Washington (CNN) -- The good news is that the chances an asteroid big enough to destroy a continent or all of civilization will hit Earth this year are only one in 20,000, a congressional panel learned Tuesday.
The bad news is the government needs to spend billions of dollars in coming years for new technology to prevent such a possible catastrophe, regardless of the low probability, experts told the House Science, Space and Technology Committee.
"The odds are very small, but the potential consequences of such an event are so large, it makes sense to take the risk seriously," contended John Holdren, who directs President Barack Obama's Office of Science and Technology Policy.
Current efforts to detect and analyze possible space threats like the meteor that exploded over Russia last month, injuring more than 1,000 people and causing millions of dollars in damages, have made progress in identifying the threats, NASA Administrator Charles Bolden told the committee.
He said scientists have identified 95% of asteroids more than a half-mile in diameter -- the kind that threaten human existence if they strike Earth, like the six-mile-wide one believed to have wiped out dinosaurs 65 million years ago -- and found none on a collision course with the planet.
However, the detection efforts have been less successful for smaller meteors still capable of causing major loss of life and damage, such as the one over Russia.
Only 10% of meteors more than 150 yards wide -- dubbed "potential city killers" by Holdren -- have been detected, meaning more than 10,000 are out there without our knowledge, he said.
If scientists detected a major asteroid headed for Earth now, it would take at least five years to develop an effective defense system to either alter its course or possibly destroy it, no matter how much money was spent, according to Holdren and Bolden.
Government plans to bolster detection and mitigation capabilities include an infrared sensor that would orbit Venus, as well as a laser system or other method to deflect any threatening meteor away from Earth, they said.
"We really need to have space-borne assets," said Bolden of the infrared sensor that would cost more than $500 million.
Another NASA goal endorsed by Obama is to send an astronaut to an asteroid for the first time in history by 2025, a project that would cost $2 billion, he said.
Asked by panel members about the effects of forced spending cuts this year due to the inability of Congress to agree on fiscal issues, all the witnesses described heavy impacts.
"Just about my every working moment these days is consumed with this topic," Gen. William Shelton, commander of the U.S. Air Force Space Command, said about the spending cuts that took effect March 1. He added that "we are clearly less capable."
Bolden noted that NASA's budget for detecting Near Earth Objects has multiplied in recent years to reach more than $20 million in 2012. Now, he said, Congress needs to at least maintain such funding to prevent stagnation or, even worse, atrophy.
"This is really important and it has to be continuous," he said.