Visions of the Cosmos

Life Among the Stars

Earth - An Oasis in the Cosmos

 

A gentle breeze caresses us as we wander in the woodland. The sun shines through the trees around us. The leaf bearing branches move in the gentle wind. The jig‑saw of shadows and sunlight trace a moving pattern upon the ground. We breath the air that is causing the movement and the gentle whispering noises in the forest.

 

We are in a beautiful garden which although it was built by human hands is still part of nature with the tulips, the trees and the swan on the water.  We too are part of nature, a fact we sometimes forget in the technological age in which we live.  Picture  by Author Garden in Keukenhof  in the Netherlands only a few kilometres from the ESTEC buildings.

 

Our planet is surrounded by an ever moving and turbulent atmosphere consisting of a mixture of odourless gases which are invisible to our eyes. They meander freely across the surface of the world bringing constant changes in temperature and humidity. They move the clouds that obscure the light of the sun. They bring the rain and the soft winds of summer. They feed the whirlwind and the ferocious hurricanes.

 

The main gases are oxygen and nitrogen. It is the oxygen that sustains our life yet it is also the cause of  decay. Present in smaller amounts yet just as vital to life on Earth are water vapour and carbon dioxide. Without them both the plants and animals would die. Also they retain the heat of the sun and if their concentrations were lower our world would be far colder. With more of them it would be much warmer. With too much carbon dioxide our Earth could suffer a run‑away greenhouse effect and become a raging inferno like its terrible twin planet Venus.

 

 

We take for granted the air which surrounds us. How often do we stop to wonder at the delicate balance of the atmospheric gases which has been maintained upon our most favoured planet over vast periods of geological time. It is only when we examine the discoveries of the last three hundred years that we learn to appreciate the ongoing miracle of our existence. Our atmosphere is ideally suited to our form of life simply because it developed along with that life and is itself the product of biological evolution.

 

From the temperate zones in Europe and North America to the tropical forests of South America and Asia - everywhere is life in abundance  Photographs by the Author of water lilies and tropical orchids.

 

Once upon a time about 4,600 million years ago there was a massive spherical gas cloud surrounded by a spinning disc of dust, gas and debris. Pirouetting at an enormous velocity around its axis the gas cloud attracted to itself more and more gas as it sped through the galaxy. Eventually it grew so large that in its central regions the gas changed to another form of matter called a plasma.  The temperature of the plasma in the inner regions grew so high that thermonuclear reactions were initiated. At the moment of ignition a star was born. That star was our Sun. The disc that spun around developed into the Solar System we know to‑day.

 

At its birth the Sun underwent an extremely violent phase. It pulsated with vast orgasmic explosions, the detonations of which would make a hydrogen bomb look like a glow worm at noon. Tempests of inconceivable ferocity tore through the fabric of the infant star. A massive solar wind, called a T Tauri storm, projected sub‑atomic particles at thousands of kilometres per second outwards towards the abyss of interstellar space. The planetary nebula and the protoplanets were bathed in light of huge intensity and deluged with fierce bursts of ultra‑violet radiation.

 

When the storm that had ravaged the Solar System had died down the atmospheres of hydrogen and helium that had surrounded the inner planets had been blasted into the outer regions of the Solar System  leaving their surfaces hot, airless and desolate.

 

The outer worlds were so far from the celestial fires of the day-star that even now they contain their original atmospheres . We call them the "gas giants' Jupiter and Saturn and the 'ice giants' Uranus and Neptune.

 

The Sun quietened down and entered the main sequence phase . It is still in that stage to‑day and will be so for many hundreds of millions of years to come.

 

Following the loss of their first primitive atmospheres the planets of the inner Solar System ‑Mercury, Venus, Earth, Moon and Mars underwent a process called degassing. Below the solid rocks that formed the outer crusts of the terrestrial planets there were molten oceans of hot silicon compounds which also contained volatile gases under enormous pressures. This mixture is called a magma. From places in the crusts volcanoes erupted and clouds of steam and other gases exploded from the surface in violent detonations. Liquid rocks ran as lava flows across the barren landscapes of those ancient worlds. The most abundant gas was in fact steam.

