≡ Menu

Tuning Up Asteroid Threat Mitigation

Some people tell me that the dangers posed by an asteroid or comet impact on Earth are over-publicized. Surely whatever object hits us would land some place harmless, causing nothing but a flurry of news stories. Others remind me that Chelyabinsk was seriously rattled by the explosion of a small asteroid in 2013, an event that could have created appalling damage with a slight deviation in trajectory. My own view is that guessing at the odds doesn’t do much for us. I favor a strong research effort into asteroid deflection and risk mitigation strategies.

Normally planetary protection wouldn’t be high on the agenda on Centauri Dreams because I focus on deep space issues and our exploration possibilities far from Earth. But asteroid deflection merits our attention because I’m convinced it is one of the drivers for space research. Protecting the planet means learning not only how to deflect potentially risky objects but also how to detect them long before they pose a problem. The two work together in that some impactors could come from far out in the system and need long-term strategies.

Thus I’m interested in learning that Vishnu Reddy of the University of Arizona’s Lunar and Planetary Laboratory is working with NASA’s Planetary Defense Coordination Office, the federal entity in charge of coordinating efforts to protect Earth from hazardous asteroids, on an observational campaign to test how well our networked resources might respond to a threat. Unlike earlier, similar exercises, this one engages our response to an actual near-Earth asteroid known as 2012 TC4. The Chelyabinsk reference comes in handy here — 2012 TC4 is thought to be roughly the same size as the asteroid that lit up the Chelyabinsk sky in 2013.

Image: No photos of asteroid 2012 TC4 exist, but this image of Itokawa, another near-Earth asteroid, helps visualize its approximate size: next to Itokawa, which is half a kilometer long, TC4 would appear about the same size as the “bunny tail” feature visible on the left. Credit: JAXA.

2012 TC4 was discovered by the Pan-STARRS 1 telescope on Oct. 5, 2012, at Haleakala Observatory (Maui). It is expected to pass as close as 6800 kilometers from the Earth on October 12 of this year. The idea of the exercise is to test systems involving observations, modeling, prediction and communications on an object that we can actually track.

When it becomes visible to Earth-based telescopes in early August, the asteroid’s orbit will need to be ‘recovered,’ meaning nailing down its parameters. Objects 50 meters across or less (about 12000 known near-Earth objects are larger than this) should disintegrate in the atmosphere, a heartening thought, though the 20-meter Chelyabinsk bolide, exploding high in the atmosphere, still resulted in thousands of injuries. The odds on a 1-kilometer or larger asteroid impacting the Earth are small, but exercises like this one will help test systems that one day might be called into play to evacuate an area where a small impactor might hit (see this interview with Paul Chodas, manager of the Center for Near-Earth Object Studies at JPL).

Image: On Oct. 12, 2017, asteroid 2012 TC4 will safely fly past Earth. Even though scientists cannot yet predict exactly how close it will approach, they are certain it will come no closer to Earth than 6,800 kilometers. Credit: NASA/JPL-Caltech.

More than a dozen observatories, universities and laboratories across the globe are involved in the upcoming 2012 TC4 flyby exercise. Let’s see how we do at pulling resources together to run an exercise on an actual flyby. Meanwhile, bear in mind that between 80 and 100 tons of various kinds of debris — dust, small asteroid fragments and so on — fall into the atmosphere every day.

Things falling down on us from above are, in other words, inevitable, but we’d like to know about the bigger stuff. Chelyabinsk-class events take place once or twice a century, but exactly when, given an NEO catalog that is incomplete, cannot always be predicted. Exercises like this one should help us tune up our response and suggest areas where we might improve.

Those other drivers for space exploration I mentioned earlier in today’s entry? To a large extent, they work in synchrony with asteroid mitigation. Astrobiology is clearly one, a search for the parameters of abiogenesis that dovetails with getting payloads to distant targets. An impact threat from further out in the Solar System than our population of near-Earth asteroids would demand proficiency at deep space propulsion and operations far from home. Add in the essential fact of human curiosity and the will to explore, and our push outward is sure to continue, whether with human crews or robotics, and despite inevitable budgetary constraints.


Comments on this entry are closed.

