In recent years, a theory has been developed concerning of the effect on evolution of life on earth of the impact of comets and other large "rocks" at apparently regular intervals. Lately, this has received quite a bit of publicity and I feel that this is not something which we should too easily forget about. Over the past 20 years, the following story has unfolded…
An Oil surveyor was making a magnetic / gravitational anomaly map in the Gulf of Mexico when he noticed a highly unusual circular feature on the map. At the time, he couldn't really say what it could possibly be. The feature was partly in the Gulf, and partly in the Yucatan. After some strife, he was able to make a deep borehole to take a rock sample. At the depth which corresponded to the end of the Cretaceous Period, he noticed that the "smooth" look of the layered rock completely changed in the next layer to a jumbled mass. Another geologist had independently found a similar sample.
Another geologist, working on the coast of Texas, noticed how in one particular layer - the one at the end of the Cretaceous, the strata structure was badly skewed out over several feet and there was a jumble of large boulders intermixed with other elements of the rock. This was difficult to explain in terms of any of the "normal" geological processes.
Another Geologist working in Haiti had noticed for many years an unusual strata in the rocks he was studying (at some altitude). Other rocks from this strata had already been studied and found to contain tektites, whose presence was not easily explicable.
Piecing together these bits of evidence, it would appear that there was an enormous catastrophe in the Gulf of Mexico at the end of the Cretaceous Period - an object, estimated to be 6 miles in diameter, travelling at quite a few miles / second, crashed into the earth, causing ejecta to be blasted into orbit and causing a deadly rain of molten rock, which started global forest fires - the ash of which appears to be evident in corresponding geological layers elsewhere in the world.
Though, I think myself, it is now almost indisputable that the Dinosaurs were wiped out by the effects of this impact at the end of the Cretaceous period, there appears to be some evidence for regular "purges" of species once every 26 million years. According to what I've heard, if one looks at fossil evidence, there appear to be whole sets of species wiped out every 26 million years. A bizarre theory which has been put forward to explain this is the "Nemesis Theory". Approximately 1 light year from the Sun, there appears to be a cloud of material called the Oort Cloud (named after Dutch Astronomer Jan Oort) which it is believed to be the "Birthplace of comets". Additionally, it has been suggested that our Sun has a faint, distant, orbital companion star (possibly a small brown dwarf - not much bigger than Jupiter), which passes closest to this Oort cloud once every 26 million years - thereby disturbing material, initiating a cascade into our solar system. This would produce a "cyclic" pattern of cataclysms. Could it be that if these cataclysms had not occurred, the reptilian order would have remained dominant and evolved into higher, more intelligent creatures?
In 1908, we were lucky - whatever object it was (probably
a piece of Encke's Comet), exploded in Tunguska, which is virtually
uninhabited. How long will it be before another large, uninvited
lump of rock hurtles towards our little oasis in space? It is
a potential natural disaster which is on a scale like no other.
And how many potentially lethal near-earth asteroids are there
- 10, 20, 1000? No one seems to be sure, but at least it seems
clear that we are lucky to have Jupiter as our Jolly Big Vacuum
Cleaner, as Shoemaker-Levy 9 has shown us.
I recently read a book which discusses the theory and other related matters - "Fire on Earth" by John & Mary Gribbin, published by Simon & Schuster. So informed was I by this book that I was prompted to write to the Minister for the Environment (in the UK):-
"Dear Sir / Madam,
I am writing to you regarding something which may seem insignificant and, indeed, it may well be. However, it could also be of the greatest importance - to an enormous number of people.
You are probably aware of current stories which have centred around the extinction of the dinosaurs - recent documentary programs have brought to our attention a great deal of evidence that the dinosaurs - and many other species - were completely wiped out by a terrible catastrophe. In the Gulf of Mexico and along the South Coast of America, there is a substantial amount of Geological data / evidence which shows that an object - a comet or asteroid - approximately 6 km in diameter collided with the earth some 65 million years ago. The resulting effect was obviously devastating - enormous tidal waves, burning matter ejected into orbit from the explosion which then caused global forest fires. Indeed, there is additional evidence which suggests there were 3 large collisions in different parts of the world within a few hours or days of one another.
