DREADFUL SORRY, CLEMENTINE

By LEON JAROFF

During the 3 or 4 billion years that it has existed on Earth, life has been devastated, and on occasion nearly wiped out, by the explosive impact of giant asteroids or comets. Now terrestrial life has finally evolved to the point where it is intelligent and capable enough to defend itself against the next such threats from space--if it has the will to do so.

That is why some scientists are so distressed by President Clinton's line-item veto last week of the $30 million that Congress had allocated for the Clementine II project next year. Clementine is a spacecraft that was to be launched in 1999 to approach an asteroid named Toutatis and send a camera-equipped rocket barreling toward it. The missile, after taking close-up pictures of Toutatis, would smash into its surface while Clementine recorded the impact flash and analyzed any ejected material. The goal was not only to test our ability to rendezvous with an asteroid but also to determine Toutatis' composition and mechanical strength--important considerations in designing weapons to ward off incoming comets and asteroids.

Reasons for the veto, an Administration spokesman explained, included concern that the project might violate the Antiballistic Missile Treaty, that it was a thinly disguised supplement to other Pentagon projects and more logically belonged in the NASA budget. Another--but unspoken--reason, say scientists familiar with the budget debate, is the "giggle factor," the tendency of many in government to scoff at the danger posed by asteroids.

Astronomers estimate that about 2,000 objects large enough to cause a global catastrophe are hurtling on paths that either intersect or come close to Earth's orbit. Yet only 200 or so of these have thus far been identified and tracked. Just last year, a previously unknown asteroid some 1,600 ft. across was spotted four days before it whipped by Earth, missing us by only 280,000 miles--a hairbreadth by astronomical standards. Had it struck Earth, scientists say, the explosion would have been in the 3,000-to-12,000-megaton range, roughly equivalent to the explosive power of all the world's nuclear weapons going off at once.

In an attempt to assess the danger, a few dedicated astronomers have been scanning the skies, borrowing time on large telescopes, building their own detectors out of off-the-shelf parts and barely scraping by on the $1 million or so that NASA contributes annually to the total effort. Their goal is to identify and determine the orbits of the still undiscovered "near Earth" asteroids. That would enable them to predict, sometimes many years in advance, the possibility of a disastrous encounter. Those predictions and knowledge gained from missions like Clementine II would give Earth's defenders time to mount the appropriate defense, using missiles to deflect or destroy a threatening intruder.

With a bit more funding and access to the Air Force's satellite-tracking telescopes, say astronomers, they could find and track the most threatening asteroids within a decade. The cost to taxpayers, they estimate, would be a few million dollars more a year. If you think of it as an insurance policy for the entire planet, it's a small price to pay.