If efforts fail to cap the leaking Deepwater Horizon wellhead in the Gulf of Mexico (map), oil could gush for years—poisoning coastal habitats for decades, experts say.

(See satellite pictures of the Gulf oil spill's evolution.)

Last week the joint federal-industry task force charged with managing the spill tried unsuccessfully to lower a 93-ton containment dome (pictures) over one of three ruptures in the rig's downed pipe.

Crystals of methane hydrates in the freezing depths clogged an opening on the box, preventing it from funneling the spouting oil up to a waiting ship.

Yesterday a smaller dome was laid on the seafloor near the faulty well,