Privately and publicly looking for Earth-threatening asteroids

By Phil Plait | June 28, 2012 12:53 pm

[Note: In the interest of full disclosure, I am friends with many of the folks on both teams described below. I have tried to be scrupulously fair to both missions, and to be honest - as I say below - the best thing to happen would be for both missions to be locked, loaded, and looking for potentially hazardous rocks.]

The B612 Foundation is a group of scientists, astronauts, astronomers, and engineers who have come together to do nothing less than literally save the world: they want to find and deflect asteroids that can potentially hit the Earth. While really big asteroids are rare — after all, the one 10 km (6 miles) across that wiped out the dinosaurs only hits Earth every few hundred million years — smaller ones in the 100 meter range are far more common and can still do devastating damage. Even one just 50 meters across (smaller than a football field) can impact and explode with the yield of millions of tons of TNT. That’s in the range of the biggest nuclear weapons ever detonated.

Finding these asteroids is notoriously difficult. They’re small and dim, and sometimes only discovered once they’ve already passed us! The best way to find them in large numbers is to launch a space telescope to survey the sky, tuned to the infrared where these asteroids are far brighter and easier to spot.

Today, B612 made a big announcement: they want to build just such a mission. They call it Sentinel, and it will be the first privately funded deep space mission ever launched. Built by Ball Aerospace and launched on a SpaceX Falcon 9 rocket, it will be placed into a Venus-like orbit, giving it a good view of the volume of space where these asteroids prowl:

[Click to chixchulubenate.]

The plan is to raise the money philanthropically, like museums do: donations from private funders. Observatories have long been funded this way, and the proposed cost of a few hundred million dollars is roughly on par with many civic projects. Their target launch date is 2017 to 2018, and the mission will last about 5 years.

Interestingly, a group of scientists and engineers with NASA/JPL is planning a similar mission! Called NEOCam (for Near Earth Object Camera), it’s based on previous missions like WISE and Hubble.

Sentinel and NEOCam have many similarities: they both use a 50 cm or so telescope, both are tuned to infrared, and both will launch into orbit to get a better view of potentially threatening asteroids. Unlike Sentinel, NEOCam will stick closer to the Earth, placed into an orbit that keeps it about a million miles away. The advantage of this is that being closer, the rate at which data can be sent to Earth is very high. That allows more and higher-resolution observations to be made. While Sentinel is designed to look at one broad region of the infrared spectrum, NEOCam will look in multiple wavelengths, giving it the ability to characterize the size and chemical composition of asteroids more accurately.

This part is important: the two missions do two different things! Sentinel is designed to find and get accurate positions and orbits for these asteroids. NEOCam will also find lots of asteroids, but is optimized for science, to understand the asteroids’ physical characteristics. Both of these factors are critical and complementary. We need both.

The missions also look at different parts of the sky, so that means more coverage of space. That’s very important too: those rocks are out there. There are thousands of near-Earth asteroids bigger than 100 meters across, and millions in the 30 – 50 meter range. We’ve only found a fraction of these rocks, and so the critical first step is to simply find them and figure out their orbits. Both NEOCam and Sentinel will do this, including ones that are very difficult to observe from the Earth.

At some level these missions are in competition, since NASA is involved with both. However, since Sentinel is privately funded and NEOCam the result of NASA funding, I think it’s entirely possible — even preferable — that both of these missions are built! The more eyes we have on the sky the better. Not only that, but missions that do different observations, as these do, are necessary as well.

The threat from asteroid impacts is real. We have to be careful not to get hysterical (every time I report on some near miss a lot of people get really scared — but you have to remember the point is that they missed!), and instead look at this threat rationally. The reason you’ve heard more about near-Earth asteroids recently is that we’re getting better at detecting them. These missions will increase hugely our ability to find hazardous asteroids. And once we find them, we can take that next all-important step: moving them out of the way.

But first things first. Launch both these birds!

