Speculations on life’s origins

In my last post I described what it was like on Earth some 3.8 billion years ago when evidence indicates that life first appeared on Earth. The atmosphere was made up of volcanic gases like carbon dioxide, methane, sulfur dioxide, ammonia etc. but no oxygen.  That meant there was no ozone layer in the upper atmosphere to absorb the ultraviolet rays of the sun that cause chemical bonds between atoms to break. That meant that for chemistry to become more advanced and life to originate, it had to have happened in an environment where there was a source of energy and that was away from the light of the sun.

Just such an environment was provided in hydrothermal vents deep in the ocean.  On the map upper left, these vents are indicated by the red dots and are commonly found near places where the Earth’s tectonic plates are moving apart and sea water seeps into cracks in the Earth’s crust. This causes superheated seawater rich in dissolved inorganic compounds, to spew out of the vents and they supply the chemical energy to support up to 100,000 times as many more living organisms as ordinary seawater. These organisms depend on populations of microorganisms that ingest sulfur compounds for their energy to stay alive and reproduce . At first these strange microoranisms, that could withstand such tremendous heat and pressure in the dark depth of the oceans, were thought to be a special type of bacteria but, with the advent of the relatively new science of genetics, astonishingly, an entirely new form of life called Archaea were identified in the early 1970’s – see the ‘Tree of Life’ diagram below on the left.

At present, the most popularly held speculations about how life started on Earth center on thermal vents but, for lack of conclusive evidence, there are still at least 7 plausible theories and there have been lots of suggestions that life might have had a free ride on comets from other star systems. Actually, even if life came from outer space, the question of how life began there would still remain. 
Whatever theory prevails - eventually a loop of chemical reactions occurred in a closed environment that could reproduce itself. Self replication is the fundamental aspect of what we call life because it means there is a whole new set of rules that, once started, takes over  – Darwin’s law of natural selection. The replicas react to their immediate environment and if they possess some change from the original parent, then the offspring can survive normally only if the change is an improvement on the parental design.  Since there have been many
inevitable errors in replication and thus improvements, it is easy to imagine how step-by-step more complex and adaptable offspring proliferated. Evolution was unstoppable. 

Indeed all the evidence points to a single ancestor from which all other life forms on Earth evolved. As a case in point, all the DNA and RNA molecules found in every living cell have a structure such that the information on replication is in a particularly reliable arrangement as is the energy storage system using the Adenosine triphosphate [ATP] molecule. 

A number of scientific teams are using their impressive know-how and ingenuity to try to create life in an artificial environment but I must say I am concerned about their efforts!  They are tampering with the very basis of our existence and - as is illustrated by what has happened here on Earth – once started, life is amazingly persistent.  It also happens to be chiral and in a posting I did on right and left handedness in molecules shows, getting it wrong just in that one sense could be fatal.  Rie 

The Sun Revisited

Like a precious spring in the vast empty desert of space, the Sun makes our Earth a beautiful living oasis in the cold, dark universe around us.

Have you ever thought what makes the Sun shine and keep on putting out such colossal amounts of energy for billions of years? It is amazing to me that, like most people, I didn’t ever ask that question when I was growing up. Maybe it was because the Sun is so awesome that I didn’t think anyone could possibly know the answer.

But Einstein figured it all out in 1905 when he developed his famous equation: E=mc²

That equation says that energy (E) and matter (m) are interchangeable -- one can be turned into the other. In the Sun, incredible amounts of energy (E) are created when very, very small amounts of matter (m) are destroyed. That’s because the constant (c²) that is on the same side of the equation as the mass (m) stands for the enormous speed of light multiplied by itself.

The Sun is made up of gases, about 75% hydrogen and 25% helium. In the very very hot centre of the sun (15 million degrees Celsius), two hydrogen nuclei fuse when they collide, and the helium nucleus that forms as a result has a mass (m) that is very slightly less than the combined masses of the two hydrogens. That lost mass (m) is converted to the prodigious amount of energy (E) in the form of heat and light that the Sun gives off and has been giving off for billions of years. Watching this short YouTube clip helps visualize this thermonuclear reaction happening in the Sun.

So far the Sun has used up only about half its hydrogen, so no worries, there is no reason it won't keep flooding planet Earth every single day with an amount of energy that is equivalent to the whole of the world’s oil resources. That constant and beautiful supply of energy has been a major cause of the truly awe-inspiring evolution that has occurred on our planet – that, and of course the laws of nature.

One of nature's laws - the famous Second Law of Thermodynamics – says that in an isolated system, Entropy, or disorder, increases. But what about a system that is not isolated and that is receiving the wonderful energy from the Sun constantly? A relatively new theory, Complexity Theory, recognizes that if you pump energy into an isolated system, order will increase!!

Darwin certainly made great breakthroughs – recognizing evolutionary patterns and coming up with his ‘survival of the fittest’ dictum. But consider the tremendous driving force for the increasing complexity on the planet that is now being directed by us. And where do we get our energy? Indirectly, like everything else on Earth, from that marvelous thermonuclear reaction going on in the Sun!   Rie