Venus's atmosphere is 93 times heaver than Earth's, the air is mostly carbon dioxide, the planet is covered in sulfur dioxide clouds,and ground temperatures reach 860 degrees. And yet lightning works exactly the same way on both planets.
If you take the two atmospheres out of the equation, it's no wonder that astronomers often refer to Venus as Earth's twin. They have similar size, mass, and interiors, making the two planets look nearly the same if you never bother to look at their different surfaces. Of course, when you do take their atmospheres into consideration, then the two planets couldn't be any more different. Short of flying straight into a gas giant or landing onto the surface of Sun, the Venusian surface might be the most extreme and inhospitable place for a human in the entire solar system.
And it isn't just that the atmospheres are composed of very different combinations of chemicals. Planetary scientists long thought that the underlying mechanics of the two atmospheres were fundamentally different, which is why the discover of very Earth-like lightning on the planet is such a shock. Indeed, some theorists thought Venusian lightning was an impossibility, because the clouds there are essentially smog clouds, which don't usually generate lightning on Earth.
Researcher Christopher Russell explains how they made this discovery:
"We have analyzed 3.5 Earth-years of Venus lightning data using the low-altitude Venus Express data (10 minutes per day). By comparing the electromagnetic waves produced at the two planets, we found stronger magnetic signals on Venus, but when converted to energy flux we found very similar lightning strength."
The exact mechanics of lightning generation is still a bit of a mystery, but essentially it's an electrical discharge caused as clouds form around solar energy left in the air. Lightning is very important because of the incredible temperatures it can create - as high as 54,000 degrees Fahrenheit - which can temporarily create conditions that allow certain molecules to form that could never occur under normal atmospheric conditions. In fact, there's some thought that lightning helped spark the beginnings of life on Earth by creating vitally needed molecules.
Obviously, lightning didn't help create life on Venus. Even so, it does appear to operate and function in much the same way as it does on Earth, which suggests Earth and Venus really are essentially similar, even on the surface.
[Space; image by Christopher Russell is artist's conception of future probe monitoring Venusian lightning.]