The Murchison meteorite contains complex organic molecules – including carbon, hydrogen, oxygen, nitrogen and sulphur.

Credit: Wikimedia

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SYDNEY: Previously unknown organic molecules have been discovered in a 100 kg meteorite that hit Australia in 1969, suggesting that our early Solar System contained a soup of highly complex organic chemistry long before life appeared.

In a recent study scientists analysed the Murchison meteorite, which landed in Murchison near Melbourne, Australia, in 1969.

The meteor is thought to have originated in the early days of our Solar System, perhaps even before the Sun formed around four and a half billion years ago.

Previous studies emphasised simple molecules

Murchison is one of the most studied meteorites, already recognised for the diversity of its organic chemistry – the chemistry of compounds containing carbon.

While 70% of the carbon content in the meteorite has been classified as insoluble, previous studies have identified more than 500 organic chemical structures in the soluble fraction, resembling known biomolecules.

However, analyses of the solvent extracts up until now have all been targeted to selected classes of compounds with an emphasis on amino acids as a potential source of life on Earth, according to the study published in the U.S. journal, Proceedings of the National Academy of Sciences.

Large chemical diversity

Now, for the first time, scientists have used advanced ultra-high resolution mass spectrometry to conduct a non-targeted experiment.

In previous studies, the average formula was C₁₀₀H₇₀O₁₂N₃S₂, with a high degree of aromaticity in the associated compounds. In this study, researchers found an average formula of C₁₀₀H₁₅₅O₂₀N₃S₃, showing a higher oxygen content and higher aliphaticity (hydrogen-rich compounds not containing aromatic rings).

In old studies and in this new study, only a small number of molecules contained phosphorous, the other of the six major elements involved in life.

The researchers found 14,197 distinct elemental formulas. Taking into account the limitation of the instrument used, the researchers estimate that there may actually be more than 50,000.

Each elemental formula can have a number of different physical structures, called isomers. The molecules that the researchers discovered are large, and contain a high proportion of atoms other than carbon and hydrogen, which makes the number of possible isomers huge. The researchers estimate a “realistic minimum of several thousand isomers for any given elemental composition”.

In total, they estimate that “several millions of different chemical compounds might be present … as a result of abiotic chemistry.”