The most used image on earth IS an image of earth.
NASA, as a US government institution, in producing images, automatically has them in the public domain? there needs to be better wording for this.
Anyway, this blue marble image, it is in the pbulic domain because it was created by NASA > section 101 and 105 of the us Copyright act > copyright protection does not apply to any work created by the US Government...
so, what is this image?
Examples of the NASA blue marble in all sorts of funny places?
The troubling part of the Public Domain when used like this is that these creations that use the Blue Marble ARE not free, neither in price, nor in copyright. You can use a public domain image to CREATE a copyrighted, protected, non-free culture image.