Images Show Oil’s Invasion Along Louisiana Coast
These images, acquired on May perhaps 24, 2010 by the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA’s Terra spacecraft, show the encroachment of oil from the former Deepwater Horizon rig into Louisiana’s wildlife habitats. The source with the spill is located off the southeastern (bottom suitable) edge from the images.
Dark filaments of oil are observed approaching the shores of Blind Bay and Redfish Bay at the eastern edge on the Mississippi River delta, and also nearing Garden Island Bay and East Bay farther towards south. These areas are house to several varieties of fish. To the north, the arc-shaped pattern of land and runoff is associated with the Chandeleur Islands, which are part of the Breton National Wildlife Refuge. This refuge is the second oldest inside the United States and can be a habitat for dozens of seabird, shorebird and waterfowl species. Oil is reported to have reached the islands on May possibly 6. Eighteen days later, this image shows filaments of oil crossing the island barrier — which had been heavily eroded by Hurricane Katrina in 2005 — and entering the Breton and Chandeleur Sounds.
The left-hand image contains information from MISR’s vertical-viewing camera. It is shown in near-true color, except that data in the instrument’s near-infrared band, where vegetation appears bright, have been blended using the instrument’s green band to enhance the appearance of vegetation.
The Mississippi River delta is located below the picture center. The slick is observed approaching the delta from the lower suitable, and filaments of oil are also apparent farther for the north (towards the top). The oil is made visible by sun reflecting off the sea surface at the same angle from which the instrument is viewing it, a phenomenon known as sunglint. Oil makes the surface look brighter under these viewing conditions than it would if no oil were present. Even so, other factors can also cause enhanced glint, for example reduced surface wind speed. To separate glint patterns caused by oil from these other factors, additional information from MISR’s cameras is employed inside the right-hand image.
Previous MISR imagery in the spill shows that the contrast of the oil against the surroundings is enhanced by using a combination of vertical views and oblique-angle views. The right-hand panel was constructed by combining data from various MISR channels. In this false-color view, oil appears in shades of inky blue to black; silt-laden water as a result of runoff in the Mississippi River shows up as orange, red and violet; and land and clouds appear in shades of cyan.
