Meteorite Impacts on Early Oceans May Have Created DNA Building Blocks

Meteorite impact reactions may have generated building blocks for life in the oceans of the prebiotic Earth, says a team of scientists led by Dr Yoshihiro Furukawa of Tohoku University, Japan.

Formation of nucleobases in meteorite impact reactions. Image credit: Yoshihiro Furukawa.

All the genetic information of modern life is stored in DNA as sequences of nucleobases.

However, formation of nucleobases from inorganic compounds available on the early Earth had been considered to be difficult.

In 2009, Dr Furukawa and his colleagues from Japan reported the formation of the simplest amino acid, glycine, by simulating meteorite impacts.

“In our previous study, in which we showed the formation of glycine, solid amorphous carbon was used as the carbon source,” the scientists said.

In a new study, published in the journal Earth and Planetary Science Letters, they replaced the carbon source with bicarbonate and conducted hypervelocity impact experiments at 1 km/s using a single stage propellant gun.

“Bicarbonate, which is a common dissolved carbon species in carbon dioxide-rich atmospheric conditions, was presumably the most abundant carbon species in the early oceans and in post-impact plumes,” Prof Furukawa and co-authors explained.

They found the formation of nucleobases (cytosine and uracil), various proteinogenic amino acids (glycine, alanine, serine, aspartic acid, glutamic acid, valine, leucine, isoleucine, and proline), non-proteinogenic amino acids, and aliphatic amines.

“The present results expand the possibility that impact-induced reactions generated various building blocks for life on the prebiotic Earth in large quantities through the use of terrestrial carbon reservoirs,” they said.

“Such impact-induced reactions could have produced organics in extraterrestrial bodies that were covered by oceans or ice containing ammonia and bicarbonate.”

“This possibility suggests a new genetic model for the formation of organic molecules on other planets and comets.”

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Yoshihiro Furukawa et al. Nucleobase and amino acid formation through impacts of meteorites on the early ocean. Earth and Planetary Science Letters, published online August 16, 2015; doi: 10.1016/j.epsl.2015.07.049