Atmosphères

Atmosphères is the plural form of atmosphere in French and is used in both scientific and cultural contexts. In science, it designates the gaseous envelope surrounding a planetary body or moon, and more loosely the condition or quality of the air in a given environment. On Earth, the atmosphere is essential for weather, climate, and shielding life from space radiation.

Earth's atmosphere is mainly nitrogen and oxygen, with argon, carbon dioxide, and trace gases making up the rest. Water vapor and aerosols vary with location and season. It is layered by temperature into the troposphere, stratosphere, mesosphere, thermosphere, and exosphere, with pressure and density decreasing with altitude. Photochemistry and dynamics produce clouds, winds, and chemical cycles.

The atmosphere regulates the transfer of energy from the Sun, drives weather via convection and condensation, and sustains the hydrological cycle. It also creates the greenhouse effect, warming the surface, while ozone in the stratosphere absorbs ultraviolet radiation. Human activities alter atmospheric composition, affecting climate, air quality, and radiation balance.

Other planets and moons show a wide range of atmospheres, from thick carbon dioxide envelopes on Venus to thin air on Mars, to near-vacuum conditions on airless bodies. Exoplanets may host diverse atmospheres, from hydrogen-dominated layers to heavy vapors, with consequences for their climate and observability.

In cultural contexts, atmosphères can describe mood, tone, or ambience in literature, music, and film, reflecting place and time as vividly as a physical envelope does. In science, measurements by satellites, weather stations, and spectroscopic techniques help characterize atmosphères and their evolution.