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Sizing Up the Asteroid Threat

The potential threat from near-Earth asteroids can sometimes seem purely theoretical, an academic exercise in how orbits are calculated and refined. But when we start quantifying possible damage from an asteroid strike, the issue becomes a little more vivid. Modeling potential impact points all over the planet, a University of Southampton (UK) team has worked out some stark numbers. The University’s Nick Bailey presented the results at the recent Planetary Defense Conference in Washington.

The researchers put a software package called NEOimpactor to work on asteroids under one kilometer in diameter and assumed an impact speed of 20 kilometers per second. Obviously, larger objects are out there and the impact velocity is arbitary, but asteroids in this size range seem to hit the Earth every 10,000 years, frequent enough that the next one that does hit will probably fit this description. Says Bailey:

‘The consequences for human populations and infrastructure as a result of an impact are enormous. Nearly one hundred years ago a remote region near the Tunguska River witnessed the largest asteroid impact event in living memory when a relatively small object (approximately 50 metres in diameter) exploded in mid-air. While it only flattened unpopulated forest, had it exploded over London it could have devastated everything within the M25.’

Indeed, while a 100 meter asteroid could cause relatively localized damage across several countries, doubling the object to 200 meters causes tsunamis on a global scale, assuming an oceanic hit. In terms of casualties, the study sees China, Indonesia, India, Japan and the US as the most vulnerable, though obviously a direct hit on any heavily populated area would be catastrophic.

Asteroid infrastructure damage

Economically speaking, where the infrastructure is tells much of the tale. Put dense development along the coastlines of economically prosperous areas and you open yourself to the threat of tsunamis and earthquakes emmanating from a wide variety of impact areas. Sweden’s long coastline thus places it in high danger economically, while an impact in the north Atlantic could send devastating tsunamis into both Europe and America. Severe economic effects would clearly result from a strike involving China or Japan.

Image: The areas of maximum infrastructure vulnerability following an asteroid impact. Credit: Nick Bailey/University of Southampton.

Although we’re currently engaged through projects like the Spaceguard survey in cataloguing NEOs larger than one kilometer in diameter, the smaller objects represented in the Southampton study are largely undetected. The risk of being blindsided by such an object emphasizes our need to develop a space-based observation platform for tracking asteroids of this size, along with providing more accurate information about the movements of larger Earth crossers. Bailey again: “The threat of the Earth being hit by an asteroid is increasingly being accepted as the single greatest natural disaster hazard faced by humanity.”

Comments on this entry are closed.

  • ljk April 3, 2007, 10:07

    Deep Impact

    The American Prospect Mar. 28, 2007


    According to a new report from the
    National Aeronautics and Space
    Administration, some 100,000
    asteroids and comets routinely pass
    between the Sun and the Earth’s
    orbit. About 20,000 of these orbit
    close enough to us that they could
    one day hit the Earth and destroy a
    major city. But the really worrying
    news from NASA is that over a


  • Marc April 3, 2007, 13:08

    [q]In terms of casualties, the study sees China, Indonesia, India, Japan and the US as the most vulnerable, though obviously a direct hit on any heavily populated area would be catastrophic.[/q]
    Just curious, why not Europe?

  • Administrator April 3, 2007, 13:14

    Marc, I think they’re saying that these are the areas most vulnerable to catastrophe from an ocean strike that causes tsunamis (i.e., greater coastal area that’s highly populated). They varied the size of the impactor in their simulations and studied how severe would be the effects of each type of impact. Averaging out, you would get more chance of an ocean strike in any case just because of the proportion of ocean to land area.

  • Marc G Millis April 3, 2007, 18:30

    I recall the following quote that I pulled from a NASA cite about NEO’s almost a year ago:

    “the most likely warning today would be zero – the first indication of a collision would be the flash of light and the shaking of the ground as it hit.”

  • Marc G Millis April 3, 2007, 18:31

    Oops, forgot to give URL. I hope it comes through this time.

  • Marc G Millis April 3, 2007, 18:32
  • Administrator April 3, 2007, 19:18

    Marc, I remember Claudio Maccone talking about this up at Princeton at Ed Belbruno’s astrophysics conference two summers ago. He’s worked out an interesting planetary defense theory against NEOs with stations at some of the LaGrangian points — I’ve got to write this up soon — and he also indicated that an impact coming undetected, ‘out of nowhere,’ is the most likely scenario.

  • Tim G April 4, 2007, 4:28

    Why is there a red pixel near Barrow, Alaska?

    I suppose the superimposition isn’t perfect and that Anchorage should have
    been reddened.

  • Administrator April 4, 2007, 8:43

    Tim, that is weird. The pixel does indeed look as if it’s over Barrow rather than Anchorage. I don’t have an answer on that one. Damage to oil pipeline infrastructure, maybe?

  • Robert Canamar April 11, 2007, 18:52

    When you developed this, did you take into account that Earth is really fissured. A 100 meter Asteroid hitting ANYWHERE along the San Andreas
    fault, will set that fault off. The combination of the shock wave from the
    impact and the shock wave from the San Andreas fault will be enough to
    send a wave around the world about 2 to 2.5 times. That much force in a
    shock wave will be enough to create a wave that will send the upper crust,
    and every thing on it about 2 or 3 miles into the air. Needless to say, this
    would be the end of life, especially when you add in the fact that this will set off every volcano in the world. That is not a very good prospect.

