Do We Need a Crash Effort to Thwart Killer Asteroids?

January 04, 2008

Astronomers’ recent announcement that an asteroid has about a 1-in-25 chance of smashing into the surface of Mars brought back the memory of those alarming headlines in 2002, when a 1,000-to-1,300-foot-long rock named 2001 YB5 hurtled toward Earth. What CNN labeled the "killer asteroid" turned out to miss our planet by 375,000 miles, about 1.5 times the distance between Earth and the moon. But by asteroid standards, that’s way too close for comfort.

Sure, sizeable asteroids don’t strike the Earth very often — on average, an object 1 kilometer (.6 miles) or larger hits every 500,000 years. But when they do, all hell usually breaks loose. Scientists believe an asteroid 6 miles in diameter struck the Yucatan peninsula 65 million years ago, releasing energy that was the equivalent of 100 million megatons of TNT and generating a planet-wide heat pulse so intense that according to one recent study, it probably killed off the dinosaurs in a matter of hours. In 1908, another asteroid probably caused the Tunguska Event in Siberia, a mysterious aerial explosion that generated enough force to level 80 million trees and cause an earthquake estimated at 5 on the Richter scale.

Nobody is sure how many potential killer asteroids are out there, but astronomers already have discovered more than 5,000 Near Earth Objects (NEOs) — that is, asteroids, comets and meteors whose orbits bring them within 124 million miles of Earth. About 900 of these have been classified as Potentially Hazardous Asteroids (PHAs), objects at least 500 feet in diameter that come within 46.5 million miles of our planet (about half the distance between Earth and the sun).

Even the least imposing PHAs have the potential to cause a devastating tsunami, while the bigger ones could wipe out an entire city and kill millions of people. (Imagine, for example, what would have happened if the Tunguska Event object had exploded over Moscow.) But it’s the exceedingly remote but nevertheless possible collision with a Yucatan Event-sized asteroid that really gives cause for concern, because it could wipe out the great majority, if not all, of the living creatures on Earth.

So if we’re threatened with the prospect of annihilation from the cosmos, what are we doing about it? If life were a Hollywood movie — say, the 1998 Hollywood disaster flick Armageddon — NASA simply would launch Bruce Willis and his intrepid team into space on a mission to land on the giant asteroid, drill an 800-foot-deep hole, drop in a nuclear bomb, and then remotely detonate it, cutting the PHA precisely in half so that both pieces narrowly miss Earth. (As the Bad Astronomy blog notes, splitting an asteroid in half might well cause one of the pieces to hit Earth with even greater velocity.) In reality, NASA isn’t doing much at this point beyond surveying space and attempting to identify and chart the NEOs and PHAs out there, a project for which the government has allocated a relatively minuscule $4.1 million a year. (NASA hopes to have that job 90 percent complete by 2020.) A 2007 NASA report to Congress only briefly touches upon possible killer-asteroid mitigation strategies. Instead of trying to split an asteroid into pieces, scientists have contemplated using the gravitational attraction of a giant spacecraft to pull the asteroid in a different direction, or using a giant mirror to focus solar energy on the asteroid’s surface and boil off material, creating thrust that would change its path.

In order to actually be able to do any of these things in the foreseeable future, however, we’d likely have to allocate many billions of dollars to an effort vastly more ambitious than the Manhattan Project or the Apollo program to put men on the moon. Developing effective asteroid-diverting technology might well divert resources and attention away from other important priorities, such as the efforts to mitigate global warming. On the other hand, if a killer asteroid strikes Earth, we might not be around to worry about climate change any more. So what do you think? Should we launch a crash program to deal with the threat of killer asteroids? Offer your opinion below.

Comments

[Mothra]

I think this is a good idea. It's a logical extension of environmentalism, because if one of these things hits us, we're not going to have any environment to protect.

Btw, I'm wondering whether a near-miss by an asteroid would cause problems on earth, such as disruption of weather or the Earth's magnetic field.

[Chuck H.]

Could the U.S. mount an asteroid defense project by itself, or would we have to seek the help of other nations? An international effort to prepare a response to this problem could help people and nations all over the world to put aside their differences.

