Which Planet is the Windiest?

Question posed by Alfie. I'm going to focus on our own solar system, here, as we don't know much about weather on exoplanets just yet!

Well, it's not Mercury, as that doesn't really have an atmosphere, so there's no air to make wind out of.

Mars has a very thin atmosphere, and although famous for its dust storms, Martian winds only reach about 97 km/h (60 mph). I regularly drive that fast (when legal and safe to do so, of course). So it's not Mars.

Venus has a very thick atmosphere, so lots of air to blow around. Having said that, whilst the weather is pretty extreme, wind speeds only reach about 300 km/h (186 mph). So it's not Venus.

Here on Earth, the fastest wind speed ever recorded was 408 km/h (253 mph), on Barrow Island, Australia, in 1996. This is a bit more than the fastest speeds achieved by Formula 1 racing cars. That's pretty quick, but still not the fastest wind in the solar system, so it's not Earth.

Wind speeds experienced on Uranus (stop sniggering at the back) have been measured up to 900 km/h (560 mph). So not Uranus, then.

Jupiter's famous Red Spot is a storm more than 16,000 km (10,000 mi) across - that's big enough to fit our entire planet Earth inside it. It's not a permanent feature and will disappear one day, but humans have been observing it for more than 150 years. Wind speeds in this region of more than 644 km/h (400mph) are fairly typical, but elsewhere on the plant winds of more than 1,448 km/h (900 mph) have been recorded. Now we're talking! That's faster than the speed of sound back on Earth. But it's still not Jupiter.

On Saturn, wind speeds have been recorded exceeding 1,600 km/h (1,000 mph). It's still not Saturn, though. While we're here it's worth mentioning that Saturn's moon Titan is the only moon in the solar system to have an atmosphere, so it also has wind! In 2005 an imaginative experiment used transmissions from the Huygens probe to calculate wind speeds experienced as it passed through the atmosphere to land on Titan's surface. The speeds measured were up to 430 km/h (267 mph), which is very respectable for a moon!

That leaves Neptune. Wind speeds here can reach 2,000 km/h (1,200 mph). The windiest planet is definitely Neptune. Click and drag below for a brief look at Neptune's visible surface, which is the top of a thick atmosphere including clouds of frozen methane. You can also see a large, dark spot which is probably an enormous storm; Neptune's version of Jupiter's Great Red Spot:

The windiest planet in our solar system, that is...

Having said that I was going to stay inside our solar system, I did find out that wind speeds have been measured on some planets outside of it. The fastest wind speed so far was observed on the catchily-named planet HD 189733b, which is about 64.5 lightyears away. The highest windspeed picked up there was about 8,700km/h (5,400 mph). That's pretty breezy. Apparently it also rains molten glass!

Here's everything above, but in a diagram:

Windiest Planets Diagram by T. Briggs is licensed under CC BY-NC-SA 4.0



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