The Deepwater Horizon oil rig exploded on April 20, 2010, killing eleven men. The oil rig then sank on April 22, 2010. Since then, oil has been spilling into the Gulf of Mexico. Attempts to stop the oil spill have been met with only limited success.
NASA has taken another picture of the oil from its Terra satellite using the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. Up in the right hand side of the image you can see the Mississippi River delta as it empties into the Gulf of Mexico. Down to the southeast you can see a long tail of the oil. You can click on the annotated image for a larger view.
Oil slicks are not always visible in natural-color satellite images. A thin sheen of oil on an already dark background may be impossible to detect. On this day, however, the slick was located in the sunglint part of the image, which makes the slick stand out.
Sunglint is the mirror-like reflection of the Sun off the water. If the ocean surface were as smooth and calm as a mirror, a series of perfect reflections of the Sun would appear in a line along the path of the satellite’s northeast-to-southwest orbit. Instead, waves blur the reflection, creating a wide, washed-out strip through the ocean.
A coating of oil smoothes the sea surface relative to the oil-free water, causing it to reflect light differently. Depending on where in the sunglint area it occurs, the slick may look brighter or darker than adjacent clean water. In this image, the slick appears as an uneven shape of varying shades of bright gray-beige.
