Chemical analysis of some of the world鈥檚 oldest rocks, by an international team led by 黑料不打烊 University researchers, has provided the earliest record yet of Earth's atmosphere. The results show that the air 4 billion years ago was very similar to that more than a billion years later, when the atmosphere -- though it likely would have been lethal to oxygen-dependent humans -- supported a thriving microbial biosphere that ultimately gave rise to the diversity of life on Earth today.