Preventing the Asteroid Apocalypse

by Daniel Brenton on January 3, 2010

in Space

We have the technology to save the world from asteroid and comet impacts. What part of “extinction” don’t we understand?

The Asteroid Apophis
Dateline: MOSCOW – Russian Space Agency Chief Anatoly Perminov denies rumors that a planned mission to destroy the Earth-grazing asteroid Apophis was inspired by its uncanny resemblance to former U.S. President George W. Bush.

 

Start: I spend some time now and then on the forums for The Paracast, Gene Steinberg’s and David Biedny’s premier podcast/radio show on the paranormal. A couple of days ago, David Biedny posted a link to this article from Yahoo News: “Russia may send spacecraft to knock away asteroid.”

As David noted … thank God the Russians are here to save us.

(If that seemed a bit sarcastic to you, well … you’re right.)

The article notes that the near-Earth object (NEO) Apophis, an asteroid about 887 feet wide, has been concerning astronomers for nearly six years now, due to how close it would be passing the Earth in 2029. According to this news release from NASA’s Jet Propulsion Laboratory, a collision with the Earth has been ruled out for the 2029 encounter, and for the remainder of the 21st century.

(I guess the Russians don’t trust our mathematics. Or something.)

False Steps Toward a Real Threat

However, this doesn’t rule out objects we don’t know about creating havoc on our planet. We are constantly being surprised by near-misses, such as the one described in this Universe Today article in 2004, a 33 foot wide object that passed overhead only about 4000 miles up.

Objects this small naturally pose little risk, but the real hazard is that this object was detected only shortly before its closest approach. Likewise the article notes that other objects have been detected only after they pass.

As confused as the Russian Space Agency Chief seems to be, he is correct in that asteroids — as well as yet-to-be-discovered long-period comets — pose enormous risks to our species. The suggestion that asteroidal and cometary impacts have triggered planet-wide extinction events has long been seriously discussed by the scientific community, and, despite our species’ arrogance, we are hardly any better prepared than the dinosaurs to preserve our existence should this ugly possibility occur today.

More of a “Boom” Than a “Bang”

So how much of a “boom” do we have to worry about?

There’s a neat little page at the University of Arizona website called the “Earth Impact Effects Program.” Assuming the formulae these physicists have set up here are correct (this is an assumption, I confess, because I am neither a physicist nor an engineer) this gives us some food for thought.

Let’s just assume that Apophis is going to hit the Earth at some point. Using this Earth Impact Effects Program, I ran a couple of calculations.

If you go to the page, you’ll see that it asks you to plug in some values: distance from impact, projectile diameter and density (with some default selections), impact velocity and angle, and the target type (water — depth to be specified — or two different kinds of land).

Here I’ve given the links to a couple of results of this program. I’m sticking to the 270 meter (887 feet) diameter given to us in the article above, which I verified through the Wikipedia page here.

My assumptions:

Since this object is a near-Earth asteroid (it has an orbit that does not range far from the Earth’s, is not tilted significantly from the Earth’s, and has a year only about a month shorter than ours), I’m assuming the impact velocity would in the ten miles per second range. (Any math geeks out there, feel free to correct me, but I’m assuming any difference in the velocity of the object compared to the Earth, and that the object would be accelerated seven miles a second by its fall into Earth’s “gravity well.”)

I don’t know Apophis’ density (I’m not sure anyone does), so I’m assuming the default value of “dense rock.” It appears that a lot of asteroids may be little more than big clumps of dust that have accumulated like interplanetary dust bunnies because of the action of gravity over huge amounts of time, but I decided to be conservative here and make it a big hunk of rock.

I’ve chosen an impact angle of 45 degrees. This is an arbitrary choice, really — splitting the difference between coming straight down and a glancing blow as it heads on by.

And, of course, I’m assuming it comes down on land, on sedimentary rock, as opposed to crystalline rock.

Here’s what the program gives us — an impact explosion of 840 megatons. I’m assuming I’m a mile away from impact, so I’m actually in the crater, which means I’m vaporized.

(Oh well … wouldn’t have to worry about health insurance any more.)

But … if we successfully blow this thing into pieces that are only about one quarter of the diameter of the original, there is an airburst of — only! — 13.8 megatons as the object breaks up at about 10,000 feet, with possibly some fragments hitting the ground.

No, I wouldn’t want to be under that, but the program claims I wouldn’t even notice the overpressure from the airburst.

So, then — do you see why I’m for pulverizing Apophis with thermonuclear explosives, with as many as is practical?

Try a Little Tenderness

Admittedly, the brute force methods for dealing with asteroids and comets as depicted in the theatrical films Armageddon and Deep Impact may work in some cases, but only in some. In the instances where asteroids are loose conglomerations of dust and rock — or when dealing with comets made of rocks loosely buried in methane slush — nuclear devices could actually make the problem worse.

It has been suggested that, given sufficient lead time, a spacecraft with sufficient mass could gently nudge the trajectory of an asteroid simply by the microscopic amount of gravity its mass produces.

Personally, I feel the way to eliminate the problem posed by these objects is to dispose of them as they are identified. Given the sophistication the American space program has shown in using the “gravity assist” of celestial bodies in accelerating space probes and sending them to varied destinations, perhaps the asteroids and comets that show the greatest potential for mining can be gently maneuvered and eventually captured into a high Earth orbit for eventual use. Less useful objects could be deliberately smashed into the Moon, simply to remove them as hazards. In the case where the threat is immediate, maybe using the sledge hammer of nuclear devices could serve as a quick “band aid,” and more sophisticated techniques could follow to clean up the resulting mess.

Just Do It

If we as a species are really concerned about our future … as in, having one … we need to take decisive steps, and quickly. Personally, I don’t care if we violate the Nuclear Test Ban Treaty with the Soviet Union — which doesn’t exist any more anyway, does it? — and use nuclear devices in space if needed for the Earth’s protection, and I don’t have the slightest objection to the United States acting unilaterally in that regard. This has to be done if we are to survive as a species.

Let’s get on with it, shall we?

Copyright © 2010, by Daniel Brenton. All Rights Reserved.

End

Related Article: Dr. Dyson’s Space Patrol

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