 

Mercury and the Moon would soon have lost their water molecules by evaporation into space due to their low gravity. Certainly on the Earth, almost certainly on Mars and perhaps on Venus the steam condensed to water. For countless periods of time huge torrents of rain deluged the Earth and great oceans formed in the lower lying regions of the planet to form what is called the hydrosphere.

 

On Earth and possibly on Mars and Venus the stormy seas lapped the shores of lifeless lands in those far off days when the planets were young. The cocktail of other gases involved in the violent volcanic eruptions that tore at the surfaces of those young worlds consisted largely of steam, carbon dioxide, sulphur dioxide  the bulk of which dissolved in the water and nitrogen.  Other substances were given off in smaller amounts which played m important part, at least on the Earth, in the process of the evolution of life. Among them were oxides of nitrogen and phosphorus as well as hydrogen sulphide, hydrogen fluoride, hydrogen cyanide, methane and ammonia all of which participated in chemical reactions either in the gas phase or dissolved in the water. Nitrogen together with smaller amounts of argon, methane, carbon dioxide and water vapour formed the atmosphere that blew across the oceans and the solid land of those arcane worlds.

Complex organic compounds were produced in the shallow regions of the ancient seas and in hydrothermal vents.  Some of the most complicated of the molecules begun to reproduce themselves. The main chemical elements in these compounds were carbon, hydrogen, oxygen, nitrogen, phosphorus and sulphur with smaller amounts of chlorine, fluorine, iodine, sodium, potassium, calcium, magnesium, copper and iron. The first biochemical substances were produced and biochemical pathways began to evolve.

 

Eventually, at least on the Earth, the first single celled organisms began to populate the seas. They lived in an environment that would be highly toxic to most forms of life to‑day. Even so there are pockets where ancient life forms still thrives to-day.

At some stage in the Earth's long history a series of events occurred which we sometimes collectively referred to as the oxygen revolution. The process of photosynthesis begun in primitive plant cells and a new constituent entered the atmosphere, namely oxygen.

 

    6CO2        +        6H2O        =        C6H12O6        +        6O2

carbon dioxide                           water                                       sugar                                  oxygen

 

 

 

Yet other cells developed which fed on the plants and used them together with oxygen as m energy source.   They used the opposite process to photosynthesis called respiration

 

C6H12O6        +        6O2             =            6CO2        +        6H2O

                                                                                             sugar                                  oxygen                               carbon dioxide                         water

 

To produce sugars from carbon dioxide mid water required energy mid this came from sunlight.   Other bacterial cells that did not photosynthesise were able to reverse the process and use oxygen to react with sugars to give back carbon dioxide and water and energy.  This process is called respiration.   At night in the absence of sunlight  the photosynthetic organisms also underwent  respiration to continue their life processes.   

 

The illustration on the left shows a picture of the Earth from space with the Infra-red absorption spectra superimposed over the globe

Thus the first steps towards the evolution of our modem life forms was taken. It was also the first step in the evolution of a new type of atmosphere in which oxygen played a major role. It reacted with any so called reducing substances such as methane, hydrogen and carbon monoxide and increased its own concentration in the atmosphere to a high level. The Earth is the only planet in the Solar System where oxygen is a major constituent of the atmosphere and this is entirely due to life processes. We can now see that not only is all life one life but that the very air we breath is also one with life itself.

The picture on the right shows two the important factors which maintain life on our beautiful planet - our star the Sun and the waters of the sea at sunset.  Photo by Author taken at Noordwyk a few kilometres from the ESTEC Buildings  in the Netherlands.

