Astronomy
Constraints on Early Earth's Atmosphere and Habitability
Quick fact
The early Earth's atmosphere was not like today's—it was dominated by volcanic gases like carbon dioxide, nitrogen, and water vapor, with almost no oxygen. This planet-wide chemistry experiment set strict limits on when life could appear.
Why this is interesting
Earth is the only world we know with life, yet its early atmosphere was anything but friendly. What made it finally suitable for life?