Scientists at the Foundation for Applied Molecular Evolution announced today that ribonucleic acid (RNA), a DNA analog that was likely the first genetic material for life, forms spontaneously in basalt lava glass. This type of glass was abundant on Earth 4.35 billion years ago. Similar basalts of this age survive on Mars today.

“Communities studying the origins of life have diverged in recent years,” said Steven Benner, co-author of the study that appears online in the journal Astrobiology.

“A community revisits classical questions with complex chemical schemes that require difficult chemistry performed by expert chemists,” Benner explained. “Their beautiful craftsmanship appears in brand name magazines such as Nature and Science.” However, precisely because of the complexity of this chemistry, it is not possible to explain how life on Earth actually originated.

In contrast, the Foundation’s study takes a simpler approach. Led by Elisa Biondi, the study shows that long RNA molecules, 100 to 200 nucleotides in length, are formed when nucleoside triphosphates do nothing more than seep through basalt glass.

“Basalt glass was everywhere on Earth at that time,” says Stephen Mojzsis, an Earth scientist who also participated in the study. “For several hundred million years after the Moon formed, frequent impacts along with abundant volcanism on the young planet formed molten basaltic lava, the source of basalt glass. The impacts also evaporated water to give dry land, providing aquifers where RNA could have formed.”

The same impacts also dropped nickel, which the team showed produces nucleoside triphosphates from nucleosides and activated phosphate, which are also found in lava glass. Borate (like borax), also from basalt, controls the formation of these triphosphates.

The same impactors that formed the glass also temporarily reduced the atmosphere with their iron-nickel metal cores. In such atmospheres, RNA bases are formed, whose sequences store genetic information. 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 alien genetic polymers on Mars. “Mix the ingredients, wait a few days and detect the RNA.”

The same rocks resolve the other paradoxes by producing RNA in a path from simple organic molecules to the first RNA. “For example, borate manages the formation of ribose, the ‘R’ in RNA,” Benner added. This pathway starts from simple carbohydrates that “could not have formed” in the atmosphere on the early Earth. These were stabilized by volcanic sulfur dioxide and then rained down to the surface to create organic mineral deposits.

Thus, this work completes a pathway that creates RNA from small organic molecules that were almost certainly present on the early Earth. A single geological model starts from one and two carbon molecules to give RNA molecules long enough to support Darwinian evolution.

“There are still important questions,” 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.” Likewise, the bonds between the nucleotides may be variable in the material synthesized on basaltic glass. The significance of this is unknown.

Mars is relevant to this announcement because the same minerals, glasses and impacts were also present on the Mars of that ancient time. However, Mars has not suffered from the continental drift and plate tectonics that buried most of Earth’s rocks more than 4 billion years old. Therefore, rocks from the era in question remain on the surface of Mars. Recent missions to Mars have found all the necessary rocks, including borate.

“If life arose on Earth through this simple path, then it probably arose on Mars as well,” Benner said. “This makes it even more important to search for life on Mars as soon as possible.”