With another Earth Day upon us, aren't you getting just a little tired of reading about hyped global "catastrophes" like global warming or ozone depletion? Even if the Earth should warm a little, it likely will benefit agriculture. And if ozone depletion turns out to be real, it may raise the intensity of solar ultraviolet radiation by a few percent--but so would moving only 60 miles to the south closer to the equator. These "threats" are creating much noise and causing us to spend some two billion dollars per year of US tax money.

Yet there are real threats out there that are not being addressed. Millions of people watched Comet Hyakutake earlier this year. It came close enough to be easily seen with the naked eye but missed the Earth. We may not always be so lucky.

The cosmic missile that impacted 65 million years ago, releasing energy equivalent to 100 million 1-megaton hydrogen bombs, wiped out the dinosaurs and many other species. Human beings, had they been around then, would not have survived.

Calculations show that the earth is hit by an NEO (near-earth object) of this size, some 10 km (6 miles) in diameter, every 100 million years--on average. This does not mean that the next impact will occur in 35 my; it could happen next year--or tomorrow. And there are many more NEOs that are smaller, more numerous, and impact more frequently. Astronomers estimate over 2000 NEOs with diameters greater than 1 km and 10,000 bigger than 0.5 km--large enough to cause major damage and loss of life. After all, meteorites hit the Earth every few weeks.

We can do something--if we have the will. Planetary defense is not so different from defense against intercontinental ballistic missiles. There is first the problem of detection--with powerful radars or telescopes. Next, a timely determination as to whether the object is headed for a collision with our planet. Finally, an interception that would nudge the object out of its course.

Although the chance of a major NEO collision is tiny, the potential damage is so large that the risk of being killed is comparable to that of an airplane accident. It is strange therefore that so little attention is being given to this real threat while billions are being expended on fashionable phantom threats. As it stands now, even if we could detect an incoming NEO on a collision course, we would be unprepared to do anything about it--except to shout the all-too-true "The end is near."

An editorial in Aerospace America, the house organ of the respected American Institute of Aeronautics and Astronautics, has it about right: "If some day a large asteroid does strike the Earth...and we could have prevented it but did not...it will be the greatest abdication of responsibility in human history." Not to mention, its end.