[Fantabulous Frank]

This proposal sounds to me like a recipe for wasting a huge amount of money, since the actual chance of the Earth being struck by another Yucatan-sized asteroid in 2008 is one in 65 million or therabouts. We would be better off focusing our efforts on curbing global warming, which already is happening and which threatens to kill off a lot of species, not to mention a lot of humanity.

Btw, I know everybody is jumping on the Obama bandwagon these days, but his plan for fighting global warming is vague, beyond saying that he would institute a cap-and-trade system and try to develop alternative energy sources. (http://www.barackobama.com/issues/energy/#reduce-carbon-emissions). Hillary Clinton's plan is a lot more detailed and much more aggressive. (http://www.hillaryclinton.com/issues/energy/) For example, she would set a minimum CAFE standard of 55 mpg for the auto industry by 2030, start a national initiative to cut U.S. energy consumption by 20 percent, compel the oil industry to invest $50 billion in developing alternative energy sources, and retrofit poor people's homes to make them more energy efficient.

[Manwich]

So what is Obama's position on killer asteroids? It's time that he got more media scrutiny.

[Caffeine Driven Stress Magnet]

I think this is a more serious problem than global warming, because global warming can be controlled by changing basic human behavior. (Of course we would have to change it on a large scale.) An asteroid isnt going to go away because we all start using flourescent light bulbs or driving a Prius. We have to be prepared to do something if the situation arises. And who knows? If we invest in preparing for the asteroid problem, scientists may find some new technology or energy source that would help us with the global warming problem.

[The 12 year old.]

In my opinion this would not be a good idea, NASA is working hard to try to protect our earth from meteors, comets and asteroids. This does not convince me, but it does get my attention. Breaking it in half is most likely not to work, as it says in what you wrote, chunks may fall off and hit the surface of the earth, but at an even greater speed since it is so little. This would cause a likely amount of damage, and it would hit about everywhere. Our Earth's gravitational pull, will, most probably, slingshot the asteroid somewhere else, just like Jupiter, with its huge gravitational pull threw the Probe at lightning speed across our galaxy, but not exactly to Saturn. NASA is working on new ideas to destroy or dismount the so called "Killer asteroids", since its not very likely one will be hitting us very soon, patience is the required key to this mission.

And yes if you were wondering my name is TRUE, I am a 12 year old.

[Patrick Kiger]

A seriously great post, 12 Year old...I should let you write the blog next time! Hope you'll continue to share your insights on topics to come.

[Astroboy]

The 12 Year Old Wrote: Our Earth's gravitational pull, will, most probably, slingshot the asteroid somewhere else, just like Jupiter, with its huge gravitational pull threw the Probe at lightning speed across our galaxy, but not exactly to Saturn.>>

I would agree, but with a caveat. Asteroid 2004 MN4 is supposed to come within 18,600 miles of Earth on Friday the 13th in 2029, but its trajectory will be bent 28 degrees by the Earth's gravitational pull, according to NASA's calculations. But some fear that the Earth's pull will slingshot the asteroid on a path that could bring it even closer to the Earth when it comes back in 2035. NASA is discounting that possibility, but nobody will know for sure until we gather more data, which probably won't happen before 2013. The asteroid is about three football fields across, and if it hit, it would release enough energy to devastate an area the size of Texas.
http://science.nasa.gov/headlines/y2005/13may_2004mn4.htm

[Patrick Kiger]

Here's a link to a 2005 Christian Science Monitor article (http://www.csmonitor.com/2005/0726/p01s04-stss.html) that discusses the risk of being hit by that asteroid in 2036, and what might done about it. An interesting snippet:

Within the object's range of possible fly-by distances lie a handful of gravitational "sweet spots," areas some 2,000 feet across that are also known as keyholes.

The physics may sound complex, but the potential ramifications are plain enough. If the asteroid passes through the most probable keyhole, its new orbit would send it slamming into Earth in 2036. It's unclear to some experts whether ground-based observatories alone will be able to provide enough accurate information in time to mount a mission to divert the asteroid, if that becomes necessary.