Image credits: ESA/Rosetta, NASA/NEAR; B612 Foundation; NASA/JPL


Related Posts:

- My asteroid impact talk is now on TED
- Asteroid 2011 AG5: a football-stadium-sized rock to watch carefully
- A brief bit about asteroid 2012 DA14

Comments (30)

  1. Jess Tauber

    Let unmarried women do the search- they’re hoping for big rocks anyway…

  2. Ian

    “the one 10 km (6 miles) across that wiped out the dinosaurs only hits Earth every few hundred million years”

    I’m reasonably sure that one will probably not be hitting us again.

  3. I’d be interested if either of these can operate in a “warm” phase, like Spitzer. Will one or both have a limited supply of liquid helium (or solid hydrogen)? It would be interesting if an Earth orbiting scope could have a new can of coolant docked to it, say, three years after launch, giving it another 3+ years.

    But a Venus-like orbit should let us spot all the NEOs. Maybe that wouldn’t take too long.

  4. Chris
  5. Okay, Phil, I have one question about the whole tug thing versus blowing up the asteroid.

    Now, it’s often said that we should not try to blow up an asteroid, because it would just split it into a few big asteroids.

    I’m sure you will agree that there is a quantity of energy that would completely destroy an asteroid so that it is not in any form that could do harm. There is an amount of energy that is capable of turning a solid asteroid into a cloud of dust and dispersing that dust in all directions. There is a quantity of energy that will vaporize or ablate nearly every atom in the asteroid and turn it into something of such low density that it would fly past earth like walking through a cloud of steam.

    I am sorry if I am butchering this quote, but Edward Teller (father of the H-bomb) stated “There is no limit to how big you can make them. We could build one many gigatons in size if we so desired. The materials you need are common enough as well.”

    Assuming you were to use a large number of the largest rockets we can build and topped each with the largest explosive we could construct, you could quite possibly deliver multiple teratons of explosive power to the area of an asteroid. A difficult, though not impossible engineering challenge.

  6. Phil:
    Nitpick – it should be chicxulubenate.

  7. You may want to try rephrasing this sentence:

    “after all, the one 10 km (6 miles) across that wiped out the dinosaurs only hits Earth every few hundred million years”

    The same asteroid hits Earth every few hundred million years?

  8. Dutch Railroader

    @3 Stephen: NEOCam uses passive cooling, while Sentinel uses cryo-coolers. Neither mission has expendable cryogens.

  9. Chris A.

    Think, just think, about how exciting it would be if we could find a potentially hazardous asteroid in sufficient time to deploy a mission to divert it. The sheer awesomeness (and concomitant sense of the oneness of humankind) as the whole world watches (via the wonders of telescopes, space probes, and the Intertubes) as it zips harmlessly past us instead of ruining someone’s entire day would be tantamount to what we felt upon the landing of Apollo 11 at Tranquility, I suspect.

  10. timbebinder

    I’m just about done reading the first Firestar novel. Anybody else read those books?

  11. wright1

    Defense in depth; I like it a lot. By all means, let’s get those eyes up there.

    @Chris A: very good point. A cooperative space project with far more immediate appeal than the ISS.

  12. Steve D

    In response to the other Steve (#3), an asteroid 50 m on a side and density 3000 kg/m3 (typical meteorite density) will have a mass of 3.8 x 10^8 kg. It takes millions of joules to vaporize a kilogram of silicate rock, so we’re talking megatons.

    Explosions on earth are mostly effective because of the atmosphere. The atmosphere transmits a shock wave. Also, nuclear explosions create a fireball of incandescent atmosphere, which produces most of the thermal effects. That’s why nobody talks about explosives much as space weapons – they’re all kinetic energy or radiation weapons. Set off a nuke next to an asteroid and you’ll vaporize the surface nearby, maybe create an internal shock wave capable of breaking it up into big chunks, but the vast majority of the energy will be radiated away into space. So you will need lots of nukes well placed to vaporize the asteroid. On the other hand, vaporized bomb material plus escaping rock vapor will probably change the trajectory of the asteroid, maybe making things worse if you’re careless, but possibly also nudging it away from an impact trajectory.

