Friday, May 22, 2015

BM 5 * . More Lunar coincidences.

We have already woke up to the core reality that the moon is part of an engineered Earth and this part of the story outlines just how several improbable aspects are critical for the success of life on Earth.  In fact it puts the Pleistocene nonconformity in clear relief as the last necessary act for the final phase of Terra-forming Earth.

 Earth is an engineered paradise for life.  I also expect that this is been done in other solar systems throughout the universe or at least in this Galaxy.  I hate to say it but our true evolution toward a global paradise reads like a science fiction tale. 

Our blessing is that we are part of it even if we do not know it.  It is a fantastic adventure.
 More Lunar coincidences.

Of course, none of this would be possible if the vast majority of water on the Earth was not in a liquid state. Only two per cent of Earth’s water is locked up in glaciers and the icecaps, with ninety-seven per cent being the water of our seas and oceans and just one per cent available for human consumption as fresh water. With only a small change in the overall temperature of the Earth, or an alteration in the seasonal patterns, the nature of the water on our planet would change. As we have seen, a more pronounced planetary tilt could well lead to a freezing of the oceans. This would result in an overall loss of temperature at the surface of the planet, with even greater freezing. 

On the other hand, if the Earth were not tilted at all, the equatorial regions would become unbearably hot and weather patterns across the planet would be radically changed. In addition, the biodiversity, that scientists are now certain has been so important to our evolution, might never have developed in a world with more polarized areas of temperature. 

It has therefore been vital for our existence that the tilt of the Earth has been maintained at around 22.5 degrees for an extremely long period of time, and yet, bearing in mind the composition of the planet this is a very unlikely state of affairs. Venus is the nearest planet to Earth and the most similar to our own, but it has toppled over in the past and other planets in the solar system show signs of having varied markedly in their tilt angle across time. The Earth is very active internally and highly unstable, yet, despite a few periodic wobbles, it keeps the same angle relative to the Sun. 

Astronomer Jacques Laskar, a Director of Research at the National Scientific Research Centre (CNRS) and head of a team at the Observatory of Paris is in no doubt that the Earth would indeed topple over, if it were not for the presence of the Moon!18 

With computer modelling, Laskar showed in 1993 that all the other Earth-like planets (Mercury, Venus and Mars) have highly unstable obliquity, which, in the case of Mars for example, varies wildly across time between 0 degrees and 60 degrees. The same computer modelling indicates that in the case of the Earth the obliquity would vary even more, between 0 degrees and 85 degrees – but for the stabilizing influence of our incredibly large Moon. Nobody knows for certain how long it would take for the Earth’s obliquity to change significantly if the Moon was not exerting such a massive influence. There is a constant transfer of energy taking place between the two bodies, which in addition to stabilizing Earth’s obliquity has also significantly slowed our planet’s rate of spin. This constant obliquity has made the Earth a perfect crucible for advanced life by providing many millions of years of stability for life to develop from its simplest form to the complex patterns it adopts today.

Although the Earth is significantly more massive than the Moon, the Moon is still a very large body. Tides in Earth’s oceans, seas and lakes are caused by the gravitational interaction of the Earth, the Moon and the Sun. Tides have an effect on dry land as well as oceans but this effect can only be detected by careful measurement. Solar tides (the point of greatest gravitational pull by the Sun) are twelve hours apart but since the Moon is also moving, lunar tides are slightly more irregular, occurring every 12.42 hours on average. 

The height of tides in any particular part of the ocean is dependent on a number of factors such as the shape of any nearby landmasses and the depth of the seabed. In some areas of the world, tides hardly seem to lift the level of water at all – this is just as well for some low-lying places such as the islands of the Maldives in the Indian Ocean because their average height above sea level is less than one metre. In other places, like the British coast, tides can have a huge range between high and low water. 

Figure 10 

The Moon has sufficient gravity to pull a bulge of water from the oceans of the Earth closest to its position towards it. It also distorts the Earth, creating a corresponding bulge in the oceans on the opposite side of the Earth. Because of the Earth’s rotation the bulge on the Moon side runs slightly ahead of the Moon. 

