Menacing asteroids also treasure troves, astronomers say

Wildcat File Photo Arizona Summer Wildcat John S. Lewis

Two recently released films, "Armageddon" and "Deep Impact," portray the planet under siege from an incoming asteroid or comet.

But there is an upside to near-Earth asteroids, said John S. Lewis, a University of Arizona planetary sciences professor who spoke last night to an audience of about 50 in the Space Sciences building.

Lewis said the asteroids could provide humankind with virtually unlimited resources.

"NEAs could support a population of 10 billion people forever," he said.

Near-Earth asteroids have orbits that bring them within 1.3 astronomical units of the Earth. An astronomical unit is the distance from the Earth to the sun.

There are estimated to be some 1,700 near-Earth asteroids larger than 1 kilometer in size. An asteroid of that size impacting Earth would have results similar to one that is commonly thought to have wiped out the dinosaurs 65 million years ago.

Still, Lewis said there were opportunities as well as threats.

"I'm a strong advocate of turning these swords into plowshares," Lewis said at the first fall meeting of Students for the Exploration and Development of Space.

He said the technology for retrieving metals from the surfaces of asteroids is within reach.

Lewis said a project called the Near-Earth Asteroid Prospector, a privately owned deep-space mission, is slated for launch in less than two years.

Missions to near-Earth asteroids could substantially lower the price of going into space, Lewis said. He said it costs about $6,000 per pound to send a craft into space, but using the water and other materials on asteroids as propellants could bring the cost down to $600 per pound.

"That's about the same price per pound that you pay for a house," Lewis said. "For space travel, that's pretty cheap."

Lewis said the UA's Spacewatch Project pioneered near-Earth asteroid identification. There are five other groups worldwide that also scour the skies for comets and asteroids.

"Spacewatch is the granddaddy of all of them," Lewis said. "They showed the way."

Stephen Larson, research associate at the UA's Lunar and Planetary Lab, keeps watch over the Earth, looking for near-Earth asteroids that might someday collide with the planet.

"The probabilities are very low, but if it were to happen, it would be catastrophic for everyone," Larson said.

Professor Tom Gehrels, who leads the Spacewatch group, said that for now, Earth seems to be safe from major impact.

"There is no menace in the sky that we know of at this time," Gehrels said.