Ancient Soils found in Western Australia

A week or so ago, scientists reported that soils collected in Western Australia contain tiny micrometeorites, compact balls of cosmic dust. When these soils were formed, about 2.7 billion years ago, cosmic debris was penetrating our atmosphere and seeding the ground with cosmic dust which persists in our soils today.

High-resolution microscope view of a tiny iron micrometeorite the size of a grain of sand. Analysis of these particles shows that Earth’s atmosphere used to contain a lot more carbon dioxide 2.7 billion years ago. Image via Andrew Tomkins/ Penn State.

The study of these micrometeorites is revealing the chemistry of Earth’s atmosphere nearly three million years ago and should also reveal the chemistry, and possibly some of the biology, of our ancestral soils.  

These new peer-reviewed findings were published in the journal Proceedings of the National Academy of Sciences on January 21, 2020, with one of the authors, Owen Lehmer, from the University of Washington. As the authors explain:

“Carbon dioxide concentrations have varied widely over the Earth’s 4.54-billion-year history. This new work helps quantify the elements that made up Earth’s atmosphere in the very distant past.

The tiny iron micrometeorites that were studied are no larger than grains of sand. They were discovered in ancient soils – called paleosols – that are about 2.7 billion years old. The soils were collected in the Pilbara region of Western Australia. These scientists believe the micrometeorites fell from space during the Archean eon, when the sun was weaker than today.”