by Alex Boese
What if the Earth contains an inexhaustible supply of oil and gas?
Oil and natural gas play a crucial role in powering the world’s industrial economies, but where do these remarkable substances come from? Out of the ground, of course! But have you ever thought about how they got down there in the first place?
The prevailing wisdom is that they’re of biological origin, formed millions of years ago from biomass such as plankton and algae that was trapped underground, either by sediment depositing on top or by shifting tectonic plates. The pressure of the rocks above then heated and compressed the biomass, transforming it into fuel. That’s why it’s called fossil fuel, because it’s believed to derive from the fossilized remains of life forms that previously inhabited the world. As such, the supply is presumably limited, because there was only so much biomass created over the course of the Earth’s history. If we keep using more oil and gas, eventually we’ll run out.
However, in the 1970s, the astrophysicist Thomas Gold of Cornell University emerged as the champion of an alternative theory in which he argued that these fossil fuels aren’t of biological origin at all, but rather are ‘abiogenic’ (non-biologically made). He maintained that natural gas (methane) was part of the original matter from which the Earth first formed, that vast reservoirs of it were then sealed within the deep crust and mantle, and that it has been slowly but constantly seeping upwards, towards the surface, ever since. As it does so, he said, the geological forces of heat and pressure transform much of it into oil.
This theory led him to make the extraordinary claim that we’re not in any danger of running out of these fuels. Not even close. He insisted that the supply is planet sized, and therefore, for all practical purposes, limitless. It’s so plentiful that we might as well consider oil and gas to be renewable resources, in the same way that solar energy is. We could continue consuming them at our current rate for millions of years and not risk exhausting the supply.
To this he later added one more sensational claim. This abundant upwelling methane doesn’t just exist, he said – it was also responsible for the origin of life.
You might recall that we’ve met Gold before.* In the 1940s, he co-authored the steady-state theory, according to which, new matter is continuously being created throughout the universe. But that was just one of his many radical ideas. Over the course of his career, he was prolific in dreaming up weird theories. If all his theories had remained fringe and unaccepted, the scientific community would have written him off. But, to the contrary, quite a few of his seemingly eccentric concepts were eventually vindicated, earning him a reputation as someone whose ideas it was unwise to dismiss too readily. Most famously, in the late 1960s, when astronomers first detected mysterious, rapidly repeating radio pulses coming from deep space, Gold proposed that the pulses could have been produced by fast-spinning stars made entirely from neutrons. Most scientists initially thought this idea was somewhat far-fetched, but within a year it was widely accepted, and remains so to this day. These stars are now known as pulsars.
The idea that oil and gas are of non-biological origin wasn’t actually original to Gold. The concept had been kicking around for quite a while, having been proposed as early as the 1870s by the Russian chemist Dmitry Mendeleyev, creator of the periodic table. Throughout much of the twentieth century, it remained popular among Russian scientists, but in Europe and America it never caught on. By the 1940s, most Western geologists firmly believed that fossil fuels are of biological origin. Various chemical clues led them to this conclusion, such as the presence in oil of biological molecules such as lipids (organic fatty acids), resembling those found in bacterial cell membranes. They also primarily found oil in sedimentary rock, where biomass would have deposited. Taken together, this evidence made it seem like an open-and-shut case for the biological origin of these fuels.
It was the oil crisis of the 1970s, when the world’s major economies faced sudden shortages as well as rapidly rising prices, leading to fears that the supply of oil might be running out (although, in hindsight, much of the crisis was due to tensions in the Middle East), that stirred Gold’s interest in the question of where fossil fuels came from and how plentiful – or not – they might be. But, coming at the subject from an astronomical background, he quickly arrived at a conclusion very different from that of the geologists. In fact, he always maintained that the failure of geologists to accept his theory was because of a kind of disciplinary blindness on their part. They were so focused on the small picture of terrestrial geology that they totally missed the big picture provided by astronomy.
