A paleoatmosphere refers to an atmosphere that existed in the past on Earth. It is not the current atmosphere or an atmosphere on another planet. The term “paleo-” indicates a geological timescale, suggesting that the paleoatmosphere represents the atmospheric conditions that prevailed during specific periods of Earth’s history. By studying proxy materials and fossil data, scientists can infer the composition and characteristics of these ancient atmospheres, providing insights into Earth’s atmospheric evolution over time.