Looking up: Astrochemistry and the big step

One of our oldest quests is origin of life. There are several methods to find results. Palaeontologists make their way using fossils and astronomers look up to understand the atmosphere of primitive Earth.

But another method has developed in recent times and it’s called Abiogenesis — the chemical origin of life. It’s the study of the ‘start of everything’... some 4 billion years ago. Scientists use geophysics, chemistry and biology to simulate and understand the abiogenesis environment of prehistoric Earth.

Complex organic molecules have been found in the Solar System and in interstellar Space, and these molecules may have provided the ‘starter pack’ for the development of life on Earth. Recently, we discovered chiral molecules, an important group of molecules in living things, in the interstellar medium. How all these different molecules are formed in interstellar space is one of the trust areas of modern research and we have named this field, astrochemistry — a fusion of chemistry with astronomy.  

The breakthrough in abiogenesis came from an Urey-Miller experiment. In this classic experiment test from 1952, Stanley Miller and Harold Urey simulated early-Earth conditions and produced an ensemble of the so-called ‘Primordial soup’. They made a racemic mixture of amino acids-monomeric units of proteins, from a mixture of water (H2O), methane (CH4), ammonia (NH3), and hydrogen (H2). They used continuous electrical sparks that fired between the electrodes to simulate lightning in the water vapour and the gaseous mixtures. It was quite the time-travel experiment.

Since then, abiogenesists have been stimulating this primitive ooze to discover the secret of the chemical origin of life. Here, an astrochemist’s knowledge of both astronomy and chemistry comes very handy. It can help him or her understand the chemical reactions  in Space, the earliest mixing of separate elements to create the things we see around now.

The Interstellar medium mainly consists of gas and dust in ultrahigh vacuum and ultra-cold temperatures. It has been proposed that chemical synthesis may be occurring on the surface of micro-sized dust grains in this cold. On these dust grains, tiny ‘chemical factories’ are powered by high-energy radiation and also by low energy secondary electrons which are produced when any ionizing radiation interacts with solid ice.

So basically, all you need to simulate the interstellar conditions are creating ultra-high vacuum (UHV), ultra-cold temperatures and the radiation sources.

The story of Glycolaldehyde, a precursor to ribonucleic acid (RNA), gives a glimpse to the type of studies being conducted in this area. This molecule was first reported in 2012 around a protostellar binary IRAS 16293-2422, located 400 light years from Earth. The finding suggests that complex organic molecules may have formed in stellar systems prior to the formation of planets... billions and billions of years ago.

Today, it’s Glycolaldehyde that’s being used in the interstellar simulated atmosphere to understand what could have happened during the Big Bang days. And Indian scientists at the Tata Institute of Fundamental Research is at the forefront in the modern-day race to understand how life itself was born in the Universe.

The author is a scientist and a writer.