By Derrick H. Pitts

Considering the recent close calls our planet has had with various asteroids, meteors, and comets, it's time to develop an early-warning system - a cosmic "heads up" - to detect the wanderers zooming through the solar system.

The major concern, of course, is whether any of these space travelers is on a collision course with Earth. Our geologic record clearly indicates that not only have we been hit before, but in one instance, the object was large enough to significantly change the planet's environment, triggering the demise of the dinosaurs about 65 million years ago. If they couldn't survive an impact, what chance would mere humans have to survive?

The major difference in surviving a "Big One" is brain power. Dinosaurs had walnut-sized ones. Humans have much bigger and more highly developed brains. Putting that gray matter to work, we could effectively defend ourselves against a threatening interloper if we develop two complementary systems: one to detect earthbound asteroids and the other to deflect or redirect any threats so we don't have a "close encounter" of the worst kind.

Right now, there are eight search programs in operation around the world trying to get a bead on potential impactors. NASA has done a very good job of detecting 90 percent of the objects that would significantly damage our planet. The real problem, though, is detecting objects that are 100 to 300 meters in size, which are numerous and difficult to spot.

While it's tempting to think that smaller objects would be less worrisome - and that's true if the impact occurred in an uninhabited region - the meteor that exploded over Chelyabinsk, Russia, last month suggests otherwise. About 20 meters in size, the meteor didn't impact the ground, yet it still caused 1,200 injuries and millions of dollars in damages. Imagine what would have happened if it had reached the surface.

That's the danger - smaller asteroids could easily destroy a city and cause tremendous loss of life. NASA's capability to detect these smaller objects is improving, but not fast enough.

John Holdren, director of the White House Office of Science and Technology Policy, says we need an infrared sensing telescope in a Venus-like orbit. The cost is estimated at $500 million to $750 million. However, inadequate funding has prevented NASA from reaching its asteroid-detection goals, as set by Congress in 2005, and the sequestration will only further impede efforts. At current funding levels, NASA won't be able to identify all potentially Earth-threatening asteroids for 20 years.

Scientists and engineers have thought out the basics of asteroid deflection, but there is no NASA agency-level work being done to develop a defense system for astronomical threats. In fact, NASA Administrator Charles Bolden says that if an asteroid were discovered just three weeks from an Earth hit, NASA couldn't do anything about it.

We've known about this threat for decades and have understood the risks, but we have deferred action to protect against a collision by not making this work a priority. Obviously, in light of all the other budgetary challenges, funding for NASA to address this item falls far down Congress' list of imperatives.

However, if we think back to what happened 65 million years ago, and understand what it meant for the dinosaurs, we might decide that Congress should assign this threat a much higher priority. With proper funding, we can develop an asteroid-collision warning system, similar to what we currently have for potentially damaging storms. With the right system, we could limit the loss of life and property, at a minimum, and possibly save the planet when - not if - the "Big One" comes along.

Call your member of Congress and ask what he or she is doing to protect us from becoming the next big cosmic extinction.

Derrick H. Pitts is chief astronomer of the Franklin Institute Science Museum. E-mail him at