Sunday, April 23, 2006

Apophis

Copyright © 2006 by Joel Marks
Revision of “Reckoning Might Come from Sky,” New Haven Register, April 13, 2006, page A6

Twenty-three years from today, on April 13, 2029, the residents of this planet will witness an unprecedented harbinger of their doom. An asteroid the size of the Empire State Building will be visible to the naked eye as it hurtles by at a distance of less than the earth’s circumference.

The asteroid's scientific name is 99942 Apophis. Its proper name comes from the Greek rendering of Apep, the ancient Egyptian spirit of destruction. This name fits. If Apophis were to strike the earth, it would wreak untold havoc. And given certain as-yet unknown contingencies of the asteroid's orbit, it might do just that.

It is especially meet to reflect on this today, which commemorates the ancient Passover, when people in Egypt took steps to assure God’s slaughterous spirit would pass over or spare them.

Apophis was discovered on June 19, 2004, when it was given the preliminary name “2004 MN4,” and has been tracked closely ever since. It raised significant alarms as early data suggested a greater chance of Earth-impact than had ever before been predicted by modern science. These estimates were subsequently reduced, but the asteroid is still rated 1 on the 10-point Torino Impact Hazard Scale because there is a small but non-zero probability of its hitting the earth exactly seven years after its 2029 flyby, that is, thirty years from today.

Unbeknownst to most of the population of the world, this kind of threat hangs over us at all times. The good news is that astronomers are keeping an eye out for it. It may come as a surprise to you to see, for example, the level of daily monitoring that is in evidence at the NASA Website http://neo.jpl.nasa.gov/neo/ devoted to NEOs or Near Earth Objects.

The bad news, however, is twofold. First, the detection program is limited: It targets only the largest objects, like the one that wiped out the dinosaurs, and also does not include comets, which tend to be discovered only haphazardly rather than systematically. But a comet can do as much damage as an asteroid, and a relatively small object can be catastrophic. Apophis itself, whose impact would pack a wallop 65,000 times that of the “Little Boy” atomic bomb dropped on Hiroshima, comes in way under the threshold size of one kilometer that Congress has order NASA to inventory.

The second bit of bad news is that detection is not enough. For one thing, it obviously would not help humanity if an object large enough to disrupt or even destroy all life on earth were discovered but we couldn’t do anything about it.

In fact there are various more-or-less feasible proposals on the drawing board for averting disaster. But the critical factor is lead time. The political, economic, and engineering effort demanded could require decades for its implementation.

Meanwhile, consider some recent “near misses” by NEOs. Asteroid 1996 JA1 came to within almost the distance of the moon to the earth on May 18, 1996. This asteroid is 1/3-mile in diameter and was discovered only four days prior to its closest approach. Then on June 14, 2002, Asteroid 2002 MN came to within 75,000 miles of the Earth -- less than 8 Earth diameters. It is 100 meters long – three times the size of the meteoroid that laid waste the Siberian region of Kunguska in 1908 -- and was only discovered three day after its closest approach!

In a little more than a year we have seen, and many have experienced, the devastation of the Christmas Tsunami and then Hurricane Katrina. More than likely an incoming asteroid or comet would hit water, which constitutes 70 percent of the earth’s surface. Thus we have some sense of the “ripples” such a large “pebble” hitting such a large “pond” would make, albeit the recent events have been minor by comparison to the global reach of a large impactor.

I recommend, therefore, that we all support the B612 Foundation, chaired by former astronaut Rusty Schweickart, which is lobbying hard for increased attention to this ultimate threat. Their Website contains updates and simulations. See also my own more extended treatment of this subject, "Stones and Fish Falling from the Sky."

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