Cosmic dust could have sparked life on Earth

In a recent study published in the Monthly Notices of the Royal Astronomical Society, Stephen Thompson, I11’s principal beamline scientist, and Sarah Day, I11 beamline scientist, explored how amino acids like glycine and alanine could survive the harsh conditions of space and make their way to Earth embedded in cosmic dust.  

Amino acids are the molecular foundations of proteins and enzymes, which drive every biological process in living organisms. While scientists have long debated whether these molecules formed on Earth or arrived from space, this new study offers compelling evidence that cosmic dust may have played a crucial role in delivering them. 

The team synthesised tiny particles of amorphous magnesium silicate, a major component of cosmic dust, and deposited amino acids - glycine, alanine, glutamic acid, and aspartic acid - onto them. Using infrared spectroscopy and synchrotron X-ray powder diffraction, they then examined how these molecules behaved when the silicate particles were heated, simulating the warming that occurs as dust grains travelled through the early solar system. 

They found that only glycine and alanine successfully adhered to the silicate particles. These amino acids formed crystalline structures and in the case of alanine remained stable at temperatures well above its melting point. The study also found that the two mirror-image forms of alanine (L- and D-alanine) behaved differently under heating, with L-alanine showing more reactivity than its D-form. Glycine, on the other hand, was lost from the silicate at temperatures lower than its pure decomposition point, indicating that it detached from the grain surface rather than breaking down.  

The team prepared two batches of amorphous silicate and subjected one batch to heat treatment prior to depositing the amino acids. This was to remove hydrogen atoms from the silicate surface, producing two silicates with differing surface properties, which were also found to influence the temperatures at which the amino acids were lost.    

These subtle differences may have had profound implications for the types of molecules that seeded life on Earth. 

Although the study was limited to a single cosmic dust component, the findings could point to the existence of a possible “astromineralogical selection mechanism”, a natural filtering process where the limited range of available dust grain surfaces means that only specific amino acids attach to dust grains. Amino acids are formed within the icy mantles that coat cosmic dust grains, and such a mechanism would come into play as the ice mantles are sublimated away into space, along with the amino acids within them, when the dust grains cross the so called “snow line” and encounter the warmer, inner regions of  the early solar system. This in turn could have influenced which molecules were ultimately delivered to Earth, shaping the planet’s early organic inventory. 

The study supports the idea that amino acids formed in interstellar ice mantles could have transferred to silicate dust grains and survived long enough to be delivered to Earth. This would likely have occurred between 4.4 and 3.4 billion years ago, a period bracketed by the formation of the Earth’s crust and oceans following the end of the so called late heavy bombardment and the appearance in the geological record of the first micro fossils.  

Antarctic micrometeorites and samples from comets like Wild 2 and 67P/Churyumov–Gerasimenko have shown high concentrations of organic material, including amino acids. Furthermore, although impacts by comets and asteroids, both of which contain amino acids, would still have occurred at that time the influx of micrometeorites is believed to have been so high that it was likely to have been the dominant source of organic carbon on the early Earth. This showering of the Earth’s surface with space dust rich in life’s precursors, is believed to have potentially compensated for the limited quantities of amino acids produced from terrestrial synthesis alone, allowing life on Earth to begin. 

The team’s research adds a vital piece to the puzzle of life’s origins. It shows that interstellar dust grains are not just carriers of molecules - they may actively influence which organics survive and reach planets like Earth. By understanding these processes, scientists can better grasp how life might emerge elsewhere in the universe. 

The study also highlights the importance of interdisciplinary science, combining astronomy, chemistry, and geology along with the advanced experimental techniques available at large scale research facilities like Diamond, to explore one of humanity’s oldest questions about the origins of life.  

To find out more about the I11 beamline, please contact Principal Beamline Scientist Stephen Thompson: Stephen.thompson@diamond.ac.uk  

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