LIFE IN THE COSMOS
Even before our ancestors began to fashion tools and learn the art of making fire they must have gazed at the wonders of the Earth and the marvels of the star studded heavens and asked such questions as why are we here, what made us, why are we born and why do we die? They made myths and legends of how the Earth and the plants and animals that inhabited almost every nook and cranny of its surface came to be. Above all they wondered about the presence of men and women in the world. At first they endowed every plant and animal with a spirit - later they invented a whole world of gods and goddesses and still later the great religions and philosophies were born. These religions tried to answer the ultimate question which is still unanswered. They depended on BELIEF and FAITH. Science however came along and began to find out HOW the Universe operated - it left the ultimate question of WHY to religion. That is why at the highest level science and religion are not in opposition to one another. My other website www.visionsofthecosmos.co.uk covered a very wide field of geology and astronomty. This new website proposes to examine in depth the question of LIFE. As such it concentrates on the new science of ASTROBIOLOGY. Firstly it surveys the evidence for the possible exitence of life on planets other than the Earth. It then deals with our knowledge of life on Earth and what is known of the chemistry and biology of living processes.
Sad Story of a Genius
To realise that there have been terrible acts of barbarism commited throughout history we have only to look at the tragic life of Giordano Bruno. He was born at Nola near Vesuvius in 1548 and grew up to have one of the most enquiring minds of his age. He was frank, outspoken and lacking in reticence and was gifted with the most amazing memory. It was not an uncommon thing for scholars to wander from place to place and soon Bruno started his long journeys across Europe. In 1574 Bruno spent some time is Geneva, the home of Calvinism. In 1581 he went to Paris and began to give lectures on philosophy. Bruno found a royal patron in Henry Ill and it had much to do with the success of his short carrier in Paris. There came a time when Bruno felt that it was time to move on. He went to England to begin over again and to find a fresh audience. While in England he had a personal audience with Queen Elizabeth 1. Soon he was to go on his travels again and he went to Germany. Between the year 1582 and 1592 he was persistently, openly and actively spreading the news about the discoveries of the Polish mathematicial Kopernik (Copernicus). All the time Bruno was spreading his ideas across Europe and writing numerous books. From the point of view of this website his most notable contribution to philosophy was his work entitled De l'Infinito Universo et Mondi (On the Infinite Universe and Worlds which was published in 1584. In this work he stated that the stars were other suns and were surrounded by planets some of which were inhabited by people. Finally he made the fatal mistake of returning to Italy. In Venice he was tricked and double crossed and handed over to the authorities in Rome. He was imprisoned for 8 years and horribly tortured. Despite this he refused to recant and held on firmly to his ideas. Finally at the age of 52 he was sentenced to death. On 17 February 1600 he was burnt at the stake in the Campo del Fiori in Rome and his ashes were thown into the Tiber. He has not been forgotten - In 1897 a statue was erected in his honour in the Via dei Fiori where he had been burnt to death. Five hundred ansd ten years after the judicial murder of Giordano Bruno, Lord Martin Rees in the Reith Lectures (third lecture BBC 4) mentioned him and said that two of his statements had been proved by modern science. - namely that the stars were other suns and that they were accompanied by planets. As to his third supposition we are now actively engaged in searching for life on planets outside the Earth. The picture on the top left was drawn in Paris by C.Meyer Image: Christian Bartholm�ss, Jordano Bruno (Paris: Libaririe Philosophique de Ladrange, 1846). In the bottom left we see a bronze plaque of the trial of Bruno by the Roman Inquisition by Ettore Ferrari. The picture on the right shows a picture of the statue erected in the Via del Fiori in the place where he was burnt to death. (This is a file from the Wikimedia)
