AS THE OIL SLICK from the destroyed Deepwater Horizon rig drifted northward in the Gulf of Mexico toward the U.S. coast through the weekend, predictions about the possible damage steadily worsened. The latest: If BP can't soon arrest the flow of oil from three breaks in the rig's well pipes, the spill could be as large as that of the notorious Exxon Valdez in 1989 -- or worse.
This tragedy doesn't change the basic math on America's oil dependency. Like it or not -- and we don't -- America is going to require decades' worth of crude, even if the country aggressively invests in clean energy. That addiction comes with a long list of geopolitical and environmental risks. Domestic offshore drilling isn't the panacea some on the right seem to think. America will probably have to import a large balance of the oil that it consumes, regardless. But the alternative to tapping domestic resources is importing even more from offshore fields in places such as Azerbaijan and Nigeria, where regulation might be even less robust.
To what extent the tragedy changes the politics of offshore drilling remains to be seen. Until now, allowing more drilling off America's shores seemed key to attracting the Republican support needed to pass comprehensive climate and energy legislation. And without a real climate bill, America might be addicted to oil a lot longer than it needs to be. President Obama is right to allow to proceed his plan to open parts of the Outer Continental Shelf to drilling. That process is only in the earliest stages of what will be extensive safety and environmental review.
But it's also right that no significant steps be taken until the current situation is dealt with, its causes are understood and the adequacy of the response is investigated. The first priority obviously is to stop the gushing. On Friday, Mr. Obama said he also had ordered Interior Secretary Ken Salazar to produce a report on what caused the rig to explode. Questions abound. Mr. Salazar's analysis, due in a month, might shed light on:
-- whether a defective blowout preventer is to blame;
-- whether the explosion could have been prevented if the government had required the equipment to have an "acoustic valve," as Norway does;
-- whether the machinery was properly maintained;
-- whether there were deeper design or workplace safety flaws that contributed.
Any findings, the president says, will inform regulation on new rigs that might begin operating in formerly protected waters in coming years.
Mr. Obama stressed on Sunday that BP is responsible for this "massive and potentially unprecedented environmental disaster," and he pledged full federal efforts to end the crisis. But so far those efforts have been unavailing. Once again, a "fail-safe" mechanism has failed. The Gulf region and the country need to know why.