From Emily at The Planetary Society blog comes word that one of Jupiter’s belts has disappeared… again.

This image, by the accomplished amateur astronomer Anthony Wesley, shows what’s up. Usually, the Great Red Spot is accompanied by a dark reddish belt that goes all the way around the planet, like the one in the northern hemisphere you can see in the picture. However, the Southern Equatorial Belt, as it’s called, is gone!

This has happened before, in fact. It’s not clear exactly why this sort of thing occurs, though. The belts (and their lighter-colored cousins, called zones) are weather patterns that stretch around the planet, a bit like the jet stream on Earth. They can be affected by temperature, chemical composition, and other factors. It’s possible that a belt can sink lower in the Jovian atmosphere if it cools slightly. Clouds then pour in on top of it, hiding it from view. It’s still there, just hidden; if the temperature rises it can float back up like nothing ever happened.

Jupiter is a weird place. Remember, we only see the very tops of the clouds. They go all the way down, tens of thousands of kilometers deep, where the pressure gets so great the gas just sorta gradually turns into a liquid. So having a belt sink a little bit and disappearing is perhaps less unlikely with such a freaky planet than it would be on Earth.

But there is a very cool thing about this: you can see it for yourself! It only takes a small telescope to see Jupiter, and with a modest ’scope the belts are visible. Well, usually visible; not this one so much right now, but you get my drift. If you want to see this for your very own self, you’ll have to get up early: Jupiter doesn’t rise until very early morning. Get up an hour or so before dawn and you should be able to get a good look. It’ll be the very bright starlike object in the East, brighter than anything else in the sky except the Moon, so it’s easy to spot.

But if you prefer your astronomy to be virtual, you can check out other pictures at Wesley’s site, as well as Astro Bob’s blog.

I wonder how long the belt will be gone? It could be months, or it might pop back up sooner. Either way, it’s a good reminder that we still have a lot of stuff to figure out when it comes to the Universe around us.