Evidence for life on Earth 4.1 billion years ago has been found in a speck of graphite within a zircon mineral from Western Australia. This estimate is 300 million years older than previously though and suggests that life on Earth started almost instantly after the planet formed. The results of this study were published in the Proceedings of the National Academy of Sciences this week, and have significant implications for the presence of life across the universe.
Scientists from UCLA have carefully studied more than 10,000 individual Zircon crystals for traces of biogenic carbon, and used Raman Spectroscopy to study the 3D structure and composition of the ancient microorganisms. Zircon is a mineral that forms from magmas, trapping small inclusions during growth which preserve details of their formation environment. Zircon is a durable mineral which is not often altered after formation and so acts as miniature time capsule. Zircon contains radioactive uranium and its daughter product lead, and the ratio between these elements allow the age of the mineral to be determined.
The graphite (pure carbon) inclusion identified within the zircon is thought to be biogenic in origin, and the ratio of carbon-12 to carbon-13 suggests the presence of photosynthetic life. The new age for life existing on Earth 4.1 billion years ago, is 300 million years older than previously thought. This age is also significant as it suggests that life either survived or revived after the late heavy bombardment of the Earth and other terrestrial planets 3.9 billions years ago. It also suggests we need to rethink our idea of the early earth being a dry, hot, hellish world, as it would appear that the Earth as we know it today has been the same for 4 billion years.