This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

23 March 2008

NyTimes Opd-Ed from the Past:Op-Ed: Killer Comets Are Out There. Now What? (Arthur C. Clarke, 1994)

From the NYTimes...

Every week, the Opinion section presents an essay from The Times's archive by a columnist or contributor that we hope sheds light on current news or provides a window on the past. This week's offering comes from Arthur C. Clarke, the science fiction novelist, who died on Wednesday. In 1994, he urged Op-Ed readers to look to the skies--or risk going the way of the dinosaurs.

"Op-Ed: Killer Comets Are Out There. Now What?"
Sunday, August 14, 1994
Arthur C. Clarke

COLOMBO, Sri Lanka — At 0946 G.M.T. on the morning of 11 September, in the exceptionally beautiful summer of the year 2077, most of the inhabitants of Europe saw a dazzling fireball, appear in the eastern sky. . . . Moving at 50 kilometers a second, a thousand tons of rock and metal impacted on the plains of northern Italy, destroying in a few flaming moments the labor of centuries. The cities of Padua und Verona were wiped from the face of the Earth; and the last glories of Venice sank forever beneath the sea as the waters of the Adriatic came thundering landward after the hammer blow from space. . . .

After the initial shock, mankind reacted with a determination and a unity that no earlier age could have shown. Such a disaster, it was realized, might not occur again for a thousand years -- but it might occur tomorrow. . . . So began Project Spaceguard.

-- "Rendezvous with Rama," 1973

Soon after the last fragments of the comet Shoemaker-Levy 9 crashed into Jupiter last month, the monsoon skies above my home in Colombo cleared momentarily and I hurried to set up my 14-inch Celestron telescope. I didn't really expect to see anything, so I could hardly believe my eyes when I clearly observed a line of dark bruises spread out across the planet's southern hemisphere.

Some imaginative souls suggested that the comet might have a catastrophic impact on Jupiter, but its effect will be largely cosmetic. And it will certainly have no effect on Earth, despite the inevitable alarmist warnings by religious fanatics. But the spectacular collision between the newly discovered comet with the solar system's largest planet has brought sudden new attention to a genuine threat: the chance that a rogue comet or asteroid could strike Earth, with possibly devastating consequences.

As a result, the fictional "Project Spaceguard" I described in my 1973 novel has now begun in reality -- if Congress approves an amendment to the 1994 NASA authorization bill requesting the space agency to identify and catalogue within 10 years "the orbital characteristics of all comets and asteroids greater than one kilometer in diameter in orbit around the Sun that cross the orbit of the Earth."

Though this amendment was prompted by the Shoemaker-Levy comet, it is really the result of an "International Near-Earth-Object Detection Workshop" organized by NASA in 1992. With a nod to "Rendezvous with Rama," the official report of this workshop was entitled the Spaceguard Survey.

I wonder what Thomas Jefferson would have thought of these developments, in view of his famous remark on hearing of a meteorite landing in New England: "I'd rather believe that two Yankee professors lied than that stones fell from the sky." Certainly no one could have imagined how quickly and how dramatically a cosmic event so apparently removed from everyday affairs would become prime-time news.

In view of the number of collisions that have taken place in this century alone -- most notably, a comet or asteroid that exploded in 1908 in Siberia with the force of 20 hydrogen bombs -- there is a very good case for a global survey of the possible danger, particularly as the shared cost among nations would be negligible compared to most national defense budgets. (Incidentally, historians might also be advised to undertake some surveying. Just as the numerous meteor-impact craters on Earth were never found until we started looking for them, so there may have been disasters in history that have been misinterpreted. Sodom and Gomorrah have a good claim to be meteorite casualties; how many others are there?)

Many people would probably prefer not to know of impending cosmic doom, if nothing could be done to avert it. Yet given sufficient warning time -- which we hope Spaceguard would provide -- we should be able to develop the technology necessary to ward off, or even destroy, such intruders from outer space.

There are at least three ways in which oncoming asteroids, or their cometary cousins, might be deflected. The first is the brute force approach: nuke the beast. A sufficiently large bomb -- probably in the gigaton class, or the equivalent of about a billion tons of high explosive -- could split an intruder into many fragments. This would not necessarily be a Good Thing, because some of the pieces might still be heading straight toward us. The atmosphere, however, would burn up most of the smaller fragments, and at least instead of massive devastation in one area there might be minimal damage spread over numerous sites.

Needless to say, such a pre-emptive strike is advocated by enthusiastic and currently underemployed bomb designers. Perhaps a better solution is one I adopted in another novel, "The Hammer of God," in which a potential killer asteroid is detected a year before it will collide with Earth, giving astronauts barely enough time to make a rendezvous and deflect it into a harmless orbit by mounting rocket thrusters on its surface.

Given enough warning time -- at least several years -- this could be done with very modest amounts of power. An initial deflection of only a few centimeters, at the beginning of a multimillion-kilometer journey, could insure that the asteroid steered well clear of us.

Although the orbit of a solid body like an asteroid can be calculated centuries in advance (once the object has been discovered!) the rocket-thruster solution might not work so well with comets. These flying icebergs warm up as they approach the sun and begin to vent gas. The resulting "jet propulsion" makes their future position uncertain, so if we ever have to deflect an oncoming comet, we would have to allow a very significant safety margin.

An even more elegant solution has been proposed by scientists at NASA and elsewhere: "solar sailing." The plan would be to attach a huge lightweight mirror of metal foil to the comet or asteroid, capturing the minute but continuous pressure exerted by sunlight. Unfortunately, the acceleration produced by this feeble pressure would be so minimal that years, even decades, of warning time might be required.

All these solutions would require a vast investment in new technology. But people who say "Why waste money on space?" should remember the dinosaurs, whose extinction it is now widely believed was caused -- or at least accelerated -- by the impact of a giant meteorite around 65 million years ago.

And NASA's increased commitment to identifying threatening bodies in space could have another benefit: it could give new inspiration to America's flagging space program, and restore some of the lost magic of the Age of Apollo.

Link: NYTimes Op-Ed Classic

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