    If we spot the asteroid a few years out, it will make several orbits before impact, traveling billions of kilometers. We only need to nudge it at most 7000 km (one earth radius plus a cushion,) or roughly one part in a million.

    There are, by the way, practical limitations on how big a nuke can be, mostly having to do with how much energy you can release before the bomb is blown to smithereens. You can have enough tritium for a petaton explosion, but if the blast scatters it all into space before it fuses, so what?

  13. HP

    It seems to me that if a private company developed the technology to safely and reliably divert an Earth-destroying asteroid, they could basically hold the planet hostage, supervillain-style.

  14. Steve D:

    That’s not exactly true. Nuclear weapons actually can work quite well in space. The Safeguard Program was based on using really big nukes to destroy incoming ICBM warheads. The idea being, with a big enough nuclear weapon, you don’t even need a direct hit on it, just being within a kilometer or so will do the trick.

    They used “radiation enhanced” nuclear weapons. Weapons that were designed to create a massive burst of X-rays and neutrons. At a kilometer or two, they would fry the electronics and possibly cause pre-iniation of a bomb. At a couple hundred meters, the massive flux of x-rays would vaporize everything.

    The energy radiates isotropically (spherical and reducing in intensity according to the inverse square law) so you never get all of it to land on the rock. Still, get it close enough and make the bomb big enough and you will get a lot of energy onto that rock.

    Again, there being no upper limit on size, the only limit you really face is the global supply of deuterium, lithium and uranium. That supply is quite large.

    So obviously you want to get these explosives, which could be orders of magnitude greater than anything humanity has ever produced as close as possible. In fact, you could land it on the asteroid. You could have the entire surface covered with several hundred explosives, each one being many hundreds of megatons and each of those times to explode within nanoseconds of each-other.

    I propose that either this would work, or if it does not work, then it simply proves that you must not have used enough of them.

    Now, you may ask me, why on earth would you want to use more explosive power than was stockpiled during the entire Cold War, when you could just divert it with much less?

    BECAUSE I LIKE EXPLOSIONS. I like big ones better than small and I like really big ones better than big ones. I watch Mythbusters. I like dropping sodium into water and I like fireworks.

  15. I would think that given the current and likely near future political environment as regards NASA there is probably very little chance of them really getting anything like this going. Unfortunately the private effort is probably the only one that has a realistic chance.

  16. Bob P

    How does this compare, compete or coordinate with what Planetary Resources is planning? The first stage of their master plan is to use a large number of small space telescopes to find and characterize a lot of near earth asteroids.

  17. VinceRN

    @Bob #16 – I think that they are looking at different asteroids in a different place, though their data could probably still be useful for this, and their eventual methods for exploiting asteroids might be useful for defending the Earth from them. Someone here know the answer to at least three significant digits and probably soon be posting it in detail though. Likely proving me wrong in the bargain.

  18. DaveN

    @13/HP:
    Shhhhhhh…… you’ll spoil everything!!!

  19. Illectro

    WISE did a great job of discovering asteroids – witness the discovery pattern around 2009

    http://www.youtube.com/watch?v=ONUSP23cmAE

  20. Blargh

    The big question for me – unanswered in this article, the Sentinel fact and spec sheets, and the B612 FAQ – is what B612 is going to do with the Sentinel data.
    Will they keep it for themselves or will it be open for everyone?