Tides would not cease if the Moon were not present because they are also created by the Sun. However, they would be very much lower than they are now because although the Sun is massive and the Moon much smaller, the Moon is extremely close and the Sun much more distant. It is the interaction of solar and lunar tides that makes it rather complicated to predict when tides will occur and how high or low they are likely to be. 

The highest of the lunar tides occur when the Moon is either in its full or new mode, because at such times it is in line with the Sun and its gravitational forces are added to those of the Sun. Much lower tides are on the first and last quarters of the Moon when the gravity of the Moon and the Sun are working against each other. 

Life in the tidal margins of the oceans and seas has evolved to take advantage of tides, either in a daily or a monthly sense. Some species of crabs for example, lay their eggs in the sand at the high-water mark at the time of the full or new Moon so that they will be safe from marine predators during incubation. There are also many creatures that leave the ocean on the high tide at night to scavenge in the inter-tidal margins, before seeking safety with the next high tide. 

Many shellfish are absolutely dependent on the ebb and flow of the tides for the purpose of feeding and it was shown in the 1960s that oysters are sensitive enough to be aware of the Moon’s position, either overhead or at the opposite side of the planet. Oysters, which obviously have no eyes, were taken from the ocean and placed in tanks in the Rocky Mountains where they began to open and close, as they would have done in the ocean, had it extended so far inland. Because other stimulus such as current or wave motion were absent, it suggests that they are able to feel minute increases and decreases in the gravitational pull of the Moon and the Sun. 

If molluscs, our very distant evolutionary cousins, can somehow sense such astronomical movements – then there would seem to be no reason why humans would not be able to do the same. This just might point the way forward in investigating a possible causation for variations in human behaviour according to the phase of the Moon. 

It probably is not too surprising that some creatures have learned to exploit tides, which are tiny these days in comparison with the remote past when the Moon was much closer to the Earth. The tremendous forces created by a very close Moon would have generated much heat and might even have caused parts of the Earth’s surface to melt. However, this phase did not last all that long because the very transfer of energy that promotes tides is also causing the Moon to drift further and further away from the Earth. This happens because the Earth rotates around its own axis more quickly than the Moon revolves around the Earth. The rapid rotation means that the tidal bulge of the Earth forward of the Moon, (see figure 11) is always ahead of the Moon’s position. The tidal bulge exerts a pull on the Moon and this increases the Moon’s overall energy. Meanwhile, friction between the Earth’s surface and its own oceans is actually slowing the rate of Earth rotation. It is not much, but it does amount to around 0.002 seconds in a century. 

The end result of this dance will be that the Moon will continue to move away from the Earth until a situation of equilibrium is achieved, which is expected to happen in about fifteen billion years. The Moon will then be 1.6 times further out from the Earth than it is now and the Earth will have a solar day that is equal to the orbit of the Moon, which by then will be fifty-five days. However, we do not have to lose too much sleep about this eventuality because the Sun will have become a red giant about a billion years before that, at which time the Earth will have ceased to exist in any case. 

Figure 11 

As the Earth revolves, it takes the tidal bulges with it, but because of the gravity of the Moon, the water in the bulges is trying to travel in the opposite direction. As a result, waves ground on the bottom of the oceans and on seashores, causing friction. The friction slows the Earth and the energy is passed to the Moon, which responds by speeding up. As it does so, the laws of physics dictate that its orbit must widen. 

Over huge periods of time the gp relationship between the Earth and the Moon changes, so we find ourselves living in what amounts to a ‘tiny snapshot’ of the overall situation. At present the Moon takes 27.322 days to go around the Earth and because the Earth is also going around the Sun, full and new Moons are ruled by a slightly longer cycle that takes 29.53 days. Both these figures have been significantly different in the past and will be different again in the future but the changes are very slow and, according to NASA, the Moon is becoming more distant from the Earth by around 3.8cm per year. 

