Extraterrestrial organic matter has been found in volcanic sediment in South Africa, dating from 3.3 billion years ago.
The traces of carbon could come from ancient meteorites which hit our planet, and are thought to be the oldest extraterrestrial organic matter ever found.
The find doesn’t prove that aliens visted our planet – but it lends weight to the idea that the building blocks of life may have arrived in rocks from space.
Frances Westall from the CNRS Centre for Molecular Biophysics said, ‘This is the very first time that we have found actual evidence for extraterrestrial carbon in terrestrial rocks.
‘The organic matter from the carbon-rich meteorites must have been raining down at quite a high rate.’
Westall and her team found a 2mm thick rock layer with ‘anomalous’ signals in South Africa’s Makhonjwa Mountains.
The researchers found signals suggesting the presence of carbon, and of nanoparticles of nickel, chromium and iron, commonly found in meteorites.
The researchers say that the presence of both is puzzling.
The researchers write, ‘It is difficult to envisage a single impact event preserving both organic matter and spinel particles in such a thin sedimentary layer.
‘On the one hand, hydrogenated organic matter can survive only if the temperature of the falling matter does not exceed a few hundred degrees. On the other hand, cosmic spinels are formed by a high degree of melting of the object, as it falls towards the Earth’s surface.’