Rough numbers, back of envelope calculation: 500 trillion square meters on earth * 50 pixels per square meter * 3 byte pixel depth = 75 petabytes uncompressed.

Rough numbers, back of envelope calculation: 500 trillion square meters on earth * 50 pixels per square meter * 3 byte pixel depth = 75 petabytes uncompressed. Assume 90% image compression and remove the 71% of earth that is oceans and you're down to a little over 2PB.