The Biggest Dig
A
mega-drill will go where no machine has gone before: into Earth's mantle
By Rena
Marie Pacella | October 2005
Traveling to the center of the Earth is a
fanciful concept, but consider the reality: We have so
far drilled just 7.5 miles into the Earth's rocky crust, leaving roughly 3,962
more miles to go. The new Japanese research vessel Chikyu
won't exactly breach Earth's core, but it will drill to an unprecedented depth,
beginning in late 2007 when it embarks on its first scientific mission off the
southwestern coast of
The 57,500-ton rig is equipped with a 5.9-mile-long drill
designed to blast four miles into Earth's crust and strike the semi-molten
mantle that lies beneath it. There, scientists hope to dig up primordial
creatures—such as hydrogen- feeding microbes that may be thriving under the
same conditions as those of the early Earth—and possibly reveal new clues to
the origin of life. "It is the only place where you might find such
ancient life-forms," says Asahiko Taira, director of
Ordinary drills can't reach the mantle through the ocean because
their boreholes collapse beyond a depth of 1.3 miles, where pressure can exceed
7,000 pounds per square inch. To make walls pressure-proof, the Chikyu drill will pump high-density artificial mud into the
borehole as it burrows into the Earth. If all goes well, scientists hope to
strike the mantle by 2012.
HERE'S THE DRILL
Operators pump artificial mud—composed of clay minerals, viscous polymers and
seawater—into the drill pipe. As the "mud" pours through the drill
bit, it lubricates the nozzle and clears it of rock cuttings. Mud and the
debris circulate back up the borehole, coating the borehole walls and helping
them to resist collapse.
