New Report Spotlights Impact Hazards

Given the odds of some giant space rock crashing into Earth and what it might do when it hits, scientists now estimate that on average 100 people will die each year from a cosmic impact. How much this number scares you depends on how far out you want to look into the crystal ball. Within the next couple of centuries a Tunguska-like blast might match the devastation of the earthquake that just devastated Haiti. Or fast forward 10 million years, and you can expect a titanic crash powerful enough to wipe out a billion people worldwide.

Apophis and Earth in 2029
On Friday the 13th in April 2029, a 1,000-foot-wide asteroid named Apophis will pass close enough to Earth (within 20,000 miles) to briefly appear as a 3rd-magnitude star in the night sky.
Dan Durda
So should you be worried or not? Put another way, to what lengths — and at what cost — should we go to try to protect ourselves from some asteroid or comet "going rogue" in the foreseeable future?

In 1998 Congress felt worried enough about the sky falling that it tasked NASA with finding 90% of all the near-Earth asteroids at least 1 km across within 10 years. (Anything this size would likely trigger global devastation during and after its collision.) Then Congress raised the bar in 2005, mandating that NASA find 90% of all the threatening asteroids with diameters down to 140 meters (460 feet) by 2020.

It looks good on paper, but neither Congress nor NASA have ever anted up the dedicated funds to do those searches. Back in the mid-1990s, NASA scientist David Morrison famously observed that fewer people are watching for asteroids able to collide with Earth than work in a typical McDonald's franchise. And while more observers are warily sweeping the sky these days, including many capable amateur astronomers, they're doing so by coattailing on other space surveys not optimized for the task.

In short, there aren't enough bodies or telescopes in the impact game to meet the 2020 deadline set by Congress. Don't take my word for it — read the 149-page report released today by an A-list panel of experts assembled by the National Research Council. Titled Defending Planet Earth,, it explores both the best ways to track down all the hazardous near-Earth objects (NEOs) and what to do once it becomes clear that one of them is destined to have a run-in with Earth.

The NRC report both summarizes the state of the searches to date and lays out the steps that NASA or the National Science Foundation (which funds most professional astronomy in the U.S.) would need to take to get serious about cosmic threats. "This is a huge milestone," observes small-body specialist Richard Binzel (MIT), who had no role in the committee or its findings. "The asteroid problem is now a grownup, joining the table of other natural disasters for which mitigation strategies are developed."

Pointedly, the NRC panel states that the Congressional target simply can't be met by 2020. If NASA and NSF managers decide they want to complete the survey as soon afterward as possible, then they'll need to fortify observers not only with dedicated ground-based efforts like the proposed Large Synoptic Survey Telescope but also with a infrared-sensing space observatory. Or ground-based telescopes could go it alone, which would keep costs down but delay the completion date until about 2030.

Concerning mitigation strategies, the panel assessed four approaches and found them all viable and complementary. For the smallest and thus localized impact threats, the most cost-effective approach is simply to move people out of harm's way, either by sheltering or evacuating them.

Bigger NEOs, ranging up to 100 m across, would affect too large an area to make civil defense practicable. So a passive space-based defense — using a spacecraft to pull or push the body enough to alter its path — would work better. For still-larger impactors, up to 1 km in size, a salvo of spacecraft might need to strike it head-on to change its course. But both of these methods would make only slight trajectory redirections and thus require many orbits, over decades of lead time, to avert a disastrous collision.

For the biggest threats, or if one of the other methods fails or if the lead time is short, the panel concludes that the "only current, practical means" are nuclear explosions. These wouldn't be used disrupt the incoming body but rather to give it a Really Big Push all at once. (No need to cue Bruce Willis and his Armageddon team — these would be delivered robitically.)

There's more. As noted in its preliminary findings, released last year, the NRC panel emphasizes the crucial role being played by the unique radar capabilities of Arecibo Observatory Puerto Rico — a facility that an NSF review team felt ought to find its funding elsewhere or be shut down.

