Electrically-Charged Dust Creates Hazards on Mars and the Moon — an Invisible Carbon Layer May Explain Why

As we set our sights on future Mars and moon missions, we face a surprisingly troublesome foe: electrically charged dust. On the lunar surface, jagged, ultra-fine dust acts as a sharp abrasive. It clings stubbornly to solar panels, damages spacesuits, and even poses a severe inhalation hazard for astronauts.

On Mars, friction between airborne dust particles can trigger sparking, creating a major risk for sensitive circuitry. The culprit behind these extraterrestrial encounters is the familiar shock of static electricity. The word “electricity” itself derives from the Greek word for amber, a material early scholars often used to demonstrate the phenomenon.

Yet, despite being one of the oldest observed physical phenomena, its exact mechanics have remained remarkably elusive.

“When any two objects touch, they exchange electrical charge, and scientists are clueless as to why,” Scott Waitukaitis, a physicist at the Institute of Science and Technology Austria, told Discover.

Now, Waitukaitis and an international team of researchers have identified a hidden factor governing how particles transfer charge in mid-air. In a landmark paper published in Nature, they discovered that an invisible layer of environmental carbon may dictate the entire charging effect in certain cases.

Read More: Potential Biosignatures on Mars May Reflect Ancient Life in Mineral-Rich Rocks

Understanding Colliding Oxide Particles

This breakthrough is particularly critical for insulating oxides, a class of rocky materials that make up most of our planet’s crust, as well as the dust on the moon and Mars.

“From electrical disturbances in Saharan dust storms to volcanic lightning,” Waitukaitis said to Discover, “charging between oxide particles is perhaps the most important manifestation of static electricity in nature.”

A central puzzle in studying these materials has been the question of symmetry. Whether in extraterrestrial sandstorms or Earthly volcanic plumes, the colliding oxide particles are often chemically identical.

“If two grains are made of the same material, then how is it possible for one to charge positive and the other one negative?” explained Galien Grosjean to Discover, a physicist at the Autonomous University of Barcelona who co-authored the study.

Using Acoustic Levitation to Measure Electrical Charge

To uncover the mechanism, physicists needed to measure the electrical exchange during a single microscopic collision. At this minute scale, any physical handling by traditional instruments would instantly corrupt the data with unwanted charge.

The team overcame this severe limitation by opting for acoustic levitation. By using highly controlled sound waves to create a pressure cradle in mid-air, the scientists could suspend a half-millimeter sphere for a completely touch-free experiment.

To simulate a collision, the researchers briefly stopped the sound, dropping the particle onto a target plate of the same material. After it exchanged charge upon contact, they reactivated the levitation to catch it on the upward bounce. Computers would then precisely measure the particle’s newly acquired charge.

Because this sequence was fully automated, the system recorded thousands of consecutive collisions. The results revealed that the critical “symmetry breaker” allowing identical rocks to charge differently wasn’t a property of the rock itself, but rather an often-overlooked cocktail of ubiquitous molecules known as adventitious carbon that form thin layers over nearly any surface.

“Adventitious is just a fancy word for ‘random stuff from the environment,’” Grosjean told Discover.

Spectroscopy has confirmed the presence of these carbon-based molecules on Mars, the moon, and even within distantly forming solar systems.

Providing the Engineering Framework to Protect Against Space Dust

When the researchers stripped this carbon from a single sample, the particle consistently adopted a negative charge after bouncing. If they removed the carbon from both colliding objects, the charge transfer vanished.

“A layer less than one molecule thick is enough to completely flip the sign of charging,” Grosjean told Discover.

As carbon resettled onto the oxide surface over the course of a day, the particle’s charge evolved at the exact same rate. Because this environmental carbon coating is never perfectly uniform, no two particles are ever truly identical at the molecular level.

Identifying this atmospheric variable could provide a framework for engineers developing mitigation strategies for dust hazards. Mission planners can now base their equipment designs on the actual mechanisms of charge transfer.

But the implications stretch far beyond engineering, offering insights into the formation of our world. In the chaotic early days of our Solar System, static charging between swirling silicate and oxide particles is strongly theorized to have driven the initial clumping of dust into protoplanets. Electrical interactions in the early atmosphere may even have created important ingredients for life, paving the way for the first cells.

“Before, we couldn’t even identify what mattered in contact electrification,” said Waitukaitis to Discover. “Now that we’ve identified the role of adventitious carbon, we can start to ask why.”

Read More: Giant Spiderweb Formations on Mars Contain Ancient Evidence of the Planet’s Waterlogged Past

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