Journey to the Center of the Earth

In the novel Journey to the Center of the Earth, a scientist and his nephew travel across Iceland, descend through a crater, and visit an inner-Earth realm of a sunless sea and ancient civilizations. While Jules Verne's subsurface world certainly doesn't exist, much about Earth's insides remain a mystery. Hoping to promote the study of our planet's inner workings, a scientist has proposed a mission to travel to its heart.

In a paper published this week by Nature, California Institute of Technology planetary scientist Dave Stevenson outlines his plan of sending a probe to Earth's core. Immersed in a blanket of molten iron, the probe would sink through to the core while transmitting information concerning temperature and composition along with other readings.

The probe and molten iron would find their way into Earth's interior through a crack, possibly created by a controlled explosion. To accommodate the necessary millions of tons of iron, the crack would have to be several hundred meters in length and about 12 inches (30 centimeters) wide. Gravity and the incredible weight of the iron will cause the crack to propagate downward, eventually reaching the core 1,864 miles (3,000 kilometers) days later.

According to Stevenson, this explosion-iron combination has a distinct advantage over drilling. "Once you set that condition up, the crack is self-perpetuating," he explains. "It's fundamentally different from drilling, where it gets harder and harder - and eventually futile - the farther you go down."

The probe, about the size of a grapefruit, would have to be resistant to immense pressure and heat. Also, because radio waves cannot transmit through Earth, data collected would have to be returned via low-intensity mechanical waves.

Though no practical designs have been laid, Stevenson estimates the cost of such a mission to be comparable to a high-end, unmanned planetary mission. Considering the revenue spent on studies of other planets and the limited knowledge of Earth, Stevenson feels it's a worthwhile venture. Scientists do not know the exact temperature or composition of the core and its surroundings, so the findings of direct probe observations deep within Earth could be on par with those from successful missions to other planets.

"We've spent more than $10 billion in unmanned missions to the planets, but we've only been down about 10 kilometers into our own planet," says Stevenson. "When we fly to other worlds, we are often surprised by what we find, and I think the same will be the case if we go down."

Realizing that many may react to his idea as if it were science fiction, Stevenson named his paper "A Modest Proposal," borrowing the title from a satirical essay by Irish author Jonathan Swift. While his proposal is not as outlandish as Swift's (which suggested Irish citizens eat their children in tough economic times), Stevenson acknowledges an element of lightheartedness in his paper.

"Ninety-five percent of the scientists who read the article may laugh at an enjoyable read," Stevenson continues, "but if the other five percent seriously consider the goal of probing Earth's core, then I'll be happy."