It seems you're asking about the gases present in the early Earth's atmosphere, often referred to as the "primitive atmosphere". While we don't have direct samples from that time, scientists have developed hypotheses based on evidence like:

* Volcanic activity: Early Earth was very volcanically active, releasing gases like water vapor (H2O), carbon dioxide (CO2), nitrogen (N2), sulfur dioxide (SO2), methane (CH4), and ammonia (NH3).

* Meteorite composition: Meteorites contain gases that are thought to have been present in the early solar system, providing clues about the initial composition of Earth's atmosphere.

* Geochemical analysis: Studying rocks from that era helps determine the composition of the atmosphere at the time.

The most commonly accepted hypothesis for the composition of the early Earth's atmosphere is:

* Dominated by: Water vapor (H2O), Carbon dioxide (CO2), and Nitrogen (N2).

* Significant amounts: Methane (CH4), Ammonia (NH3), and Sulfur dioxide (SO2).

* Very little: Free oxygen (O2).

Important Note: This is a hypothesis, and research continues to refine our understanding of the early Earth's atmosphere.

Let me know if you'd like more information about any of these aspects!