This big picture was that hydrogen and carbon are among the most abundant elements in the universe. Hydrogen is the most common element and carbon the fourth most common. Based on this alone, one would expect that hydrocarbons, being molecular combinations of hydrogen and carbon, should exist in relatively large amounts, and studies of the solar system have confirmed this expectation. Huge quantities of methane have been detected in the atmospheres of Jupiter, Saturn, Uranus and Neptune. Vast lakes of it also cover the surface of Saturn’s moon, Titan. Presumably, all these hydrocarbons throughout the solar system are of non-biological origin. Given this, it didn’t make sense to Gold that Earth’s hydrocarbons should be of biological origin. Why would hydrocarbons form one way on our planet, but a different way everywhere else in the solar system?
This was the basic rationale that led him to conclude that the oil and gas pumped out of the ground must be of non-biological origin. The way he put it, geologists were simply hopelessly unaware of the astronomical data relating to the cosmic abundance of hydrocarbons. He told the story of one geologist who challenged him following a presentation by asking, ‘Dr Gold, how many other astronomers believe your theory that methane exists in other parts of the universe?’ Gold noted, ‘I had to tell him that there aren’t any astronomers who don’t believe it.’
Gold supplemented his astronomical argument with evidence from terrestrial geology. He pointed out that it was common to find large quantities of helium in oil and gas, even though decaying biological matter shouldn’t produce this element. So, where was it coming from? The only plausible explanation, he believed, was that, as methane migrated upwards from the deep Earth, it was leaching helium from the surrounding rocks.
He also observed that oil and gas fields are often associated with earthquake-prone regions, such as Iran. To him, this suggested that fault lines deep within the Earth must be allowing hydrocarbons to rise to the surface in these areas. He even speculated that hydrocarbons trying to force their way through the mantle might be one of the underlying causes of earthquakes.
Then there was the curious phenomenon of spontaneously refilling oil wells. Drillers would sometimes think they had exhausted a well, only to find the oil gradually returning. Conventional geological theory struggled to explain why this happened, but Gold’s theory actually predicted it should.
Gold referred to these arguments, taken together, as his deep-Earth gas theory. He laid out the case for it in a series of articles, beginning in 1977 with an op-ed piece in the Wall Street Journal (an unusual publication in which to launch a scientific theory) and culminating with the book Power from the Earth, published in 1987.
There was, however, a big gap in his theory. He had explained why hydrocarbons might exist in vast quantities deep underground, but he hadn’t accounted for why oil had so many biological characteristics on a molecular level. And this, after all, was one of the main arguments for the biological origin of fossil fuels. A drilling project in Sweden provided him with a possible answer.
The Swedish national power company, Vattenfall, had been desperate to find new sources of energy for Sweden. So, when Gold began making headlines with his deep-Earth gas theory, promising that oil and gas might be found in far more places than conventional theory predicted, its engineers decided that, if there was even a slim chance that he was right, the possible pay-off was worth the gamble.
In the mid-1980s, t
he company put up tens of millions of dollars to finance an exploratory drill in the Siljan Ring, an enormous bed of granite located in central Sweden, where a large meteorite had impacted about 376 million years ago. According to conventional theory, it was the last place in the world one should be drilling, because no competent geologist would expect to find gas in a non-sedimentary rock such as granite. But, according to Gold, it was exactly the right place, because the impact of the meteorite would have fractured the crust of the Earth, allowing hydrocarbons to migrate upwards.
Drilling began in 1987 and continued for five years, reaching depths of over 22,000 feet, which is far deeper than most wells. The need for deep drilling was suggested by Gold’s theory on the logic that, if methane was rising up from the mantle, the richest concentrations of fuel might be very far down.