Here's more:

Timing is everything, astronomers say. If officials attempt to divert the asteroid before 2029, they need to nudge the space rock's position by roughly half a mile - something well within the range of existing technology. After 2029, they would need to shove the asteroid by a distance as least as large as Earth's diameter. That feat would tax humanity's current capabilities.

[Greg Peterson]

We should expand our search for killer asteroids - while also doing everything we can to protect the environment and stop the man-made causes of global warming.
Both are global killers.
Intelligent humans should do everything we can to preserve our species while praying we get smarter by not slitting our own environmental throat through greed and lack of common sense.
I realize money is one problem - especially when the war on terror is also important because I believe the extremists - bent on killing Americans and anyone who loves freedom - are planning their next major attack which will be to nuke or detonate a dirty bomb in a major U.S. city making it unuseable for decades if not centuries.
I expect Chicago to be the target because of the winds that would spread the deadly effects and the chance that one bomb could pollute all the Great Lakes.
Plus money is needed to fight poverty, provide medical care and attack the other social issues that plague our society.
With the assassination of Mrs. Bhutto, it proves that the sociopaths of the world - who thrive on chaos, fear and a desperate need to dominate others - must be dealt with severely because they will no just fade away and give up.
God bless and protect her son.
But it also proves to me that America is still the best country in which to live - despite our flaws and problems.
As the volunteer media guy for the Michigan Earth Keepers, I urge everyone to do their part to protect the environment.
Every person can make a difference.

[Patrick Kiger]

Hey Greg: I just looked at a YouTube video about the Michigan Earth Keepers (http://www.youtube.com/watch?v=JymNVzZ9AEc) and I think what you all are doing is really tremendous. If you have a web site, please post a link. Hopefully, people elsewhere will follow your example.

[ClaireK]

Since the beginning of recorded time, how many asteroids have struck inhabited areas on Earth? Zero. I just don't see this as a pressing worry, compared to, say, global warming or the AIDS pandemic.

[Patrick Kiger]

Here's a link to a NASA study assessing the threat from asteroids (http://impact.arc.nasa.gov/downloads/spacesurvey.pdf)

This section caught my eye:

Category 3: 1 km to 5 km diameter impactors
At these larger sizes, a threshold is finally reached at which the
impact has serious global consequences, although much work
remains to be done to fully understand the physical and chemical
effects of material injected into the atmosphere. In general, the crater
produced by these impacts has 10 to 15 times the diameter of the
projectile; i.e., 10-15 km diameter for a 1-km asteroid. Such craters
are formed on the continents about once per 300,000 years. At
impactor sizes greater than 1 km, the primary hazard derives from the
global veil of dust injected into the stratosphere. The severity of the
global effects of large impacts increases with the size of the impactor
and the resulting quantity of injected dust. At some size, an impact
would lead to massive world-wide crop failures and might threaten the
survival of civilization. At still larger sizes, even the survival of the
human species would be put at risk.
What happens when an object several kilometers in diameter strikes
the Earth at a speed of tens of kilometers per second? Primarily there
is a massive explosion, sufficient to fragment and partially vaporize
both the projectile and the target area. Meteoric phenomena
associated with high speed ejecta could subject plants and animals to
scorching heat for about half an hour, and a global firestorm might
them ensue. Dust thrown up from a very large crater would lead to
total darkness over the whole Earth, which might persist for several
months. Temperatures could drop as much as tens of degrees C.
Nitric acid, produced from the burning of atmospheric nitrogen in the
impact fireball, would acidify lakes, soils, streams, and perhaps the
surface layer of the oceans. Months later, after the atmosphere had
cleared, water vapor and carbon dioxide released to the stratosphere
would produce an enhanced greenhouse effect, possibly raising
global temperatures by as much as ten degrees C above the
pre-existing ambient temperatures. This global warming might last for
decades, as there are several positive feedbacks; warming of the
surface increases the humidity of the troposphere thereby increasing
the greenhouse effect, and warming of the ocean surface releases
carbon dioxide which also increases the greenhouse effect. Both the
initial months of darkness and cold, and then the following years of
enhanced temperatures, would severely stress the environment and
would lead to drastic population reductions of both terrestrial and
marine life.