Hydrothermal vent systems could have persisted millions of years,incubated life (Forwarded)

University of Washington
Seattle, Washington

Contact:
Sandra Hines, University of Washington
206-543-2580,

Cheryl Dybas, National Science Foundation
703-292-7734,

Scottee Cantrell, Duke University
919-613-8074,

FOR IMMEDIATE RELEASE: July 24, 2003

Hydrothermal vent systems could have persisted millions of years, incubated life

The staying power of seafloor hydrothermal vent systems like the bizarre Lost
City vent field is one reason they also may have been incubators of Earth's
earliest life, scientists report in a paper published in the July 25 issue of
Science.

Discovered just 2-1/2 years ago during a National Science Foundation-funded
expedition in the mid-Atlantic Ocean, Lost City has the tallest vents ever seen
-- the 18-story behemoth at the site dwarfs most vents elsewhere by at least 100
feet. Water is circulated through the vent field by heat from serpentinization,
a chemical reaction between seawater and the mantle rock on which Lost City
sits, rather than by heat from volcanic activity or magma, responsible for
driving hydrothermal venting at sites scientists have been studying since the
early 1970s.

If hydrothermal venting can occur without volcanism, it greatly increases the
places on the seafloor of early Earth where microbial life could have started.
It also means explorers may have more places than previously thought to look for
microbial life in the universe.

Although the Lost City vent field is a youthful 30,000 years old, Lost City-type
systems might be able to persist hundreds of thousands, possibly millions, of
years, says lead author Gretchen Früh-Green of the Swiss Federal Institute of
Technology and co-authors from the University of Washington, Duke University and
National Atmospheric and Oceanic Administration. One can imagine how such
stable, long-lived systems pumping out heat, minerals and organic compounds for
millennia might improve the chances for life to spark and to be sustained until
it could take hold, say these scientists.

"It's difficult to know if life might have started as a result of one or both
kinds of venting," says Deborah Kelley, University of Washington oceanographer,
"but chances are good that these systems were involved in sustaining life on and
within the seafloor very early in Earth's history."

As far as longevity and stability, it's possible that black-smoker systems might
last as long as 100,000 years but it's unlikely, Kelley says. That's because
black-smoker systems typically form where new seafloor is being created, a
process that -- even if a volcanic eruption doesn't bury a hydrothermal vent
field in lava -- will eventually shove the seafloor bearing the vents away from
the source of volcanic heat needed to power them.

Lost City is already nine miles from the nearest volcanically active spreading
center and sits on 1.5 million-year-old crust. Seawater permeating deeply into
the fractured surface of the mantle rocks transforms olivine into a new mineral,
serpentine. The heat generated during this process is not as great as that found
at volcanically active sites -- where fluids can reach 700 F -- but it is enough
to power hydrothermal circulation and produce vent fluids of 105 to 170 F.

Tectonics, the movement of the Earth's great plates, contributes to the
fracturing of the mantle rock. But a big reason this kind of system is so
self-sustaining, the Science report says, is that fracturing also happens
because rocks undergoing serpentinization increase in volume 20 percent to 40
percent. Kelley likens it to water seeping into tiny cracks in roads, then
freezing and expanding to cause ruts and frost heaves in the pavement.

Scientists think many Lost City-type systems were possible on early Earth
because so much of the mantle had yet to be skinned over with crust, putting it
in contact with seawater and making serpentinization possible, Kelley says.

Lost City is the only vent field of its kind known today but scientists say more
could exist. Within a 60-mile radius of Lost City are three similar mountains
and there are other, potential sites along thousands of miles of ridges in the
mid-Atlantic, Indian Ocean and Arctic.

Beyond Earth, peridotite -- the mantle material that reacts with seawater during
serpentinization -- is abundant on all the terrestrial planets in our solar
system, says Jeff Karson, Duke University professor. "Peridotite can be exposed
by tectonic processes or by major cratering events. This means that Lost
City-type venting could occur, or has occurred, in oceans on other planets, and
such venting would have the potential to support microbial systems."

Lost City-type systems also may be conducive to life because their fluids are
high pH and rich with organic compounds compared to black-smoker systems.

Black smokers get their name because it can appear as if smoke is billowing from
the vents. What's actually being seen are dark minerals precipitating when
scalding hot vent waters meet the icy-cold ocean depths. Water venting at Lost
City, in comparison, is hot enough to shimmer but not "smoke." Because of the
different chemistry, black-smoker vents are a darkly mottled mix of sulfide
minerals whereas the Lost City vents are nearly 100 percent carbonate, the same
material as limestone in caves, and range in colors from white to cream to gray.

The field, named Lost City in part because it sits on a seafloor mountain named
the Atlantis Massif, was discovered Dec. 4, 2000, when scientists weren't even
looking for hydrothermal vents.

"The discovery of the Lost City vent field is a wonderful example of serendipity
in science -- studying one problem and discovering something totally new and
unexpected," says David Epp, program director in NSF's marine geology and
geophysics program. "The detailed work is just beginning and should change the
way people think about vent systems."

This spring, the NSF funded the first major scientific expedition to Lost City
since its discovery. Led by Kelley and Karson, the expedition is documented at:
http://www.lostcity.washington.edu/

Other Science co-authors are the Swiss Federal Institute of Technology 's
Stefano Bernasconi, University of Washington's Kristin Ludwig and Giora
Proskurowski, and National Atmospheric and Oceanic Administration 's David
Butterfield.

###

To reach Früh-Green and Kelley, contact UW's Sandra Hines, 206-543-2580,


Press release about 2003 expedition at
http://www.washington.edu/newsroom/n.../k041503a.html

IMAGE CAPTION:
[http://www.washington.edu/newsroom/n...nge-072403.jpg (273KB)]
A snow-white carbonate flange, about 7 feet tall, grows out the side of 85-foot
vent at the Lost City Hydrothermal Vent Field. Photo credit required: University
of Washington/Science

Just-released images from 2003 expedition:

[Image 1:
http://www.washington.edu/newsroom/n...ive-072403.jpg (227KB)]
Vigorously venting hydrothermal fluid between 105 and 170 F at Lost City
shimmers while minerals precipitating from the fluids create feathery spires and
mounds of carbonate, such as this 3-foot beehive-shaped structure, on the sides
and tops of large chimneys. Photo credit required: University of Washington

[Image 2:
http://www.washington.edu/newsroom/n...ers-072403.jpg
(441KB)]
Lost City chimneys no longer venting hydrothermal fluids become a creamy gray
color and can be pitted like these 12-foot spires topping an extinct vent. The
cliff face behind is old mantle material and carbonate. Photo credit required:
University of Washington

2003-expedition video, contact NSF's Dena Headlee, 703-292-7739,

Map, 2000 images at for use by news media:
http://www.washington.edu/newsroom/n...ages/lostcity/