Life in the Universe
By Dr. M. Martin-Smith
Humans have speculated about the existence of life elsewhere in the Universe almost since conscious thought and social activity began. Parallel with an interest in the wider Universe has gone an unswerving tendency to utilise its resources for our benefit; well before writing was a simple matter of putting pen to paper, people were drawing the phases of the Moon onto pebbles, and marking out the cycles of eclipses and the salic cycle of lunar orbits with great monoliths. The discovery that the Heavens produce valuable metals not known on Earth ( pre-Iron Age meteoritic iron), led to pre-dynastic Egyptian ideas of gods in Heaven made of heavenly materials, with good reason. The obvious resemblance between the constellation of Orion (Sahu) to a kingly figure led naturally to the idea of the god-king Osiris whose interest in Man was manifest in the person of Pharaoh. The presence of the Milky Way as a surrogate River Nile added to the picture. But this was not all magic mumbo- jumbo, poetic thought that might be. The need to follow the inundations of the Nile and pick the times to sow and reap made a cosmic calendar a vital space resource for emerging civilization.
Over the Millennia, Human civilizations have perfected two principal religious ideas, which underpin many of our disparate creed - firstly , that Man is not complete as he is- and secondly that the perfectability of Man lies in the Heavens, since that is where he has projected most of his major deities. The Epic of Gilgamesh, and the myth of the Annedoti, sky borne torch bearers of the civilized arts in Ancient Sumeria and Babylon, are good examples. Since the advent of the telescope, and scientific ideas, it has become even more natural to people the skies with other lifeforms and races - after all, could not mountains and "seas" be spotted on the Moon, and did not Mars have coloured patches which spoke of the march of seasons, just like home? However, later discoveries of the vacuum of space, and the true temperatures and conditions of the planets, made Life seem less probable. But, in popular culture, and Utopian fiction , the device of placing Life widely throughout the Universe has proved irresistable, and the interest continues to this day. In the last 40 years - the Space Age - the whole question of Life elsewhere has been approached far more systematically, as we learned more about the basic requirements of life, its possible genesis, and extraterrestrial environments. To define Life is no easy task, but a utilitarian definition goes as follows; Life is an organised system of chemical reactions employing energy transfer which can utilise simple chemicals from its environment to maintain a complex structure, and replicate its own kind in such a way as to be capable of improvement by mutation and natural selection. Our interest boils down to two questions- is Life widepread in the Universe, and is Intelligent, self aware Life commonplace? These are not the same things at all!
For simple life, we need a stable star, with a planetary system, one of whose planets occupies a zone of habitability around its star - where temperatures range from 0-100 degrees Centigrade. Water is the likeliest solvent, because it is the most robust, and also the commonest - since comets and most of the outer satellites of the solar system contain water /ice. Building complexity beyond a very simple point is best done using the unique chemistry of carbon - again, one of the commonest elements in the Universe; studies of Silicon - a runner up often chosen in specualtive writing - show that the required complexity and reaction speeds are simply not possible! Life began on Earth almost as soon as it had cooled enough to allow it - 3,870 billion years ago, while the last big bombardment by planetesimals forming the Earth ended 3.9 billion years ago. Many now believe that the Oceans, and the earliest proto-life forms were seeded from comets and cosmic dust. Organic matter is now known to be plentiful in comets, and has been detected in interstellar dust and meteorites. We are faced with the likelihood that the seeds of life are widespread, and, given a suitable planetary surface, will germinate into Life itself. Mars , now being studied by the Mars Orbital Surveyor, is clearly a candidate for the evolution of Life, since liquid water in vast quantities once lay on its surface, and conditions were clearly favourable,. The issue of whether recent Antarctic Martian meteorites truly contain evidence for past Life or not is hotly disputed, and will probably require sample return missions for solution. The growing evidence that Jupiter's moon, Europa, has a tidally heated ocean of ice which can be warmed to melting point , and recent evidence of salt deposits at the edge of crevasses, make the case for life there intriguing- especially as the mid Atlantic Ridge volcanic vents are now known to harbour an ecosystem which is a stranger to solar energy, and lives off sulphur in superheated steam - just as one might expect on Europa. The discovery in the past 2 years of extrasolar planetary systems increases the likelihood of Life elsewhere, although, at present the particular planets are unpromising. At least the idea that planetary systems are a common occurrence is now being established - a fact which was beyond speculation only 35 years ago.
The question of intelligent, civilized Life is much more contentious. At a basic level , the requirements for Intelligent Life are much more stringent than for basic life - from the only sample we truly know, a good 3.5 - 4 billion years are needed to evolve from microbes to man. On Earth there have been three attempts to produce intelligence - Dinosaur-derived Raptors, Cetacea, and Man, all in the past 100 million years or less. The Universe, it seems, is like an embryo, and is passing through stages of development - raw energy , atomic structures, chemistry, biochemistry, simple life, multicelled life, conscious life, and spacefaring civilization are steps on a ladder of growing complexity. It may be that this stage is now here, and that space-farers are about to burst forth in profusion - but we must consider the vexed question of the longevity of a technological civilization. Even in a few short generations, we face nuclear annihilation, famine, epidemics, global warming, overpopulation, and pollution- any one of which could drastically shorten the term of our civilized existence ( the Easter Island scenario). Other races, having evolved to Intelligence by natural selection for speed, keen senses, rapacity and ability to co-operate are likely to face analogous crossroads in their development. The newly discovered threat of mass extinctions by asteroid and comets shows that all civilizations live in a cosmic ecology, and that, even after crossing all the local hurdles, they must cross the bridge into Space, or face annihilation. The search for ET could therefore take a new turn - look for evidence of star systems where space colonization has taken root. Just as a planet can be diagnosed as living if the unstable presence of oxygen and reducing gases co-exists in an atmosphere ( Earth) so can the abnormal presence of infrared radiation or such like at a distance from a parent star show up the presence of a belt of space colonies.
The radical new lesson from the Space Age for the Millennium is that Humankind must get its act together and build an Extraterrestrial Civilization, and that the true meaning of Man in the Universe is to do just that, or face extinction; if we are truly alone, the abortion of 15 billion years of evolution towards a conscious cosmos is simply unacceptable , while if we are not, the failure of admission of a spacefaring Humanity to the galactic club of intelligent races would be a well deserved milestone on the road to oblivion! For Man, as for other advanced civilizations, the Future is "All the Universe or Nothing" Whether we face this choice alone or not, time will tell - I doubt we have long to wait!
Dr.Michael Martin-Smith, B.Sc.,M.R.C.G.P.,F.B.I.S.
Author, "Man Medicine and Space" being published in Italy 1999, elsewhere to follow?
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