25 April 2010. In the top image, the Mississippi Delta is at image centre, and the oil slick is a silvery swirl to the right. The oil slick may be particularly obvious because it is occurring in the sunglint area, where the mirror-like reflection of the Sun off the water gives the Gulf of Mexico a washed-out look. An emergency response effort is under way to stop the flow of oil and contain the existing slick before it reaches wildlife refuges and beaches in Louisiana and Mississippi. The slick may contain dispersant or other chemicals that emergency responders are using to control the spread of the oil, and it is unknown how much of fuel that was on the oil rig burned in the fire and how much may have spilled into the water when the platform sankPhotograph: Aqua/MODIS/NASA