It's going to take me a few more days to digest all the content in Defending Planet Earth. Click here if you'd like to download it for your own perusal, or click here for a news summary posted by the NRC's news office.

10 thoughts on “New Report Spotlights Impact Hazards

  1. Anthony BarreiroAnthony Barreiro

    Sometimes it makes sense to compare apples and oranges.
    A one-ton pallet of apples has already started to drop on all our heads, and there’s a virtual certainty that the apples will keep falling, more and harder, in the coming decades. At the same time there is a very small probability that a one-ton pallet of oranges will fall on our heads. Clearly we should urgently invest as many resources as possible to stabilize the apple pallet. We can probably get away with just crossing our fingers and hoping the oranges don’t hit us.
    Global warming, species extinction, and other human-caused environmental devasatations are the apples. Asteroids are the oranges. There is a much greater need to “defend planet earth” from ourselves than from asteroids.

  2. rrsauder

    I sure hope we do not spend any already extremely stretched tax dollars on ANY expensive solutions to any more imaginary problems! This country is NOT responsible for saving the world from every silly notion that some wanabe scientist comes up with! Remember “Smokey” the forest fire poster bear? All he ever accomplished was to preserve underbrush until any spark, either natural or man-made, simply lit the pile and created an unmanageable fire storm that cost many lives and the destruction of much property. That silly congress needs to be overhauled to prevent them from issuing silly mandates to do crazy stuff without funding. This nation can’t afford the funding anyway.
    You all know the definition of “PRO” and “CON”. So, what is the opposite of “progress”? You guessed it, “Congress.”

  3. Grant Martin

    Rrsauder, I sincerely hope you are right in your assessment of the risk of a celestial impact. However, there’s plenty of evidence of huge impacts in the past, some of which were responsible for mass extinctions. We are the first species of life on the planet to be aware of the problem, and we are now at the point at which we can do something about it if we see an asteroid or comet coming. It won’t take a huge outlay to search for potential impactors, nor will it take much to design and build a series of spacecraft that could intercept an inbound asteroid. Chances are, we won’t see it in our lifetime. But the odds are dead certain that an impact will happen again at some point in the future — unless we do something to prevent it.

    I agree on one point– it shouldn’t be the U.S. alone footing the bill. The entire earth is at equal risk; all nations should chip in.

  4. Grant Martin

    Rrsauder, I sincerely hope you are right in your assessment of the risk of a celestial impact. However, there’s plenty of evidence of huge impacts in the past, some of which were responsible for mass extinctions. We are the first species of life on the planet to be aware of the problem, and we are now at the point at which we can do something about it if we see an asteroid or comet coming. It won’t take a huge outlay to search for potential impactors, nor will it take much to design and build a series of spacecraft that could intercept an inbound asteroid. Chances are, we won’t see it in our lifetime. But the odds are dead certain that an impact will happen again at some point in the future — unless we do something to prevent it.

    I agree on one point– it shouldn’t be the U.S. alone footing the bill. The entire earth is at equal risk; all nations should chip in.

  5. D. Paterno

    I’d like to prefix this by stating that I am not an engineer. I have read some articles on Impact hazards and NEO’s. I have seen suggestions of blowing up NEO’s, but if they are large ones, it might not work and subject earth to more pieces from the blasted Meteor. It is my opinion that the best way to handle a threatening Meteor is to use its own momentum, by using an outside force from behind to deflect its direction. This is a technique thaught in martial arts when paring the blow of a larger or stronger oponent to a different direction.

  6. Tony Flanders

    An average of 100 per year is a startlingly small number. In terms of dollars per life saved, it seems hard to justify spending any money at all searching for NEOs. (The scientific value, of course, is an entirely different matter.) But I wonder. At a gut level, a 1-in-1000 chance of 100,000 people dying in any given year seems quite different from a certainty of 100 people dying. And again at a gut level, not all deaths are equal. We spend far more money per life saved fighting terrorism than (say) fighting the seasonal flu. But somehow, a death from a terrorists bomb seems more terrible than a death from flu. I also wonder how money spent on NEO research per life at risk compares to money spent on (say) earthquake prediction compared to life at risk.

