Early Life On Earth: Could Salt Crusts Be Key Ingredient In Cooking Up Prebiotic Molecules?
ScienceDaily (Sep. 17, 2009) — German scientists investigating the complex chemical mixture thought to be present in the early Earth’s oceans have found that amino acids can be ‘cooked’ into many other important chemical building blocks of life when embedded in salt crusts.
Results of the laboratory experiments will be presented by Dr Stefan Fox at the European Planetary Science Congress in Potsdam, Germany, on Thursday 17 September.
Approximately 4.5 - 3.8 billion years ago, the Earth was probably covered by a salty ocean, rich in organic compounds, dotted with active volcanic islands and short-lived continents. The team from the University of Hohenheim in Stuttgart has simulated some of the chemical processes that might have taken place along hot volcanic coasts during this Hadean era by evaporating solutions of artificial primordial seawater and then baking the salty residue in an atmosphere of nitrogen and carbon dioxide to volcanic temperatures of 350 degrees Celsius. They found that compounds such as pyrroles, which are contained in chlorophyll and haeme (the oxygen-carrying component of haemoglobin), are created.
A synthetic salt crust obtained from artificial sea salt and an alpha-amino acid. (Credit: Bioinorganic and Prebiotic Chemistry Department, Univ. Hohenheim)
The group’s experiments show that interaction of amino acids with metal ions in the salt crusts fundamentally changes the thermal behaviour of the molecules, preventing them from turning into gas at high temperatures and allowing unexpected compounds to form.
“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. 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,” said Dr Fox.
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