 

Venus

In the earlier part of the twentieth century before the coming of the space age many people thought that Venus might be like Earth full of tropical seas and steaming jungles. With the coming of the space probes the romantic picture that they painted was destroyed forever. To‑day we know the truth. The space probes, the infra-red telescopes and the radar instruments have unmasked the mystery of what lies beneath the canopy of clouds. It is possible that Venus passed through a stage of ocean formation in the earlier years. After the reverberations of the T Tauri storm had died away the Sun was less hot than it is today. If it ever was an Earth‑like planet we must surmise that as the Sun grew hotter the temperature rose and the seas grew hotter.  Eventually the oceans would have boiled, any carbonate rocks would have decomposed and a run‑away greenhouse effect would have taken control. The other possible scenario is that the temperature of the atmosphere was always too high to ever allow water to condense and that the combined greenhouse effect of steam and carbon dioxide ensured that the planet rapidly reached the kind of conditions which exist to‑day, without passing through an 'ocean stage'. Whichever theory is true it does not alter the fact that, although Venus and Earth may have passed through very similar early histories, they we now as different as any two worlds could be.

To‑day Earth's twin planet, that shines like a beautiful jewel as the 'morning star' or 'the evening star', is the nearest place to hell in the Solar System. The clouds that hid the surface for so long are composed of concentrated sulphuric acid. Beneath the upper layers there is a hue of droplets of liquid or solid sulphur, sulphur dioxide, hydrogen sulphide and fluoro‑sulphuric acid.

 

About 30 kilometres above the surface the atmosphere is surprisingly clear and the sinister orange light that penetrates through the clouds is remarkably brilliant. At the surface a suffocating atmosphere which is composed mostly of carbon dioxide with minor mounts of nitrogen  bears down on the rocks at a pressures of almost a hundred atmospheres. Just like the pressure, the temperature varies with altitude but is close to 480 degrees Celsius which is more than enough to melt lead.

Gently rolling upland plains cover about 65% of the surface of Venus.  About 20% of Venus is covered by extremely flat plains and are comparable to lowland regions. The highland regions are known as Terra and cover only 10% of Venus. There are only two major highland regions that rise above the lowland regions. They are called Ishtar Terra and Aphrodite Terra.

The highest mountain on Venus rises above the Ishtar Terra and is the only place on the planet to have a masculine name.  It is the Maxwell Mountain after the famous scientist James Clerk Maxwell.

 

 

 

Those who hope that it may one day be possible to terraform Venus will be sadly disappointed to learn that it has lost almost all its water. In the upper atmosphere of Venus and the Earth solar radiation splits water molecules into hydrogen and oxygen by a process called photolysis. The high gravitational fields of Venus and Earth hold on to all gases except hydrogen and perhaps helium almost indefinitely. Hydrogen however evaporates into space. However not only hydrogen but oxygen will also evaporate into space by another process - Earth is protected by a strong magnetosphere but Venus is not and oxygen as O+ ions is lost by being forced out by the solar wind. On Earth almost all the water is in the liquid phase but on Venus there is little doubt, that although it should have started with about the same mount of water as Earth, it has lost most of it by the evaporation of the hydrogen component into space.   There is isotopic evidence from the ratio of deuterium to hydrogen that there was very likely considerable amounts of water on Venus a long time ago.

 

This view of the volcano Sif Mons (24N, 352E) was obtained by combining Magellan altimetric measurements and a radar backscatter image. Sif Mons is about 2 kilometres high and about 300 kilometres in diameter. A series of bright and dark lava flows extends for a distance of approximately 120 kilometres from the summit area, suggesting very fluid lavas. If Venus lava flows have the same structures as those on the Earth, the bright lava flows may be aa lava, while the darker flows may be pahoehoe. (These are names of types of lava found on Hawaii).  Note that the vertical scale of the image has been exaggerated to accentuate the subtle relief of the volcano.

JPL Magellan MGN P-37342.

The picture on the right is taken by radar simulation of a venusian mountain credit ESA.  The picture on the left is an artists impression of the Venus Express spacecraft in orbit around Venus.