  • Alex Tolley August 8, 2017, 15:05

    In the more distant future, even small asteroids will be important for humans living on [near] airless worlds and moons. Even if our presence is in underground cities, there will still be surface excursions that will leave people vulnerable. Deflecting or destroying asteroids will become important as these populations increase. Learning to do this and building the institutions and infrastructure to handle it will be a feature of human expansion into our system.

  • DJ Kaplan August 8, 2017, 15:53

    My cynical thought for today? The unschooled hoi polloi will become alarmed at the perceived threat, without comprehending the odds (in comparison to other threats), and cry for science funding. Winning!

    • Ashley Baldwin August 8, 2017, 17:42

      I don’t think we necessarily know the relative risk of 50-300m asteroids hitting Earth. Once or twice a century for Tunguska like events is more than enough to make me nervous. And that’s assuming such events are genuinely random as opposed for instance to a cloud of debris resulting from a disrupted larger body . The survey of such near Earth objects is still far complete despite the best efforts ground based surveys like PAN-STARRS and non bespoke space based NEO/WISE . LSST will improve things further but still leaves a big hole in observable space for objects orbiting near the Sun, crossing Earths orbit and going interior to it . That requires the Venus like orb ( looking out awards )of the B612 Foundation 0.6m Sentinel concept NIR telescope or similar JPL NEOCAM in an SEL1 orbit.

      What constitutes “science ” was what did for NEOCAM’s “survey ” only approach to cataloging potentially dangerous NEOs in the latest Discovery programme selection. The scoring system for this allocates 40 % of the marks for science and as such obviously heavily favoured LUCY and PSYCHE , which won hands down given their proposed much more detailed and up close categorisation of asteroid/ Trojan targets.

      NASA have a quandary . They obviously want a NEOCAM / Sentinel type survey but don’t have the funds for a stand alone funded mission yet their planetary science programmes aren’t really geared up to allocate space to such a mission. They have compromised to a degree in granting funds for ongoing work at JPL on NEOCAM but it’s difficult to see how it will be selected against pure planetary science concepts for future Discovery rounds. An international collaboration seems the best bet for what would amount to a relatively “cheap” 5 year 500 million dollar telescope survey . What price Earth ?

      Watch that space . Meantime , if a 150 m iron/nickel rock hits the Earth at several tens of thousands of Kms /HR , that’s one big splash. And remember , that’s just the survey. Mitigation technology is only currently hypothetical and a long way from development now ARM has been cancelled .

      • Marshall Eubanks August 9, 2017, 13:05

        NEOCAM should be done with programmatic funds. I must admit that, when Jim Green announced that 2 Discovery missions might be selected, I thought that that was a way to fudge the issue and select NEOCAM + a high ranking science mission*. I was impressed that they actually picked two other missions – but, of course, we still need to do that survey.

        * Note: This does NOT mean that I thought that good science wouldn’t result from NEOCAM – I do – it’s just that that mission proposal was the only one with a Congressional thumb on the scale.

      • Antonio August 10, 2017, 3:54

        Gaia can detect near-Sun asteroids.

  • Geoffrey Hillend August 8, 2017, 16:00

    Quote by Paul Gilster: “Others remind me that Chelyabinsk was seriously rattled by the explosion of a small asteroid in 2013, an event that could have created appalling damage with a slight deviation in trajectory.” The Chelyabinsk meteor exploded with the power of 400 to 500 kilotons, the power of a small hydrogen bomb. It hit the atmosphere at a shallow angle. If the trajectory was more steeper or perpendicular to the ground, it would reach the ground and cause more damage? It was a chondrite type meteor. It was only 20 meters in diameter according to Wikipedia. That could destroy a city. We should definitely invest in a planetary protection program.
    Meteor crater is over one kilometer in diameter and it was caused by a 50 meter in diameter meteor which is estimated to have exploded with 20 to 40 megatons in power. Wiki. It was iron metallic in composition, but even a chondrite of this size would still explode in the megaton range if it hit at the right angle or any angle.

    • ljk August 9, 2017, 8:54

      Imagine if the Tunguska event had hit a city rather than remote Siberia. Or happened today with our nuclear hair trigger warning systems.

      Eighty million trees for 830 square miles around the Tunguska detonation zone were flattened. The devastation was still visible when an expedition finally reached the remote region in 1924. A man sitting on his porch 40 miles away was knocked off his chair.