Perhaps it is just as well that an expanding Sun will overtake us before the Moon does get to its final position relative to the Earth. By the time the Moon and the Earth reach their ultimate stations, the Moon will be too distant to exert enough influence on our planet to keep its obliquity steady. Bearing in mind the Earth’s unstable core, this would almost certainly mean rapid and perhaps catastrophic changes in both obliquity and climate. Neil F Comins, Professor of Physics and Astronomy at the University of Maine, has written about the consequences if the Moon did not exist. He explains that the Earth would be turning so fast that a day would take just eight hours and complex life would not exist yet. If higher life forms did eventually manage to evolve, such creatures would be very different to us without, for example, any communication through speech.19 

One thing is certain then: no Moon would mean no humans! 

Humans are incredibly robust creatures considering we are little more than animated bags of water hanging on a mineral frame. We can withstand difficult conditions and even survive without food for many weeks, yet we die quickly without air to breath or with direct exposure to unusually high or low temperatures. It is thanks to eons of Darwinian evolution that we are perfectly designed for our environment – but perhaps we should not be too casual about the extraordinary good fortune that brought us to this point. Every human is very special. We differ from other creatures, so we are told, because we are able to define ourselves by our own self-awareness resulting in a situation where there is a simple polarity to the Universe. We all know that: ‘There is me and then there is everything else.’ Each and every one of us is an emotional-intellectual island connected to that ‘everything else’ by the complex interaction of our five senses. 

Two small regions of our skin have developed the ability to decode energy reflections in the form of sight, two more make sense of a cacophony of colliding compression waves in the gases around us giving us hearing. Then we have skin sensitive enough to tell us about shape and texture, a mouth that accurately differentiates between different chemical substances we are about to consume in the form of taste and we have an air inlet that can pick out the presence of a specific molecule within a million others in the atmosphere as the sense we call smell. 

These five connection modes cause us to have interaction with the ‘everything else’ – especially other humans, so we do not exist alone. These points of stimulus combine to give life to the most remarkable array of aspects of self. Love, fear, loathing, compassion, laughter and countless other emotions make us special and mark us out as entities that are utterly different to the rest of creation.
But how and why have we become so spectacularly differentiated from other combinations of recycled stardust? What makes Neil Armstrong more special than the 3.5-billion-year-old rock he first lifted from the lunar surface? 

Those with religious faith turn to their interpretation of God to explain the unexplainable and the more scientific amongst us turns to the Anthropic Principle. The good old ‘Anthropic Principle’ is less there to help us answer the BIG question than to avoid having to deal with it. It accepts the vanishingly tiny probability of human existence by stating that the rules of the Universe that produced us have to be exactly as they are or we would not be here to perceive them. 

To us, this is rather like defining moving, emotionally stimulating music by merely expressing it as ‘music that is good’. The statement is correct but it does not compare with the experience! 

What the Anthropic Principle does is to stop us worrying too much about the fact that we really have no right to exist. Of the two approaches, anthropic or divine, at least the God scenario is an attempt to move the problem on a notch rather than utilizing a principle that seems to have been conceived to ignore it. Most scientifically minded people probably subscribe to the theory that humans, like everything else, are the product of billions of years of random chance. However, the most famous scientist of all time, Albert Einstein, was very unhappy about nature being based on randomness. He said about quantum physics: ‘God does not play dice.’ 

The more we looked into how our planet developed into a paradise for living creatures the more surprised we became. The miracle of life on Earth is due to our narrow temperature band that provides us with liquid water and, as we have explained, it is the Moon that is responsible for maintaining the perfect tilt that provides our benign climate. But amazingly, it was the very act of the Moon’s creation that produced the first link in the chain of events that would lead the Universe to make you! 

In 1911 a brilliant young scientist by the name of Alfred Lothar Wegener was browsing through the library of his university in Marburg, Germany, when he came across a scientific paper that listed a host of identical plant and animal species that could be found on opposite sides of the Atlantic. Although having obtained a PhD in astronomy at a very early age, Wegener was particularly interested in geophysics, a field of study that was in its infancy at the time. 

Something in the paper caught Wegener’s imagination and he began to spend time looking for other examples of similar plants and creatures separated by oceans. There was, at the time, no reasonable explanation as to how such a state of affairs could have come about. It had been postulated that the solution to this puzzle had to be land bridges that must have existed in very ancient times and that had allowed both plants and animals to move between continents. However, there were many examples that could not be explained in this way. 

