How did molecular oxygen (O₂)get into Earth's atmosphere?

Question

Quizplus · Accepted Answer

Molecular oxygen (O₂) was released by life through the process of photosynthesis. Early bacteria and algae began to produce oxygen as a waste product, which eventually accumulated in Earth's atmosphere. This process took billions of years and played a crucial role in the development of the atmosphere and the evolution of life on Earth. Option B is incorrect as molecular oxygen could not have been captured from the solar nebula as it requires a planet like Earth that can support life. Option C is not completely incorrect as volcanoes do release oxygen, but it is not in the form of molecular oxygen. Option D is incorrect as there is no evidence to suggest that molecular oxygen came from chemical reactions with surface rocks.

How Did Molecular Oxygen (O₂)get into Earth's Atmosphere