Since NASA studies both Earth and other planets, what we learn from Earth's oceans can help us make sense of clues to the watery pasts of other planets. Water is essential at the molecular level to moving life beyond its basic building blocks; thus, searches for extraterrestrial life usually involve a search for liquid water.
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For the first time in Earth's history, there is a species (homo sapiens) that can affect the Earth system on a global scale in a very short time -- and tip the balance into chaos. But paired with that awesome potential for destruction is our ability to study these changes on a global scale, and with the knowledge we gain perhaps avoid radical jolts to Earth's systems.
Some Earth observing satellites measure the characteristics of light, or radiance, coming from the Earth's surface. To learn about what is in the water using observations from space, we must first know what influences the color of water. Samples of ocean water are taken and their concentrations of phytoplankton and their chlorophyll are analyzed; these concentrations will then be correlated with the measured radiances.
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.
Sea ice is formed when ocean water is cooled below its freezing temperature of approximately -2°C or 29°F. Such ice extends on a seasonal basis over great areas of the ocean. Sea ice is important to the study of oceans because it impacts oceanic chemical and physical properties, density structure, oceanic dynamics, and exchanges between the ocean and the atmosphere.
Ocean and atmospheric circulation play an essential role in sustaining life by moderating climate over much of Earth's surface. An important part of the circulation of heat and freshwater and other sea water constituents are ocean surface currents. Their strength and variability play a role in weather and climate, impact environments for all life on Earth.
In the United States, hurricanes have been responsible for at least 17,000 deaths since 1900 and hundreds of millions of dollars in damage annually. Worldwide, there were 10 hurricanes in 1998, making that the worst hurricane season in the last 200 years. One of them, Mitch, killed over 10,000 people in Central America. The beginning of a hurricane can be observed as winds swirling off the coast of Africa days before clouds form.
Although everyone knows that seawater is salty, few know that even small variations in ocean surface salinity (i.e., concentration of dissolved salts) can have dramatic effects on the water cycle and ocean circulation. Throughout Earth's history, certain processes have served to make the ocean salty. The weathering of rocks delivers minerals, including salt, into the ocean. Evaporation of ocean water and formation of sea ice both increase the salinity of the ocean.
Instruments aboard NASA's and NOAA's spacecrafts use their vantage point from space to collect global measurements of the ocean's surface temperature. Each day these instruments make thousands of measurements of broad swaths of the Earth - creating concurrent data sets of the entire planet. By developing global, detailed, and decades-long views of Sea Surface Temperature (SST), data obtained from NASA and NOAA satellites provide the basis for the prediction of climate change, ocean currents, and the potent El Niño-La Niña cycles.