You may think I am writing to point out "we will all die by fire", or that I make some other "dark prophecy". This is not exactly my intention. I wish to bring it to your attention that though this well publicised case is an extreme and a very rare event (seemingly happening once in a few tens of millions of years), there is still great cause for concern that something on a smaller scale could happen sometime in the next 100 years. To make my point, I would like to draw your attention to other documented evidence.
In June 1908, there was an enormous explosion in Tunguska, Siberia - several hundred square miles of forest were flattened. There are many eye-witness accounts of this event, and its after effects. Astronomers have calculated that this "event" was caused by a piece of a comet (a mixture of ice and rock) entering the atmosphere and exploding at a height of 5 miles above the ground. Indeed, Astronomers believe it may have been part of Encke's comet.
So what? In 1908 we were lucky - had the comet chunk arrived a few hours earlier, it would've struck St. Petersburg, a few hours later - New York. Yes, so what? It didn't. In 1972, we were again lucky - an American amateur film shows a bright fireball streaking across the daylight sky in the rocky mountains. This lump of rock and ice (thought to be bigger than the one which caused the Tunguska event) bounced off the earth's atmosphere. Had it not done so, some part of Monatana would've been destroyed.
In 1994, a significant fireball explosion over the sea was, spotted by 6 US Spy Satellites. There is a rumour that President Clinton was woken by his defence staff who were uncertain whether the event was natural or man made. The object was travelling at 45000 miles per hour.
So what's happening? It is clear that the earth regularly travels through cometary debris - witness regular meteor showers in August and November, for example. There is some evidence that we are in the aftermath of a cometary fragmentation which happened perhaps 20,000 years ago. As a result of this fragmentation, there are lumps of rock floating around the inner solar system - some are tiny, some are quite large - maybe up to a few hundred metres across. Unfortunately, they are black, and therefore not easy to see (though not impossible - some are known about). Having read what I have read, it seems quite realistic to suggest that these lumps of rock are something worth worrying about. Not so much because of their size, but their speed (kinetic energy). There is also some historical evidence for the effects these smaller rocks could produce - perhaps even "The Little Ice Age" in the 17th Century and numerous "fire from the sky" events in many myths and legends from the last few thousand years of our history.
You may also have witnessed the almost awe-inspiring collision of comet Shoemaker-Levy 9 with Jupiter in 1994 - another cometary fragmentation event.
The chances of something large hitting the Earth are small - but I would not class them as insignificant. The point is, that when something hits us, it could affect / injure / kill several hundred thousand or even several million people - even if the impact were in the sea.
I therefore ask a question, and suggest an idea. What attitude to, or policy on, this matter does the Government have? If it seems like a stupid question, then let me re-phrase it. What insurance can the Government offer against a lump of cometary matter destroying a significant part of London, Manchester or Birmingham? Yes, the chances are small, but not negligible. If it happened, many people will be affected.
It's not something that's difficult to do something about. Our insurance is to try to observe and catalogue these "Near-Earth Objects" . I understand America has already started a small-scale programme (but it's not really big enough). I am therefore simply suggesting that the government offers some collaboration in this programme, and maybe undertakes a small-scale programme of its own - perhaps offering some small sums to Universities and Observatories to buy equipment to look for more of these NEOs. (Obviously, I realise that Britain already funds or jointly funds a number of Astronomical projects / departments / facilities etc, but I feel this matter merits individual attention.) Once they have been properly observed, their orbits can be calculated and we can determine if they pose a threat. If they do, then there are ways to reduce or remove the threat. The sooner we know, the more chance we have of acting successfully to prevent what could be a terrible catastrophe which would not recognise national or economic boundaries.
I seem to have taken a long time to make my point, however, I believe there is strong evidence to support it, and it is one of great importance to all of us, transcending many, if not all, worldly matters I can think of.
In summary, I am suggesting that the government starts a small scale initiative, involving Theoretical and Observational Astronomers, as well as Physicists to begin a programme of cataloguing Earth-Grazing Asteroids and objects.
The electorate may not thank you, their children may not, but their grandchildren or millions of people in another country just might.
Yours Sincerely,
Andrew Johnson.