Wegener had also noted, as had others before him, how many cases there were in which the coastline of one continent looked as though it could fit snugly into that of another, such as the west coast of Africa and the east coast of South America. He also found that if the continental shelf is studied, rather than the apparent coastline shaped by current sea level, the fit is often very much better. 

Alfred Wegener began to ask himself if the answer to these anomalies might lie not in land bridges but in the fact that the continents were once joined together in one large continent, and that this had somehow broken up and drifted apart. Later in his life he wrote about this process of logical deduction. ‘A conviction of the fundamental soundness of the idea took root in my mind.’ 

Wegener spent a considerable period collecting further examples of extended flora and fauna and the available evidence continued to support his early theory. For example, he found the fossils of plants and creatures in places where the climate must have been significantly different when they were alive and flourishing, such as fossilized cycads – ancient tropical plants found as far away from the tropics as Spitsbergen in the Arctic. 

From the weight of evidence he had collected, Wegener deduced that all the continents had once been part of a single landmass, which he chose to call ‘Pangaea’ – a Greek word meaning ‘all the Earth’. 

He suggested that this supercontinent had broken up and had begun to drift apart 300 million years ago. He called the process ‘Continental Drift’ and although he wasn’t the first to suggest that there had originally been a single continent, he was able to provide substantial evidence to back up the claim. Wegener first published his findings and his hypothesis in his book The Origin of Continents and Oceans.20 Although it was brilliantly argued, his ideas were not widely accepted at the time. A flood of scientific indignation broke over Alfred Wegener. This happened for a couple of reasons: firstly, his theory was revolutionary, which inevitably clashed with the conservative tendencies of other experts; and in addition, although Wegener was certain that continental drift must have taken place, he had no theory as to how or why this might have happened. 

The best he could suggest was that the continents, influenced by centrifugal and tidal forces as the Earth spun on its axis, were simply ploughing their way across the surface of the planet. Dissenters pointed out that, if this was the case, the coastlines of the continents could hardly be expected to have remained so similar to the original ‘fit’ that it could still be observed. On the contrary, they would have been distorted beyond recognition. It was also suggested that tidal and centrifugal forces would be far too weak to move entire continents. 

Poor Alfred Wegener didn’t have the chance to look too much further into the matter; he died in 1930 whilst taking part in a rescue mission to deliver food to a party of explorers and scientists trapped in Greenland. Wegener did have some notable supporters but in general his ideas remained on the shelf until as recently as the 1950s, by which time greater exploration and understanding of the Earth’s geophysical makeup had begun to catch up with the idea of continental drift. The truth of the matter is that Wegener was wrong in terms of his suggested mechanism, but quite correct in his basic assumption. Rather than ploughing their way across the planet’s surface, the continents ‘float’ on what is known as the ‘asthenosphere’, the underlying rock of our planet. This is under so much pressure and becomes so incredibly hot that it acts more like thick treacle than solid rock. 

Figure 12 

One of the factors that made Wegener’s ideas more acceptable was the study of mountain ranges. An earlier position held by many experts had been the ‘contraction theory’. This suggested that the Earth had begun its life as a molten ball and that as it cooled it had cracked and folded up on itself. This folding, the theory suggested, was what had created mountain ranges. The real problem with the contraction theory was that all mountain ranges should therefore be of the same age and it was rapidly becoming apparent that this could not be the case. Wegener had suggested that mountains were constantly being created as landmasses came into contact, exerting unbelievable pressure and pushing up land at or close to the points of contact. 

Just a year before Alfred Wegener’s death some corroborative evidence had been forthcoming, but it wasn’t well accepted at the time. In 1929 Arthur Holmes, a physicist at the Imperial College of Science in London suggested that the mantle of the Earth undergoes ‘thermal convection’. The Earth’s mantle is that region immediately below the outer crust. It extends all the way down to the Earth’s core. Its composition varies with increased pressure and temperature but it makes up the biggest part of the Earth. 

Holmes knew that when a substance is heated, its density decreases. In the case of the mantle this would cause material to rise to the surface where it would gradually cool, become denser and then sink again. A similar process takes place with porridge that is boiling in a saucepan. Holmes was quite taken with Wegener’s idea of continental drift and suggested that the tremendous pressures caused by thermal convection could act like a conveyor belt. This might cause the continents to break apart and to be ‘carried’ across the surface of the planet. 

