The Deep Hot Biosphere. - Review - book review

Whole Earth, Winter, 1999 by Robert Scarborough

THE DEEP HOT BIOSPHERE Thomas Gold. 1999; 235 pp. $27. Copernicus Books.

"Surface chauvinism," proclaims Thomas Gold, is why we've developed such a lopsided view of life on Earth. Whales and redwood trees we can relate to. Below that, as we plunge into a new place, Earth's bowels--home of Gold's proposed "deep hot biosphere"--our observational intensity rapidly declines.

In The Deep Hot Biosphere, Gold marries a "deep-earth gas" theory he proposed in 1977 with a "deep hot biosphere" theory he first published in 1992. The synthesis contains three heated revisions of Earth history. First, the origin of petroleum is nonbiological! And petroleum pervades much of the Earth's upper crust, not just the sedimentary rocks where petroleum companies hunt for riches. Second, life on the planet originated not in shallow sea waters but in deep sea vents, and today the entire crust of the Earth, to a depth of several miles, is populated by living creatures--the great bulk of Earthly life. Third, the non-biological hydrocarbons continue to leak up and to replenish oil fields. Our supply is not limited to the next fifty years. So with one sweeping hypothesis, Gold single-handedly proposes a new location and mechanism for life's origin, and claims we may continue to mine petroleum well beyond its now-predicted extinction.

Is there unequivocal evidence for a deep hot biosphere? By 1990, holes as deep as 6.7 kilometers (4.2 miles) had been drilled at Siijan (Sweden) using contamination-free drilling techniques. Definite quantities of volatile petroleum gas and light oils were recovered, along with a strange black puttylike fluid that carried a strong, objectionable odor and was thick with microscopic particles of magnetite. Two kinds of living thermophylic iron-reducing bacteria (which extract oxygen from hematite, changing it to magnetite) were cultured from the sludge. A later pump test of the well produced twelve tons of "normal-looking" crude oil mixed with fifteen tons of fine magnetite particles. This appears to be conclusive proof that there is life very deep within the Earth. How much, is as yet unknown.

The standard story about petroleum formation is that the hydrocarbons originated in the biological debris of marine algae, were further processed by microbially aided warm-temperature distillation, and ultimately settled as sediment beneath the waters of shallow seas or lakes. The giant Arabian and Texas Gulf Coast oil fields are found in youthful marine sediments and are perfect examples of where Cretaceous trash oil ought to be found. However, Gold reminds us, no one has ever converted cellular trash into petroleum hydrocarbons in the laboratory; and sedimentary rocks may simply be locations with more empty spaces than igneous bedrock.

Gold argues that hydrocarbons (HCs) can be "primordial" (dating to the solar system's origin). Light HCs are found on several other planetary bodies and moons. Saturn's Triton seems especially well endowed with methane, ethane, and other HCs, presumably nonbiological in origin. One class of Earthly meteorites (carbonaceous chondrites) contains a rich assortment of tarry, carbon-based polymers. Gold believes these primordial hydrocarbons are the unrecognized ingredient of today's petroleum reserves, and that they continue to bubble up from the Earth's depths.

He adds a third ingredient to the combo of primordial hydrocarbons and Cretaceous trash: a kingdom of thermophylic microbes (the bacteria-like Archaea) living in the upper ten kilometers of the crust. He argues that there is a distinctive fingerprint in oil (haponoids) which can only come from Archaea. Before the primordial hydrocarbons rose near the surface, the Archaea worked them over. Says Gold: "Liquid petroleum and its volatiles are not biology that has been reworked by geology, but geology that has been reworked by biology." Gold is not alone in his new recipe for petroleum. In 1963, pioneer petro-chemist Robert Robinson wrote, "Petroleum ... [seems to be] a primordial hydrocarbon mixture into which bio-products have been added."

If he is to be convincing, Gold must prove an interpretation of Earth history that most geoscientists do not accept -- that the early planet never heated up so much that the core wholly melted (that action would likely have purged HCs upwards, leaving nothing in the deep). In order to prove that petroleum rose from the deep, rather than sank from surface swamps, he must prove that the core's early radioactive furnace was not as hot as is now believed.

Gold also takes on the origin of coal from "swamps" -- glibly assumed in most textbooks. A number of uneasy questions (high purity, unexplained petroleum-like chemistry) give Gold reason to seek an alternate, nonorganic explanation. The question is open: Scientists cannot reconstruct the transformation of a swamp into coal any more than they can a swamp into petroleum. Unfortunately, Gold does not review critical evidence for alternate viewpoints, particularly the distribution of coal beds.