A group of scientists, joined by a member of Congress, used the 100th anniversary of the Tunguska asteroid event this week to draw attention to their belief that the United States is not doing enough to defend the planet against the dangers posed by near-Earth objects.
"We are not prepared at this time to prevent the massive death and destruction that would occur if an object from space hit the Earth as it did in Tunguska," said Rep. Dana Rohrabacher (R-Huntington Beach) at a news conference at the Pasadena offices of the Planetary Society.
If an asteroid the size of the one believed to have exploded in the air above Tunguska, in Siberia, were to explode over Los Angeles, he said, the destruction would range over an area from Catalina Island to San Bernardino.
Although no one is positive what caused the Tunguska event, which flattened trees over an 800-square-mile area on June 30, 1908, most scientists believe an asteroid about 150 feet across exploded above the remote river valley in eastern Russia. No one was killed.
NASA has established a Near-Earth Object Program Office at the Jet Propulsion Laboratory in La Canada Flintridge to monitor potentially dangerous asteroids. The most scrutinized is Apophis, which has about a one-in-45,000 chance of hitting Earth in 2036, according to Don Yeomans, manager of the Near-Earth Object Program Office. Apophis is about five times the suspected size of the Tunguska object.
But Alan Harris, a senior research scientist at the Space Science Institute in Boulder, Colo., said the greatest danger does not come from the objects we know about but from the ones we haven't identified.
In one example of the lack of attention the issue is receiving in Washington, Rohrabacher said, funding for the Arecibo, Puerto Rico, radio telescope, which hunts near-Earth objects, is in danger in next year's budget.
If scientists are able to identify a potential killer asteroid, the deeper question is how to deflect it. Theorists have proposed a variety of possible solutions, including using a nuclear weapon to blow it up or sending a spacecraft that would use gravity to drag the object off its destructive path.