Hadean

The Earth’s surface was largely molten during much of the Hadean, with water vapor and volcanic outgassing playing significant roles in shaping its early atmosphere. 

During the Hadean, the Earth was still undergoing accretion, a process by which particles in the early solar system clumped together to form larger bodies. The planet’s surface was dominated by magma oceans, and its atmosphere was composed primarily of hydrogen, helium, methane, ammonia, and water vapor—substances that were released by volcanic activity. These early conditions were hostile to life as we know it. Geological evidence of this time comes mainly from detrital zircons, which are the oldest minerals ever found, providing clues to the cooling and solidification of the Earth’s crust. 

Research on ancient zircons from the Jack Hills in Western Australia suggests that the Earth’s crust may have cooled enough by around 4.4 billion years ago to allow liquid water to exist, possibly forming the first oceans, which would have been critical for the development of a habitable environment.