Should we build a defense system against meteorites?

We were promised that today, the 2012 DA14 asteroid would pass just 27,700 km away from the surface of Earth today (watch live later tonight). That would be the closest distance recorded by humans for an object of this or larger size (diameter about 50 meters).

Also, we were told that no object would actually hit the surface of Earth on Friday 15th, 2013. Technically speaking, that was wrong. ;-) An unrelated meteor (Google News) was seen – and affected – the Chelyabinsk region in central Russia, 300 km South from our (Pilsen's) twin city of Yekaterinburg (formerly Sverdlovsk, named after a bloody communist murderer of the tzar family) where I spent July 1988. See a collection of amateur videos (plus YouTube) of this meteorite that is said to be the largest one since the 1908 Tunguska event (yes, Russia seems to have a monopoly in this field: Gagarin was just a minor example of this fact).

Despite the "uniqueness status" of both objects and their taking place on the very same day, these two events are almost certainly unrelated. The speed of DA14 relatively to the Earth was about 7.8 km/s while the speed of the Russian meteor relatively to the surface was about 15-30 km/s. It's remarkable that no one can provide us with more accurate numbers. It must be possible to extract the exact velocity vector from the amateur videos, right?

It's also being said that the direction of the Russian meteor was different (almost opposite) from that of the 2012 DA asteroid: DA14 went from South to North, the Russian rock went in the opposite direction.




What was the impact of the Russian meteor? People saw an impressive fireball in the sky, followed by a loud sound wave. The latter shattered lots of windows and broken windows and similar things injured about 1,000 people (mostly bruises), 50 of whom were injured somewhat more seriously.

The Russian officials reacted quickly and brought specialists to the scene. They also quickly offered a compensation for the broken windows. Russian citizens – who have been trained for 70 years how to maximally benefit from the socialist state's offers – were even faster. They immediately bought all the plastic temporary windows in the shop and as soon as they learned about their generous post-socialist government, they started to break their windows by their hands in order to get new ones and some money, too. ;-)

That's it. This is what meteorites do to us for one typical century. See how authentic Russian folks reacted.

Now, Anthony Watts believes that instead of global warming, people should spend lots of money for this threat. He kind of suggests that he considers the threat posed by similar cosmic objects to be as serious as global warming is serious according to the global warming alarmists.

Well, I surely agree that some folks should get millions and maybe even billions of dollars to develop technologies to monitor asteroids and/or destroy them by nuclear weapons sometime in the future. But to spend those global-warming-like trillions of dollars for asteroids? No way.

One should be reasonable about the costs-and-benefits analysis. If we were hypothetically able to prevent the damage caused by meteorites similar to the Russian one (by size as well as population density in the target), we could save millions or billions of dollars per century. No human lives so far. So we surely don't want to spend trillions per decade for avoiding this threat, especially because it's impossible.

I am more thinking about the larger – and less frequent – asteroids that sometimes hit the Earth. It would be good to have some plan in the case that those are seen – and most of the large ones may be seen. See NASA's Near Earth Object Program and its list of current threats. We could discuss the plans to break these objects into pieces by nuclear weapons etc. – I don't have too much original stuff to say that would go beyond the movies about these scenarios.

We're talking about objects that hit the Earth once per thousands or millions of years; I don't want to be too specific. Let me use the room in this paragraph to clarify some terminology. "Asteroids" used to be the name for small planet-like objects between Mars' and Jupiter's orbit but the word got abused so that it could represent vastly smaller objects, too. Therefore, when it comes to the size, the word "asteroid" is almost completely ill-defined these days. On the other hand, a meteoroid should be smaller than 10 meters or so. A meteoroid is the name for such an object while it's flying in the outer space; when it enters the atmosphere and shines, it becomes a meteor; and if and when it hits the surface of the Earth (some meteors are burned before they achieve this goal), it becomes a meteorite. Fine.

But let me return to the meteorites of the Russian size. Unlike Anthony, I think it's mostly preposterous to try to fight against similar threats. One may emit impressive numbers about the meteoroid's carrying the energy of 700 Hiroshima bombs but you know, it's not too much. The Russian H-bomb had somewhat higher energy still and it hasn't killed anyone. The same is true for most of such celestial objects because they don't try to hit the people.

And if we're unlucky, they will kill some people locally. But even in that sad case, you must see the damages in some proper context. A meteorite similar to the Russian one is as harmful as an earthquake of a certain moderate magnitude (try to insert the right number into this sentence). It has a similar local impact, too. Earthquakes of this equivalent magnitude are taking place much more frequently than the collisions with the Russian-size meteoroids. So the overall impact of the meteorites of this size is a small fraction of the impact of the earthquakes – and we don't really fight against the earthquakes too efficiently, either (even the arresting of innocent Italian seismologists fails to be an efficient way to fight earthquakes). Earthquakes don't exterminate the whole mankind.

Moreover, the collision with this particular Russian meteoroid couldn't have been mitigated. The object was invisible simply because it was coming from the Sun – not quite precisely but precisely enough so that it was overshadowed by the sunshine most of the time. Perhaps, we could see such a body 1,000 seconds or 15 minutes in advance. Multiply it by 20 km/s to get 20,000 kilometers – the distance from the Earth in which this object could become visible. But 15 minutes before the impact may already be too late.

