According to scientists, a thin layer of rock 3.3 billion years old contains an unexpected treasure: organic material that was transported to Earth by meteorites when the planet was still young and was buried due to past volcanic activity.
“This is the first time we have found real evidence of extraterrestrial carbon in Earth rocks”, explained astrobiologist Frances Westall, who participated in the research.
So far, we know that organic molecules, from methane to amino acids, exist in space, and it’s possible that these molecules were brought to our planet via asteroids. Scientists studying these rocks in South Africa appear to have discovered evidence of the oldest examples of these extraterrestrial molecules.
The Makhonjwa Mountains are in eastern South Africa and Swaziland and contain 7 to 20-meter-thick deposits of 3.3 billion-year-old volcanic rocks called Josefdal Chert. Between the layers of volcanic ash are layers of carbon, deposited during periods of low volcanic activity, and the entire region appears to have been altered by the presence of water.
The researchers analyzed samples collected during field campaigns, divided them into dozens of pieces and analyzed them with electron microscopes, protons from a particle accelerator and continuous wave electron paramagnetic resonance (cw-EPR). In essence, the researchers measured how electrons in the samples responded to a slowly changing magnetic field.
Using the technique of electron paramagnetic resonance (EPR) spectroscopy, the researchers discovered that the rock had two types of insoluble organic matter, both suggesting non-Earth origins, the oldest yet identified.
The signals emitted by the equipment resemble something scientists have noticed before: ancient meteorite samples containing organic compounds.
Researchers were not surprised to find extraterrestrial material in its sediments; meteorites likely fell on ancient Earth, carrying organic carbon molecules.
What surprised them is that there were somehow enough of these materials present in the area to still be detectable 3.3 billion years later.
They proposed that perhaps the layer they analyzed could have formed after a meteor impact that produced a layer of dust in the atmosphere that settled beneath a layer of volcanic ash.
The discovery supports the idea that organic, carbon-based chemicals from space provided some of the raw materials for the first life on Earth.
However, this could complicate the search for life on other planets, as finding layers of extraterrestrial organic carbon from asteroids would hamper efforts to detect similar-looking biosignatures on other planets, such as Mars, as the signature of a deposited asteroid could match look like the signature of life.
Research continues to show that our planet’s rocks preserve an incredible history, and not just our own history, but the history of the entire Solar System.