  21. Georg

    Nuclear weapons
    (presumably of special design) might be a choice nevertheless.
    Of course not to “blow” asteroids in a Hollywood style, but as a
    source of impulse to deflect the asteroid a little bit off its orbit.
    One had to “place” the bomb at right angle to the path of the
    asteroid, some meters or hundreds of meters away, then ignite
    the bomb.
    This would deflect the path a bit, some parts of course would
    fly away (loose debris on the surface in any case), but the main
    part of a rocky asteroid would survive. Calculating/experimenting
    to find the optimum distance would feed hundreds of scientists for
    years :=)
    The ionic drive does the same thing in the end, the question is, how
    do I get the biggest amount of deflection “power” close to that asteroid?
    Either batteries or nuclear batteries feeding a ionic drive, or a
    nuclear bomb device?. The latter has a tremendous energy content,
    but lower efficency in kicking the asteroid, the ionic drive would
    contain much less energy, but would transmit that energy to the
    asteroid “100″ percent.
    I cannot decide/calculate which is better, but some physicists
    from the bomb faculty can, I suppose.
    Georg

  22. Tom H. Type

    Steve It think your large nuke idea has merit. It’s just, who would build such a weapon? The US, Russians, Iran?
    I can just see it now…”We’re building this Gigaton nuclear bomb for…eh, Asteroid control”…sure!
    Besides, there are treaties and international laws that would take years, if not decades, to renegotiate in order for anyone to launch such a device.

    How about a solar powered “Laser” in orbit.
    No, Not weapons grade, but sufficient in output to produce small but steady Photon pressure on the Asteroid, until it’s orbit has been deflected enough to miss us. We can place it over Antarctica, that way, most would feel safer.

  23. DukeTG

    @Blargh: In one of the press releases, I believe it says that the data is kept for 6 months and then shared.

    http://www.bizjournals.com/denver/news/2012/06/28/ball-aerospace-picked-for-1st-private.html?page=2

  24. Mike

    Do we have an idea of the distribution of asteroids relative to the orbital plane? Are the fields of view of current instruments and the proposed telescopes sufficient to see the presumably more rare out of plane threats?

  25. CodyG

    Exploration and Discovery … THIS is the meaning of life, of where we are coming from, of where we are going and about the percentages of us getting there. Let’s get locked and loaded and get the mission done! Make Gene Proud!

  26. Gary Ansorge

    14. Steve

    Slight problem with the super sized nuke.

    1) It only requires a fission core(say, about 20 kg of U239). We don’t use tritium for H- bombs anymore. It makes the bomb way too massive. Instead, we use a lithium shell, which gets irradiated by the free neutrons from the fission bomb when it goes off. That inner core shock wave causes it to fuse. There IS some upper limit to the size of the lithium shell but I don’t know what it is. Mainly, it has to do with how many neutrons are available to irradiate the lithium and those are only able to penetrate so far into that shell, before the expanding shock wave from the core blows it all apart. As fas as I know, the largest nuc ever planned was 100 megatons, but the Ruskies only set off theirs at about 40 megatons. That was enough to convince them that a 100 megaton nuc would be…excessive…

    Gary 7

  27. Sam

    @ #23 Tom H.Type

    Actually by my reckoning the only practical use for a multi gigaton device would be asteroid busting, so it might not be that implausible at all. We already have devices capable of causing continent wide EMP, and even for destroying either large area targets, or hardened pinpoint ones, once you get above a certain megatonnage (double figures) you’re just overkilling. From memory the largest weapons ever widely deployed were around 25-30 MT.

    The Soviets tested the largest weapon ever built in the bad old days at around 50 Mt. That was spectacular enough, but the design was capable of twice that. At that size it would have been too dangerous to test, and just impractical as a war fighing weapon, since it would create more problems effects wise for whoever used it than it would solve. It was done more as a propaganda exercise than anything else.

  28. Nigel Depledge

    @ 28 & 29 -
    According to wikipedia, the Tsar Bomba design was scaled back from the original conception of 100 MT to c. 50 MT, to reduce fallout and to prevent the detonation from destroying the drop plane (!). Depending on which source you believe, its yield was 50 MT, “over” 50 MT or 62 MT (although I can’t recall where I read this last figure, the first two are on different pages in wikipedia).

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