An asteroid hurtles through the solar system, on a collision course with Earth, only to be deflected from its deadly orbit just in the nick of time. It's the stuff of movies such as "Deep Impact" and "Armageddon." But as "Tech Live" reports tonight, truth may be more frightening than fiction.

"The Earth orbits the sun within a small asteroid belt. We're part of a cosmic shooting gallery and we know the Earth has been hit over time many, many, times," NASA scientist and asteroid-watcher David Morrison said. "If we could see all the craters that've been made on the Earth, it would be as many craters as there are on the moon."

Case in point: An asteroid the size of a football field passed extremely close to Earth just last week, missing us by a mere 75,000 miles. That's one of the closest cosmic collisions ever recorded.

Blindsided

Despite the close call (the distance was about one-third the distance to the moon) the asteroid went undetected by astronomers until days later. How could we have missed such a close call?

In many cases, asteroids are fairly small objects, and if they measure less than a mile in diameter, they can be faint and tough to detect unless they're close to the Earth, Dr. Don Yeomans of NASA's Near-Earth Object Program says. Many asteroids also come from the direction of the sun and are only visible in the nighttime sky.

"Doesn't really matter," Morrison said. "There are no extra points for getting it on the way in. We just want to find them, catalog them, project their orbit, and make sure they're not a threat to us."

Is sooner better?

Questions have been raised as to whether our ability to detect asteroids as they hurtle near the Earth is undermined by underfunding. Some places on Earth, specifically in the Southern hemisphere, might not have the observation labs and technology needed to keep on top of asteroids.

In fact, Congress has mandated that NASA hunt down and track 90 percent of near-Earth objects with a diameter of a mile or more by 2008.

Morrison says that more funding above NASA's current $3 million Near-Earth Object survey budget would be nice, but that it won't do much more to protect the Earth from asteroids. Instead, the extra money would speed up things that don't really need to be sped up, he says..

"If we had more telescopes, we could accomplish the survey faster, or we could go to fainter objects. If we had telescopes in the Southern hemisphere, that would be a special advantage," he said. "But it's just a matter of speeding it up. We'll get there even with the telescopes we have."

The same goes for the issue of high-concept technologies, such as putting a telescope on the moon or in orbit around Mercury. These are great ideas, but some critics have asked, isn't the money better spent on homeland defense or on other major threats?

"The real question," Morrison said, "is how important is this hazard vs. others?"