SCIENCE sciencemag.org 21 DECEMBER 2018 • VOL 362 ISSUE 6421 1343Jamieson on the mother ship, Pressure Drop.
It has space for three scientists, a wet lab, and
a $1.5 million multibeam sonar to map the
sea floor and verify its deepest spots.
Once a dive site is chosen, Vescovo will
plunge in the sub, following three land-
ers dropped several kilometers apart. The
landers, which contain cameras and baited
traps, collect water and sediment samples.
They also emit acoustic beacons for the sub
to follow on its seafloor traverses. Along
the way, it will record video with four wide-
angle, low-light cameras. Floodlights will
help the crew collect rocks or slow-moving
organisms with a manipulator arm.
The sub can spend about a dozen hours
at the bottom per dive, but the ship will
linger only a few days at most sites. Even a
cursory look could open windows on trench
ecosystems. Examining specimens could
reveal their adaptations, and genetic analy-
sis back in Newcastle should yield evolu-
tionary relationships of organisms from
various trenches. Jamieson wants to know
how species are influenced by temperature,
depth, or the downward-drifting supply of
food. He also wants to understand why fish
in trenches seem to live shorter lives than
those on the 6000-meter-deep abyssal plains.
Jamieson thinks landslides and rockfalls in
the steep-sided trenches may be taking a toll.
The new high-resolution maps could also
yield insights into how tectonic forces created
the deepest parts of the trenches—revealing
cliffs created by faults, for example—says
Heather Stewart, a geologist with the British
Geological Survey in Edinburgh, who will be
visiting at least the first two trenches. Sam-
pled minerals could provide estimates of the
water that subducting tectonic plates take
into the mantle. These water-bearing miner-
als weaken the plates, perhaps reducing their
potential for shallow earthquakes, and they
also drive a deep water cycle in which water
is swept into Earth’s interior and returned to
the surface in volcanic eruptions. Rocks col-
lected from known locations should be more
informative than those hauled up randomly
in a trawl, says Lara Kalnins, a marine geo-
physicist at the University of Edinburgh.
“They can take images and videos—all of this
is context you ordinarily don’t get.”
After the team leaves Puerto Rico this
week, it will head for the South Sandwich
Trench, in the Southern Ocean near Ant-
arctica. Then comes the Indian Ocean and
the Pacific, and finally the Arctic. For the
final leg of the expedition, in September
2019, Pressure Drop will sail up the Thames
River to London, and Vescovo and Jamieson
will give a lecture at the Royal Geographi-
cal Society. Then Vescovo hopes to sell Pres-
sure Drop, the sub, and the landers, slightly
used, for $48.2 million. j
National Academies urges
renewed commitment to fusion
U.S. should stick with ITER, build a power plant, panel says
FUSION ENERGYT
he United States should prepare to
build its own prototype fusion power
plant, according to leading energy
scientists. The compact power plant
(CPP), able to produce sustained elec-
tric power, would be a follow-up to
ITER, an international megaproject under
construction near Cadarache in France that
aims to demonstrate that a fusion generator
can produce more energy than it consumes.
To be built in the 2030 s, the CPP would be
smaller and cheaper than ITER, says a report
released last week by a committee of the Na-
tional Academies of Sciences, Engineering,
and Medicine. But it will
depend on as yet unproven
technologies and a long-shot
infusion of money.
“The fundamental mes-
sage is that the U.S. fusion
program has to have an
ambition to drive through
and generate some kilo-
watts of power,” says Steven
Cowley, director of the
Department of Energy’s
Princeton Plasma Physics
Laboratory in New Jersey,
who was not on the panel.
“What’s the point of having
a fusion program if you don’t have a goal to
develop the first fusion power plant?”
In nuclear fusion, light nuclei fuse to form
heavier ones and release energy. Physicists
have struggled for decades to turn fusion
into a practical source of power, generally by
using intense magnetic fields in doughnut-
shaped devices called tokamaks to confine
and squeeze ionized gases, or plasmas, of
deuterium and tritium so that the nuclei
fuse to make helium. ITER will heat plasma
to 150 million K and aims to be the first to-
kamak to realize a net gain in energy.
Researchers around the world have plans
to build prototype power plants after ITER.
For example, scientists in Europe want to
build the Demonstration Power Station, a
tokamak even bigger than ITER. In con-
trast, the CPP would generate more power
in a device a fraction of ITER’s size.
To shrink the CPP, physicists would
ramp up its magnetic field to twice thatof ITER’s, Cowley says. That field would
squeeze the plasma to a pressure four times
greater than ITER’s—and twice as great as
the pressure in the ocean’s 11 - kilometer-
deep Mariana Trench. The quadrupled
pressure would quell turbulence and limit
heat loss, so that the CPP could shrink to
one-eighth the volume but crank out twice
as much power. Whereas ITER’s main mag-
net coils are 9 meters wide, the CPP’s coils
might be just 4 meters wide.
The CPP will require major advances in
materials, computing, and plasma physics.
For example, whereas ITER’s main super-
conducting magnet coils consist of con-
ventional niobium-tin wire, the CPP would
use coils made from exotic
high-temperature super-
conductors such as bismuth
strontium calcium copper
oxide. Those materials are
relatively brittle ceram-
ics. So far, researchers can
fashion them into coils with
bores just centimeters wide,
not the meters needed for
tokamak coils.
To build the CPP, re-
searchers will also need
the knowledge they’ll gain
from ITER, Cowley says.
In the past, lawmakers in
the U.S. Senate have called for the United
States to withdraw from the project. But
the report argues against a pullout, noting
that the country would first have to build
its own version of ITER before launching
the CPP. “There is no shortcut” around
ITER, says Michael Mauel, a fusion physi-
cist at Columbia University and co-chair of
the report panel.
To realize the committee’s vision, the
report also calls for increasing U.S. fund-
ing for fusion research by $ 200 million
per year, a 35 % increase over the current
$ 564 million annual budget. “Adding
$200 million [per year] for 2 decades is an
extremely unlikely scenario,” says William
Madia, a vice president at Stanford Uni-
versity in Palo Alto, California. However,
one Democratic staffer in the House of
Representatives says, “I wouldn’t say that
these numbers are wildly out of step with
what’s possible.” jBy Adrian Cho“What’s the point
of having a fusion
program if you
don’t have a goal
to develop the
first fusion
power plant?”
Steven Cowley, Princeton
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