Scientists have found additional evidence that life on earth may have first
been found on the ocean floor. As this ScienCentral News video reports, the
evidence is also providing clues for looking for life on other planets.
Life's Underwater Origins
A mysterious, alien environment is helping scientists learn more about the
origins of life on Earth, and perhaps on other planets as well. That environment
is right here on Earth, on portions of the sea’s floor where heat creates
pools of life that is often very different from that found on Earth’s
surface.
Hydrothermal vents are geysers on the seafloor, formed as the earth vents volcanic
heat. They continuously spew hot, mineral-rich water that helps support a
diverse community of organisms. The 1977 discovery of these chimney-like structures,
the hottest of which are nicknamed "black
smokers," changed the way scientists looked at how life on Earth
may have evolved.
Now, scientists writing in the journal Science
have investigated a different type of vent formation, discovered in the mid-Atlantic
on December 4, 2000, called “Lost
City.” Its name is partly based upon the myth of the lost city of
Atlantis. Lost City is located on a large undersea mountain about the size
of Mt. Rainier called the Atlantis
Massif, and is the size of two football fields, with some spires 18 stories
tall. Lost City is different because, instead of volcanic activity, it relies
upon a chemical reaction to create its heat.
A black smoker image: Univ. of Washington
Deborah
Kelley, associate professor of oceanography at the University
of Washington and one of the three people on the first manned dive to
Lost City, says the two kinds of formations are very different. “When
you drive up to a black smoker system on the sea floor in a submarine or a
robot,” says Kelley, “you see billowing black clouds of smoke,
and those are very fine grains, particulate of iron sulfites and other metal-rich
minerals. At Lost City, it’s a much gentler environment. There’s
no black clouds at all that typify most of them. These are very clear fluids
and the chimneys are bright white."
It's also a more stable environment than black smokers, which can only sustain
life during irregular periods of volcanic activity. Kelley says Lost City
“is about 30,000 years old" and adds, "from looking at how
it formed, we think it could last up to a hundred thousand to perhaps a million
years old."
Instead of volcanoes, Lost City’s heat comes from a chemical reaction
between the mantle rock and seawater called serpentinization.
The heat from this reaction is not as high as from a volcano, but it is high
enough to circulate the water.
If hydrothermal vents can occur without volcanoes, the number of places on
young Earth's seafloor where life could have begun greatly increases. This
is crucial information for scientists looking for life on other planets, such
as one of Jupiter’s moons, Europa.
Europa shows evidence of water, but it does not appear at the moment to be
volcanically active.
"What it says is that volcanoes are no longer required for life to evolve,"
says Kelley, "and you may find planets like Europa where there may not
be active volcanism right now, but similar rock types to what we see beneath
Lost City. So we’re hoping we can use what we learn from Lost City as
guides for life elsewhere."
Whether searching for life on other planets or for a better idea of its origins
on this one, scientists plan to revisit Lost City for more study, and are
also on the lookout for other Lost Cities. "The world's oceans are really
an undiscovered place," says Kelley. "We don’t know a lot
about them, and what this discovery highlights is that there are still some
very spectacular things out there."
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