Up in the Makhonjwa Mountains of South Africa is a sliver of volcanic rock originating from 3.3 billion years ago.
More than its age, scientists are awestruck at what they found within the ancient rock: evidence of organic matter from outer space.
"This is the very first time that we have found actual evidence for extraterrestrial carbon in terrestrial rocks," Frances Westall, study author and astrobiologist at the CNRS Centre for Molecular Biophysics, told New Scientist.
Plenty of previous research have suggested that organic molecules that kick-started life on Earth came from outer space, brought to the planet by asteroids.
Westell and her colleagues' new findings published in the journal Geochimica et Cosmochimica Acta support these theories and open up more possibilities about extraterrestrial life.
South America's Extraterrestrial Organic Matter
In the Moakhonjwa Mountain region, the scientists analyzed a volcanic deposit known as the Josefsdal Chert. With the use of electron paramagnetic resonance spectroscopy, they discovered that a 2-millimeter rock layer in the deposit contained two types of organic matter that point distinctly at extraterrestrial origins.
One of the strange EPR signals detected is similar to signals found in carbonaceous chondrites, which are primitive meteorites rich in organic compounds.
The other anomalous signal suggests the presence of nanoparticles of nickel, chromium, and iron, which isn't typically seen in rocks of terrestrial origins. Known as cosmic spinels, these are formed upon the entry of extraterrestrial objects in the planet's atmosphere, according to study author Didier Gourier from PSL Research University in a paper published in 2018.
The presence of these two EPR signals in such a thin layer of sediment from the same time period is something that's puzzling to the scientists, Science Alert notes. Hydrogenated organic matter from the carbonaceous chondrites survive only if the temperature of the falling object isn't any higher than a few hundred degrees, while cosmic spinels form only if the object melts from an extremely high temperature while falling to Earth.
The authors hypothesized that the layer formed when a meteor impact created a cloud of dust particles that ended up getting preserved under a layer of volcanic ash.
"The organic matter from the carbon-rich meteorites must have been raining down at quite a high rate," Westall said.
The Hunt For Alien Life Becomes More Challenging
While the study findings is significant and supports the theory that carbon-rich meteors deposited life-forming matter to Earth, it may make it more complicated to find evidence of life in other planets such as Mars.
After all, the biosignature of organic matter deposited by asteroids can look very similar to the signature of life originating from a planet.