text: NASA Satellite Imagery Keeping Eye on the Gulf Oil Spill. On April 29, the MODIS image on the Terra satellite captured a wide-view natural-color image of the oil slick just off the Louisiana coast. The oil slick appears as dull gray interlocking comma shapes, one opaque and the other nearly transparent. Sunglint -- the mirror-like reflection of the sun off the water -- enhances the oil slick's visibility. The northwestern tip of the oil slick almost touches the Mississippi Delta. Credit: NASA/Earth