Scientists Discover the Oldest Space Rocks Ever Found on Earth
Scientists have just unearthed the oldest meteorites ever discovered. These micrometeorites came to Earth in the form of shooting stars 2.7 billion years ago, and have persisted since then in the limestone Tumbiana Formation of Western Australia.
Not only are these rocks a piece of Earth's history in themselves, they have traces of Earth's early atmosphere that give us a glimpse into its composition. The most significant insight gleaned so far is the presence of oxygen, since the meteorites come from a time when scientists thought the atmosphere was mostly anoxic.
There have been several respected studies which indicate that there were only small traces of oxygen in Earth's atmosphere during this time period, but they all focused on the lower atmosphere. The researchers believe that the meteorites have captured Earth's upper atmosphere, approximately 75 km above sea level. The levels were not only higher than scientists originally thought, they were nearly as high as the oxygen levels today: up to 20%. The oxygen would have been formed from ultraviolet light splitting atoms of elements such as hydrogen, carbon dioxide, and sulphur dioxide at high altitudes, releasing the oxygen atoms in the upper atmosphere.
Studying these meteorites and others like them is a veritable treasure trove of information about the early life of our planet, and according to Tompkins, we could conduct similar studies on extraterrestrial meteorites when we visit other planets: