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The Threat is Out There

More than 100,000 asteroids hurtle past our planet. But only one—that we know of—may hit us in the next 30 years.
Published in the December 2006 issue.

Scientists at Arizona's Kitt Peak National Observatory first spotted the Apophis asteroid in June 2004. (Photo: Bryan Allen)

Friday the 13th of April 2029 could be a very unlucky day for planet Earth. At 4:36 am Greenwich Mean Time, a 25-million-ton, 820-ft.-wide asteroid called 99942 Apophis will slice across the orbit of the moon and barrel toward Earth at more than 28,000 mph. The huge pockmarked rock, two-thirds the size of Devils Tower in Wyoming, will pack the energy of 65,000 Hiroshima bombs—enough to wipe out a small country or kick up an 800-ft. tsunami.

On this day, however, Apophis is not expected to live up to its namesake, the ancient Egyptian god of darkness and destruction. Scientists are 99.7 percent certain it will pass at a distance of 18,800 to 20,800 miles. In astronomical terms, 20,000 miles is a mere stone's throw, shorter than a round-trip flight from New York to Melbourne, Australia, and well inside the orbits of Earth's many geosynchronous communications satellites. For a couple of hours after dusk, people in Europe, Africa and western Asia will see what looks like a medium-bright star creeping westward through the constellation of Cancer, making Apophis the first asteroid in human history to be clearly visible to the naked eye. And then it will be gone, having vanished into the dark vastness of space. We will have dodged a cosmic bullet.

Maybe. Scientists calculate that if Apophis passes at a distance of exactly 18,893 miles, it will go through a "gravitational keyhole." This small region in space—only about a half mile wide, or twice the diameter of the asteroid itself—is where Earth's gravity would perturb Apophis in just the wrong way, causing it to enter an orbit seven-sixths as long as Earth's. In other words, the planet will be squarely in the crosshairs for a potentially catastrophic asteroid impact precisely seven years later, on April 13, 2036.

Radar and optical tracking during Apophis's fly-by last summer put the odds of the asteroid passing through the keyhole at about 45,000-to-1. "People have a hard time reasoning with low-probability/high-consequence risks," says Michael DeKay of the Center for Risk Perception and Communication at Carnegie Mellon University. "Some people say, 'Why bother, it's not really going to happen.' But others say that when the potential consequences are so serious, even a tiny risk is unacceptable."

Former astronaut Rusty Schweickart, now 71, knows a thing or two about objects flying through space, having been one himself during a spacewalk on the Apollo 9 mission in 1969. Through the B612 Foundation, which he co-founded in 2001, Schweickart has been prodding NASA to do something about Apophis—and soon. "We need to act," he says. "If we blow this, it'll be criminal."

If the dice do land the wrong way in 2029, Apophis would have to be deflected by some 5000 miles to miss the Earth in 2036. Hollywood notwithstanding, that's a feat far beyond any current human technology. The fanciful mission in the 1998 movie Armageddon—to drill a hole more than 800 ft. into an asteroid and detonate a nuclear bomb inside it—is about as technically feasible as time travel. In reality, after April 13, 2029, there would be little we could do but plot the precise impact point and start evacuating people.

Diagram: How to Off An Asteroid
Click to enlarge
Click to enlarge
Fortunately, Apophis needs to be nudged only about a mile to avoid a gravitational "keyhole" in space—a region that would send the asteroid on a collision course with Earth. Otherwise, it would have to be diverted 5000 miles for it to miss our planet. This reduces the energy required to deflect Apophis by a factor of about 10,000—making it theoretically possible using current technology. A number of methods have been proposed to do the job.
According to projections, an Apophis impact would occur somewhere along a curving 30-mile-wide swath stretching across Russia, the Pacific Ocean, Central America and on into the Atlantic. Managua, Nicaragua; San José, Costa Rica; and Caracas, Venezuela, all would be in line for near-direct hits and complete destruction. The most likely target, though, is several thousand miles off the West Coast, where Apophis would create a 5-mile-wide, 9000-ft.-deep "crater" in the water. The collapse of that transient water crater would trigger tsunamis that would hammer California with an hour-long fusillade of 50-ft. waves.

BUT DON'T EVACUATE just yet. Although we can't force Apophis to miss the Earth after 2029, we have the technology to nudge it slightly off course well before then, causing it to miss the keyhole in the first place. According to NASA, a simple 1-ton "kinetic energy impactor" spacecraft thumping into Apophis at 5000 mph would do the trick. We already have a template for such a mission: NASA's Deep Impact space probe—named after another 1998 cosmic-collision movie—slammed into the comet Tempel 1 in 2005 to gather data about the composition of its surface. Alternatively, an ion-drive-powered "gravity tractor" spacecraft could hover above Apophis and use its own tiny gravity to gently pull the asteroid off course.

In 2005, Schweickart urged NASA administrator Michael Griffin to start planning a mission to land a radio transponder on Apophis. Tracking data from the device would almost certainly confirm that the asteroid won't hit the keyhole in 2029, allowing everyone on Earth to breathe a collective sigh of relief. But if it didn't, there still would be time to design and launch a deflection mission, a project that Schweickart estimates could take as long as 12 years. It would need to be completed by about 2026 to allow enough time for a spacecraft's tiny nudge to take effect.

NASA, however, is taking a wait-and-see attitude. An analysis by Steven Chesley of the Near Earth Object program at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., concludes that we can safely sit tight until 2013. That's when Apophis swings by Earth in prime position for tracking by the 1000-ft.-dia. radio telescope in Arecibo, Puerto Rico. This data could also rule out a keyhole hit in 2029. But if it doesn't, the transponder mission and, if necessary, a last-resort deflection mission could still be launched in time, according to Chesley. "There's no rush right now," he says. "But if it's still serious by 2014, we need to start designing real missions."
Reader Comments
12. RE: The Threat is Out There
Apophis is a messenger of doom and his advent may have a great message, somewhat divine, uncertainly evil, undoubtedly destructive. It could be a reminder from the Holy One, the owner of this planet and Apophis (could be a minor subordinate) set to inform us that another asteroid greater than him could arrive should we continue destroying this great blue planet Earth. Apophis may or may not hit us - his creator gauging what we would do, how would we respond, when would we start caring about the homeworld. The coming of a greater problem would mean we could have simply shrugged our shoulders and could have ignored the message from above. The Holy One, the mighty GOD, would not let us people destroy what is His. HE himself will do it and He will do it in style, massive, to the max. After everything else, He may create again. Another big bang, a new Earth, a new Adam and Eve. Sort of another cycle (my guess only) would occur. Like starting all over again. And then if the new creation never learn to care for the environment, another Apophis would be ressurected. And what could be the name of his elder brother? (Am very sorry the effect of last night's beer got stuck in my head.) I always guess that Genesis and Apocalypse are occuring in cycle, until SOMETHING is perfected. What is that something I could never understand. I might just augment the number of beer bottles I would drink tonight to get close to something that could enlighten me, with peanuts on the dish, cigarette sticks by the table, and having my wife as the guest relations officer by my side. I must so often cherish every moment with her so that if Apophis arrive sooner, at least I have done my part.

11. RE: The Threat is Out There
Mr. Willis won't be around to do another heroic deed. He has done it already, thanks to him. And Mr. Wood, hey, he may have started out a family on his own after that deep impact, he may no longer be interested. Okay, they are fictional characters in sci-fi movies. Let NASA do the worrying then. With the help of NGOs and the scientific community of the world (excuse the Philippines, we may have the brilliant people but we don't have the money), counterforce strategies and technologies would have been invented by 2013 or sooner. No Apophis can dampen the human spirit - his coming would unite us all, be they white or black, brown or yellow, or something in between, be they iconoclasts or flexibles, theologic or profane. Apophis offers a test for us all and we don't think we can fail his proposal of destruction. We here in the Philippines could not just stand by or sit in fences as thw world waits - we can help in many ways we can. Thousands of us will start digging mountain-size holes in squatter areas within Metro Manila to accomodate the Egyptian infiltrator. Just nudge him in certain way so as to allow him to fall right there at our hole. Like the greatest party it would be. Thousands more will be standing by the edges to put the soil back and inter Apophis for good.

10. RE: The Threat is Out There
I really think that NASA should consider doing something about this problem. I mean, 2+0+2+9=13. It is scheduled to hit us on FRIDAY 13th. It is NEO #99942. What's a 9 upside-down? I'm not one of those freaks about "pre-decided fate," but that's just a little coincidental.

9. RE: The Threat is Out There
yeah, i think we should fund the space programs... we have the ability to do whatever we want, so why not? Aren't the ancient calendars, (that we're perfect, never having to adjust with time) supposed to end around 2012? It really doesnt matter, we all will kill ourselves before anything natural comes to wipe us out...

8. RE: The Threat is Out There
I have deep respect for all NASA workers especially the NEO program, I want to kiss them! I hope and pray they will come up with a solution no matter how or what the chances are. I'd like for humankind to survive and thrive. Even If I'm a little older before 2026, I would like for other generations to flourish.

7. RE: The Threat is Out There
Funding must be secured. It's not if, but when and we cannot afford to sit on our hands until we have a confirmed end of the world scenario. What's wrong with us?

6. RE: The Threat is Out There
ok ill agreee nasa needs funding.but to eradicate an entire region juss because a percentage of it is unppeacefull is just WRONG

5. RE: The Threat is Out There
Hey direct it to hit the afghanistan/pakistan border area and eradicate the real problem with our world.

4. RE: The Threat is Out There
I just hope if theres 1 theres no't 2 out there. NASA needs funding and a new direction. The ancients new.

3. RE: The Threat is Out There
It all sounds good, but I heard we most lilely won't know its there untill it is crashing threw our atmosphere.

2. RE: The Threat is Out There
Keep us informed about Apophis! My Middle School science classes will be looking for more informationabout this asteriod.

1. RE: The Threat is Out There
If the risk of impact is so low, then why are we and other nations going to all the trouble with setting up an "Ark" on the moon? Anyone? Click below, then check your shorts.

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