Andrews reported in late 2020 that a flicker of light spotted by a spacecraft orbiting the planet could bring a 40-year quest to an end. If the flash is lightning, what’s making it? Astronomers hunting for the answer to this question believe it could revolutionize what we know about the skies of Venus. The planet’s sulfuric acid clouds are unique in the solar system, so traditional models of lightning generation don’t apply to Venus, Aplin says. One issue is that its clouds are thought to conduct electricity relatively well, which may prevent electricity from accumulating in one place to the point where lightning is triggered.
Earth’s clouds separate electrically charged water droplets and ice crystals through convection—when warmer clouds move up and cooler clouds sink down—leading to lightning. But it’s not clear how much vertical mixing happens in Venus’ clouds, says Paul Byrne, a planetary scientist at North Carolina State University. And Akatsuki can’t place the altitude of the flash, so if it was lightning, it could have struck from anywhere between the upper atmosphere and the main cloud deck tens of miles deeper.
One possibility is that flashes of lightning on Venus follow volcanic eruptions. Although no eruption has yet been directly observed through the planet’s obscuring clouds, circumstantial evidence has many planetary scientists convinced that eruptions are nevertheless taking place. Explosive events producing ashy, electrically excited plumes could generate bolts of lightning. Whether this detection turns out to be genuine or not, planetary scientists will continue to search for more flashes, eager to know if lightning’s alchemic power is at work on Venus.
“Lightning is charismatic, as a process. It’s active,” Izenberg says. It “could be one of the potential engines for prebiotic chemistry on Venus,” meaning the blasts of energy could stitch together molecules that are needed for life. If this process occurs in parts of the atmosphere that are known to be watery, temperate, and sunlit, it could create a potential haven for photosynthetic microbes.
Lightning may also be responsible for making the gas phosphine, a compound that was recently detected on Venus—though some experts have questioned whether the detection is valid—and is known to be produced by microbes on Earth. If this gas really does exist in the Venusian clouds, some of it may be forged by lightning interacting with the atmosphere.
Dual observations made by terrestrial telescopes and Akatsuki would go a long way to convincing the community that lightning has been identified, Curry says. But until humanity sends a new mission to Venus to dive through the atmosphere or fly close to the cloud tops, the presence of lightning will likely remain an open question, Byrne says.
We know surprisingly little about Venus, a world that is about the same size and composition as Earth but whose evolution has differed dramatically. This flash, Izenberg says, is “yet another argument that says we have to go back.”
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