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Ghost Crab Eats OilA ghost crab eats oil from the Gulf of Mexico spill, shown glowing yellow-orange under ultraviolet light, at Gulf Islands National Seashore near Pensacola (map), Florida.Late last week coastal geologist Rip Kirby was on the seashore as part of an effort to detect oil by shining UV lights—widely used to spot blood at crime scenes—on Gulf beaches. The method, he hopes, will allow scientists and cleanup crews to tackle hard-to-spot oil, such as crude mixed with mud or light stains on sand, that's washed ashore from the sinking of the BP-leased Deepwater Horizon rig.Under UV light, clean sand appears purple or black. Some minerals, such as calcium carbonate in seashells, glow blue, as does a shovel handle in the picture above.Although hydrocarbons have long been known to fluoresce, or glow, under ultraviolet light, this may be the first time the technology has been used outside a lab to spot oil. "The use of UV light to identify [types of] oil is an industry-wide process," said Kirby, a graduate student at the University of South Florida. But "I've always seen it in a [lab] machine," he said."The first time I took the UV flashlight out on the beach to see if it would work, it was beyond my wildest dreams," Kirby said. "It was easy to see that there was oil on the beach ... the contamination was widespread."—Chris Combs

Photograph by Chris Combs, National Geographic