The correct option is Loss of primordial atmosphere -> Degassing -> Photosynthesis.
Explanation
The evolution of Earth's atmosphere is a geological process generally categorized into three distinct stages: the removal of the early atmosphere, the release of gases from the Earth's interior, and the modification of the atmospheric composition by biological processes.
Chronological Analysis:
- Stage 1: Loss of Primordial Atmosphere
The early atmosphere, consisting primarily of light gases like hydrogen and helium, was stripped away by intense solar winds. This occurred shortly after the formation of the Earth when the solar wind was most powerful. - Stage 2: Degassing
As the Earth cooled, gases and water vapor were released from the interior through volcanic eruptions and fissures. This process, known as degassing, created a secondary atmosphere rich in water vapor, nitrogen, carbon dioxide, methane, and ammonia, but significantly lacking in free oxygen. - Stage 3: Photosynthesis
With the emergence of life, specifically cyanobacteria and later plants, the process of photosynthesis began. This biological process consumed atmospheric carbon dioxide and released oxygen, eventually leading to the oxygen-rich atmosphere present today.
Key Takeaway:
The correct chronological sequence for the evolution of the atmosphere is the loss of the primordial hydrogen-helium layer, followed by volcanic degassing, and finally the modification of atmospheric gases through photosynthesis.