If you’ve read anything about the early days of Earth, you’ve read about how our home planet had a thick, heavy atmosphere, filled with greenhouse gases that trapped heat and allowed early plants and other organisms to take root and ultimately thrive. That was the prevailing scientific consensus.
Recent studies of gas bubbles trapped in a lava flow that occurred 2.7 billion years ago show that the atmosphere of the early Earth was much, much thinner than scientists had assumed — less than half as thick, in fact, as our current atmosphere. That’s a surprise, because it is clear that the sun was weaker in those days, and a thick atmosphere was thought to be needed to make the Earth warm enough to support life. With a thin atmosphere, Earth must have been a daunting place for the early photosynthetic life forms — but somehow those hardy little creatures survived anyway and started the process that ultimately led to . . . us.
It’s long been clear that the environment of planet Earth is ever-changing, but the studies of the gas bubbles indicates that the changes over time are even more significant than was suspected. That’s an interesting discovery, but it might also have practical consequences in our search for life forms on other moons and planets. Scientists searching for extraterrestrial life tend to look for planets that are “Earth-like” in the sense of modern-day Earth — but it turns out our own planet wasn’t very “Earth-like” at all in its early days. The range of places that could support life therefore is likely much wider than previously suspected.
So scientists are wrong about the early atmosphere on Earth, just as they have been wrong about countless other things during the long and rich history of science. That’s the great thing about science — inaccuracy and failed hypotheses are just an inevitable part of the process. In this case, the scientific error also happens to tell us something useful and gratifying about just how tenacious life forms can be.