by Charles Baum
carbon dioxide. Our bodies convert sugar molecules along with the
oxygen we breathe to produce water plus the waste gas carbon dioxide.
There’s an elegant chemical symmetry to this story; the biological
world seemed much simpler when the Sun was life’s only important
energy source.
DEEP ECOSYSTEMS
Our view of life on Earth changed forever in February 1977, when Or-
egon State University marine geologist Jack Corliss and two crewmates
guided the submersible Alvin to the deep volcanic terrain of the East
HEAVEN OR HELL?
97
Pacific Rise, 8,000 feet down. This undersea ridge off the Galápagos
Islands was known to be a zone of constant volcanic activity associated
with the formation of new ocean crust. Oceanographers have docu-
mented thousands of miles of similar volcanic ridges, including the
sinuous Mid-Atlantic Ridge that bisects the Atlantic Ocean—the long-
est mountain range on Earth.
On this particular dive, just one of hundreds that Alvin had logged,
the scientists hoped to locate and examine a submarine hydrothermal
vent, a kind of submarine geyser where hot water jets upward into the
cool surrounding ocean. What Corliss and crew discovered was a vi-
brant and totally unexpected ecosystem with new species of spindly
albino crabs, football-sized clams, and bizarre 6-foot tubeworms. One-
celled organisms also abounded, coating rock surfaces and clouding
the water. These communities, thriving more than a mile and a half
beneath the sea, never see the light of the Sun.
In these deep undersea zones, microbes serve as the primary en-
ergy producers, playing the same ecological role as plants do on Earth’s
sunlit surface. These one-celled vent organisms exploit the fact that the
cold oxygen-infused ocean water, the hot volcanic water, and the sul-
fur-rich mineral surfaces over which these mixing fluids flow are not
in chemical equilibrium. This situation is similar to the disequilibrium
between a piece of coal and the oxygen-rich air. Just as you can heat
your house or power machinery by burning coal (thus combining un-
stable carbon and oxygen to make stable carbon dioxide), so too can
these deep microbes obtain energy by the slow alteration of unstable
minerals.
The unexpected discovery of this exotic ecosystem was news
enough, but Corliss and his Oregon State colleagues soon tried to push
the story further. They saw in the vents an ideal environment for the
origin of life. Details of this story have become clouded by more than
20 years of sometimes revisionist history. Corliss claims the idea for
himself: “I began to wonder what all this might mean, and this sort of
naïve idea came to me,” he told an interviewer more than a decade
later. “Could the hydrothermal vents be the site of the origin of life?”
[Plate 5]
A different history emerges from others close to the story. Accord-
ing to John Baross, a former faculty colleague of Corliss and an expert
on microbes in extreme environments, the hydrothermal vent theory
of life’s origin was first proposed and developed by a perceptive Or-
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GENESIS
egon State graduate student named Sarah Hoffman. She wrote the ba-
sic outlines of the hypothesis in 1979, as a project for a biological
oceanography seminar taught by Charles Miller, another OSU ocean-
ographer. Hoffman, in frequent consultation with Baross, developed
the novel idea as it would appear in print. The two of them claim that
the more senior Corliss seized the paper as his own, allowing them, as
his coauthors, to expand and polish the prose to conform to the con-
ventions of scientific publishing, after which he submitted the work
and placed his name first on the author list. With three coauthors—
Corliss, Baross, and Hoffman—the paper would forever be known as
“Corliss et al.” Corliss would get the fame, while Hoffman and Baross
were effectively relegated to footnote status.
Whoever deserves the credit, the hydrothermal-origins thesis is el-
egantly simple and correspondingly influential. Modern organisms do,
in fact, thrive in deep hydrothermal ecosystems. Fossil microbes recov-
ered from 3.5-billion-year-old hydrothermal deposits reinforce this
observation. Even without the energy of sunlight, nutrients and chemi-
cal energy abound in hydrothermal systems. The OSU scientists saw
hydrothermal systems as “ideal reactors for abiotic synthesis,” and they
proposed a sequence of chemical steps for the potentially rapid emer-
gence of life.
The controversial manuscript was not eagerly received; it bounced
around for the better part of a year. First it was rejected by Nature, then by Science. At the time, Stanley Miller and his protégés dominated the
origin-of-life research game, which had seen more than its fair share of
quacks and crackpot theories. They were not about to let such unsup-
ported speculation sully their field. Hydrothermal temperatures were
much too hot for amino acids and other essential molecules to survive,
they said. “The vent hypothesis is a real loser,” Miller complained to a
reporter for Discover magazine. “I don’t understand why we even have
to discuss it.”
Miller’s followers found other good reasons to attack the paper.
