Real NASA photos are probably easier, but they sort of look...messy, if you know what I mean. I think it may be the 256 colours, or the fact that they're always stretched. Are those 256x256? You can crank them up to 512x512 and possibly 1024x1024, but that's untested.
As for making it, I mostly used Axion and twirl, to varying degrees, and over and over again. That's probably where the speed is coming from

. I got the colours using one of PSPs photo correction tools, Automatic colour balance at about 8000K. The shape was originally Circular, and made oval using various perspective tools when I was satisfied with the overall effect. As mentioned earlier, Burn at 22% got rid of the circular outline.