Where's the Oil? Much Has Evaporated, Underwater

For a spill now nearly half the size of Exxon Valdez, it's hard to pin down where the oil from the Deepwater Horizon disaster has gone.

Although the government has been slow to say what's happened to it, a picture can be drawn from a publicly available model called the Automated Data Inquiry for Oil Spills.

The model shows that about 35 percent of a hypothetical 4.8 million gallon spill of light Louisiana crude oil released in conditions similar to those found in the Gulf now would evaporate.

It also shows that between 50 percent and 60 percent of the oil would remain in or on the water and the rest would be dispersed in the ocean.

Ed Overton, a Louisiana State University chemist analyzing the spill, says he thinks most of the oil is floating within 1 foot of the surface.