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In a plot worthy of Jules Verne, a prominent California planetary scientist believes it may be possible -- and very educational -- to send a probe all the way to Earth's core.

"My point is to get people to realize that we have dedicated immense resources to exploring space. I'm advocating balance," said Dave Stevenson, professor of planetary science at the California Institute of Technology in Pasadena.

Interior exploration could be accomplished by applying proven technologies and some well-grounded scientific assumptions about the planet, he says in a paper published in the latest edition of the journal Nature.

Still, "the main reaction I'm expecting is laughter," the scientist admitted.

"It's wildly over-optimistic ... the arguments he gives are very vague," said Ray Jeanloz, professor of geology & geophysics at the University of California, Berkeley. "But ... he's exactly right about the knowledge that could be gained."

Stevenson's proposal calls for a crack to be opened in the earth, maybe with a nuclear bomb. According to his figures, the crack will need to be several hundred meters (yards) in length and depth, and about 30 centimeters (12 inches) wide, to accommodate a volume of about 100,000 to several million tonnes (tons) of molten iron.

EARTH WOULD DO THE WORK

"The Earth will do the work for you," he explains. Like a volcano in reverse, the molten iron, carrying a heat-proof probe, would sink straight to the core, sending temperature readings, compositional information, and other data.

"There really are questions about whether this puddle of metal would go any distance. What's to prevent this thing from freezing up?" Jeanloz said.

Inside the grapefruit-size probe will be instrumentation for data collection, which will be relayed through low-intensity mechanical waves of some sort -- radio waves wouldn't be able to transmit through the layers of the planet.

"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," Stevenson said.

But some laws are set -- gravity for instance would keep the molten iron from diving beyond the center of the planet, the scientist notes. "When we go out into space we don't find that Newton was wrong," Stevenson said.

He puts the cost of a such a project at about $10 billion.

"We've only been down about 10 kilometers (6.2 miles) into our own planet," Stevenson says, and little has been directly observed about its inner workings. Scientists do not know, for example, the exact composition or even the temperature of the core, which is about 3,000 km (1,864 miles) from the surface.

Jeanloz said a trip to the core might be valuable in determining the state of Earth's magnetic field.

Geology shows that the Earth's magnetic field "flips" every couple of hundred thousand years -- although some periods have been steady for millions of years. "The last flip was 700,000 years ago. We're long overdue," Jeanloz said.

Stevenson said he's been thinking about this for 10 years, but a consultation call last year from producers of "The Core," a recent movie about a manned journey to the center of the Earth, triggered the article, called "A Modest Proposal."


 
05/14/03 20:07 ET
   
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