According to one theory, what was the Earth's early atmosphere similar to?

The Earth’s early atmosphere is thought to have been similar to that of Mars and Venus today because both of these planets have atmospheres rich in carbon dioxide and lacking in oxygen. When Earth was forming, it experienced high volcanic activity which would have released gases like carbon dioxide, water vapor, and ammonia, closely resembling the current conditions on Mars and Venus.

The comparison with Mars and Venus is particularly significant because their atmospheres are heavily influenced by greenhouse gases, making them inhospitable for life as we know it. This idea supports theories about the evolution of Earth's atmosphere, suggesting that it may have transitioned from a hostile environment to one capable of supporting diverse life forms through processes like photosynthesis, which increased the oxygen content over geological time. Understanding the composition of the early Earth's atmosphere in relation to these planets helps scientists piece together the history of our planet and the development of life.