The oldest sedimentary rocks
on the planet are 3.7 billion years old. They seem to indicate that the climate
was about 10 ºC warmer than now.
The atmosphere would have
mainly the composition of volcanic gases, such as water, carbon oxides, sulfur
oxides and chlorine, nitrogen and hydrogen, as well as ammonia and methane.
The first primitive life may
have appeared at 3.8 billion years.