The Atmosphere: Connections with the Earth’s Mass and Distance from the Sun

This book investigates the billion-year takeover of planet Earth by its organisms and ecosystems. This chapter explores the original nature of the Earth’s atmosphere in the Solar System and some of its connections with organisms, and considers the main atmospheric gases and their interactions with ecosystems. It also examines: the atmosphere of Earth and the other planets in the Solar System, and that of exoplanets, that is, planets outside the Solar System; astronomical and planetary effects on the Earth’s atmosphere; and the connections between atmosphere and climate. The atmospheres of some the numerous moons of planets Jupiter, Saturn and Neptune, and of dwarf planet Pluto are also included. The main atmospheric gases considered in this chapter are: water vapour, nitrogen, oxygen, ozone, carbon dioxide, and methane. The consideration of exoplanets leads to the notion of habitability and the Goldilocks principle, which refers to the children’s story “The Three Bears”. It is explained that two conditions that allow planet Earth to retain its atmosphere are its relatively large mass and safe distance from the Sun. Comparing the different atmospheres of Earth and Venus shows that the natural greenhouse effect can hinder or favour organisms and ecosystems. Different environmental conditions on the two planets led Earth to lose most of its atmospheric carbon, whereas Venus retained an atmosphere with a very high concentration of carbon dioxide (CO2). The chapter ends with a summary of key points concerning the interactions between the Solar System, Earth, its atmosphere, and its ecosystems.