A year ago NASA launched the Aquarius Satellite . The satellite is the first designed to study ocean salinity from space. It takes 300,000 measurements per month, using three sensors, for a mission that is a joint U.S.-Argentina effort.
Over the last year, the instrument has sent back data showing the sometimes striking variations in salinity in the world's oceans and seas, and has also confirmed Earth-bound observations.
Oceanographers have long known that the Atlantic Ocean is saltier than the Pacific and Indian oceans, and the satellite images show the same. It has also shown that the world's longest rivers carry tremendous amounts of fresh water from land and spread plumes far into the sea. And in the tropics, extra rainfall makes equatorial waters somewhat fresher.
The satellite technically measures the "brightness temperature" of a tiny layer atop ocean waters - a slice just 0.4 inches (1 centimeter) thick. Land masses tend to be "brighter" than water, so any measurements near the coast are skewed by their proximity to land. But as the mission progresses, NASA engineers will be able to sort out the signals in the data caused by bright land, and get the true measure of salinity in coastal areas.
Aquarius is another tool being used to monitor climate changes and the effect on oceans as well as better understand the variations across the globe.