On the horizon

When limbs became fins

It's a story worthy of Rudyard Kipling in a lab coat: "How the Whale Lost Its Hind Legs." Scientists from the US and India have pieced together a story of how whales, dolphins, and porpoises - cetaceans - underwent a remarkable transformation from four-legged animals to denizens of the deep, a process that began roughly 50 million years ago.

The biology behind the change has been a puzzle. Fossils and DNA studies indicate that whales once shared a common ancestor with deer, hippos, sheep, goats, and camels. But once cetaceans' ancestors took to the sea, they had to become more streamlined to survive. Front legs became fins; hind legs vanished. Some scientists have argued that the genetic shifts needed to foster the loss of the hind legs happened somewhat quickly. But a team led by Hans Thewissen at Northeastern Ohio Universities College of Medicine in Rootstown, found evidence that the change was far more gradual - more along the lines Charles Darwin described for evolution.

Evidence from modern spotted-dolphin embryos suggests the genetic switch for the hind limbs' disappearance came only after they underwent millions of years of downsizing. Results appear in the current issue of the Proceedings of the National Academies of Science.

For a team of researchers studying undersea volcanoes, Brimstone Pit has become the star of the show. Scientists report they have observed an eruption on the flank of an underwater volcano some 37 miles from Rota, a tiny Pacific island in the Marianas chain. Researchers have observed eruptions along mid-ocean ridges, where lava replenishes Earth's massive crustal plates. But the team says this marks the first time scientists have directly seen and sampled material from an ongoing volcano eruption that could one day become an island.

Brimstone Pit is a 50-foot-wide crater near the summit of the volcano, which rises some 7,000 feet above the sea floor. The team, led by Robert Embley of the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle, also found that the surrounding water was as acidic as lemon juice - producing a habitat fit only for microbes and a few species of shrimp. The scientists suggest that these habitats may be unique to such "arc" volcanoes. Their work appears in Thursday's issue of the journal Nature.

At only two-billionths of a meter across, carbon nanotubes would demand a lot of pucker from a milk-shake drinker hoping to draw a taste of chocolate. But for a team of Bay Area scientists, these tubes could be just the ticket for slashing the amount of energy it takes to separate chemicals by passing the mixture through porous membranes. This method is a widely used separation technique, but the process can be energy intensive.

But researchers at the University of California at Berkeley and Lawrence Livermore National Laboratory found that water and gas flow through their porous nanotube arrays far faster than predicted. The team suspects the higher flow rates stem from the exquisitely smooth surface inside the nanotubes.

If the approach can be scaled up, other researchers say, it could provide an economical way to "scrub" gases such as carbon dioxide from power-plant emissions. The results appear in the current issue of the journal Science.