October 11, 2007
Credit: Reto Stockli, NASA
Above are two new "Blue Marble" images of Earth's Eastern and Western Hemispheres, including cloud cover, oceans, phytoplankton activity, topography, and city lights in the nightime part of the hemisphere.
The original project, Blue Marble 2000, was completed for the 30th anniversary of Earth Day and aimed to recreate the view of Earth that Apollo astronauts had from space. The final image, released in April 2000, displayed cloud cover from a single day, the oceans, exaggerated topographic features and vegetation for the Western Hemisphere.
The new images have combined even more of Earth's features into more complete, higher-resolution images of both the Eastern and Western hemisphere. The data used to create the new images span a longer period of time than the original and have a resolution of 500 meters (1,600 feet), versus the 1,000 meters (3, 273 feet) resolution of the older image.
Measurements of reflected sunlight taken by the NASA instrument Moderate Resolution Imaging Spectroradiometer (MODIS) (aboard both the Terra and Aqua satellites) in July 2004 were used to recreate the land surfaces. MODIS observations of daytime sea ice between late August and early September 2001 were used to recreate polar sea ice in the image.
The ocean was generated by combining Terra MODIS observations of the reflectance of sea water with Aqua MODIS observations of chlorophyll content data over the open ocean to represent the activity of phytoplankton.
Cloud cover is taken from a single-day snapshot by MODIS on July 29, 2001.
City lights as they would appear on Earth at night were taken from data collected by the Defense Meteorological Satellite Program mission between 1994 and 1995.
Topography is based on radar data collected by the Space Shuttle Endeavor during an 11-day mission in February 2000.
The new project, dubbed Blue Marble: Next Generation, also includes other images that are monthly composites of the Earth that show the seasonal variations in vegetation and ice cover over an entire year.