158
After studying the role of iron sulfide in the chemical reactions that could have led to the origin of life on our planet, an international research team has discovered in laboratory conditions processes that contribute to the transformation of carbon dioxide (CO2) into organic molecules of ancient hot springs. The discovery will help explain the origin of molecules — precursors of life, and will also be useful to astrobiologists.
When life on Earth was just beginning, hot springs and minerals containing iron sulfide (FeS) may have played a key role in its emergence. This inorganic compound is known for its ability to accelerate chemical reactions and resembles coenzymes involved in modern biochemical processes.
That is why, in 1988, the German lawyer and chemist Günter Wechtershäuser proposed the hypothesis of the world of iron sulfides, according to which the first organism on Earth originated in a volcanic hydrothermal flow (at high temperature (100°C) and high pressure) on the surface of sulfide crystals. This life form with a complex chemical structure used catalytic centers based on transition metals such as iron and nickel (and possibly zinc, cobalt, manganese and tungsten).
However, the role of iron sulfides in the conditions prevailing in ancient times hot sources, still remained poorly studied.
A team of scientists led by Jingbo Nan from the Nanjing Institute of Geology and Paleontology (PRC) and Martin J. Van Kranendonk from the University of New South Wales (Australia) modeled the environment of ancient hot springs in the laboratory. This allowed them to study in detail the role of iron sulfides in carbon fixation at the first stage of the evolution of life.
Using an anaerobic chamber and gas chromatography (a physical-chemical separation method), the researchers synthesized a series of nanosized iron sulfides from mackinawite, including pure iron sulfide and iron sulfides enriched in common elements from hot springs (marga).
Scientists found that at a temperature of 120°C, manganese-enriched iron sulfide increased the production of methanol (CH₃OH) by five times compared to pure iron sulfide. Recall that methanol is a simple organic molecule that could serve as a building block for more complex compounds.
The catalytic activity of iron sulfide was also enhanced by exposure to ultraviolet and visible light. This is important because at the dawn of life, solar radiation was probably more intense and played an important role in chemical processes on the planet's surface. Thus, experiments in laboratory conditions and theoretical calculations showed that the intermediate product resulting from the reverse reaction of the "water-gas" shift was carbon monoxide (CO), which was then transformed into methanol.
The discovery will help to understand how simple inorganic compounds could be transformed into organic molecules without the participation of living organisms, and to explain the emergence of the first molecules — precursors of life on Earth, and even to determine the conditions that contributed to this. The results may be useful for astrobiologists to search for life on other planets with similar conditions.