For years these ideas were dismissed, until knowledge caught up with the theories. By the 1960s there was a greater understanding of the ‘oceanic ridges’–regions where, it was being realized, Holmes’ thermal convection might actually be taking place. It was also realized that oceanic trenches occurred, together with arcs of islands, close to the continental margins. All of this meant that convection was not only probable but certain. Two other scientists, R Deitz in 1961 and Harry Hess in 1962 separately published similar hypotheses based on mantle convection currents, and continental drift became universally accepted. 

Deitz and Hess between them modified Holmes’ original theory of convection and came eventually to their own mechanism for continental drift, which is based on what they termed ‘seafloor spreading’. This spreading, it is uggested, begins in the mid-oceanic ridges. These are huge mountain ranges in the middle of the Earth’s largest oceans. So large are the mid-oceanic ridges that they are higher than the Himalayas and are more than 2,000 kilometres wide. Associated with the ridges are great trenches that bisect the length of the ridges and which can be as deep as 2,000 metres. The greatest heat flow from the ocean floor takes place near the summit of the mid-oceanic ridges. There are also far more earthquakes on and around the ridges than are experienced elsewhere, showing these to be geologically active areas. 

An increase in understanding of the Earth’s magnetic field led to the realization that periodically this reverses. Such fluctuations can be detected with a device called a magnetometer. It was discovered that, either side of the mid-oceanic ridges, it was possible to detect these past reversals in the Earth’s magnetic field. The conclusion was that new material was constantly being thrown up on the ridges and was being pushed outwards on either side. The reversals of the magnetic field demonstrated that this process was ancient but that it was still taking place. 

Also of interest were ‘deep-Sea trenches’. The trenches are generally long and narrow and they are often associated with, and parallel to, continental mountain ranges. In addition they run parallel to the ocean margins. There is great seismic activity associated with the deep-sea trenches, indicating that they too are associated with the process of seafloor spreading and that they are directly related to the oceanic-ridges. 

What is now thought to be happening is as follows: underneath the Earth’s outer crust is the asthenosphere. This is a malleable layer of heated rock. It is kept hot because of radioactive decay in elements such as uranium. The source for the radioactivity, which also includes thorium and potassium, lies deep within the planet. The asthenosphere, constantly heated, rises to the surface, pushing new material out at the mid-oceanic ridges. Magma escapes along the cracks formed at the ridges, forcing the new seafloor in different directions. The new material spreads outwards until it makes contact with a continental plate and will then be ‘subducted’ beneath the continent. The lithosphere at this point sinks back into the asthenosphere, where it once again becomes heated. Few experts disagree with this basic explanation, partly because it can be seen at work. India, for example, started its life on a completely different part of the planet. It is now being forced up into the body of Asia and the Himalayas are the result – a huge mountain range forced up by the pressure of the two landmasses meeting. 

The whole process is known as plate tectonics and scientists were keen to see whether or not a similar process was taking place on the other terrestrial– type planets in our solar system – Mercury, Venus and Mars. Probes sent to these planets have now shown conclusively that plate tectonics do not take place on any of our companion worlds, making it a strictly Earth-bound phenomenon, at least as far as our own solar system is concerned. 

This is something of a puzzle. What is taking place in the Earth system that is so different from the other Earth-like planets? What caused plate tectonics to commence in the first place and what is the engine that keeps driving the process? There is a growing body of evidence to show that in both cases the answer is almost certainly the Moon. What is more, it is now being suggested that without plate tectonics the Earth may not have proved to be a suitable haven for life at all. 

Dr Nick Hoffman, a geophysicist at the Department of Earth Sciences, Melbourne University, Australia, has recently suggested that the Moon made plate tectonics happen simply by coming into existence. 

As we have discussed, the origin of the Moon is still shrouded in mystery, no matter how much proponents of any specific theory of its origin may pretend. However, there are certain facts that are known for sure. As we have seen, the Moon is definitely made of the same stuff as the Earth, but not all of the Earth. Rather the composition of the Moon closely resembles the material in the Earth’s crust, without many of the heavier components, such as iron, that make up the Earth’s core. 

