The Primordial Soup. That well known prebiotic amalgam of simple, organic molecules that miraculously conglomerate and just like that, life is created.
Well, it is one theory anyway. The Primordial Soup was first proposed by Russian biochemist, Alexander Oparin; he effectively developed a prequel to Darwin’s theory of evolution. However, there is a small problem: the complex organic molecules (those that contain 6 or more carbon atoms) that are required for life, are virtually non-existent in the universe. Moreover, we don’t know how they could have come to exist… until now.
Together, two recent studies have found the missing link for the Primordial Soup theory. And where they found it is magical.
The building blocks of life
In the early days of Earth, the atmosphere was bubbling with ammonia, hydrogen, water vapour and carbon dioxide. These contain a small handful of atoms: carbon, oxygen, hydrogen and nitrogen – the crucial players of organic molecules. It is accepted, that from the Primordial Soup came life – some 4 billion years ago.
From organic molecules, the more complex organic molecules, including biomolecules, are developed – these are the crucial components that make up all living things.
Some of the most important classes of biomolecules are carbohydrates (which are burned to create energy), lipids (which are used for energy storage), proteins (a huge class that ranges from enzymes that assist the digestion of food to the very make-up of your body) and nucleic acids (the constituent parts that make up DNA).
Without biomolecules, we simply would not exist. Every component of our bodies are made from them – and not just us, but animals, plants and even bacteria.
Yet, despite this seemingly logical progression of events, there is one problem – where did these simple molecules come from? How did life appear from lifeless material?
Bringing matter to life
Perplexingly, scientists are unsure exactly how simple organic molecules combine to create the biological building blocks that create the world around us.
It is well documented that we are all made up from star dust – every atom that exists on Earth is, indeed, formed deep in the centre of a dying star. Well, apart from the 2 smallest atoms, hydrogen and helium; they were born of the Big Bang.
As beautiful as this sounds, it is a huge jump to go from a collection of atoms to abiogenesis – the creation of life from lifeless material. And, how the primordial soup came be, is crucial to this step.
So the search for the primordial soup began. Of course, the most logical place to start is in stellar nurseries in deep space.
Researchers from the Arcetri Astrophysical Observatory in Italy and the Harvard-Smithsonian Center for Astrophysics analysed data from the Green Bank Telescope, IRAM 30 and SMA interferometer to allow the researchers to explore a wide range of spectral and spatial information.
Greenbank’s telescope is the largest fully steerable and can pick up even the faintest radio waves from around the cosmos.
Finding molecules from across the Milky Way
Towards the hot centre of the star-forming region, memorably named ‘G31.41+0.31’, a 10-atom biomolecule has been detected.
Using various techniques to detect and analyse star forming regions, the researchers found that the formation of certain biomolecules, namely ethylene glycol (the simplest hydrocarbon chain with an oxygen and hydrogen molecule attached to each end), form via the “dust-mediated coupling” of two radical molecules. A radical is a highly reactive molecule which, in this case, is composed of carbon, oxygen and hydrogen.
The researchers also note that the brighter the star, the higher the ratio of complex organic molecules at its centre.
Meanwhile, researchers from the National Radio Astronomy Observatory have found a chiral molecule (that is – a molecule which can only be in one orientation) in interstellar space, close to the Milky Way’s Galactic Centre. Chiral molecules are imperative to life. For example, DNA would not be able to form without chiral molecules. Discovering this molecule in the Galactic Centre will surely provide a stepping stone towards understanding where the very molecules of our beings came from. As stated by the authors:
“Critically, the detection of …propylene oxide toward the Galactic centre provides a molecular target for such observations and demonstrates that interstellar chemistry can reach sufficient levels of complexity to form chiral species.”
Xin Su of the American Chemical Society discusses how these results affect our knowledge of the “building blocks of life”:
“These latest findings provide useful information about prebiotic chemistry in space, especially about the mechanisms of COM formation from simple organic compounds. Taken together, these studies are an important piece of the missing link in abiogenesis… These [are] vital steps toward understanding the origins of life.”