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.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.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 five 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. 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. As we live on the land we often forget that three quarters of our planet is covered by oceans, seas, lakes and rivers. If we stand by the sea shore then perhaps we realise that life arose in the sea and water is the very substance that lubricates the processes of life. When we watch the sunset or sunrise we remember that other imnportant factor thaat sustaines life on the planet. It is the Sun (poeticaslly called the day star for it is so brilliant that all the other stars are invisible in the daytime). The picture taken by the author ot sunset over the sea at Noordwyck in the Netherlands illustrates the fact that our life as land animals depends on the presence of liquid water, 'solid' land and a stupendous thermonuclear furnace (a star) which we call the Sun. Noordwyck is the home of ESTEC, the technical headquarters of the European Space Agency. The picture on the right was taken in the Kerkenhof Gardens in the Netherlands not far from ESTEC. When we examine the other planets of the Solar System and consider the reasons why Earth is such a special place,we realise that even on planets orbiting other stars the conditions for life are likely to be relatively rare. The Earth is indeed an oasis in the deserts of space. But many scientists believe it is not by any means the only oasis. The most important factors seem to be the presence of water in the liquid form over large parts of the planets surface and its existence for vast periods of geological time. The presence of a stable star is also of enormous importance. Without the presence of liquid water life processes as we generally know them would seem to be unlikely and for most of this web-site we shall consider our type of life. Other important factors BUT probably not essential in the same way as the presence of water are the presence of a large moon, plate tectonics and the presence of the ozone layer and the magnetosphere. Let us now consider the important question of the habitable zone. The diagram on the left below shows a diagram of the Inner Solar System shoiwn by courtesy of NASA. It can be seen tha the Earth lies between Venus and Mars. Earth lies at a distance from the Sun that prodiuces temperature conditions that allow water to remain over most of the planet in the liquid phase for vast periods of geological time. It lies in the HABITABLE ZONE. This is sometimes poetically described as the GOLDILOCKS ZONE. Venus is too near the Sun and is too hot - Mars is too far away from the Sun and is too cold. Earth is just right for life to evolve.
The Formation of the Solar System
Once upon a time long long ago there
was a floating gas cloud consisting of hydrogen and helium with traces of other
gases like carbon monoxide. The clouds also contained tiny particles of
dust. Left to itself it may have drifted on for thousands of millions of
years. Close by however there was a massive star burning very, very
brightly. This star had not got long to live - it had already burnt most
of its core hydrogen to helium and the temperature of its inner regions was
rocketing. It got so hot that the
helium was burning to carbon - the
carbon to oxygen and so on to iron. When it got to iron it underwent a
catastrophic explosion which we call a supernova. Some of the iron
contracted into a neutron star or black hole and the outer layers were ejected
into interstellar space at a great velocity. The cloud was so hot that
large quantities of the iron within the cloud were converted into chemical
nuclei higher up the periodic table. A huge shock wave hit the quietly
drifting gas cloud and under gravity a number of stars were born.
Employing a bit of astrophysical forensics, researchers have located
fingerprints of relatively short lived radio-isotopes such as 26Al,
36Cl, 41Ca, 53Mn, 60Fe, 107Pd,
129I, 182Hf, 244Pu, long since decayed to more
stable daughter elements, in primitive meteorites. For those radioisotopes to
have been incorporated into primordial solar system bodies they must have been
delivered, freshly synthesized, from some nearby cataclysm, whether a stellar
explosion known as a supernova or an ailing star throwing off layers of material
in less dramatic fashion. One of
these stars was our Sun. (credit toDr.
Alan P. Boss, Carnegie Institution for Science,Department of Terrestrial
Magnetism, Washinton DC.)
