My mom mentioned, some time ago, that she likes my use of the title “Blue Marble” for the Earth so thought I’d share the derivation of the terminology.
The Blue Marble is a famous photograph of the Earth, taken on December 7, 1972, by the crew of the Apollo 17 spacecraft, at a distance of about 45,000 kilometres (28,000 mi).
The name has also been applied by NASA to a modern series of image data sets covering the entire globe at relatively high resolution, created by carefully sifting through satellite-captured sequences taken over time, to eliminate as much cloud cover as possible from the collated set of images.
The original caption to this photo was, “View of the Earth as seen by the Apollo 17 crew traveling toward the moon. This translunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is the first time the Apollo trajectory made it possible to photograph the south polar ice cap. Note the heavy cloud cover in the Southern Hemisphere. Almost the entire coastline of Africa is clearly visible. The Arabian Peninsula can be seen at the northeastern edge of Africa. The large island off the coast of Africa is Madagascar. The Asian mainland is on the horizon toward the northeast.” ~ Wikipedia
I also love this animation (click on the picture to view) of the earth each month of the year and watch the snow move from north to south and then back again.
The Bis Key Chronicles 
Interesting. Thanks for the share. ABC’s image of the globe that is earth this year also looks like a blue marble. Pretty!