We’ve all got stuck out in or witnessed very strong winds here on Earth, from gusts that turn your umbrella inside out to tornadoes that rip up everything in their path. You might think these winds are a force to be reckoned with, but unless you’ve had a day floating around the gaseous atmosphere of ice giant Neptune you haven’t seen anything yet!
You might think that Neptune’s distance from the Sun, which creates temperatures as low as -218 degrees Celsius (-360 degrees Fahrenheit), would mean a world frozen solid by the subzero climate with not much going on in terms of weather. However, you would be incorrect. The winds that race through its hydrogen, helium and ammonia-laden atmosphere can reach maximum speeds of around 2,400 kilometres per hour (1,500 miles per hour), making this dark horse probably the most violently stormy world in the Solar System, and making our most powerful winds look like light breezes.
Neptune’s fastest storms take the form of dark spots, such as the anticyclonic Great Dark Spot in the planet’s southern hemisphere and the Small Dark Spot further south – thought to be vortex structures due to their stable features that can persist for several months – as well as the white cloud group, Scooter.
So what causes these winds? Neptune might be extremely frosty, but astronomers think that the freezing temperatures might be responsible; decreasing friction in the gas giant to the point where there’s no stopping those super-fast winds once they get going.
Delving into its layers of gas, we find another possibility pointing to just how these active storms came about as the temperature starts to rise. As things get more snug closer to the centre, the internal energy could be just what is driving the most violent storms that we’ve ever witnessed.