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Meteorites and gamma rays may have led to life on Earth

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Even though the James Webb Space Telescope’s detailed images of distant galaxies show us a larger part of the universe, scientists still don’t agree on how life came to be here on Earth. One hypothesis is that meteorites brought amino acids , the “building blocks of life”, to our planet. Now, researchers have told the ACS Central Science journal that they have experimentally demonstrated that amino acids may have formed in these early meteorites from reactions driven by gamma rays produced within space rocks.

 

Ever since Earth was a recently formed barren planet, meteorites have been hurtling at high speed through the atmosphere towards its surface. If the initial space debris had included carbonaceous chondrites – a class of meteorites whose members contain significant amounts of water and small molecules, such as amino acids – then they could have contributed to the evolution of life on Earth. However, the source of the amino acids in meteorites has been difficult to pinpoint. In previous laboratory experiments, Yoko Kebukawa and colleagues have shown that reactions between simple molecules, such as ammonia and formaldehyde, can synthesize amino acids and other macromolecules, but liquid water and heat are required. The radioactive elements, such as aluminum-26 (26Al) – which is known to have existed in the first carbonaceous chondrites – when they decay they release gamma rays, a form of high-energy radiation. This process could have provided the heat required for the production of biomolecules . Kebukawa and colleagues therefore wanted to see if radiation could contribute to the formation of amino acids in the first meteorites.

They dissolved formaldehyde and ammonia in water, sealed the solution in glass test tubes and then irradiated the test tubes with high-energy gamma rays produced by the decay of cobalt-60. . They found that the production of α-amino acids, such as alanine, glycine, α-aminobutyric acid and glutamic acid, and β-amino acids, such as β-alanine and β-aminoisobutyric acid, increased in irradiated solutions with increasing total dose of gamma rays. Based on these results and the predicted gamma ray dose from the decay of aluminum-26 in the meteorites, the researchers estimated that it would take between 1,000 and 100,000 years to produce the amount of alanine and β-alanine found in the Murchison meteorite, which landed in Australia in 1969. This study provides evidence that reactions catalyzed by gamma rays can produce amino acids, possibly contributing to the origin of life on Earth, say researchers .

  • Gamma-Ray-Induced Amino Acid Formation in Aqueous Small Bodies in the Early Solar System (pubs.acs.or)
 
 

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