Alian Wang simulated lightning in a lab to explore how the phenomenon could affect the atmosphere of Venus.
Lightning may be spectacular, but its ingredients are surprisingly simple. All it takes is an atmosphere containing gas, aerosols, liquid droplets, and/or dust particles. When these components rub together, they can create triboelectric charges (electricity generated by friction), building the potential for a static discharge. If a planet has an atmosphere, there’s a good chance it also has lightning.
Spacecraft have witnessed dramatic lightning bolts crackling across the skies of Jupiter, Saturn, Neptune, and Uranus. But perhaps the most intriguing electrical storms take place on Venus, a planet blanketed by a thick atmosphere that obscures the view from space. That hasn’t kept scientists from looking.
“A lot of missions have been sent to Venus, and almost all of them have observed some electromagnetic activity,” said Alian Wang, research professor of Earth and planetary sciences. In March 2020, a Japanese orbiter detected an intense flash in the atmosphere — so far, the most direct optical evidence of an actual Venusian lightning bolt.
Nobody knows how often lightning storms occur on Venus, but it’s clear that lighting — or some type of electrical discharge — is likely an important catalyst for the planet’s atmospheric chemistry, Wang said.
To better understand the potential importance of lightning on Venus, Wang and colleagues, including Earth and planetary sciences graduate student Quincy Hongkun Qu and McKelvey School of Engineering associate professor Elijah Thimsen, created simulated lightning in a chamber designed to recreate the conditions on Venus.
As recently described in the journal JGR Planets, the researchers sent simulated arc-type electrical discharge into a sealed ceramic tube containing the key components of Venus’s atmosphere — mostly carbon dioxide and nitrogen, with some sulfur dioxide added later — at pressures that might be found 50 to 75 km (31 to 47 miles) above the planet’s surface.
The lab-born lightning supercharged the creation of highly reactive free-radical compounds such as nitrous oxide, ozone, cyanide, and an “excited” state of sulfur that binds readily with other compounds. In the actual atmosphere of Venus, these compounds would go onto start other reactions in a chemical cascade, Wang said. Excited sulfur species, for example, react with water to form sulfuric acid, a common component of Venusian clouds.
Many scientists interested in the forces that help shape the Venusian atmosphere have previously focused on photochemistry, chemical reactions driven by sunlight. But Wang’s new study suggests that lightning-powered chemistry — or electrochemistry — might be even more important. “Electrochemistry would be localized and sporadic, but it has much greater potential than photochemistry to produce free radicals,” she said.
The power of electrochemistry could also help solve an almost century-old mystery about why the atmosphere of Venus looks streaky in UV images. The chemical reactions set off by lightning would roil the atmosphere like waves in an ocean, Wang said.
Wang isn’t the only WashU researcher taking a closer look at Earth’s sister planet. Paul Byrne, associate professor of Earth and planetary sciences, along with graduate student Rebecca Hahn, recently published an atlas of the roughly 85,000 volcanoes on Venus.
Wang’s interest in electrochemistry isn’t limited to Venus. Earlier this year, she published a study in Geophysical Research Letters quantifying how electrical discharges in dust storms on Mars could play a role in that planet’s chlorine cycle.