Academic scientists are challenging the Obama administration's assertion that most of BP's oil in the Gulf of Mexico is either gone or rapidly disappearing -- with one group Thursday announcing the discovery of a 22-mile "plume" of oil that shows little sign of vanishing.

That plume was measured in late June and was described Thursday by scientists from Woods Hole Oceanographic Institution in Massachusetts. The biggest news was not the plume itself: For weeks, government and university scientists have said that oil from BP's damaged well is still underwater.

(Photos: The oil spill cleanup)

The news was what is happening -- or not happening -- to it.

The scientists said that when they studied it, they saw little evidence that the oil was being rapidly consumed by the gulf's petroleum-eating microbes. The plume was in a deep, cold region where microbes tend to work slowly.

"Our data would predict that the plume would still be there now," said Benjamin Van Mooy, a Woods Hole researcher.

(Gulf driller to light up cigar after job is done)

Their research came after a week in which other scientists had taken issue with the government's portrait of where all the oil went. On Thursday afternoon, Jane Lubchenco, the Oceanic and Atmospheric Administration's administrator, defended the government's work, saying it was done by the "best scientific minds" and reviewed by outsiders.

(Transocean accuses BP of withholding data)

"We remain confident in our assessment," she said.

The Woods Hole research, published in the peer-reviewed journal Science, provided one of the most detailed pictures yet of what this oil is doing under the surface.

The scientists said that, using a robot submarine that zigzagged across the deep gulf, they found a plume of oil droplets that was as tall as a 65-story building and more than a mile wide. The plume, whose droplets were so small that the water appeared clear, extended off to the southwest of the well, 3,600 feet deep.