According to this site http://planet--earth.ca/ (Go to Electro-L Images, then Image Gallery) the full image is too expensive to host and he's providing a torrent soon.

Would be a fun project, perhaps, to chop it up into tiles, host them on amazon s3, and use the CATiledLayer class to build an iOS viewer - or the equivellant in one's platform of choice.

You can see it on Gigapan, works on iOS: http://gigapan.com/gigapans/103187

"Size 1.12 Gigapixels"

There was a down-sampling step somewhere between the source image and that Gigapan image.

The image went from 0.121 GP to 1.12 GP, It was not down-sampled, it's the oposite. Maybe to meet Gigapan's minimum 1GP?