Deep-sea microbes
heat up search for life signs in space
But if nearby moons and distant stars' planets harbor
nothing, we might be alone
July 6, 1999
by Joun Yaukey
Half a millennium ago, Copernicus evicted us from the
center of the universe by pointing out that Earth orbits
the sun.
Centuries later, Darwin challenged divine creation
with evolution.
Now, many scientists say we are poised for another
titanic revelation about our sense of place in the
cosmos.
"Our search for other life is going to help decide
which of two very different views of the universe is
correct," says New York University chemistry professor
Robert Shapiro, author of Planetary Dreams, in which he
suggests that the notion of life beingunique to Earth
could prove implausible.
Down one road, we discover that life is common in the
universe, that the cosmos is in the business of making
life. Space probes suggest that several of the solar
system's planets and moons harbor microbes or eventually
could. And, as with Earth, where there are microbes,
there eventually could be intelligent life.
The other path leads to a kind of biological
existentialism. We concede we live on a freakish Eden,
adrift in an otherwise lifeless sea. Probes sent to the
vast oceans of the Jovian moon Europa, which scientists
are eager to explore for signs of life, find only
lifeless slush. None of the recently discovered planets
outside the solar sys- tem shows signs of water or
atmospheric chemistry indicative of life below. We
conclude that if there is life, it's so far away or
foreign in structure that we won't find it or won't
recognize it if we do.
"Confirmation of life elsewhere -- even the most
primitive of microbes -- would be the defining discovery
of humankind," American University astrophysicist
Richard Berendzen says. "And we live in a time when we
will soon be able to look for life outside our own solar
system."
In their search to better characterize the cosmos,
scientists are exploring not only the black pastures of
space, but also the silt-enshrouded canyons of the sea.
The two seemingly opposite environments have become
linked as scientists study newly discovered microbes
thriving in the scalding, lava-heated vents deep in the
sea and wonder whether such primitive but tenacious life
could arise elsewhere.
|
'Biosphere' theory starts with enemy of status
quo
ITHACA, N.Y. --
Thomas Gold might have grown tired of tilting
at windmills long ago had he not destroyed so
many.
Throughout his 50-year
career, the Cornell astronomer emeritus who
helped develop radar and radio astronomy has
flouted conventional wisdom with outlandish
theories that later became conventional
wisdom.
"When I see a glaring error,
I feel compelled to put it right," the
Vienna-born Gold says. As in the past, his
latest attempt promises either to rewrite
time-honored text or die amid the snickers of
critics.
In The Deep Hot Biosphere,
Gold overturns conventional ideas about how
life started. He believes that life developed
from primitive microbes in the scalding layers
below the oceans, where they fed on the
chemical energy in oxidized minerals.
Gold doesn't deny logging
many miles down the path less taken: "In
choosing a hypothesis, there isn't any virtue
in being timid."
And he hasn't been.
In 1967, he was laughed at
for his theory that pulsating energy detected
in the distant universe was coming from old
stars that had spent their nuclear fuel and
were collapsing. The subsequent observation of
pulsars won two other scientists a Nobel Prize
and proved Gold correct.
His radical theory of
hearing, developed after his work on radar,
was written off for 30 years before the
medical establishment realized it was correct.
In 1992, Gold predicted what
NASA would announce four years later: Martian
meteorites might contain microbial fossils.
Nobel Prize-winning
physicist Freeman Dyson has said, "Gold's
theories are always original, always
important, usually controversial and usually
right."
But when Gold blunders, he's
famously wrong. He was among a trio of
scientists who concocted the steady state
theory of the universe. It says that although
the galaxies are rushing apart from each
other, new matter is being created to fill the
voids at a rate that keeps the universe
looking the same.
The big-bang theory
obliterated the steady state concept. But Gold
held on to it for years and became the butt of
jokes.
Gold is quite familiar with
that tight spot between a rock and a hard
place. As far as he's concerned, that's where
life started. |
Life at extremes
In 1977, a small submarine dubbed Alvin descended to
about 8,000 feet near the Galapagos Islands where the
sea floor was cracking under the pressure of volcanic
activity.