Like all other stars the Sun was surrounded by a disc of debris which was made up of hydrogen and helium gas and, most importantly from the point of view of life, dust grains containing the higher elements produced in previous generations of stars - many of them supernova, including the one that caused the compression shock wave. The disc is called the protosolar disc. Since it now seems that all stars are accompanied by such discs the usual term is protoplanetary disc. This is shown in the accompanying artists diagram by Pat Rawlings coutesy of NASA. Thus the carbon, oxygen, nitrogen, phosphorus, sulphur, chlorine, sodium, potassium, magnesium, calcium, iron and many trace elements were used in that wonderful chemistry we call LIFE. All the elements found in living organiisms, with the exception of hydrogen which was produced seconds after the BIG BANG, were produced in massive stars. Thus we can say that we are all made of stardust. The formation of the planets took place within the proto-solar disc. Under gravity the dust particles coagulated and formed pebbles then stones then boulders then mountains and the tiny planets we call planetisimals. Finally five planets orbited the Sun in the inner Solar System. They were Mercury. Venus, the Proto-earth, a planet about the size of Mars, which we shall call Orpheus, and Mars itself. The orbits of the proto-Earth and Orpheus were close and finally 20-40 years after their formaatioon thwe two planets clollided to form a somewhate enlarged Earth and a shower of debris wwhich coagutated to form the Moon. It is probable that Mercury and Venus also underwent collisions - Mercury seems to have lost some of its silicate rocks and Venus spins very slowly in the opposite direction to all the other planets of the Solar System. After their formation Mercury and the Moon were too small to hold an atmosphere or oceans of water. The Earth and very very likely Venus and Mars became enveloped in oceans and gaseous atmospheres. Exactly how life began on Earth is not yet clear although a great deal of work is being carried out on the newly developing science of astrobiology. VENUS: There is isotopic evidence from the ratio of deuterium to hydrogen that there was very likely considerable amounts of water. When the temperature of the oceans reached a tipping point, the hydrosphere underwent a run-away greenhouse resulting in the oceans boiling and a rapid development to the hostile conditions which exist to-day. The planet is now surrounded by an ocean of carbon dioxide with a pressure of over 90 atmospheres with the temperature of around 480 degrees Celsius on the rocks. 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 are 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 and hydrogen sulphide. 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 pressure of almost a hundred atmospheres. Just like the pressure, the temperature varies with altitude but in th lowlands it 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 high 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. Much work is being carried out on studies of the atmosphere by the European space Agency's orbiting satellite 'The Venus Express'. 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 direct evaporation of the hydrogen component into space and the loss of much oxygen as O+ ions by scouring by the solar wind. 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 (strictly speaking a superfluid) 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 illustrations above were obtained by radar surveys and are are taken from the European Space Agency's gallery and from NASA the author is very grateful of the help given by these organisations. The top left shows the Venus Globe. The middle right shows a high mountain Maat Mons and the bottom left shows an area of three craters. MARS - In earlier times, Mars is believed to have had an atmosphere of carbon dioxide dense enough to produce a greenhouse effect high enough to allow liquid water to exist on the surface and it appears that the low lands in the northern hemisphere are the remains of an ocean. Today it is a cold and arid desert. However there is still plenty of water on Mars in the form of ice which sublimes directy to water vapour since the atmosperic pressure is too low to allow water to exist in the liquid state. An interesting book entitled 'The Snows of Olympus ' was written by Arthur C Clarke in which he described how it may be possible in the future to produce Earth-like conditions on Mars - a process described as TERRAFORMING. The illustration of the twin peaks taken by the Mars Pathfinder in 1997 gives some idea of the lonely red wilderness of Mars. It is on the right hand side ot the page. We now know that, if life exists in the sulphuric acid clouds of Venus, under the soil of Mars or in the oceans that lie beneath the ice of Europa, Ganymede,Callisto or Titan , it will be very primitive. To find another wonderful biosphere like that on Earth we must look beyond the Empire of the Sun to planets orbiting other stars separated from us by the vast distances of interstellar space. This is the subject of the next page of this web-site entitled EXOPLANETS
About the Author
The author Ray Goodwin holds B.Sc. Degrees from the London University in Chemistry, Geology and Physiology and an M.Sc. in Biochemistry and spent most of his professional life teaching in Colleges of Technology.On his retirement he has entered the field of astronomy, astrochemistry, astrobiology and space sciences. He has spent a great deal of his retirement in visiting amateur astronomy societies and in attending European Space Agency Symposia in ESTEC in the Netherlands and other scientific conferences in England and Sweden. He regularly attends the yearly European Astrofest in South Kensington London and other meetings in the UK. He has written scientific articles and given a number of lectures on diverse scientific subjects e-mail addresses firstname.lastname@example.org ray@lifeinthecosmos mobile phone 07791021944. Readers of this web site are invited to e-mail the author and discuss their opinions of the topics dealt with and suggest any changes which they think may be helpful.