Scientists from the Cambridge University have suggested that molecules vital to the development of life could have formed from a process known as graphitisation. Once verified in the laboratory, the finding could allow scientists to recreate plausible conditions for life's emergence.
It has long been debated how the seemingly fortuitous conditions for life arose in nature, with many hypothesises reaching dead ends. But scientists have now modelled how the necessary ingredients for life could occur in substantial quantities.
Life is governed by molecules called proteins, phospholipids and nucleotides. Past research suggests that useful molecules containing nitrogen — such as the nitriles cyanoacetylene (HC3N) and hydrogen cyanide (HCN), and isonitriles including isocyanide(HNC) and methyl isocyanide(CH3NC) — could be used to make these building blocks of life. However, there has been no clear way to make all of these ingredients in the same environment and in substantial amounts.
In a recent study published in Life, researchers from the Cavendish Laboratory and the Department of Earth Sciences and Institute for Astronomy have found that significant quantities of these useful molecules can be theoretically made through a process known as graphitisation. If the model can be verified experimentally, this suggests that the process was a likely step for early Earth on its journey towards life.
A key problem with previous models is that a range of by-products are created along with the nitriles. This makes a messy system which hinders the formation of life, “a big part of life is simplicity,” said Paul Rimmer, from the Cavendish Laboratory, and co-author of the study. “It’s coming up with a way to get rid of some of the complexity by controlling what chemistry can happen.”
Graphitisation is however a neat process, since it exclusively creates these nitriles and isonitriles alongside mostly inert side-products. “At first, we thought this would spoil everything, but it makes everything so much better. It cleans the chemistry,” said Rimmer.
This means graphitisation could provide the simplicity scientists are looking for, and the clean environment required for life.
The authors think that this process was likely kick-started by a major impact early in Earth’s history, around 4.3 billion years ago. “Something the size of the moon hit early Earth, and it would have deposited a large amount of iron and other metals,” said co-author Oliver Shorttle, who is jointly based at Cambridge’s Department of Earth Sciences and the Institute of Astronomy.
This iron would have reacted with water at Earth’s surface; and the products of that reaction would have condensed to form tar. Rimmer and Shorttle think that this tar would have reacted with magma at temperatures exceeding 1500°C; the extreme heat converting carbon in the tar into graphite.
“Once the iron reacts with the water, a mist forms that would have condensed and mixed with the Earth’s crust. Upon heating, what’s left is, lo and behold, the useful nitrogen containing compounds,” said Shorttle.
The evidence to support this theory partly comes from the presence of ancient komatiitic lavas on Earth; a type of volcanic rock formed when super-hot magma cools. “Crucially, we know that these rocks only form at scorching temperatures, around 1700°C,” said Shorttle, “that means the magma would already have been hot enough to heat the tar and create our useful nitriles.”
Now the researchers say they must try to recreate these conditions in the lab, “though we don’t know for sure that these molecules started out life on Earth, we do know that life’s building blocks must be made from molecules that survived in water,” said Rimmer. “If future experiments show that the nitriles all fall apart, then we’ll have to look for a different way.”
Paul Rimmer and Oliver Shorttle, ‘A Surface Hydrothermal Source of Nitriles and Isonitriles’, Life 2024. DOI: 10.3390/life14040498
Feature image: An artist's concept of the young Earth. Credit: NASA Goddard Space Flight Center on Flickr.
Story by Dhruv Shenai, first published here.