Even amongst the alien worlds of the deep sea, a recently discovered seafloor "hot spring" is an oddball. The 1,300-foot (400-meter) long area, called a hydrothermal vent field, is studded with spindly chimneys that gleam white and cream in the lights of an underwater robot. Clear water rises from underwater geysers in a nearly invisible shimmer, and tiny worms dot the seascape like daisies scattered across a meadow.

"The chimneys have a kind of fairy-castle look to them," says Dave Clague, a marine geologist at the Monterey Bay Aquarium Research Institute (MBARI) in Moss Landing, California. That's because the "snow white" spires are built of calcium carbonate, or limestone, he explains.

But despite the fairytale appearance of it all, these