But how could such a large amount of the Earth leap from the planet’s surface into a position tens of thousands of miles in space? 

Scientists were puzzled. And then a potential explanation was put forward in the form of the original Big Whack theory – the suggestion that maybe some object, about the size of Mars, collided with the young Earth and that the Moon was formed from surface material that was blasted off the face of the infant Earth. There did not seem to be any other possibility, so it is now regularly taught as though it is a fact. The major problem of the Earth’s current speed of rotation was tentatively explained away by proposing a second impact from the opposite direction occurring quite soon after the first. 

To us this sounds like a rather desperate scenario to believe in. And as we have seen, other problems remain for this would-be explanation; not least the question of where the material from the incoming objects went to. If the Double Whack theory as correct, the Moon should be made up of three different sets of material, but it is not. It is made of Earth rock alone. 

Nick Hoffman, as an acclaimed expert on the terrestrial planets within our solar system, has suggested that the removal of the material that went to make the Moon may have triggered plate tectonics by creating the space for the planet’s skin to shift. He points out that on Venus, for example, the same sort of forces are at work but the crust of the planet is so thick, the stresses within the crust simply cancel each other out, with the exception of a few wrinkles here and there. Hoffman has noted that if the seventy per cent of Earth crust that was destined to become the Moon was returned to the Earth, it would ‘fill the ocean basins with wall-to-wall continent’. 

What would the Earth be like without plate tectonics? 

Hoffman suggests it would be a water world, covered with oceans and with only the tips of extremely high mountain ranges poking out above the surface of the water. Of course there is nothing to suggest that life could not have existed on such a planet and Hoffman agrees that life is most likely to develop in a watery environment. It’s a fact, though, that what we term as being ‘intelligent life’, such as our own species, has developed on land. The use of fire would not be possible in a watery habitat and the use of tools, one of the factors that is generally accepted as the starting point of our advance, is also a dry land phenomenon. 

In any case, as we will see, the Moon is so important in other ways that even a watery world may have proved to be impossible without its existence. 

Nick Hoffman’s suggestion that the creation of the Moon removed so much material from the surface of the Earth that plate tectonics could become a reality is fascinating. It is estimated that seventy per cent of the primordial crust of the Earth would be necessary in order to create the Moon. Its removal caused the remainder of the crust to spread, allowing continental drift to take place. 

Whether or not this is the whole story, plate tectonics are a reality as far as the Earth is concerned and what is more, it is a phenomenon that only occurs on the Earth. In other words, no other terrestrial-type body in the solar system had continents travelling about its surface. 

One of the three Earth-like planets in the solar system, apart from the Earth itself, is Mars, which is half the size and a tenth the mass of our planet. It has an atmosphere that is ninety-five per cent carbon dioxide and nearly five per cent nitrogen with a pressure at the surface that is only 1/200th that of Earth. Unfortunately for any potential Martian life form, liquid water cannot exist at the ambient pressure and at the temperature of the Martian surface. On this planet, water goes directly between solid and vapour phases without becoming liquid at all. 

The puzzle as to why plate tectonics have either never started or else never been maintained on Mars has not been totally explained, but there are theories. 

Mars has no appreciable mountain ranges, though it does have giant volcanoes. Some geologists suggest that the absence of true mountain ranges gives one clue as to why Mars did not develop plate tectonics. Like Earth, Mars has a lithosphere. This is a region in the crust of the planet that is cooler than its interior – a little like the skin that forms on a cup of hot milk. The centre of the Earth is extremely hot, probably more so than that of Mars, but the presence of volcanoes on Mars must indicate a hot core. One difference might be that Mars has nowhere near as much water in its composition as Earth. It is thought that it is water trapped within the Earth which acts as a lubricant allowing different parts of its rocky surface to slide against each other. The limited amount of water on Mars seems to prevent the lithosphere from allowing fresh material from deep within the planet to rise to the surface in the way it is constantly doing on Earth. As a result the lithosphere has not been disturbed for aeons and has cooled gradually, getting thicker and thicker. When pressure has become so great within the body of Mars that it is powerful enough to escape, it has done so via volcanism and not along features like the mid-oceanic ridges on Earth. 