Corliss and co-workers had the ancient ocean chemistry all wrong, they
said. Modern hydrothermal ecosystems rely on oxygen-rich ocean wa-
ter, whose composition is an indirect consequence of plants and pho-
tosynthesis. The prebiotic ocean would not have been oxygen-rich, so
the proposed life-sustaining chemical reactions would have proceeded
slowly, if at all. The bottom line? Decades of Miller-type experiments
HEAVEN OR HELL?
99
confirm what is intuitively obvious: Life began at the surface, so why
confuse the issue?
Eventually the Corliss, Baross, and Hoffman manuscript was pub-
lished, in a supplement to the relatively obscure periodical
Oceanologica Acta, a journal that not one in a hundred origin-of-life
researchers would see. Nevertheless, good ideas have a life of their own,
and copies of the paper, entitled “An Hypothesis Concerning the Rela-
tionship Between Submarine Hot Springs and the Origin of Life on
Earth,” began circulating. I have seen dog-eared underlined photo-
copies of copies of copies on several colleagues’ desks, and I have a
pretty battered copy of my own.
New support for the idea gradually consolidated, as hydrothermal
ecosystems were found to be abundant along ocean ridges in both the
Atlantic and Pacific. It was realized that at a time when Earth’s surface
was blasted by a continuous meteorite bombardment, deep-ocean eco-
systems would have provided a much more benign location than the
surface for life’s origin and evolution. New discoveries of abundant
primitive microbial life in the deep continental crust further under-
scored the viability of deep, hot environments. By the early 1990s, the
deep-origin hypothesis had become widely accep
ted as a viable, if un-
substantiated, alternative to the Miller surface scenario.
Of the three authors, only John Baross remains active and influen-
tial in the field. In 1985, he accepted a professorship at the University
of Washington, where he has developed a leading research program on
hydrothermal life. His work on deep-sea-vent microbes, often in col-
laboration with his wife, Jody Deming, who is also a professor of ocean-
ography at the University of Washington, has placed Baross at the
forefront of the highly publicized research field of “extremophile” mi-
crobes. Sarah Hoffman’s graduate work in geochemistry was inter-
rupted by illness, and, after her recovery, she pursued a singing career.
As for Corliss, always a bit idiosyncratic, in 1983 he left Oregon for the
Central European University in Budapest, where he worked briefly on
the deep-origins hypothesis, but soon took up research in the more
abstract field of complex systems. After a 3-year stint as director of
research at the controversial Biosphere 2 environmental station in Ari-
zona, he returned to Budapest, having abandoned studies of the deep
ocean.
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GENESIS
LIFE IN ROCKS
Following the revolutionary hydrothermal-origins proposal, numer-
ous scientists began the search for life in deep, warm, wet environ-
ments. Everywhere they looked, it seems—in deeply buried sediments,
in oil wells, even in porous volcanic rocks more than a mile down—
microbes abound. Microbes survive under miles of Antarctic ice and
deep in dry desert sand. These organisms appear to thrive on mineral
surfaces, where interactions between water and chemically unstable
rocks provide the chemical energy for life.
One of the most dramatic and difficult pursuits involves deep drill-
ing for life in solid rock. The oil industry has perfected the practice of
deep drilling, thanks to decades of experience and vast infusions of
cash. They can penetrate several miles into the Earth, drill at angles
and around obstacles, and cut through the hardest known rock forma-
tions in their quest for black gold. So the problem for geoscientists
looking for microbes a mile or more down isn’t how to get there, it’s
how to get there without contaminating the drill hole with hoards of
surface bugs. Bacteria are everywhere—in the air, in the water, and in
the muck used to lubricate and cool diamond drill bits as they cut
through layers of rock. It’s relatively easy to bring up rock cores from a
couple of miles down, but those slender cylinders of rock will have
already been exposed to surface life by the drilling process. What to do?
The commonest retrieval trick is to add a colorful dye or other
distinctive chemical tracer to the lubricating fluid. When drillers ex-
tract a deep core, it becomes obvious whether or not the rock has been
contaminated in the process. Porous sediments or highly fractured for-
mations soak up the dye and thus prove unsuitable for analysis, but
many rocks turn out to be impermeable and thus are ideal for recover-
ing deep life.
The search for subsurface microbes began in earnest in 1987, when
the Department of Energy decided to drill several 500-meter-deep
boreholes in South Carolina near the Savannah River nuclear process-
ing facility. As cores were brought to the surface, drillers quickly iso-
lated them in a sterile plastic enclosure with an inert atmosphere.
Researchers then cut away the outer rind of the drill core to reveal
pristine rock samples, which were shipped to analytical facilities across
the country. The results were spectacular. The deep South Carolina
sediments were loaded with microbes that had never seen the light of
day.
