A half century after scientists failed on their first attempt to
penetrate the Earth's mantle, geologists Damon
Teagle of the National Oceanography Center in Southampton,
England, and Benoit Ildefonse from Montpellier University in
France say it's time for a second try. And unlike their predecessors,
they have the technology to turn that challenging endeavor into a
reality.
The goal is to retrieve samples from the Earth's mantle,
a feat which, if successful, would supply a trove of new
information about our planet's origins and history.
Scientists still don't have a good idea how magma moves through the
upper mantle and into the crust.
Nor do they know much about the coupling of the crust and the
underlying mantle--that is, what's pushing or pulling what.
Thus the intrigue of burrowing into a region still untouched by
human exploration.
"If we could recover pristine samples of mantle rocks then we could
make better estimates of the composition of our planet--and have a
better understanding of how our planet has evolved and
"differentiated" into the spheres (crust, mantle, core etc)," Teagle
wrote in an e-mail interview with CBSNews.com.
"A pristine sample of say 500 meters of the upper mantle could
liberate answers to these questions and much more," according to
Teagle. The search for a potential drill site in the Pacific will start
this spring, with an eye on beginning the project later in the decade.
The three most likely sites up for consideration include the coasts of
Hawaii, Baja California, and Costa Rica. Once work gets under way,
it will take between 18 months and 2 years to reach the Earth's
mantle.
The first time scientists attempted to penetrate the Pacific Ocean's
crust--in the spring of 1961--the novelist (and amateur
oceanographer) John Steinbeck went along for the ride, chronicling
the expedition for Life magazine. But the project had only limited
success--it took some core samples from the top part of the ocean's
crust near Guadalupe Island in the eastern Pacific Ocean--and
Congress canceled its funding five years later.
But Teagle noted that deep ocean drilling has come a very long way
in the last 50 years, largely as a result of the experience of scientific
ocean drilling "and because the offshore petroleum industry has
moved into deeper water." He pointed to advances, such as
thrusters, transponders, and GPS technology, to hold the ship in
place in very deep water and allow researchers to routinely re-enter
holes to replace drill bits, which typically wear out after about 50
hours of use.
"We also have a much better understanding of what we are trying to
do--we have good understanding of how the ocean crust is formed
and the difference between the crust and the mantle. However,
some details remain elusive," he added.
That's not to say all the technical hurdles have been cleared away.
The project will depend on improved drill bits, tools, and
instruments that can work at very high temperatures of around 300
degrees Celsius.
In publicizing their interest in the journal Nature, Teagle and
Ildefonse wrote that while reaching the mantle posed the biggest
challenge in the history of Earth science, it also offered an
extraordinary reward--nothing less than "a legacy of fundamental
scientific knowledge, and inspiration and training for the next
generation of geoscientists, engineers, and technologists."