I don't want to be too specific about these numbers because the technology is evolving and I am no expert in its current abilities, anyway. But what I really feel rather certain about is the other side: the expenses. We may compare the hypothetical anti-meteorite defense system with the world's best anti-missile defense system, Israel's Iron Dome which has made a real impact on the conflict with the terrorists in Gaza who try to shoot missiles to Israel all the time.

Iron Dome has deployed five batteries. Each of them costs $50 million and one anti-missile costs about $100,000. That's cheap, of course, but it's still expensive enough so that the managers of Iron Dome must ignore Hamas' missiles that are likely to land in unpopulated areas (fields). But if you want to protect the Earth against meteorites, you should count how many batteries you will need and how much more powerful, fast, and accurate they should be relatively to Iron Dome.

The problem you must realize is the speed of the meteoroids. Scuds and other Hamas' rockets move by the speed about 500-600 m/s. Only the intercontinental ballistic missiles are 13-14 times faster. At 7 km/s, they're getting closer to the meteoroid category of speeds. (The escape speed from the Earth is 11 km/s or so.) If you want to count the number of batteries you need, you must know which portion of the globe you want to protect, how much time in advance you learn about the meteoroids, and how does the speed of your anti-missiles compare with the speed of the meteoroids. And you must pray that the accuracy will be good enough.

I am convinced that even in the absence of any particular numbers, it's pretty clear that you will end up concluding that it's a waste of money to try to protect your land against the meteoroids of the Russian size. You know, it's harder to "shoot down" a very fast meteoroid than a Scud missile; they cause comparable damages; but the Scud missile arrives at least every week while the Russian-size meteoroid only hits Israel once per 2.5 million years (I multiplied 100 years for the whole Earth by 25,000, the ratio of the Earth's surface and Israel's territory). Now, 2.5 million years is about 100 million times larger than one week. It follows that the cost/benefit ratio is about 100 million times greater (less economic) for the anti-meteoroid defense system than it is for the anti-Hamas defense system. And even the latter is financially controversial! ;-)

So no, it's stupid to waste the money for these local threats. It seems to me that good folks like Anthony and others are driven by the utopia of a completely safe world where all the risks are zero. But such a world can't exist according to the laws of physics. In the real world, some risks always exist and it costs something to reduce them. You should be very rational about the costs and about the question which threats deserve to be wrestled with.

I think it only makes sense to discuss the defense against the nearly continental-in-size threats posed by the celestial objects on their collision course with Earth. And in that case, we're getting to the science-fiction realm whose typical time scale is counted in thousands or millions of years. Unless we are unlucky, we won't see such a continentally or globally devastating object hitting the Earth for centuries and probably much longer than that.

And it seems reasonable that such large objects would actually be visible years or decades in advance. They should have some quasi-elliptical orbits and we should be able to see them many periods ahead of the collision, just like in the NASA's Near Earth Object Program. If we have decades for the preparations, we should be able to invent something. In some sense, I think that decades of time is a lot of time for thinking and it is useless to do the preparations before we (or our descendants) actually face the threat. Even after 3 seconds of thinking, one may invent the idea of simply sending some thermonuclear weapons against the celestial object and try to tear it apart. I guess that with a year (or years) of discussions among true experts and best engineers, one could get better or more reliable solutions.

It seems to me – although, strictly speaking, I don't have a proof – that dinosaurs and other ancestors of ours didn't have the required know-how and weapons. Apologies if my reasons look racist to you but I just find these lizards rather stupid! ;-) We have a much better chance to protect ourselves against certain continental types of destruction – perhaps with the help of evacuation, too.

What about even larger events similar to the Cretaceous-Tertiary extinction event 66 million years ago? I am not sure whether we have a chance. I think that we would know about the threat many, many years in advance, too. It's just unlikely that something sufficiently large enters the Solar System along a hyperbolic (or parabolic) trajectory because the surrounding space is rather empty and boring.

I am sure that people will try their best if they learn about the looming extinction. And if they decide that the Earth is doomed, I am sure that they will try to create Noah's arc to protect some species in outer space or on the Moon or other planets (so that they may return to the Earth once it's safe again). If it were a top priority, I am confident we could store some species and humans etc. on the Moon, too. Just multiply the funding for NASA by a factor of 100 and you will see some improvements.

Of course that humans shouldn't close their eyes and ignore all conceivable threats. And if they see a threat, of course that humans shouldn't be – and won't be, whether we think that they should or shouldn't be – waiting for the Armageddon to devour us. However, I don't think we should be preparing for totally unspecified, abstract dangers of this sort long before we see any of them and long before we see what they exactly are. These premature preparations wouldn't improve our (or our descendants') situation too much but they could be way too costly (and grow into an irrational self-supporting hysteria similar to AGW, anyway). That's why I am probably not going to join Anthony's club of asteroid alarmists anytime soon.

And that's the memo.