Primordial seawater may shed light on Earth's chemical evolution
Tests conducted by researchers in Germany on the chemical mixture present in the young Earth's oceans point to a clear chemical pathway embedded in salt crusts, which may be the key to the chemical raw materials of life. The discovery has important implications for Earth-like planets orbiting other stars, and may even add weight to the theory of life beyond planet Earth. The findings of the study were presented on 17 September 2009 by the University of Hohenheim's Dr Stephan Fox at the European Planetary Science Congress (EPSC) in Potsdam, Germany. The EPSC 2009 is organised by Europlanet Research Infrastructure (RI), which is funded under the EU's Seventh Framework Programme (FP7), in association with the European Geosciences Union. Financing for Europlanet RI stands at EUR 6 million. The researchers from the Department of Bioinorganic and Prebiotic Chemistry at the University of Hohenheim in Germany used sophisticated thermal balancing equipment to reconstruct the volcanic temperatures of up to 350° Celsius. Using this apparatus, they simulated some of the chemical processes that may have taken place along hot volcanic coasts during the Hadean era, about 4.5 to 3.8 billion years ago. The researchers initially evaporated solutions of artificial primordial seawater, and then baked the salty residue in an atmosphere of carbon dioxide (CO2) to volcanic temperatures. 'We embedded the amino acid DL-Alanine in a salt crust mixture of sodium, calcium, potassium and magnesium chlorides and, after heating, we found that a compound formed with calcium salt chemically bonded to the amino acid,' Dr Fox explained. 'This particular compound has never been seen before and, although similar compounds are known to exist, we did not expect to see them in our experiments. This bond between the salt and the amino acid stabilises the compound at high temperatures and prevents sublimation. Without the bond, pyrroles would not be able to form.' The experiments showed that 'cooking' the salt crust mixture could provide a crucial chemical explanation for prebiotic molecules. The formation of these types of compounds surprised the scientists because pyrroles are contained in chlorophyll and haeme, which is the oxygen-carrying component of haemoglobin. Dr Fox pointed out that the team's aim is to identify small molecules that may have been involved in a hypothetical next step of chemical evolution. 'Our recent results show that amino acids, peptides and pyrroles could all have been present at this stage of the Earth's evolution and would be good candidates for components of those networks,' he said. The researchers believe it is possible that the amino acids - the chemical subunits of proteins - may have been created in atmospheric reactions, perhaps during lightning discharges in clouds of volcanic ash. There is also increasing evidence that they would have been supplemented by impacting comets and meteorites.
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