Scientists from the Foundation for Applied Molecular Evolution announced today that ribonucleic acid (RNA), an analog of DNA that was likely the first genetic material of life, forms spontaneously on basalt lava glass. This glass was abundant on Earth 4.35 billion years ago. Similar basalts from this antiquity survive on Mars today.
“Communities studying the origins of life have diverged in recent years,” noted Steven Benner, co-author of the study published online in the journal Astrobiology.
“A community revisits classic questions with complex chemical schemes that require difficult chemistry performed by skilled chemists,” Benner explained. “Their beautiful craftsmanship appears in brand reviews such as Nature and Science.” However, precisely because of the complexity of this chemistry, it cannot explain how life actually originated on Earth.
In contrast, the Foundation study takes a simpler approach. Led by Elisa Biondi, the study shows that long RNA molecules, 100 to 200 nucleotides long, are formed when nucleoside triphosphates just percolate through basalt glass.
“Basalt glass was everywhere on Earth back then,” noted Stephen Mojzsis, an Earth scientist who also participated in the study. “For several hundred million years after the formation of the Moon, frequent impacts coupled with abundant volcanism on the young planet formed molten basalt lava, the source of basalt glass. The impacts also evaporated the water to give dry land, providing aquifers where RNA could have formed.”
The same impacts also delivered nickel, which the team says yields nucleoside triphosphates from nucleosides and activated phosphate, also present in lava glass. Borate (as in borax), also from basalt, controls the formation of these triphosphates.
The same impactors that formed the glass also transiently reduced the atmosphere with their iron-nickel metal cores. RNA bases, whose sequences store genetic information, are formed in such atmospheres. The team had previously shown that nucleosides are formed by a simple reaction between ribose phosphate and RNA bases.
“The beauty of this model is its simplicity. It can be tested by high school students in chemistry class,” said Jan Špaček, who was not involved in this study but is developing an instrument to detect extraterrestrial genetic polymers on Mars. . “Mix the ingredients, wait a few days and detect the RNA.”
The same rocks solve the other paradoxes by making RNA in a path that goes from simple organic molecules to the first RNA. “For example, borate drives the formation of ribose, the ‘R’ in RNA,” Benner added. This path starts from simple carbohydrates that could “not” form in the atmosphere above early Earth. These were stabilized by volcanic sulfur dioxide and then rained down to the surface to create reservoirs of organic minerals.
Thus, this work completes a pathway that creates RNA from small organic molecules that were almost certainly present on early Earth. A unique geological pattern scales from one to two carbon molecules to yield RNA molecules long enough to support Darwinian evolution.
“Important questions remain,” warns Benner. “We still don’t know how all the building blocks of RNA came to have the same general shape, a relationship known as homochirality.” Similarly, the bonds between nucleotides can be variable in the material synthesized on basalt glass. The import of this is not known.
Mars is relevant to this announcement because the same minerals, glasses, and impacts were also present on Mars from this antiquity. However, Mars did not suffer from continental drift and plate tectonics which buried most of Earth’s rocks dating back more than 4 billion years. Thus, rocks from the relevant epoch remain on the surface of Mars. Recent missions to Mars have found all the necessary rocks, including borate.
“If life emerged on Earth via this simple path, then it probably also emerged on Mars,” Benner said. “This makes it even more important to search for life on Mars as soon as possible.”
Mars meteorite shows evidence of massive impact billions of years ago
Craig A. Jerome et al, Catalytic Polyribonucleic Acid Synthesis on Prebiotic Rock Glasses, Astrobiology (2022). DOI: 10.1089/ast.2022.0027
Hyo-Joong Kim et al, Stereoselective prebiotic synthesis of purine and non-canonical pyrimidine nucleotide from nucleobases and phosphorylated carbohydrates, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1710778114
Hyo-Joong Kim et al, A prebiotic synthesis of canonical pyrimidine and purine ribonucleotides, Astrobiology (2019). DOI: 10.1089/ast.2018.1935
Provided by the Foundation for Applied Molecular Evolution
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