While exploring a region in Australia, experts from the University of Western Australia and the University of Cambridge discovered ancient rocks that shed light on the emergence of life on Earth.
Discovery of Jaspilite
The 3.5-billion-year-old rocks were obtained from Pilbara, a region of northwest Australia renowned for preserving the Earth's crust during the Archean era. Since this era is the period in history when life was just getting started, the rocks serve as a time capsule that contains insights into prebiotic chemistry.
When viewed from afar, Pilbara's stripy red rock is a mix of very fine quartz (made of silicon and oxygen) and hematite (containing iron and oxygen). The combination of these minerals is called jaspilite.
Upon closer inspection, researchers found that the rocks contain hidden nanocrystals with exciting properties. The jasper beads contain fine particles of greenalite that would have ejected from a nearby hydrothermal vent and settled at the bottom of the seafloor billions of years ago.
Hidden between the iron oxides, which give the rock its bright color, are much more abundant iron clays. According to geologist Birger Rasmussen from the University of Australia, these nanoparticles are so old that they were sealed partly because of the chemically inert materials.
In terms of structure, greenalite is unusual at the nanoscale. Its particle edges are corrugated because of a misalignment in its crystal structure between the iron-rich octahedral layers and the silica-rich tetrahedral layers.
The mineral also produces a series of parallel grooves on the edges, which are the perfect size for molecules such as RNA and DNA. As such, the clay nanoparticles serve as the ideal catalytic tool for aligning the components of the biomolecules to make them easily click together. The 3.5-billion-year-old rocks from Pilbara also contained fluorapatite, a mineral composed of oxygen, fluorine, calcium, and phosphorus.
For many years, scientists have been puzzled over the abundance of phosphorus in many biological structures, like DNA, lipids, and membranes, despite low concentrations of elements in the ocean. The presence of fluorapatite in prehistoric rock provides a potential explanation: hydrothermal vents could have been a primitive source of accessible phosphorus. In short, life selected phosphorus for many essential biochemical processes because it was much more abundant during life's origin and early evolution.
Hidden Clues on Life's Origins
It is believed that billions of years ago, hydrothermal vents produced trillions of microscopic clay particles containing grooves that acted like assembly lines, concentrating on RNA or pre-RNA. These vents have long been considered a potential place for the emergence of life, providing the ideal location for this process.
As described by Rasmussen, the hydrothermal vents are a great place for chemical reactions since they are areas of extreme gradients, constantly churn seawater through magma chambers, and spew hot, smoky plumes filled with nutrients back into the ocean. The researchers' modeling also reveals that the concentration of phosphorus in deep seawater billions of years ago was possibly 10 to 100 times higher than it is today.
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