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[ Graphical: Channel4 Homepage ]
First, place some water in an ocean-sized vessel and add a pinch of salt. Then mix in formaldehyde, hydrogen cyanide, or any other simple organic molecules you can get your hands on. Fumigate liberally with methane. Decorate with mineral clays if available. Cook in a hot oven under thunderous electric skies for approximately 200 million years. When life has originated, remove and allow to cool.
At first glance, life's origins have a simple recipe. After all, we more or less know the composition of the chemical palette from which life was painted: simple organic molecules, water and other basic constituents. But the primordial soup, powerful metaphor that it is, obscures a multitude of uncomfortable truths about the origins of life.
Nobody has really got close to recreating life in the laboratory. The notion that you can feed chemicals into one end of a tube and get life out of the other is appealing, but one that is so far without basis in reality. Despite decades of experimental effort, the chemical pathway that turned simple molecules into a self-organised and self-replicating system, sustained by its own metabolic cycles, remains obscure. Figuratively speaking, we haven't even got past first base.
Take the case of the sugar ribose, for instance, a key molecular component of the DNA and RNA that is fundamental to all life. The synthesis of this sugar, one might reasonably imagine, was a key stage in the organic pathway that led to life. Now, it is easy to make ribose in the laboratory when given a free choice of starting materials and conditions. But when the options are restricted to the kinds of chemicals and circumstances found on Earth 4000 million years ago, things start to get very difficult indeed. One approach involves the polymerization of formaldehyde, but the reaction churns out dozens of other compounds, while the ribose produced is unstable and readily degrades.
What relevance do these kinds of experiments have for finding life on other planets? It is a popular belief that if we can find the kinds of chemistry and conditions that characterised the infant Earth, then we are only a short step away from finding life itself. But a long list of laboratory failures may suggest otherwise. What if life has little to do with the broader inevitabilities of organic chemistry? What if, instead, it is the product of an extremely improbable series of chemical twists and turns, impossible to retrace? What chance then, of alien life?
Life, the Universe and Everything | A Difficult Recipe | Location, Location, Location | The Realm of Possibility | Alien Titchmarsh | Find Out More
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