The abundance and taxonomic breadth of the animals we found was quite a surprise

Linda Kuhnz, Moss Landing Marine Labs biologist

"This was an epic journey in search of geological knowledge from a remote corner of the Earth," said Peter Michael, of the University of Tulsa, US.

"We have completely unexpected results," said Charles Langmuir, of Columbia University. "The ocean ridge below the Arctic is completely unique. We found 12 new volcanoes where we expected to find none, and we found unexpected and abundant hydrothermal activity."

The researchers believe they have found new organisms living around hydrothermal vents - cracks in the ocean floor through which hot mineral-rich waters flow - where none were expected. The geology of the region will change our understanding of how the Earth works.

Unique fascination

For good reason, the Gakkel Ridge is one of the least explored places on our world. It extends over 1,500 kilometres (930 miles) through the Eurasian Basin of the Arctic Ocean, from north of Greenland to the Laptev Sea off Siberia.

Gakkel Ridge holds a fascination for scientists

It is the deepest and most remote mid-ocean ridge on our planet - a place where the sea floor is being pushed apart by upwellings of magma from inside the Earth. The ridge, however, expands very slowly - at less than one centimetre a year. The spreading ridges in the Pacific Ocean, widen 20 times faster, or about as fast as your fingernails grow.

But despite, or because of, its slow growth, the Gakkel Ridge has a unique fascination. The problem has been getting at it to study it. It is five km (three miles) beneath the ice cover of one of the most inhospitable seas on Earth.

Henry Dick, of the Woods Hole Oceanographic Institution, said: "The ridge is unique because it is virtually unsampled. It is located in a very hostile environment, and logistics have prevented us from getting there until now."

Scientists are analysing the results of the first full-scale expedition to the region which took place last year.

Active surprise

From the end of July to early October 2001, researchers aboard the new icebreaker the United States Coast Guard Healy and the German Research Vessel Polarstern undertook the first systematic sampling of the Gakkel Ridge.

Researchers achieved more than they expected

"We accomplished easily a factor of two more than we planned," said Dr Michael.

Small robotic submarines, called Miniature Autonomous Plume Recorders (MAPRs), were deployed on a trawl wire during sea-floor dredging and drilling operations, in order to identify sites of hydrothermal venting, by looking in the water for the chemicals these remarkable geological features spew into the ocean.

The scientists involved in the research programme said the extent of the hydrothermal activity they detected was remarkable, especially since it was thought the prevalence of venting was related to the rate at which the sea floor spreads.

"Our discovery of these signals clearly show that hydrothermal vents similar to those present on faster-spreading mid-ocean ridges are present in abundance here, too" said Henrietta Edmonds, of the University of Texas.

New organisms

According to Charles Langmuir the expedition "found more hydrothermal activity on this cruise than in 20 years of exploration on the mid-Atlantic ridge".

"These exciting discoveries on Gakkel Ridge," said Peter Michael, "pave the way for future expeditions that will map the vents and may discover completely new organisms."

Linda Kuhnz, a biologist from Moss Landing Marine Labs in California, who participated in the expedition, added: "The abundance and taxonomic breadth of the animals we found was quite a surprise."

The isolation of the Arctic Ocean has long intrigued biologists. They hope that some of the samples recovered will help answer the question of whether the lifeforms and ecosystems in the Arctic resemble those from the Atlantic Ocean or Pacific Ocean, or whether they have evolved separately.

One of the least explored regions of the Earth