The amount of carbon dioxide on both Venus and the Earth is of the same order but on Earth it is mostly bound in the carbonate rocks or dissolved in the waters of the planet's hydrosphere whereas on Venus it is all present as a gas at a very high pressure. It is a sobering thought that had Venus been just a little further out from the Sun or had the Sun been just a little less hot it may well have been a second Earth. Even more sobering is the fact that had Earth been just a little nearer the Sun or had the Sun been just a little hotter it would have been a second Venus and we would not he here. The balance may be very fine and it may only take very small changes to trigger off Venusian conditions on Earth.

 

 

 

Venus is the planet so like our own in size, surface gravity, distance from the Sun and, we believe, in its early history. In yet, as we have leant in the last few years of the space age, it has turned out to be the most hostile and most difficult of all the smaller worlds of the Solar System to colonise.

The two illustrations are artists impressions of the European Space Agency's Venus Express Spacecraft launched on 9 November 2005 from Baikonur in Kazakstan.  It went into orbit round the planet in April 2006 and the mission is due to last for two Venusian days -about 500 Earth days.  Venus rotates on its axis extremely slowly and in the opposite direction to Earth and the other planets. 

 

 

Mars

 

The illustration of the two hemispheres of Mars are shown in the picture on the left.  The picture are colour coded for altitude.  Violet is the lowest then comes blue followed by green, yellow, and red in that order.  The really high altitudes of the summits of the volcanic mountains are shown in white.   The hemisphere on the upper left of the picture shows very clearly the huge depression of the Hellas Basin. and as the colour violet suggests is the lowest area in the planet.  Approximately antipodal to the Hellas Basin are the four enormous volcanoes.  Mount Olympus is the highest   The summit of the middle of the three volcanoes in a line is almost on the equator.

Mars is a cold and arid desert.  It is about half the diameter of the Earth but because it has no oceans the area of the 'land surface' is only very slightly less than that of Earth where about three quarters of the planet is covered by sea.  Its atmosphere is at a very low density compared to Earth and consists of carbon dioxide with small amounts of nitrogen and water vapour.   There is a considerable amount of H2O on Mars but it forms frozen ice caps at both poles and is present as permafrost all over the planet.    During the winter-time carbon dioxide also sublimes as a solid - in the south polar winter there are considerable amounts of solid CO2 in the winter.

It is possible that in the distant past the atmospheric pressure was considerably higher and the temperature was above zero degrees 

Celsius over much of the planet.     Under these conditions there may have been lakes and rivers and perhaps a northern ocean and possibly simple life may have also begun.   To-day Mars does not have a magnetic field and shows no signs of plate tectonics.  However in its very early history there may well have been a magnetic field and plate tectonics may have operated to some extent.  The presence of Andesite, a rock associated with plate activity at subduction zones on Earth has been reported by some authorities.

It may be possible one day to terraform Mars and provide it with a high pressure of CO2, liquid water and to grow plants to produce some free oxygen into the atmosphere and to even produce an ozone layer.  This is idea is admirably described by Arthur C Clarke in his book 'The Snows of Olympus'.

 

 

This image, taken by the High Resolution Stereo Camera (HRSC) on board ESAs Mars Express spacecraft, shows Coprates Chasma, a major trough located roughly in the centre of the Valles Marineris canyon system.  The Canyon System is the massive canyon seen in the bottom part of the bottom globe. and is roughly as long as the width of the United States.  This is only one if the many wonderful pictures taken by the European Space Agency's Mars Express. The Mars Express was a spectacular success.

 

Although Mars, the larger moons of Jupiter and  Saturn's large moon Titan are hostile to our form of life it is most probable that, in the future, people may well visit these alien worlds and even set up quite large colonies on Mars as described above. 

 

 

However, to find another world like ours  we shall have to find a way to cross the vast distances that separate the stars and then perhaps we may discover upon the planet of another sun a world like Earth.

 

The Earth is a rare oasis in the cosmos. Let us treasure it and heed the words of the Buddha and the Christ and all the other sages who have taught a message of wisdom and love throughout the ages and learn to live in harmony with each other and with nature on this wonderful planet of ours.

 

 

 

 

 

Solar System