Lu thinks other proposed interventions, such as detonating a nuclear bomb near an asteroid, would create more danger for Earth than they would avert.
"There's a possibility of breaking chunks off, and even small chunks could cause tremendously bad effects," he said.
(See an interactive feature on asteroid impacts on Earth.)
Scientists also described two massive new survey-telescope projects to detect would-be killer asteroids.
One, dubbed Pan-STARRS, is slated to begin operation later this year. The project will use an array of four 6-foot-wide (1.8-meter-wide) telescopes in Hawaii to scan the skies.
The other program, the Large Synoptic Survey Telescope in Chile, will use a giant 27.5-foot-wide (8.4-meter-wide) telescope to search for killer asteroids. This telescope is scheduled for completion sometime between 2010 and 2015.
(Related news: "Google Partners With High-Tech Telescope to Map Universe" [January 10, 2007].)
When both of these new telescope projects go online, they will be able to detect objects much fainter than anything today's scopes pick up, the scientists said.
David Morrison, an astronomer at NASA's Ames Research Center, said that "the rate of discoveries is going to ramp up. We're going to see discoveries being made at 50 to 100 times the current rate."
"You can expect asteroids like Apophis [to be found] every month."
The influx of new discoveries will likely increase public anxieties about the asteroid threat, which makes a concrete scientific plan of action all the more necessary, the experts said.
In the wake of the Apophis incident, many lawmakers have become convinced of the importance of devoting more attention to asteroid searches.
In 2005 the U.S. Congress amended the Space Act to entrust NASA with the specific responsibility to "detect, track, catalog and characterize" asteroids and other near-Earth objects.
But to some scientists, these efforts aren't enough.
Schweickart, the former astronaut, thinks the United Nations needs to draft a treaty detailing standardized international measures that will be carried out in response to any asteroid threat.
His group, the Association of Space Explorers, has started building a team of scientists, risk specialists, and policymakers to draft such a treaty, which will be submitted to the UN for consideration in 2009.
Schweickart believes the uncertainty involved in predicting the path of an incoming asteroid makes a coordinated global response essential.
"When you look at where something like Apophis is going to hit, it's not going to be a single point, it's going to be a line of potential points," he said. "Therefore this is going to be inherently an international decision.
"We can't prevent a hurricane or a tornado," he continued. "But we can prevent an asteroid impact, and we can do it by slightly reshaping the solar system to enhance the survival of life on Earth.
"If we don't do that, we're not that far past the dinosaurs."
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