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Watch the oil spill as it changes

Some of the most reliable witnesses to the changes in the Gulf of Mexico oil spill have been satellites in orbit. A newly released NASA video traces the changes that have taken place in the spill's extent - and there's more where that came from. Much more, in terms of pictures as well as petroleum.

NASA's regularly updated roundup of Gulf spill imagery features views from two of the space agency's Earth-observing satellites, Terra and Aqua. Those two polar-orbiting probes are equipped with imaging spectroradiometers that send back data over a wide range of wavelengths. The oil on the surface shows up as a silvery sheen, glinting in the sun.

Oil spill

Photo by NASA

A thermal image from NASA's Terra satellite, captured on May 24, shows silvery ribbons of oil in the Gulf of Mexico reaching the very tips of the Mississippi River Delta.

Other instruments on the satellites pick up thermal imagery of the Gulf. Vegetation shows up in red, and oil on the water has a silvery look. The image acquired on May 24 highlights a mysterious dark patch of water at upper left. NASA says the dark color may indicate the use of chemical dispersants, skimmers or booms. Or it may merely reflect natural differences in turbidity, salt content or organic matter in the coastal waters.

Another NASA team has been flying above the spill in a spooky-looking airplane over the past couple of weeks, taking pictures in a different set of wavelengths. The Airborne Visible/Infrared Imaging Spectrometer, or AVIRIS, sees crude oil on the surface in shades of orange and brown.

The European Space Agency's Envisat radar satellite has been tracking the spill as well. Last week, scientists drew upon Envisat data to conclude that oil had indeed entered the Loop Current that sends water circulating around the Gulf and eventually toward Florida.

AccuWeather suggests that the oil slick is in a part of the Loop Current that has been "pinched off" to create a large eddy. That means the surface slick is swirling around in the current and not approaching Florida ... at least for now. "Stopping the leak sooner rather than later would go a long way toward reducing the threat to shorelines not yet impacted by the oil spill and reducing the damage to areas already hit," according to AccuWeather's oil-slick forecast.

It's important to remember, however, that most satellites aren't good at seeing what's beneath the surface. On that score, scientists sampling the water column aren't offering much reassurance. Researchers aboard the University of South Florida's R/V Weatherbird II said they detected a wide area of the Gulf with elevated levels of dissolved hydrocarbons. The apparent plume of pollution, which was at its highest concentration 1,300 feet (400 meters) beneath the surface, is invisible to the eye but nevertheless could represent a long-term threat to marine life.

"The ramification is that what we see at the surface is not the entire story," biological oceanographer Ernst Peebles said today in a university news release. "This is not a big glob of oil drifting. These are layers. They show up on sonar as layers with clear water in between."

The bottom line? Even if the Deepwater Horizon oil leak stopped tomorrow, the effects of the spill will have to be monitored for years or decades to come - not just from space, but from the sea.

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