A team of geochemists at the University of California-Los Angeles (UCLA) has found evidence that life on our planet arose at least 4.1 billion years ago, some 300 million years earlier than previously thought, and not long after Earth formed 4.54 billion years ago. That primitive world was therefore not the dry and desolate place that scientists have described until now.
The study, published in the Proceedings of the National Academy of Sciences , would have been considered a “heresy” 20 years ago, when it was already difficult to accept that life had started 3.8 billion years ago, according to Mark Harrison, one of its authors and professor of Geochemistry at UCLA: “The truth is that terrestrial life must have arisen almost immediately , since with the necessary ingredients, it sprouts very quickly,” he adds.
This new research suggests that life already existed before the massive bombardment of the Solar System that formed the large craters on the Moon 3.9 billion years ago. “If all the signs of life had disappeared during the bombing, as some scientists argue, they should have reappeared very soon,” says Patrick Boehnke, another of the study participants. Experts have long believed that our The planet was originally a desolate desert , but this research denies it.
For Harrison, “it probably looked a lot like Earth today.” UCLA researchers, led by Elizabeth Bell, have analyzed more than 10,000 zircons, a type of mineral that formed from molten rocks or magmas , in this case from Western Australia.
Zircons are heavy and durable minerals, considered among the oldest and most abundant in the earth’s crust, capable of capturing and preserving elements from their closest environment, which is why they can serve as time-indicating capsules. Among them, they identified 656 zircons that contained dark specks that could indicate the existence of molecules and chemical structures of ancient three-dimensional microorganisms.
One of the zircons even contained graphite, or carbon, which is the basic element of life. Harrison, Bell, and the rest of the team are convinced that this 4.1 billion-year-old zircon has characteristics – a specific fringe between carbon-12 and carbon-13 – that indicate the presence of photosynthetic life.
