Greenness is an important indicator of health for forests, grasslands, and farms. The greenness of a landscape, or vegetation index, depends on the number and type of plants, how leafy they are, and how healthy they are.
In honor of our 20th anniversary, we offer a selection of some of the most beautiful, newsworthy, interesting, and scientifically important images from the past 20 years — one for each day of the calendar year.
Chlorophyll is used by algae and other phytoplankton--the grass of the sea--to convert sunlight and carbon dioxide into sugars. These maps show chlorophyll concentrations in the ocean, revealing where phytoplankton are thriving.