A Comet with Our Name on It?

by Joel Marks

Published in the Connecticut Post on November 25, 2013.

We have been hearing a lot about Comet ISON ever since its discovery in September of last year, when various indications raised hopes of its putting on a spectacular show by the time of its closest approach to the Sun later this month and into next year. Since then expectations have been tempered, but as of this writing nobody can say for sure one way or the other.

            I myself know the thrill of seeing a “comet of the century” – in fact two. You too may have witnessed the double-whammy of Comets Hyakutake and Hale-Bopp in 1996 and 1997, respectively. The first was noted for its magnificent tail right out of old engravings, while the second became a fixture in the night sky for months.

            But comets are not just pretty sights and photo ops. We now know from scientific inquiry what our medieval ancestors feared from superstition, namely, that a comet in the sky can be the harbinger of disaster. It may very well have been a comet that killed off the dinosaurs. The same could happen to us.

            What I find exceedingly odd is that this possibility is being uniformly downplayed or just plain ignored by experts and popular media alike. In fact this is doubly odd, given the ever-increasing attention both are paying to the threat of impact by asteroids.

            Why the relative neglect of comets? One reason is that we are indeed visited by far more asteroids than comets. Roughly a score of comets are sighted each year, whereas thousands of asteroids are being tracked even in Earth’s immediate neighborhood.

Another reason is that we are more likely to be able to mount an effective defense against an incoming asteroid than an incoming comet. This is because the greater distance comets must travel to reach Earth from their cosmic home beyond Neptune corresponds to their having greater velocities by the time they become visible to us. Hence we would have relatively little advance warning of an impending catastrophe.

In his book on Near-Earth Objects, NASA scientist Donald Yeomans estimates that we might have as little as nine months. This is hardly time to design, build, and launch a mission to deflect a comet, especially if it were large enough to threaten our very existence. This contrasts to the decades or even century we might have to prevent a predicted asteroidal collision.

Unfortunately, putting all of our eggs into the asteroidal basket rests on the assumption that no comet will threaten us until some far future time. The sad fact is, though, that comets appear at random.

            Case in point: Just this past January, Comet Siding Spring (C/2013 A1) was discovered to be on course to a near collision with Mars next October. This object could be at least as large as the one that wiped out the dinosaurs. What if it had been heading toward Earth instead?

            I for one am not pleased to be a sitting duck. So I am calling on an informed citizenry to urge policymakers to a greater sense of urgency about comets. We must have a defensive infrastructure in place not after but before we detect a comet with our name on it. In this era of budget sequesters and shutting down government, extraordinary political wisdom and courage will therefore be required to deal with this threat.

Former Space Shuttle astronaut Ed Lu recently said, "One-hundred years ago, if the Earth [were] hit by an asteroid ... that is bad luck. If 20 years from now we get hit again, that is not bad luck, that is stupidity." I completely agree with that statement. However I would add as a friendly amendment, “It’s the comet, stupid!”