The findings come from a revolving international contingent of scientists who sail on a unique ship called the JOIDES Resolution (the slightly ungainly name comes from the acronym for the Joint Oceanographic Institutions for Deep Earth Sampling). Originally built to drill into the seabed in search of oil, the Resolution has been turned to scientific duty; it carries on board a sophisticated geophysical laboratory that rivals the finest on land and enough computing power to run a small university.
At sea far more often than it is in port, the Resolution has been circling the globe since 1985, drilling core samples from the sediments buried on the seafloor. The ship has drilled in virtually every sea, from the Arctic to the Antarctic, from the Carribean to the Sea of Japan. So far, the Resolution has collected nearly 85 miles of cores. These specimens are stored in four repositories around the world, where they are available for scientific study.
The idea of drilling into the seafloor grew out of a project called Operation Mohole, conceived during the International Geophysical Year. The intent of that project was to find a place in the ocean where the earth's crust is thin and to drill through it into the boundary where the crust meets the mantle. Although the scheme was eventually abandoned as impractical, it made clear to many geologists that drilling into ocean sediments would provide invaluable data about the earth.
Unlike sediments deposited on land, those in the ocean are not easily erased by forces such as wind and running water or distorted by mountain building. Corings of undersea sediments and rocks therefore provide a wealth of information about the earth's interior structure and about long-term changes in the global environment.
The current effort, known as the Ocean Drilling Program (ODP), has proven its worth in a string of important discoveries. Samples collected by the Resolution have confirmed the impact of a meteorite that killed off half of all species at the end of the Cretaceous Era, provided a record of ancient ocean temperature changes that disproved a popular theory of Ice Ages, offered new insights into the formation of minerals and metal ores, obtained the first natural samples of frozen mixtures of water and natural gas (called methane clathrates), and documented intermittent changes in the earth's magnetic poles.
To observe science at sea firsthand, I have joined the Resolution on Leg 174B of the ship's travels. We departed from New York on July 21 and will arrive in Las Palmas, the Canary Islands sometime around August 10. Along the way, the ship will revisit a borehole drilled 21 years ago and install new instruments that will track the flow of water through young crust that has recently (five to seven million years ago) welled up through the Mid-Atlantic Ridge, a huge scar where new ocean floor is born.