  • ljk May 15, 2007, 16:54

    Title: Landing screw-rockets array on asteroids, digging soil and fueling engines in phase, to overcome the spin and to fly in space

    Authors: D. Fargion

    (Submitted on 12 May 2007)

    Abstract: To deflect impact-trajectory of massive km^3 and spinning asteroid by a few terrestrial radiuses one need a large momentum exchange. The dragging of huge spinning bodies in space by external engine seems difficult or impossible. Our solution is based on the landing of multi screw-rockets, powered by mini-nuclear engines, on the body, that dig a small fraction of the soil surface, to use as an exhaust propeller, ejecting it vertically in phase among themselves. Such a mass ejection increases the momentum exchange, their number redundancy guarantes the stability of the system. The soft landing of engine-unity may be easely achieved at low asteroid gravity. The engine array tuned activity, overcomes the asteroid angular velocity. Coherent turning of the jet heads increases the deflection efficiency. A procession along its surface may compensate at best the asteroid spin. A small skin-mass (about 2 10^4 tons) may be ejected by mini nuclear engines.

    Such prototypes may build first save galleries for humans on the Moon. Conclusive deflecting tests might be performed on remote asteroids. The incoming asteroid 99942 Apophis (just 5% of km^3) may be deflected safely a few Earth radiuses. Its encounter maybe not just a hazard but an opportunity, learning how to land, dig, build and also to nest save human station inside. Asteroids amplified deflections by gravity swing maybe driven into longest planetary journeys.


    28 pages, 5 figures


    Astrophysics (astro-ph)

    Cite as:

    arXiv:0705.1805v1 [astro-ph]

    Submission history

    From: Daniele Fargion [view email]

    [v1] Sat, 12 May 2007 23:50:03 GMT (353kb)


  • ljk May 15, 2007, 16:59

    From Steven Aftergood’s Secrecy News list:

    The National Aeronautics and Space Administration earlier this year
    attempted to block public access to a comprehensive report on planetary
    defense against asteroids, but the document found its way into the
    public domain anyway.

    NASA undertook the study in response to a 2005 Congressional mandate
    “to provide an analysis of alternatives to detect, track, catalogue,
    and characterize” potentially hazardous near-Earth objects (NEOs) and
    to submit “an analysis of possible alternatives that NASA could employ
    to divert an object on a likely collision course with Earth.”

    An abbreviated version (28 pages) of the resulting report, which
    generally recommended against initiation of a new planetary defense
    program, was provided to Congress and the public in March 2007.


    Strangely, however, NASA sought to prevent public disclosure of the
    full 272-page report that provided the underlying analysis for NASA’s

    To prevent uncontrolled dissemination, NASA did not distribute a soft
    copy version of the report. And altogether, no more than around 100
    copies of the hard copy document were published.

    Public requests for the document were denied, though it is

    “The document you requested was distributed in hard copy as a ‘thank
    you’ to [NASA working group] team members and is not an official,
    distributable NASA publication,” Marcus Shaw, a contractor at the NASA
    Office of Program Analysis and Evaluation, told Secrecy News.

    “Copies beyond those for the study team are not available. An
    electronic copy will not be distributed or posted by NASA,” he wrote in
    a March 13 email from NASA headquarters.

    In fact, however, the report is clearly marked as a NASA product and is
    presumptively subject to disclosure under the Freedom of Information

    A legal challenge proved unnecessary, however, as the report soon
    leaked out through unauthorized channels.

    It was obtained by the private B612 Foundation, an organization that
    advocates a more pro-active planetary defense program. (“Our goal is
    to significantly alter the orbit of an asteroid in a controlled manner
    by 2015.”)

    The full document (in a large 23 MB PDF file) was posted this month,
    along with the organization’s technical critique of NASA’s analysis,


    B612 is the asteroid home of Saint-Exupery’s Little Prince.

  • Lis Cotter May 27, 2007, 9:59

    Hi. Entered nov 6th 2007 comet, and found this site. Was told by a friend who went to see a psychic that the comet will return and hit England on Nov 6th 2007 at 12pm and that this will knock the earth off its axis. Wondered if the maths/timing adds up and whether this is a real possibility?

  • Administrator May 27, 2007, 10:08

    I think you can relax, Lis, at least about a cometary impact on that date in England. Around here we do believe it’s important to track objects that cross Earth’s orbit and expand our search for them — it’s a long-term project that should pay off in terms of planetary security — but there is no credible information that a November comet strike is going to occur.

  • Kelvin May 27, 2007, 14:30

    P. T. Barnum continues to be soooo right….

  • ljk February 22, 2008, 0:26

    Primordial black holes and asteroid danger

    Authors: Alexander Shatskiy

    (Submitted on 21 Feb 2008)

    Abstract: Probability for a primordial black hole to invade the Kuiper belt was calculated. We showed that primordial black holes of certain masses can significantly change asteroids’ orbits. These events may result in disasters, local for our solar system and global for the Earth (like the Tunguska meteorite). We also estimated how often such events occur.

    Comments: 5 pages

    Subjects: Astrophysics (astro-ph)

    Journal reference: Vestnik Moskovskogo Universiteta (in Russian), ser. 3, No4, (2008)

    Cite as: arXiv:0802.3119v1 [astro-ph]

    Submission history

    From: Alexander Shatskiy Dr. [view email]

    [v1] Thu, 21 Feb 2008 14:27:51 GMT (5kb)