In the early 1960s, geologists took their first shot at drilling all the way through Earth's crust and into its mantle with the Mohole Project. It turned out to be a disaster. Named for the Mohorovicic discontinuity, the boundary between the crust and mantle, the ambitious attempt to penetrate 6 kilometers of crustal rock was sunk by cost overruns and management problems and scrapped after a few test holes.
But out of that debacle came a highly successful international scientific endeavor. The decision to drill Mohole from a barge--to take advantage of the fact that the oceanic crust is much thin her than the continental crust--laid the foundation for modern day scientific ocean drilling. And researchers have exploited the world it opened up to make seminal discoveries about the planet. Now, those efforts are about to enter a new era.
Over the past 40 years, researchers have drilled more than 2,900 holes in the ocean floor, retrieved 319 kilometers of mud and rock core, and studied 35,000 samples. The legacy of ocean drilling includes validating the theory of plate tectonics and tracing Earth's changing climate back 100 million years, as well as inventing the field of paleoceanography.
Since 1984, that work has been carried out under the 22-country Ocean Drilling Program (ODP), a unique effort that ended in September 2003. But it will be replaced by something even more ambitious: In October 2003, Japan and the United States inked an agreement formally creating the Integrated Ocean Drilling Program (IODP). It will eventually include 20 or so other countries, cost twice as much to operate as its fore-runner, and use two, and at times three, ships rather than one.
Initially, IODP will rely on an upgraded U.S. drill ship, either a revamped version of ODP's workhorse, the JOIDES Resolution, or a new vessel with similar capabilities. By late 2006, it will be joined by a brand-new ocean drilling vessel, Japan's Chikyu, equipped with technology that will allow it to literally break new ground.
Together, the two ships will enable Earth scientists to bore more and much deeper holes than is currently possible and in locations that are now inaccessible. There are even going to be "mission-specific platforms" that will drill niche locations such as the icy Arctic Ocean and shallow coastal waters.
A new drill ship for a new era
The biggest change in operational capabilities will come when the 210-meter, 57,500-ton, $475 million Chikyu starts drilling. For all its achievements, the Resolution has serious limitations. It can't drill in shallow water or farther down than 2 kilometers. Nor can it tolerate the icy conditions of the Arctic Ocean. What's more, sedimentary basins have been largely off-limits because oil and gas deposits have posed safety and environmental hazards.
The Chikyu will overcome some of these constraints. It will have a second pipe, called a riser, that will enclose the drill pipe and allow circulation of a heavy but fluid drilling mud that will flush debris from deep holes and shore up unstable sediments. The arrangement will also protect against blowouts when the bit penetrates pressurized oil or gas deposits. Attempts at drilling very deep holes using the Resolution were frustrated by the friction and by debris piled up in the hole.
"Because of the capabilities of the riser vessel, [all sorts of drilling] projects will be more viable" said Hisatake Okada, a paleoceanographer at Hokkaido University in Sapporo.
But all of this comes at a steep price. The annual budget of ODP ran about $80 million, with 60 percent of that sum put up by the U.S. National Science Foundation (NSF) and the rest split among the other member countries. Countries spent additional funds to support scientists analyzing drilling samples and data.
In comparison, IODP's annual operating budget is expected to start at $160 million and …