|THE LATE, GREAT, PLANET EARTH||INVESTIGATE: MAR 03|
Sometimes ignorance can be bliss, but science writer Nick Sault argues the world needs to take the threat of asteroid strikes a lot more seriously...
Over the last few decades there has been a great deal of debate about the level of danger posed by impacts from asteroids and comets. Though the furore has settled down recently with various authorities downgrading the danger, I have been doing some of my own research into the phenomenon of impacts from space, and there are some really worrying aspects that I believe are being overlooked. It looks like it may be the smaller asteroids that we have to look out for, as there is mounting evidence that impacts from some of the tens of thousands of these rocks that have buzzed Earth throughout civilised history, have been responsible for some of the major disruptions to the growth of human societies. I really do not intend to be unduly alarmist, and rather than being fatalist, I believe that we can realistically counter the danger, because the objects that most commonly impact Earth destructively are within our means to destroy.
People have taken comfort in the fact that the sort of impact that is almost certain to have caused the de-mise of the dinosaurs happens only every many mil-lions of years. I do not dispute that time scale, and admit that in any case we probably could not counter an object 10 kilometers wide travelling at many kilometers per second. However, new detection techniques are revealing that much smaller bodies, a few hundred meters wide or less, criss-cross the Earths orbit constantly. The problem I see is that the authorities and even some of the experts in the field are not taking seriously the possible effects of an impact of one of these objects.
The Tunguska event of 1908 is pretty much documented now as the aerial explosion of a small asteroid over central Siberia. It is deemed by many experts that this exploding object that laid waste to 2000 square kilometers of forest was only 30 to 50 meters wide - tiny by asteroid standards. The point is that even though the devastation was local and the rest of the world slept safely, this was a fortunate hit in that it was in an uninhabited region. It would be nice and cosy to think that impacts like the Tunguska event are separated by thousands of years, but I fear that this is not the case. So, how frequent are impacts of Tunguska-size objects, and what would be the effect if one hit in a populated area?
The answer to the first question is still not known for sure, but new detection technology by organisations such as LINEAR and NEAT is showing that many objects the size of the Tunguska asteroid buzz the Earth every year. NASAs own web site provides a table (See http://neo.jpl.nasa.gov/cgi-bin/neo_ca) which shows all the objects detected that have made close approach to Earth. You can interact with this table and enter your own criteria, and if you apply the criterion that you want to display all those objects that approached within, say, 5 lunar-orbit radii (that is about 2 million kilometers), you find that there were 20 recorded for 2002. Then you find there were only 14 recorded for 2001, and only 6 for 2000.
This is a worry; that estimates of the likelihood of a hit are always based on the currently recorded detection rate, when it is quite obvious that more and more Near Earth Objects (NEOs, as they are called) are being detected as the technology improves (which is the obvious reason for the increased recorded rate for 2002, rather than there actually being more objects out there in 2002).
Another great worry is that for one of the closest approaches in 2002 (120,000 kms on June 14 only about 8 times the diameter of Earth), the object was detected only AFTER it had made that closest approach; the day after, in fact. So, what is the true statistic; that is, how many asteroids would we find if we had the technology to detect all passing rocks?
What it boils down to is that those 20 near misses of 2002 could well be 60 or 100. There is a period in each day called "daylight" during which the observatories are unable to detect objects that small. If we are conservative and take a figure of 50 rocks greater than 50 meters wide, passing within 2 million kms of Earth every year, we can mathematically confirm that a Tunguska type event can happen a couple of times a century. That might lead some to declare "so what, these 50 to 200 meter rocks only produce local devastation it is not the end of the world". That leads to the answer to the second question what is the likely effect?
Firstly, what do we mean "end of the world". It would take the hit of a small moon to end all life. Some of the major extinction events of the past have proved in the long run to be more creative than destructive, in that the species that survived began a brand new order of life. None could be called "end of the world" events. The point is that the living world could go on happily without us. But it doesnt require mankind to be obliterated completely for you and I to consider it the end of the world. Would we not call the end of our civilisation "the end of the world"?
What are we really afraid of? There are massive, almost moon-sized asteroids out there large enough to end all life within a few hours were they to hit us. But one of these has not hit our planet since the early days of its history; that is, billions of years ago. That scenario is not that scary in any case, as we wouldnt know much about it if it did happen. At the other end of the scale are the hits that I think should scare us, as they are quite frequent (on an historic scale) and can leave us in chaos rather than wiping us out. I mean a Tunguska event on an urban area. What would be the effect?
Ibelieve that the events of September 11, 2001 gave us some idea. Just several buildings of a city of thousands of buildings, produced a wave of economic turmoil; many companies failed, many were left in dire straits, and the American economy is still in low gear 15 months on. The Tunguska event is likened to 50 to 100 atom bombs. That would pretty much devastate the whole north-east seaboard of USA if it hit around New York. The physical and the natural world would survive, but would the American economy? If the American economy collapsed, how many smaller nations would collapse? If our civilisation collapsed, would we not call that the "end of the world"?
We have to ask ourselves what kind of economic collapse would bring on anarchy. When you look at the something like the crash of 1929, which really started just as a "paper" crash, accelerated by panic selling of stock, you realise how fragile are our first nation infrastructures. I think that people have not given enough consideration to the threat of relatively minor cataclysms which do not destroy great swathes of the planet, but have enough effect to bring down civilisations. And there is evidence it has happened before; many times.
What has brought this issue to head for me, and taken it from just an interest in asteroids and comets to something I believe we should be concerned about, are two very recent reports of impact craters that are quite definitely modern, in historic terms.
Very recently, a crater has been identified in Iraq that is known to be in an area of shifting sediment that was once an inland sea. This means that the feature could not possibly be older than 5 or 6 thousand years. This, of course, requires the confirmation of a research expedition, which might be somewhat difficult in the present political climate. However, there is a real and researched new crater in Italy. This one has been preliminarily dated to the 4th century AD. If that doesnt ring any bells, then I remind you that the Roman Empire fell at that time and Europe was plunged into turmoil for 500 years or so.
If you want to follow up an interest in this subject, required reading would be Clube and Napiers "The Cosmic Winter". The authors are astronomers, and their work is endorsed by many other scientists (except those that will never admit that impacts have shaped Earths history, which is as blatantly ridiculous as the sages who clung to the notion that the Earth is the centre of the universe). They cite researchers, some using tree-ring sampling and others analysing peat bogs in north-west Europe, who have confirmed dates of around 7000 BC, 3000 BC, 2300 BC, 1700 BC, 1000 BC, 500 BC, 550 AD, 850 AD, 1300 AD for effects likely to have been caused by multiple impacts from space. Many of these dates can be related to vast changes in early civilised societies. The 3000 BC or 2300 BC dates could match the Iraqi crater, and those eras are the very ones where great turmoil is reported in the Bible and other ancient scriptures, including Noahs flood, which is a common theme of several scriptures from different sources. The 550 AD date coincides with the dark ages of Europe and also with that crater newly discovered in Italy.
Also, all experts make the point that small craters, like those found in Iraq and Italy, could well be part of swarms that might have pelted many parts of the world in their respected eras. In the case of the 2300 BC date, this could easily explain the flood stories from around the world, and would not require there to have been a global flood, for which there is no geologic evidence.
So, it can be shown quite clearly that the threat from a small asteroid or comet is quite real, and can create localised damage on a scale that could destroy cities or even provinces. This has not been perceived as a major problem simply because people approach the problem of impacts with an "extinction" frame of mind, whereas it is easily possible with smaller impacts, for civilisations to be destroyed while species remain intact.
I pose the question: what if a nation like USA was to face a 100 trillion dollar bill for cleanup after a small asteroid hits one of its larger cities? What would be the effect? Could their infrastructure sustain itself? The scenario that scares me and should scare others, is the "looter" effect. We all know that when a catastrophe like an earthquake or severe hurricane strikes a modern city, the looters take advantage of the temporary loss of control; services like police and military are directed to the catastrophe, which leaves a hole for the some of the underprivileged to go in and raid unguarded facilities. Multiply that a thousand times, and what happens? After a city is hit by an asteroid, the rot may not happen at once. Failing infrastructure would follow from inability to finance the police, fire department or military (who would do those dangerous jobs without pay?), and without the full force of those services, you can be sure that many of the underprivileged would take advantage of the situation. If you are a realist, you recognise that there are millions of people in the world who would love to see the fall of the west. With the fall of USA, most of the smaller countries of the world who rely on trade with that nation, would likely follow into financial ruin.
When Rome failed, the barbaric hordes, who were really looters on a large scale, rampaged all over Europe; looting, burning, raping and destroying. Europe took centuries to recover. The old order had gone, and it then took many more centuries for our new rising civilisation to attain what the Romans had achieved. The same pattern can be seen in the great gaps that separate the three kingdoms of Ancient Egypt. As with the fall of the Roman Empire, historians have only been able to speculate why those fantastically successful civilisations of Egypt were trashed and replaced by centuries of chaos. Now we have a pair of smoking guns in those dates 2300BCand 1700BC, where researchers have identified debris left behind by impacts of objects from space, and which coincide nicely with the dates traditionally assigned to the fall of the Old and Middle Kingdoms of Egypt. There are other examples of wrecked civilisations from this period of time; too many to mention here.
