Asteroid threat has Congress' attention

As if you don't have enough to worry about, consider the subject of a hearing last week on Capitol Hill: asteroids that may be headed toward Earth. The good news: NASA is tracking most of the largest asteroids - the kind that a witness said "would likely end civilization" were they to hit.

"None of these civilization-enders thus far discovered is known to be on an impact course any time in this upcoming century," Ed Lu, a former astronaut who heads a group working to launch a space telescope to track threatening asteroids, told the House Space, Science and Technology Committee.

But there may be a lot of potential "city destroyers" up there that have yet to be detected.

"NASA has not even come close to finding and tracking the 1 million smaller asteroids that might only wipe out a city," Lu said. "We can protect the Earth from asteroid impacts, but we can't do it if we don't know where the asteroids are."

The Capitol Hill hearing Wednesday was the third on space threats since a 60-foot asteroid exploded over Russia in February, injuring about 1,500 people and causing millions of dollars in damage. On the same day, a 150-foot asteroid passed within 17,200 miles of Earth.

President Barack Obama has sent to Congress a proposed budget that includes funding to help NASA step up its efforts to identify space threats, as well as money to send an astronaut to an asteroid by 2025.

Space committee Chairman Lamar Smith, R-Texas, holding up a small piece of the asteroid that exploded over Russia, called it troubling that scientists had identified only 10 percent of the asteroids that could potentially destroy a city.

The asteroid explosion over Russia and the close flyby on the same day "demonstrate that even extremely improbable events can happen, and that it is prudent to pay attention to the problem of finding and tracking all potentially hazardous near-Earth asteroids," Donald K. Yeomans, manager of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory, said in his written testimony.

Yeomans noted that a spacecraft could ram an asteroid, "modifying its orbital velocity by a very small amount, so that over several years its trajectory would be modified and its predicted impact of Earth in the future avoided by a safe margin."

NASA officials are worried that tighter budgets could delay its work.