Imagine that we are in space, about as far away as the Moon, looking back at the Earth. What does it look like? Like many astronauts, we would likely first notice that the Earth appears blue. The reason it looks blue is the oceans - about 70% of the Earth's surface consists of water. The oceans are a key element for the existence of life on Earth. 97% of all the water on Earth, and 99% of the habitable space on this planet, is in the ocean. The atmosphere we breathe, and which controls the weather and climate, is intimately connected to the oceans - half of the oxygen produced by plants is produced in the ocean, and the oceans are also responsible for absorbing 50% of the carbon dioxide humans have released into the atmosphere by burning fossil fuels for energy.

Alaska and the Bering Sea from SeaWiFS on April 25, 1998. Bright aqua and green colors paint the ocean off the coast of Alaska and out into the Bering Sea indicating a bloom of phytoplankton (algae). Further away from the bloom, the color of the ocean water is a deep sapphire color. The bright aquamarine water is caused by the huge numbers of coccolithophores. This bloom was present in 1997 and 1998, and appears to be re-occuring in 1999. Credit: Image courtesy Norman Kuring, SeaWiFS Project.

If we take a closer look, we would see that the ocean is actually painted in a palette of blue and green. The most important influence of its variations in color are the phytoplankton drifting at the ocean surface. Phytoplankton (commonly known as algae) are to the ocean what grass and bushes and trees are to the land - the biological foundation of life, due to their ability to convert sunlight into organic matter. Phytoplankton are single-celled organisms that contain chlorophyll which allows them to carry out photosynthesis. Phytoplankton, along with microbes, share the bottom rung of the oceanic food ladder. Bacteria and viruses prey on phytoplankton, returning their nutrients to the sea as part of a very important microbial loop. At the same time, tiny animals graze on phytoplankton, and they are eaten by small fish or crustaceans, which are eaten by larger fish, whales, penguins, and everything else that swims in the ocean's salty waters. Were it not for phytoplankton, the world's largest animal, the blue whale, would not exist.

If we looked just a little closer, then we would notice the coastlines, the irregular boundaries between land and sea. There are about 620,000 kilometers (372,000 miles) of coastline. Over one-third of the total human population, nearly 2.4 billion people, lives within 100 km (60 miles) of an oceanic coast, a fact emphasized by the devastating tsunami in the Indian Ocean in 2004. Many people are most familiar with the view of the ocean from the beach, and not from space. Yet because the human population is growing, and because more and more people are living close to the ocean, the human impact on the oceans, particularly the coastal zone, is increasing as well. Increasing population and their needs for home, shelter, and food lead to depletion of oceanic fisheries, deterioration of water quality, death of coral reefs, and beach erosion. The oceans are also vital to the world's economy through shipping, mineral resources and tourism.

The reason that NASA studies the ocean from space is that we can see nearly all of the world's oceans from space, and get a global understanding of oceanic processes and problems. If we are to protect, preserve, and conserve the oceans for our life and health and for the benefit of future generations, we must use the view from space and look as closely as possible at the dynamic forces that stir the colors of the ocean.