  7. JLotte

    Given that a future impact is a certainty, it is prudent to at least look for and catalog NEOS. Much of this can be done by a coordinated effort on the part of “amateur” astronomers. This work is at virtually no cost to the government, NASA or any other agency. A network of smaller ground based telescopes collecting images and copying their findings to a centralized site. What would be required is a way to collate and verify the data. This is where NASA should be concentrating their efforts. Literally thousands of images can be collected on a given night, but sorting & collating them into an intelligible “picture” of what is out there moving around takes a massive amount of computing power. This isn’t something the average amateur astronomer has. NASA does. The average amateur astronomer would need an account on this centralized site. In this account, the user would be able to configure what equipment was used for their observation(s), when & where the observations were made, & some identifiers on the images themselves for indexing the data with other users.
    It is appalling to me that the administration is so short sighted as to cut funding for sites like Arecibo at an operating cost of ~$1 million US/year, when they fund other projects at far greater cost with less potential benefit.

  8. Louis P. Quinn

    We pay for the telescopes, they pay for the mitigation.
    We will end up seeing it coming, they will squabble over sending anything up until it is too late.

    America is a bigger target than most people think.
    A big enough impactor can produce a very large ball of plasma. A big ball of plasma will divert a section of the earths magnetic field.

    If the plasma ball is along the north to south magnetic lines that cross over the continental United States it will interrupt those lines. Its like plucking a string on a guitar. The United States electrical grid will supply the reverberation. There are generators out there that will take many years to replace. That is if we can get another country to build it. Our industrial capacity might be reduced by more than 50%.

    From page 81 of the report
    Alternatively, when the time to projected impact is short, it may be impossible to apply a sufficient ΔV without fragmentation, but the limiting factor is assembly and launch. A nuclear package with a new fuse (i.e., a fuse that is not designed for terrestrial use) and a new container requires a cylinder about a meter in length and 35 cm in diameter, with a mass under 220 kg. The longest lead-time item for incorporating such a device in a rocket system is the development of a container to deliver the device and a fusing system capable of operating with the timing constraints required by the spacecraft velocities near impact with the NEO. Specifications for a nuclear bus could be the same as those for a kinetic-impactor mission, but would be very challenging to construct and integrate with the booster rocket and the nuclear package in under a year. This “latency time” between the decision to act and the launch can be reduced dramatically (perhaps 100 fold) by designing and testing these critical components in advance of discovering a hazardous NEO.

    It would take at least a year to get an integrated package ready for launch. We should start now!

  9. Louis P. Quinn

    To make the testing entertaining and visible to the tax paying public,(and to boost telescope sales), you could have multiple system tests on real asteroids. Who wouldn’t want to see an atomic explosion on an asteroid. It might even be possible to schedule a test for the 4th of July.

  10. Enrico the Great

    Withour downplaying the dangers of Asteroid impacts–(Tunguska, anyone?)
    Does anybody else find the “neo-catastrophism” in science since 1980 or so to be an interesting, if somewhat annoying phenomenon?
    Paleontologists and Geologists aren’t as convinced that asteroid impact was the sole cause of Dinosaur extinction as are astronomeres. Nevertheless now, impact is now being proposed as an explanation for the demise of the North American megafauna (Mammoths and the like). In the popular arena, asteroid impact has been fingered in the origin of the Chicago and Peshtigo Fires, and it has been mooted that ancient myths indicate an impact in Austria IN ANCIENT TIMES—AN IMPACT THAT HAS NOT LEFT A CRATER OR OTHER SIGN! Yeesh! But, I agree that we still need to loo for potential impactors just the same!

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