atmosférou

Atmosférou is the gaseous envelope that surrounds a planetary body, held in place by its gravity and shaped by the body's mass, distance from its star, and chemical history. In planetary science and meteorology, atmospheres vary greatly between worlds, from nearly vacuum thin envelopes to dense, metal-rich layers, and they interact with surfaces, interiors, and space.

The composition of an atmosphere depends on the world. Earth’s atmosphere is mainly nitrogen and oxygen, with argon, carbon dioxide, neon and other trace gases. Other planets and moons show wide variation: Mars has a thin CO2-dominated atmosphere; Venus has a dense CO2-rich atmosphere with high surface pressure; gas giants possess extremely deep, hydrogen- and helium-rich atmospheres. Some bodies have atmospheres that are temporary or extremely tenuous, while others retain long-lived gaseous envelopes.

Atmospheres are structured in vertical layers, such as the troposphere, stratosphere, mesosphere, thermosphere and exosphere. In the troposphere, weather and clouds form; the stratosphere contains ozone in Earth’s case, which absorbs ultraviolet radiation; the exosphere marks the outer boundary where atmospheric particles gradually merge with space. Temperature profiles vary by world and layer, producing diverse weather, climate patterns, and photochemical processes.

Functions of an atmosphere include shielding the surface from harmful radiation, moderating surface temperatures, enabling weather and climate systems, and supporting possible chemical cycles essential for life. Atmospheres are studied with ground-based instruments, airborne and satellite platforms, and by analyzing spectra to determine composition, temperature, pressure, and dynamics. The term also appears in many languages with local spellings, reflecting a shared concept of a planetary gaseous envelope.