Statistically, even with a couple of potentially city-destroying impacts every century, most will miss populated areas. The majority of the Earths surface is ocean in any case. That is most likely the reason why there are few documented reports of impacts prior to the 20th century. When the population was much smaller and communications were slower than carrier pigeons, nobody would have related a tsunami in the Pacific or a massive explosion in the Sahara with the impact of a small asteroid or a train of comet debris. There are however indications from the researchers mentioned above that the periodic train of comet debris that may have produced mayhem throughout our history, returned much more recently and was responsible for what is called the "Little Ice Age"; a period around the 17th century during which Pepys in his diaries described ice-flows on the River Thames a phenomenon never seen before or since. Back then, when most of the world had never seen the "enlightened" men and women of Europe, a train of comets coming down far beyond the European horizon would have gone unpublished, while those "enlightened" masses in their cities would have been scratching their heads wondering why their winters were arctic, or why there were few good vegetables in the market, or why their skies remained bright all night.
We cannot ignore the point that even if a city is not hit, but rather the corn belt of the Ameri-can mid-west was wiped out, a substantial drop in food production worldwide could produce similar stresses on society as a whole. Also, coastal hits in the ocean could produce damaging tsunamis that could devastate even larger areas than would a continental hit. The fact is that NEOs represent a great and real potential for a cataclysm that could severely stress or even bring down the western civilisation. And I believe that the current evidence should be sufficient to convince governments that efforts should be made to put in place greater detection capability and more importantly, to develop the technology to knock these things out before they become a danger.
These are not huge objects that require the likes of Bruce Willis and his team to go drill nukes into their cores (as depicted in the movie "Armageddon"). These are rocks that we could feasibly destroy with our current technology. All we need is better detection facilities, good enough to recognise the threat several million kilometers away, and also the unmanned transport to take the necessary weaponry quickly out to that distance. The money that is spent on armament to fight amongst ourselves would easily cover the cost. It would definitely cost less than the moonshots, which were massively expensive because most of the cost involved maintaining life-support systems.
The very real possibility of impacts from society-disrupting objects needs to be taken seriously because it is almost certain that the day will come when one of these things ravages a major urban area, and nobody could say for certain that the world could survive the financial shock. We are definitely not safe from a slide into the barbaric state, if financial institutions collapsed worldwide. To believe otherwise is to really bury ones head in the sand.
1. It is not the big rocks like the one that destroyed the dinosaurs that should worry us, as they are rare in terms of their approach to Earth.
2. The smaller rocks, from 50-200 meters impact at speeds that can produce explosions tens or hundreds of times greater than an atomic bomb.
3. Possibly 5 of these objects approach within 8 diameters of Earth every year (2 of these were discovered in 2002). Since Earth presents a bullseye which is about 0.4% (1/250th) of the target area represented by these close approaches, we can calculate that one of these will hit Earth on average every 50 years (if the last one was 1908, we could be overdue).
4. Most of these will hit in unpopulated areas, but there is obviously a risk of a hit in urban areas.
5. It does not take total devastation to bring down society. An urban hit that bankrupts a country like USA, could bring down civilisation as we know it. We can be sure that many of the worlds burgeoning poor would seize the opportunity of our failing infrastructures to create anarchy.
6. There is mounting evidence that this has been the reason for the fall of a number of civilisations in the past.
7. In terms of fragility, our civilisation is perhaps more vulnerable to collapse than, say, the Roman Empire. Due to the ever widening gap between the rich and the poor, there is a now a world of 4 or 5 billion potential barbarians ready to overrun any disabled first nations. And they are much more mobile than the hordes that overran Europe after the fall of Rome.
8. For the first time in history, we have the technology to prevent the next impact. An impact is inevitable, and apparently pending. So, why arent we taking the necessary steps to deal with the threat?
As we went to press, we learned that The Workshop on Scientific Requirements for Mitigation of Hazardous Comets and Asteroids recently gathered 77 experts from the United States, Europe, and Japan. The outcome was that it was agreed that NASA should be given the task of dramatically increasing the search for Near-Earth Objects (NEOs), to the tune of something like $350 million a year. The task is expected to take 25 years in order to catalog all objects down to 200 meters in size. My comments are that, yes, this in encouraging, but that city-destroying asteroids can be anything above 50 meters across, and that means that there are substantially more dangerous missiles out there than will be cataloged by this 25 year effort. I guarantee that this threat is far more real than Iraq or North Korea, and should attract at least as much effort and hardware as the world currently assigns to the military.
That last point is my main point. In a way, it could bring the world together. It could provide a common enemy; a real enemy.
There is no doubt that with the funds that we currently use to wage war, this terror from space could be averted. The terror will surely come, because it always has.
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