The other Earth-like body, Venus, which orbits closer to the Sun than our own planet, has a surface very different to that of Mars or the Earth. In some ways Venus is more like Earth than Mars. Venus is a similar size and mass and is also compositionally quite like Earth – or at least it was once. Experts such as David Grinspoon, a research scientist at Southwest Research Institute in Boulder, Colorado, have studied Venus closely, aided by a whole series of orbital and lander space missions. 

Grinspoon is not alone in believing that in its early stages of development Venus was even more like the Earth. There is no discernable water on Venus now but there are traces in the atmosphere, which most likely indicates that in its very early stages it had proportionally as much water as Earth. This is not too surprising because the planets formed at the same time and fairly close together. 

Venus is not unlike Mars in many ways but its surface pressure is ninety-two times that of Earth. It is thought that Venus lost its water because of a greenhouse effect and it is now covered in dense swirling clouds of sulphuric acid. These clouds are so thick that only a small percentage of the sunlight that falls on Venus actually gets through to the planet’s surface, so even if it weren’t such a hell in other ways, it would be a very gloomy world. It might be thought that less sunlight would lead to a lower temperature but this isn’t the case. Rather, heat already at or near the surface is maintained and increased because it cannot escape through the dense carbon dioxide. This has caused a dramatic heating of the surface of Venus to a present temperature of 730°C. 

Like Mars and Earth, Venus has volcanoes; in fact it has more than any other planet in the solar system. But again, like Mars, the volcanoes of Venus exist as individual entities and not as part of long mountain ranges as is the case on Earth. The volcanoes of Venus are randomly spread about its surface and many of them look very recent, even though this may not be the case. 

Electrical storms rage constantly through the clouds of sulphuric acid but, even so, wind erosion on Venus is limited compared to the water-rich Earth. It turns out that erosion is extremely important in terms of supplying the right chemical and nutrient balances that have made the Earth a haven for life. 

The surface of Venus looks broadly similar wherever one looks and is thought to be comparatively recent in origin – something in the order of 600 to 700 million years. Venus has a generally smooth surface with some rifts and folds but everything appears to be the same age. It is generally accepted that between 600 and 700 million years ago some cataclysm took place on Venus that remodelled its whole surface. Whether this was as a result of the internal stresses within the planet is not known, but for some reason the planet’s surface appears to have literally melted or more likely was uniformly covered with volcanic basalt. 

Nobody knows for certain whether a similar thing will happen again on Venus, in other words whether we are seeing only one phase of a stop-start process that is taking place, but it is considered to be a distinct possibility. Probably because of its greenhouse atmosphere Venus is deficient in water and so once again may have built up a thick lithosphere. It certainly does not display any of the characteristics of plate tectonics. 

It is interesting to note that Venus has no moons, whilst Mars has two, though both of these are extremely small and can have little or no effect on their host planet. As we have seen, it is now being suggested that the very creation of such a large moon as that enjoyed by Earth was directly responsible for the start of plate tectonics, which in turn allowed life to form on the planet in the first place. 

In the early stages of its existence, the Moon was very much closer to the Earth than it is today. And it is the existence of the Earth’s oceans that is primarily responsible for the gradual lengthening of the distance between the Earth and the Moon. This is a process that has been taking place for the last four billion years and which is still taking place. 

One way of looking at the situation was presented by Neil F Comins, Professor of Astronomy at the University of Maine. Back in 1990 he had been struck by the comments of a colleague, to the effect that science educators are always looking at the world from the same old perspective. Comins suggested that it might be sensible to step aside and look at the world differently. 

As a result of this conversation Comins decided to turn his attention to something we all take for granted, namely the Earth and its relationship to the Moon – but from an entirely different perspective. He set out to consider what the Earth would have been like today if it had not enjoyed the benefits of so large a Moon. He called his hypothetical world ‘Solon’ and over a period of time he wrote a series of articles about Solon that appeared in Astronomy magazine. He eventually published his overall observations in a book, which was entitled Voyages to Earth that Might Have Been.21

No comments: