientists hypothesized that friction generated by tiny dust grains swirling and rubbing against each other in Martian dust devils could generate enough electrical charge to eventually produce electrical arcs. Called the triboelectric effect, it’s the phenomenon at play when a person walks on a carpet in socks and then touches a metal doorknob, generating a spark. In fact, it’s about the same level of discharge that a Martian dust devil could produce.

“Triboelectric charging of sand and snow particles is well documented on Earth, particularly in desert regions, but it rarely results in true electrical discharges,” said Baptiste Chide, a member of the Perseverance science team and a planetary scientist at the Institut de Recherche en Astrophysique et Planétologie in France. “On Mars, the thin atmosphere makes the phenomenon much more likely, because the amount of charge needed to generate sparks is much less than that required in Earth’s near-surface atmosphere.”

Perseverance’s SuperCam instrument is equipped with a microphone to analyze the sounds of the instrument’s laser as it zaps rocks, but the team has also captured wind sounds and even the first audio recording of a Martian dust devil. Scientists knew it could pick up electromagnetic (static) disturbances and electrical discharge sounds in the atmosphere. What they didn’t know was whether such events occurred frequently enough, or whether the rover would ever be close enough to record one. Then they began evaluating the data accumulated during the mission, and it didn’t take long to find the telltale sounds of electrical activity.

“We have good ones where you can clearly hear the sound of the spark,” said co-author Ralph Lorenz, a Perseverance scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “In the Sol 215 dust devil recording, you can hear not only the electrical sound, but also the wall of the dust devil moving above the rover. And in the Sol 1,296 dust devil, you hear all of that as well as some of the particles impacting the microphone.”

Thirty-five other releases were associated with the passage of convective fronts during regional dust storms. These fronts feature intense turbulence that promotes triboelectric charging and charge separation, which occurs when two objects touch, transfer electrons, and separate — the part of the triboelectric effect that results in a spark of static electricity.

The researchers found that electrical discharges did not appear to increase during seasons when dust storms, which overall increase the presence of atmospheric dust, are more common on Mars. This result suggests that electrical accumulation is more closely related to localized, turbulent uplift of sand and dust than to high dust density alone.

The evidence of these electrical discharges is a discovery that radically changes our understanding of Mars. Their presence means that the Martian atmosphere can become sufficiently charged to activate chemical reactions, leading to the creation of highly oxidizing compounds, such as chlorates and perchlorates. These powerful substances can effectively destroy organic molecules (which make up some of the building blocks of life) on the surface and decompose many atmospheric compounds, completely changing the overall chemical balance of the Martian atmosphere.

This discovery could also explain the disconcerting ability of Martian methane to disappear quickly, providing a crucial piece of the puzzle for understanding the constraints life may have faced and, therefore, the planet’s habitable potential.

Given the omnipresence of dust on Mars, the presence of electrical charges generated by the friction of particles between them would seem likely to also influence the transport of dust on Mars. The way dust moves on Mars plays a central role in the planet’s climate but remains poorly understood.

Confirming the presence of electrostatic discharge will also help NASA understand potential risks to electronic equipment on current robotic missions. The fact that no negative effects of electrostatic discharge have been reported during several decades of operations on the surface of Mars may be a testament to careful spacecraft grounding practices. The findings could also inform safety measures developed for future astronauts exploring the Red Planet.

Managed for NASA by Caltech, the Jet Propulsion Laboratory in Southern California built and manages operations of the Perseverance rover on behalf of the agency’s Science Mission Directorate as part of NASA’s Mars Exploration Program portfolio.

To learn more about Perseverance, visit:
https://science.nasa.gov/mission/mars-2020-perseverance

DC Agle
Jet Propulsion Laboratory, Pasadena, California.
818-393-9011
agle@jpl.nasa.gov

Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600 / 240-419-1732
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov

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