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101
Subsequent drilling studies have revealed that microbes live in ev-
ery imaginable warm, wet, deep environment—in granite, in basalt on
land and basalt under the ocean, in all variety of sediments, and also in
metamorphic rocks that have been altered by high temperature and
pressure. Anywhere you live, drill a hole down a mile and the chances
are you’ll find an abundance of microscopic life.
MINING FOR MICROBES
Earth’s deep mining and tunneling operations provide the new breed
of geobiologist with an invaluable complement to drilling. Mine tun-
nels have the advantage that researchers can visit microbial popula-
tions in their native habitat. Earth’s deepest mines, the fabled gold
mines of South Africa’s Witwatersrand District, have thus become the
site of the heroic and potentially dangerous efforts of Princeton geolo-
gist Tullis Onstott.
The East Driefontein Mine, located about 60 miles southwest of
Johannesburg, is a vast network of underground workings, reaching
more than 2 miles into the crust. A small army of miners labor around
the clock for gold. Despite one of the largest air-conditioning systems
in the world, these deep tunnels remain at an oppressive 140°F from
the heat of Earth’s interior, while air pressure is twice that of the sur-
face. Onstott learned the dangers of the place on his first descent: “It
was ‘Don’t step there, don’t touch that,’” he told a writer for the
Princeton Weekly Bulletin. “All I knew is that it was deep and dark and
hot.”
Every so often, as miners blast new adits, a small flow of water
appears—groundwater that has spent countless thousands of years fil-
tering down from the surface and has accumulated in small cracks and
fissures, nurturing a tenuous ecosystem of microbial life. Onstott’s
team, typically a half-dozen young and hearty students and postdocs,
camp at the surface with a functional array of sterile sample-collection
hardware at hand. When news of a fresh water flow comes in, they
scramble to the site, though the miles of elevators and tunnels can take
almost an hour to traverse. They have to work fast, both to avoid dis-
ruption of the mining routine and because prolonged exposure to the
hellish conditions can kill them.
They photograph the site, record its location and geological set-
ting, and collect as many gallons of water as possible fresh from the
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GENESIS
point of flow. They benefit from the seep’s positive water pressure,
which prevents much back contamination from the miners’ activities
or their own collection efforts. Exhausted and sweating profusely,
they lug the heavy water-filled bottles to the surface for further
investigation.
Remarkably, every single sample from Earth’s deepest mines holds
microbes that have never seen light, surviving on a meager supply of
underground chemical energy. Such deep life lives at a sluggish pace
that defies our experience. Isotopic measurements reveal that a single
cell may persist for thousands of years, “doing” almost nothing before
dividing into two. Colonies of organisms commonly remain isolated
from the surface for millions of years. So tenuous are the chemical
resources of
these deep rocks that reproduction and growth are luxu-
ries seldom indulged. By the same token, deep rocks provide an
unvarying safe and reliable environment: no predators, no surprises—
unless of course a miner happens to blast into your rocky home of a
million years!
THE DEEP HOT BIOSPHERE
The abundance of subterranean one-celled creatures, thriving far from
the light of the Sun, inspires the imagination and hints at novel sce-
narios for life’s origin. Of all the scientists in pursuit of deep life, none
displayed greater imagination than the late brilliant and pugnacious
iconoclast Thomas Gold.
Austrian-born Tommy Gold began his scientific career as an as-
trophysicist in Britain, but in 1959 he was lured to Cornell University
to head the Center for Radiophysics and Space Research. He would
achieve lasting scientific fame with his inspired theory that pulsars,
steady pulsating radio sources discovered in 1967, are actually rapidly
rotating neutron stars. Many honors, including election to the Royal
Society of London and the National Academy of Sciences, soon
followed.
Most scientists would have been content to excel in one chosen
area, but Gold throughout his career repeatedly ventured into new and
controversial academic domains. In the 1940s, he conducted experi-
ments on hearing and the structure of the mammalian inner ear.
Speculative papers on dramatic instabilities of Earth’s rotation axis, on
steady-state cosmological models of the universe, and on the potential
HEAVEN OR HELL?
103
danger to astronauts of deep powdery lunar soils peppered his lengthy
curriculum vitae.
In 1977, Gold, by then a safely tenured professor at Cornell, rattled
the well-established field of petroleum geology. Geologists had long
declared that petroleum is a fossil fuel, formed when huge quantities
of decaying cells accumulate over millions of years, to be buried and
processed by Earth’s heat and pressure. The evidence is overwhelming:
Petroleum occurs in sedimentary layers that once held abundant life;
petroleum is rich in distinctive biological molecules; petroleum’s car-
bon isotopes also point to a biological source. Armed with these and a
dozen other lines of evidence, the case for fossil fuels was open and
shut.
Gold disagreed. Petroleum holds lots of distinctive biomolecules,