Samples of ancient carbon deposits from this era show a marked increase in concentrations of carbon-12 relative to its heavier isotope carbon-13, indicating a lot of lighter carbon might have been suddenly released at the time.

"To cause this type of global isotopic shift, you'd have to take all terrestrial plants and burn them into carbon dioxide," Kessler says, which seems unlikely. That's led scientists to look for other culprits. "But if you look at methane in the sea floor, it's the lightest carbon source [isotopically] on the planet." So many scientists think a sea floor methane release is responsible. Additionally, because methane is a greenhouse gas roughly 25 times more potent than carbon dioxide, a big release would fit with "evidence that the temperature of the planet rose very dramatically" at that time, Kessler says.

But in the case of a big release of undersea methane, how much would escape the ocean to exert its greenhouse effects? "Knowing if it's 1% or 90% that makes it out to the atmosphere will be a very big discovery for us," says Kessler. If the methane stays dissolved, it could trigger a feeding frenzy among microbes, he says. Their consumption of oxygen could create hypoxic zones and have "a serious influence on biodiversity at those times as well,"

Answering these questions is "something we haven't been able to do without running the experiment," he says. The burst well offers just such an experiment, though at a smaller scale. So Kessler scrambled to arrange the cruise in less than 3 weeks, a process which usually takes 4 to 6 months. "Obviously, no one's ever going to allow us to dump tons of methane into the ocean to simulate one of these natural massive eruptions," says Kessler. (The amount of methane being released by the well is too little to affect climate, he says.)

But conducting a rigorous scientific study in a disaster zone has its own drawbacks, he acknowledges. "We're going to get as much as we can without being in the way," he says. They'll have to work around cleanup and containment efforts, but he says he's determined to both "get as close as we can to ground zero" and map the full extent of the plume "to get a very comprehensive map."

When it's time to place his instruments in the water, the real nail-biting begins, he says. Oceanographers generally don't usually work in oil slicks, which might damage their equipment. "Sending our instruments down through this layer of oil is something that's keeping me up at night."

Given the disaster unfolding in the gulf, says Kessler, "if we can make a little lemonade out of the lemons we've been given, then at least maybe some good will come of this."

For more on the gulf oil spill, see our full coverage.

http://news.sciencemag.org/scienceinsider/2010/06/what-the-gulf-dis...