Pyrite could play an important role in the origin of life


Figure: Planetary Atmosphere and Surfaces Chamber (PASC) at the Astrobiology Center.


Researchers from the Centro de Astrobiología (CAB, CSIC-INTA) have discovered a new mechanism of abiotic fixation of atmospheric nitrogen by pyrite. This process may have relevant implications for both prebiotic chemistry and habitability and origin of life.


Nitrogen is an essential chemical element for life, as it is one of the components of enzymes and genes. Although the Earth's atmosphere is composed of almost 80% molecular nitrogen, N2 is an exceptionally inert compound (it does not react easily with other compounds due to the high energy required to break each of the three bonds of the compound) and cannot be used directly by most living things. To do this it is necessary that molecular nitrogen is combined with oxygen or hydrogen to form compounds such as oxides or ammonium, which can be incorporated into the biosphere. This process by which nitrogen can be used by microorganisms is called nitrogen fixation.

Currently, nitrogen fixation in Earth is predominantly biological, and is caused by the conversion of molecular nitrogen to ammonia through chemical reactions catalyzed by enzymes. But, given the need for nitrogen, a prerequisite for the origin and evolution of life on Earth is the existence of abiotic processes (without intervention of living beings) that provide a source of nitrogen in a form that is biochemically usable.

Due to the high energy needed to break nitrogen bond, some of the abiotic nitrogen-fixing mechanisms that have been postulated on Earth had to be very energetic, such as atmospheric electrical appliances, volcanism or meteorite impacts on the ancient oceans.

A new study by researchers from the Centro de Astrobiología published today in the journal Scientific Reports shows that the surface of pyrite (iron sulphide) induces the abiotic fixation of atmospheric nitrogen on the surface of said Mineral. "We have found that, by means of photocatalysis induced by ultraviolet radiation in pyrite, nitrogen fixation occurs in the form of ammonium sulfate, which can be released by being in contact with an aqueous solution", explains Eva Mateo-Martí, CAB researcher and lead author of the study. "This process may have relevant implications both in prebiotic chemistry and in different planetary environments for habitability and origin of Life," he adds.

This study has been conducted under controlled conditions in the Planetary Atmosphere and Surfaces Chamber (PASC) simulation chamber at the Centro de Astrobiología, and by infrared spectroscopy (IR) and X-ray photoemission (XPS) has been able to confirm and identify the surface-fixed compound.


Fuente: UCC-CAB

Fecha: 2019-10-25


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