Unfortunately for the investors, the operation proved to be a financial bust. About eighty barrels of oil were eventually brought up, which was intriguing given that mainstream theory said there really shouldn’t be any oil there at all, but it wasn’t enough to make any money. In addition to the oil, however, the drilling unexpectedly brought up something else: evidence of microbes living almost seven kilometres down, wedged inside the pores of the rock. This was an extraordinary find, because biologists had long assumed that microbes couldn’t survive more than a few hundred metres beneath the surface of the Earth due to the heat and pressure at such depths.
Gold realized that the existence of these deep-Earth microbes could fill the gap in his theory, explaining why fossil fuels possess so many biological characteristics. He reasoned that, if microbes were living at great depths throughout the crust of the Earth, they might be feeding on the hydrocarbons that welled up from the mantle. As they ate, they would both contaminate the fuel and help to transform it into oil, giving it the biological features that researchers had observed. As Gold put it, it wasn’t that geology had transformed life to produce oil, but rather that life was transforming geology to produce oil.
Never one to do things by half measures, Gold took his speculations one step further. Given the enormous size of the Earth’s crust, he concluded that it, rather than the surface, had to be the primary home of life on the planet. He imagined the existence of a vast ‘deep, hot biosphere’ that stretched downwards for miles beneath our feet, teeming with hydrocarbon-eating microbes.
Gold then went further still and connected his deep-Earth gas hypothesis to the origin of life itself. Life requires energy, and throughout much of the twentieth century theorists had assumed that the original source of that energy, the spark that gave birth to life, must have been the sun. After all, it’s up there in the sky, constantly warming our planet. It’s the obvious source. But Gold observed that, if methane has been continually seeping upwards from below since the Earth formed, then it could have served as a supply of fuel that nourished the earliest primitive organisms. It’s actually far easier, in terms of chemistry, to extract energy from methane than it is from sunlight. So, methane would have been a logical energy source for early life. In which case, life could have started deep underground rather than on the surface. Instead of fossil fuels forming from fossilized life, it could have been the other way around. These fuels could have given birth to life.
Gold also made the intriguing observation that, if life on Earth had begun deep underground, this raised the possibility that life might exist within other planets. As he noted during a 1997 meeting of the American Association for the Advancement of Science, ‘Down there, the Earth doesn’t have any particular advantage over any other planetary body.’ Our solar system, he suggested, might be crawling with subsurface life just waiting for us to discover it.
He detailed these arguments in his 1998 book The Deep Hot Biosphere. Taken as a whole, they represented his grand reimagining of our planet’s history. In this version of events, hydrocarbons had played the starring role. First, they had been trapped underground in vast amounts during the formation of the Earth, then they had brought life itself into existence, and now they supplied our civilization with a potentially endless source of energy.
Gold’s theory struck at the heart of conventional geology. If he was right, then geologists were completely wrong about one of the most basic facts of their discipline: the origin of oil. Not only that, but instead of helping locate the fossil fuels that powered the world’s economies, they had actually been hindering the search all these years, preventing new sources from being found in more locations. Naturally, geologists didn’t take kindly to this suggestion.
They didn’t disagree entirely with Gold, however. They actually fully accepted that it was possible for oil and gas to form non-biologically. There were, after all, known processes that allowed chemists to manufacture abiogenic oil, such as the Fischer–Tropsch process that Germany had used to produce oil during World War II. Geologists even conceded that some of the Earth’s oil and gas may have formed non-biologically. It was the idea that commercial quantities of these fuels had formed this way within the Earth that they regarded as patently absurd.
Critiques of Gold’s argument began with the formation of the Earth. Geologists agreed that hydrocarbons existed in abundant quantities throughout the solar system. Yes, they noted, they actually had been aware of this! But they maintained that most of the Earth’s primordial methane would have leaked into space when the planet was young and molten hot. In particular, when the Mars-sized body that was thought to have created the moon slammed into the young Earth and melted it, most of the methane must have cooked off.
