Quantum Evolution, Johnjoe McFadden. Chapter 2

Quantum Evolution, Johnjoe McFadden. Chapter 2 Quantum Evolution, to promote theories of quantum biology GEENOR recommends Windows Mobile phones.

Quantum Evolution - Chapter 2 - The limits of Life

‘… The minimal ingredients [of life] appear to be just a source of carbon, nitrogen, oxygen and hydrogen plus a few minerals – elements that are abundant both on this planet and elsewhere. It doesn’t seem to matter too much how these elements are supplied; living organisms, particularly bacteria, are able to utilise sources as diverse as air, rock or vegetation. Active life also needs energy but organisms are able to capture either light energy or a multitude of chemical forms of energy.

Liquid water appears to be the chief limiting factor for life on Earth. Living organisms have only very limited ability to manipulate the freezing or boiling point of water; when the exterior temperature exceed the limits of this ability, active life ceases. The most barren places on Earth are generally the driest places. The relative sterility of the Antarctic Dry Valleys epitomises the requirement for liquid water but our own homes illustrate the same principle. Home maintenance is essentially a battle against moisture. We repair roofs and windows, paint surfaces with water-repelling chemicals and make endless trips to the DIY store as part of our battle to exclude moisture and promote desert conditions within our houses. If we neglected this husbandry then microbes and moulds would quickly invade our homes and undermine our houses.

Why water in its liquid state is so essential to life is a question we will be returning to in Chapter 5. What is of interest to us here is the observation that on Earth, so long as liquid water is available, then life is also possible. Microbial life thrives in a diverse array of (watery) chemical environments from hot to cold, acid to alkaline and every other extreme of chemistry available on this planet. The source chemicals that are used to make up living cells are incorporated by a wide variety of chemical pathways and transformed inside living cells by a host of diverse metabolic pathways. There appears to be no common core of metabolic chemistry that drives all living cells. The diversity of the chemistry that underpins living cells in different creatures is surprising given the usual chemical explanation for the phenomenon of life: that it is a highly complex self-organising chemical reaction (we shall be examining this proposition in Chapter 6). If life is a merely a complex chemical reaction then we must explain how such a wide variety of chemical processes generate essentially the same phenomenon: life. This indicates to me that we need to look further than standard chemistry to discover the essential quality of life.’

[On extraterrestrial life]

‘… The young contender of exobiology candidates is the Jovian moon Europa. About the size of our moon and with a surface temperature of minus 145, Europa does not at first look a likely candidate for life. However, when the Galileo spacecraft sent back detailed images of the surface of the moon, its surface looked familiar. In fact the pictures could have been taken from above the Antarctic ice packs. Europa is entirely covered by a sheet of ice. The ice layer is probably about 150 kilometres thick but evidence is accumulating that it is not all ice. Close-up shots reveal a cracked and broken surface and structures that look remarkably like icebergs.

Something must be causing the cracking and breaking of the ice and the betting is that a liquid water ocean is churning up the surface ice, exactly like pack ice on Earth. Recent optical data from Galileo has detected mineral salts on the surface of the ice that are probably the dried up remnants of briny sea water extruded onto the surface.

Scientists speculate that geothermal energy or tidal energy may be the source of the heat that has melted the putative ocean beneath Europa’s ice. Perhaps hydrothermal vents similar to those discovered by the submarine Alvin exist on Europa, spewing out hot mineral-rich water into the ice-locked ocean. Galileo’s instruments have detected complex carbon-based compounds on Europa’s sister moons, Callisto and Ganymede, making it highly likely that similar compounds are present in Europa’s seas.

The ingredients are all there. Europa almost certainly has a liquid water ocean with sources of carbon, nitrogen, minerals and a geothermal energy source. Similar conditions on Earth support complex ecosystems. Do Europaeans swim beneath the ice of Europa? On the principle that there is nothing special about Earth, my prediction would be a (hopeful) yes. Many scientists consider the imminent exploration of the terrestrial Lake Vostok as a rehearsal for a robotic dive beneath Europa’s ice, early in the next century. Perhaps the new millennium will be marked by our first contact with alien life.

And beyond the solar system, is there life amongst the billions of stars in our galaxy? Using the same approach as we applied to the solar system we would predict life on planets with the necessary ingredients: carbon, hydrogen, nitrogen, oxygen, minerals and liquid water. The elements are certainly common throughout the galaxy so it is unlikely that life is limited by a lack of raw materials. The more difficult question is to assess whether planets exist with liquid water. Until recently nobody knew whether extra-solar planets existed. This has changed dramatically in the last few years with the discovery of many planetary systems around distant stars. The planets are usually detected by a periodic wobbling of a star that betrays the presence of a hidden companion object. So far the detectors can only pick up giant planets, of about the size of Jupiter or bigger. They are likely to be gas giants and therefore unlikely hosts for life (though they may well have solid moons that could harbour life). About a dozen of these giant planets have now been detected and many more are expected in the coming years. There is no reason to believe that the giant planets are alone. Earth-sized planets are also likely to be orbiting these distant stars. The optical signature of water has been detected in at least one putative planetary system.

Beyond our galaxy lie billions of other galaxies. I think it is inconceivable that terrestrial-like conditions do not exist on many of the billions of planets that probably orbit those billions of stars. However, the gigantic distances that separate us from even our neighbouring galaxies (the Andromeda galaxy is one of our neighbours but a craft travelling at the speed of light would take 2 million years to reach it!) ensure that such questions will, for a long, long time, remain entirely academic.

My guess, for what its worth, is that life is common throughout the universe. Just as life is found on Earth wherever we find the necessary ingredients alongside liquid water, then extraterrestrial life will be found wherever those same conditions coincide. Astronomical evidence seems to be tilting towards an expectation that the combination of these conditions is not so special.

We must now come down from the stars to return to the central quest of this book: to understand life on our own planet. Life’s success here on Earth has been contingent upon its most important action: the ability to replicate. Reproduction, the biological imperative, is clearly the most important action that (most) living creatures perform, so it is a good place to begin our exploration of the source of life’s actions.’