As the searchlights scanned the sea floor, they
revealed among the barren expanses dense communities of
life clustered around vents spewing lava-heated water
and debris into the frigid surroundings. Researchers
were astonished to discover the food chain was built on
previously unknown forms of heat-loving microbes. These
organisms thrive in the inky, roiling clouds of
600-degree water and sulfur.
Temperatures can go only so high before biochemistry
breaks down. But at the limits, some microbes, dubbed
extremophiles, thrive.
Many scientists now regard deep-sea thermal vents as
a dark window into the primordial conditions that gave
rise to life billions of years ago, when Earth was far
less hospitable.
One of the most hotly debated new ideas -- known as
the theory of the deep, hot biosphere -- turns the
traditional explanation of genesis upside down. This
model has potentially far-reaching implications for
virtually all theories about life formation.
Formulated largely by Cornell University astronomer
Thomas Gold, the theory proposes that life arose not
near the surface of the early seas, where it drew energy
from sunlight, but from primitive microbes thriving in
the depths of the planet, feeding on its chemical
energy.
"We suffer from surface chauvinism," Gold argued in a
recent interview after the publication of his book The
Deep Hot Biosphere. "It is far more likely that life
began deep within the planet. But because of where we
live, we don't think much about the life below us."
There, sedimentary rocks supply chemical energy to
microbes in the form of oxidized minerals. Extremophiles
are so adept at extracting this nourishment that they
thrive even in igneous rock -- solidified lava with
almost no organic matter.
The life that covers the planet, Gold believes,
migrated upward through deep-sea vents, eventually
trading its primitive ability to feed on chemical energy
for the more complex process of photosynthesis.
This theory greatly reduces the lowest common
denominator for life.
"This makes life elsewhere far more probable, because
the likelihood of living conditions like those at the
Earth's surface are so improbable," Gold says.
In 1997, the NASA probe Galileo hurtled past Europa,
snapping a series of photos that left scientists
slack-jawed. To the untrained eye, Europa's surface
looked scratched.
To scientists, those riven lines indicated glacial
plates floating on a liquid, probably water. Scientists
had suspected Europa was wet, but these ../images were
almost proof.
Water, as opposed to ice, is so vital in the search
for life because it allows elements to mingle and form
the complex organics necessary for all known biology.
Warmed by tidal heat, Europa's apparently liquid ocean
is prompting intense curiosity about possible life there
and whether it might resemble Earth's extremophiles.
In the novel 3001, science-fiction writer Arthur C.
Clarke envisions Europa as home to a diversity of life
thriving around hot deep-sea vents.
Scientists are more cautious.
"Is there water there (Europa) now, or are we seeing
evidence of water a million years ago?" says Carl
Pilcher, director of solar system exploration at NASA.
"We need to be able to answer that and a lot of other
questions before we start talking about life."
The heightened interest in Europa comes at a time
when scientists are increasingly considering the
possibility that several planets and satellites in our
solar system contain liquid water and chemical systems
evolving in the direction of life.
In addition to Europa, two of Saturn's moons look
intriguing. Enceladus shows signs of an icy surface and
may have flowing water, and icy red moon Titan has
captured attention as a potential incubator of complex
organics.
Now en route, the Cassini space probe will study
Titan for clues about how organics form there.
The search is on
The study of extremophiles on Earth and the
possibility of liquid water on other planets together
are rewriting the odds on extraterrestrial life.
NASA's agenda is heavy with missions that will look
for life and its chemical signatures.
Robotic spacecraft have explored more than 70 planets
and satellites within the solar system, and astronomers
have discovered what appear to be planets circling as
many as eight sunlike stars.
Meanwhile, other disciplines -- from exobiology,
which theorizes about otherworldly life, to
oceanography, geology and biology -- are contributing to
a massive pool of data about life here and what it can
tell us about the likelihood of the existence of life
elsewhere.
The evidence may point to a living cosmos.
Or we may encounter only barren wastelands, vacant of
signs of life.
Research and exploration over the coming decades will
help determine which of these two different views of the
cosmos prevails.
