Late last year, a huge storm erupted in the clouds of Saturn's northern hemisphere. Huge even at the beginning, it grew even larger rapidly and eventually wound itself all the way around the planet! It grew to the incredible length of 300,000 km (180,000 miles) -- end-to-end, it would've stretched 3/4 the way from the Earth to the Moon! The folks at the Cassini mission have just released a treasure trove of new pictures of the storm, and they are very, very cool. Check this out:

[Click to encronosenate.] It looks like it's a ghost running from Pacman, doesn't it? Hmmm... maybe it is. Taken in late December 2010, this image shows Saturn in the infrared using a combination of 3 different filters. What you see here in this false-color as white and blue are actually clouds high in the atmosphere; yellow/green are mid-level clouds, and red/orange deeper material. The rings are edge-on right in the middle, and you can see the shadow they cast on the planet. From its reddish hue, this storm was deep in Saturn's atmosphere. it apparently has two eyes -- if ever that term were accurate, it's here -- with one being deeper in the clouds than the other. Clearly, the tail had just started to form. But it grew. A lot. A few weeks later, in January 2011, Cassini took this image:

This time, 12 separate filters in the infrared were used, but the color scheme is largely the same. The rings in this image appear bright blue, like a knife's edge cutting across the planet. Details in the vortices are clear, and by this time the long tail of the storm was really starting to lengthen. You can also see a more traditional Saturn storm in the southern hemisphere, below the ring shadows as well. This next picture, though, is the one that made me really smile:

This image shows two views of the storm taken 11 hours apart on February 26, 2011, to show how the system has changed during that time (much larger versions are available, too). Each picture is actually a mosaic of 84 separate images, painstakingly combined to give a complete view of this monster. The color scheme is roughly the same as the two images above: red is deep stuff, white/blue material higher up, and yellow/green in the middle. The exception is the blue oval to the far right; that's actually a deep hole in the atmosphere and is quite cold, so it absorbs and reflects light differently than the other layers in the storm. More of these amazing images are available at the Cassini website. The storm died down over the summer, though its impact can still be seen as turbulence in Saturn's clouds even now. I'll note that at its largest, it had a surface area eight times that of the Earth! It'll be some time (if ever) before everything about this storm is understood. How did it form? Why did it grow so large? How did it wind up (literally) winding itself around the planet? How often do gigantic storms like this form? Are they unique to Saturn, or could the other giant planets get them? And I'll also note that this storm was not discovered by Cassini, but instead first spotted by sharp-eyed "amateur" astronomers. Obviously, it would've been seen by Cassini scientists quickly enough, but sometimes there's no substitute for an eye to the eyepiece... ... and, of course, there's no substitute for being there, too. Storms like this are rare, and it was a good thing that not only was Cassini there to give scientists this cornucopia of data, but that the mission has been so long-lived. I certainly hope it continues for years to come. Saturn is an astonishing, dynamic, gorgeous, and fantastic place to be, and the longer we stay, the more we'll learn. Image credit: NASA/JPL-Caltech/Space Science Institute

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