Scientists from the Foundation for Applied Molecular Evolution announced that ribonucleic acid (RNA), an analog of DNA that was probably the first genetic material for life, spontaneously forms on basalt lava glass. There was plenty of such glass on Earth 4.35 billion years ago. Similar basalts of such antiquity survive on Mars today.
A study led by Eliza Biondi shows that long RNA molecules, 100-200 nucleotides in length, are formed when nucleoside triphosphates seep through basalt glass.
“Basaltic glass was everywhere on Earth at the time,” remarked Stephen Mojzsis, an Earth scientist who also participated in the study. “For several hundred million years after the Moon formed, frequent impacts coupled with abundant volcanism on the young planet formed molten basaltic lava, the source of the basalt glass. Impacts also evaporated water to give dry land, providing aquifers where RNA could have formed.”
The same blows delivered nickel, which the team showed formed nucleoside triphosphates from nucleosides and activated phosphate, also found in lava glass. Borate, also from basalt, controls the formation of these triphosphates. The same impactors that formed the glass also reduced the atmosphere for a short time with their metallic iron-nickel cores. RNA bases, the sequences which store genetic information, are formed in such atmospheres. The team previously showed 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 highschoolers in chemistry class,” said Jan Špaček, who was not involved in this study but who develops an instrument to detect alien genetic polymers on Mars. “Mix the ingredients, wait for a few days and detect the RNA.”
Thus, this work completes the pathway that creates RNA from small organic molecules that were almost certainly present on early Earth. A single geological model ranges from one and two carbon molecules to RNA molecules long enough to support Darwinian evolution.
“Important questions remain,” cautions Benner. “We still do not know how all of the RNA building blocks came to have the same general shape, a relationship known as homochirality.” Likewise, the linkages between the nucleotides can be variable in the material synthesized on basaltic glass. The import of this is not known.
Mars is relevant to this article because the same minerals, glasses, and impacts were also present on Mars in ancient times. However, Mars was not affected by the drift of continents and plate tectonics, which buried most of the rocks from Earth older than 4 billion years. Thus, the rocks of the appropriate time remain on Mars. Recent missions to Mars have discovered all the necessary rocks, including borate.
“If life emerged on Earth via this simple path, then it also likely emerged on Mars,” said Benner. “This makes it even more important to seek life on Mars as soon as we can.”
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