Scientist Outlines Plan to Probe Earth's Core

May 15, 2003 -- David Stevenson has an idea and he doesn't care if it makes you laugh out loud.

Stevenson, a planetary sciences professor at the California Institute of Technology in Pasadena, has proposed that scientists blast the ground using a nuclear bomb or a few megatons of TNT to create a crack that penetrates some 1,800 miles to the outer edge of Earth's core.

Next, they'd pour in a flood of molten iron that would contain a grapefruit-sized probe within its sloshing path. The probe would then relay back information about inner Earth's temperature and composition using high frequency seismic waves. The probe's journey to Earth's center would take about one week.

The proposal, detailed in the most recent issue of Nature, may seem like science fiction, but Stevenson says it is "modest" compared with NASA's space program. He claims it may seem unrealistic only because little effort has been devoted to the concept.

"If 95 percent of my colleagues read the proposal and laugh and then throw it away, that's perfectly fine as long as 5 percent read it, laugh and say, 'Well, there's a slight chance this could work,'" he said.

Long Imagined, Never Realized

Science fiction novels and movies have portrayed people venturing to Earth's center from Jules Verne's 1864 novel Journey to the Center of the Earth, to, more recently, The Core, a 2003 movie starring Aaron Eckhart and Hillary Swank. But, in reality, scientists have only managed to drill down less than eight miles into Earth.

If scientists managed to go much further, as Stevenson proposes, they might find answers to some long-standing questions such as what creates the huge magnetic field around Earth, what exactly makes up the Earth's mantle and core and even whether primitive life exists deep below the crust.

The task is made monumental by the huge amount of energy required to penetrate the dense material of Earth's interior. Scientists estimate the energy required to penetrate Earth is about 10,000,000,000 times greater per distance traveled than the energy needed to blast to the stars.

Still, Stevenson says, a probe would only have to travel a fraction of the distance needed to get to outer planets and the effort would be rewarded with a wealth of new data about our own planet and even others in our solar system. He adds the feat wouldn't endanger the planet since, he says, the resulting crack would be smaller than ones created naturally by volcanoes.

Although scientists have learned much about the Earth's core using seismometers, which convey the properties of rocks and material by how quickly seismic signals pass through them, he argues nothing can match actually sending an instrument to the source.

"You can learn lots of things when you look at planets with telescopes, but that doesn't reduce the need to go there," he said. "We are always surprised when we go to upper planets. Likewise when we send an instrument to Earth's core, we will be surprised."

Potential Finds: Life, Energy

Most researchers believe that Earth's core is made up of two layers. The outer core extends from 1,800 miles to 3,200 miles deep and is composed of liquid iron and nickel churning at a smoldering 9,000 degree Fahrenheit. The inner core, at 3,200 miles to 3,960 miles deep, is composed of solid iron and nickel. Temperatures at the innermost core are estimated to reach 12,000 degrees Fahrenheit — or about 2,000 degrees hotter than the surface of the sun.

That is, at least, what scientists think they know about Earth's core. But questions remain.

For example, maverick geophysicist J. Marvin Herndon argues that, rather than iron and nickel at the center of the Earth, there is instead, a massive, natural nuclear reactor. This uranium reactor, he argues, is what creates Earth's protective magnetic shield.

Herndon has found few in the scientific community who will agree with him, which is one reason why he is interested in Stevenson's proposal — as a way to gain solid evidence.

"This is the new frontier," Herndon said. "These ideas are the important first steps in science."

Another theory, by Thomas Gold, a professor emeritus at Cornell University in Ithaca, N.Y., suggests that primitive life forms may exist deep inside Earth. He ventures these organisms could have given rise to life at Earth's surface billions of years ago.

Gold has also proposed that Earth's mysterious middle could even host nearly boundless sources of energy in the form of methane.

Others have less dramatic, but still significant questions. They want to know, for example, exactly how hot is the Earth's middle? And although indirect readings suggest Earth's mantle is composed of iron and magnesium silicates, the precise composition remains uncertain. Answers for both questions would have implications for why Earth has a protective magnetic field.

"It would be nice to be able to get some definite answers," said Gary Glatzmaier, an Earth scientist at the University of California at Santa Cruz.

Potential Pitfalls

But scientists have already pointed out some critical flaws in Stevenon's core plan.

To name a few: No one has ever built a material that could endure the intense temperatures and pressures that exist near Earth's center. Glatzmaier adds because some natural cracks exist within the Earth, what's to prevent the liquid iron from gushing into existing smaller cracks, which could jam the path of the probe?

Finally, blasting a 1,800-mile long crack into the Earth is an unfathomable task that could be made especially difficult by the elastic quality of material within Earth's mantle.

Stevenson, himself, concedes his idea is somewhat "outrageous."

"Honestly, I think it has a low probability of success," he said. "But I think the consequences of success are so great that some effort should be placed into it."

Herndon further points out that the outlandish nature of past ideas hasn't stopped scientists from seeing them through.

The French writer Jules Verne may have written some outrageous science fiction about journeying deep into the Earth — but a year later, in 1865, he wrote another book called From Earth to the Moon, about a man who is jettisoned to the moon in a rocket.

"It sounded absurd at the time," said Herndon about Verne's novel. "But you know the end to that story."