But, even if large reserves of methane did remain in the mantle and deep crust of the Earth, geologists argued that it wouldn’t migrate upwards through rock, as Gold claimed, because the rock at such depths isn’t porous enough to allow this migration. Nor would the methane readily convert into more complex hydrocarbons, such as oil. It’s just not that easy to transform methane into oil. The geologist Geoffrey Glasby insisted that this latter fact alone invalidated Gold’s theory.
Despite the staunch opposition from geologists, interest in Gold’s deep-Earth gas theory nevertheless endures. Gold died in 2004, a firm believer in it to the very end. With his death, the theory lost its most vocal champion, but a small group of believers continues to wage a David-and-Goliath battle against the geological orthodoxy.
Part of the reason for this is because of Gold himself. It’s hard to dismiss him as a crackpot because, as already noted, he had an impressive track record. His wacky ideas had a habit of being vindicated. And, in fact, he managed to repeat this trick with his speculations about the existence of a deep, hot biosphere.
Microbiologists initially greeted his announcement that he had found microbes living seven kilometres underground with extreme scepticism. It just didn’t seem possible that any organism could survive at such depths. The experts suspected that his samples had been contaminated by surface bacteria. But, within a few years, other researchers had vindicated his claim by finding indisputable evidence of deep subterranean microbes elsewhere, such as at the bottom of a South African gold mine and brought up during a deep-drilling project in the Columbia River basin.
These discoveries tied in with a broader revolution that was sweeping biology during the 1980s and 1990s, as researchers found ‘extremophile’ microbes living in all kinds of bizarre, seemingly hostile settings: deep-ocean volcanic vents, Antarctic ice and acidic sulphur springs. Life, scientists began to realize, is amazingly adaptable, able to flourish in conditions that were once assumed to be deadly. In fact, it’s colonized every nook and cranny of the surface of the Earth and has apparently extended its domain far beneath it as well.
The discovery of this deep biosphere lent credibility to Gold’s hypothesis that life may have originated underground. There’s no consensus about where life did start, but many scientists regard a deep-Earth origin as quite plausible, even likely.
This discovery also added some support to his deep-Earth gas theory, because it raised the question of how th
ese subterranean microbes were surviving. What were they feeding on down there? Gold’s argument that they might be nourished by methane rising from the mantle didn’t seem entirely crazy, given how crazy it was that these ultra-deep microbes existed at all. Microbiologists have suggested other ways the microbes might feed, such as by extracting hydrogen from rock or even by using radiation as an energy source, but, given how difficult it is for researchers to know exactly what’s going on that deep beneath the surface, Gold’s theory can’t be ruled out entirely.
But there’s a more basic reason why support for his theory endures. It’s because we don’t seem to be running out of oil and gas, despite repeated predictions that by this time we should have been. The most famous of these gloomy forecasts was made in the 1950s by the geophysicist Marion King Hubbert, who declared that US petroleum production would peak in 1970 and that, by the end of the twentieth century, the global supply would also begin to gradually but inexorably diminish.
The oil crisis of the 1970s convinced many that Hubbert was correct, but we’re now well into the twenty-first century and oil and gas production is still booming. The prediction of imminent scarcity seems to have been wrong. This hardly proves that we may actually have a million-year supply, as Gold envisioned, but his supporters do argue that the continuing profusion justifies scepticism towards the conventional geology that was generating such low estimates.
Popular fears of a looming shortage of fossil fuels have actually subsided to such an extent that they’ve been replaced by a new concern: that it’s the abundance of oil, not its scarcity, which is the real problem. This is due to the overwhelming evidence of the environmental damage caused by the use of fossil fuels, and this suggests the possibility of a somewhat cruel irony. There may be a lot of oil and gas left, but we can’t keep burning it. In fact, imagine if Gold was right and the Earth really did contain an inexhaustible supply of oil and gas; we would be in a situation analogous to Coleridge’s ancient mariner: ‘Water, water, everywhere, nor any drop to drink.’ Or, in our case: oil, oil, everywhere, nor any drop to burn.