      Imagine if this less known event from 1947 involving a nickel-iron meteorite had happened in a populated area:


      • J. Jason Wentworth August 14, 2017, 23:15

        Da…spasibo, comrade! The Sikhote-Alin asteroid caught up with the Earth from behind (as that contemporary Soviet documentary shows), so a faster, head-on collision might have created a damaging air burst like the Tunguska object’s, but less intense. I’ve read that the 1908 Tunguska event would have changed history if it had occurred at a slightly different time, because (if I’m recalling the correct city) Vladivostok would have been hit, almost certainly killing Lenin in the process. Also:

        A few hours either before or after (I forget which) Desert Storm–the first Gulf War–started, an asteroid exploded in the atmosphere over either the Atlantic or the Pacific, at the same latitude as Baghdad. Had it caused an air burst over the city, with several nations having military assets in the area–and on nuclear alert at that time–our recent history would likely be very different.
        Hopefully no celestial ice, iron, or stone will fall or explode anywhere near Guam, Pyongyang, Tokyo, or Beijing any time soon…

  • Michael August 8, 2017, 16:54

    Not surprising project starshot could be used as an asteroid defence and remote probe. High speed impacts could erode, breakup or even move an asteriod.

  • Marshall Eubanks August 8, 2017, 17:06

    T012 TC4 has already been recovered, by the 8.2-m VLT at 26th magnitude.


  • Rob Flores August 8, 2017, 18:44

    I don’t think I would feel any better know that “yeah stony asteroid
    can’t take pressure, will detonate even if close to perpendicular to surfac”
    As some astro buff informed me.
    But having a 200-500 megaton stoney asteroid detonate at 20mi high, is going to be painful to any creature below it.
    Granted a nickel iron is much more lethal…but less common.

    • Ron S. August 8, 2017, 21:58

      Yes, air detonation is no blessing. All that changes is the mode of catastrophe since the energy dissipation is the same as striking the ground. One witness in Chelyabinsk who wrote of the experience was at work when it happened. He rushed to the office window wondering what the big flash of light was. He saw others standing in windows in adjacent office buildings doing the same. After a short period with nothing more happening most everyone drifted away back to work. Seconds later ever window imploded.

      Do you prefer to die by structural collapse or shrapnel?

  • Thucydides August 10, 2017, 11:03

    The “Aster Ants” proposal could be a way to combine several of these strands. A network of sensors that track asteroids NEO’s and so on and identify threats, and a small fleet of solar sail vessels that can reach these bodies and move them into new orbits (think of kite sailing in space) provides the detection and protection.

    Once you can actually reach and rendezvous with asteroids, it becomes trivial to do science experiments on the asteroid as it is being towed away, and a short step from there to mining the asteroid for resources (initially making more solar sails as a bootstrapping mechanism).

    Small steps like this are much easier to do yet can still lead to the sort of deep space civilizations that we hope outline the future of humanity.

  • ljk August 15, 2017, 22:54

    Stardust hitches a ride on meteorites more often than previously thought

    August 15, 2017

    Even tiny dust particles have stories to tell − especially when they come from outer space. Meteorites contain tiny amounts of what is popularly known as stardust, matter originating from dying stars. Such stardust is part of the raw material from which some 4.6 billion years ago our planets and the meteorite parent bodies, the so-called asteroids, emerged. Peter Hoppe and his team at the Max Planck Institute for Chemistry in Mainz have now discovered that many of the silicate stardust particles in meteorites are much smaller than was previously thought. To date, many of them have therefore probably been overlooked in studies, leading the scientists to believe that the mass of the silicate stardust particles in meteorites is at least twice as large as previously assumed.


  • ljk September 3, 2017, 11:05
  • ljk September 19, 2017, 12:42

    Nanosat fleet proposed for voyage to 300 asteroids


  • ljk September 19, 2017, 13:03

    What do we need to know to mine an asteroid?


    If we want to colonize the Sol system and explore other star systems, we need the planetoids – and comets.

  • ljk February 9, 2018, 11:03

    Asteroid 2018 CB Zips by Earth Friday: Watch it Online

    By: Bob King | February 7, 2018

    A newly-discovered asteroid passes just 44,000 miles from Earth Friday. You can watch it from the comfort of your home.