To store a 1:1 (one pixel = 1/72 inch) image of the entire surface of the Earth

gistfile1.txt

Assuming image resolution:
72ppi = 5184 pixels per square inch

Surface area of the Earth:
510,072,000 km2 = (7.90613181 × 10 to the 17th) square inches

Assuming (for a lossless PNG) an average storage size of:
~7.76 bits per pixel

    7.90613181 × 10 to the 17th  square inches
*                          5184  pixels per square inch
_______________________________
    4.09853873 × 10 to the 21st  pixels


    4.09853873 × 10 to the 21st  pixels
*                         ~7.76  bits
_______________________________
                     3.36744942  zettabytes

((7.90613181 × 10 to the 17th) * 5184) * 7.76 bits

3.36744942 zettabytes

or

3.70254979 × 10 to the 12th gigabytes

or
3,702,549,790,000 gigabytes

Note:
I realize that ppi is somewhat contentious.  I only chose 
the 72ppi figure because it was convenient-ish.  According 
to Wikipedia, photographs should be printed at 300 ppi to 
look decent.

http://en.wikipedia.org/wiki/Pixel_density

In that case, a 300ppi image will weigh in at:

58.5 zettabytes