The Blue Marble is an incredibly detailed, true-color depiction of the Earth. NASA is responsible for this dataset made from a compilation of satellite images throughout 2001. Most of the information came from NASA's MODIS, the Moderate Resolution Imaging Spectroradiometer, which is attached to the Terra satellite 435 miles above Earth. The background image of the land and oceans was created using data from June through September of 2001. This could not be done in a single day or even a week because on any given day clouds are blocking a significant portion of the surface.
The shading is true color with the oceans shades of blue and the lands varying from green to brown. The brown areas are
the sands of the deserts. The shading of the land was done using a dataset compiled by the U.S. Geological Survey's Earth Resources
Observation and Science Data Center.
Seasonal Blue Marble without clouds is a monthly composite of the entire year. The monthly evolution allows audiences to see the changing appearance of the Earth due to the season changes. The most dramatic change is the expansion of the snow cover during the winter months and then the depletion of it during the summer months.