Atmosphere

[2] Most organisms use oxygen for respiration; lightning and bacteria perform nitrogen fixation which produces ammonia that is used to make nucleotides and amino acids; plants, algae, and cyanobacteria use carbon dioxide for photosynthesis.

The layered composition of the atmosphere minimises the harmful effects of sunlight, ultraviolet radiation, solar wind, and cosmic rays and thus protects the organisms from genetic damage.

The current composition of the atmosphere of the Earth is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms.

Because of the latter, such planetary nucleus can develop from interstellar molecular clouds or protoplanetary disks into rocky astronomical objects with varyingly thick atmospheres, gas giants or fusors.

Composition and thickness is originally determined by the stellar nebula's chemistry and temperature, but can also by a product processes within the astronomical body outgasing a different atmosphere.

The atmospheres of the planets Venus and Mars are principally composed of carbon dioxide and nitrogen, argon and oxygen.

The first exoplanet whose atmospheric composition was determined is HD 209458b, a gas giant with a close orbit around a star in the constellation Pegasus.

For example, the large gravitational force of the giant planet Jupiter retains light gases such as hydrogen and helium that escape from objects with lower gravity.

However, over the past 3 billion years Earth may have lost gases through the magnetic polar regions due to auroral activity, including a net 2% of its atmospheric oxygen.

[11] Other mechanisms that can cause atmosphere depletion are solar wind-induced sputtering, impact erosion, weathering, and sequestration—sometimes referred to as "freezing out"—into the regolith and polar caps.

[12] Wind erosion is a significant factor in shaping the terrain of rocky planets with atmospheres, and over time can erase the effects of both craters and volcanoes.

When a planet generates a significant amount of heat internally, such as is the case for Jupiter, convection in the atmosphere can transport thermal energy from the higher temperature interior up to the surface.

Wind picks up dust and other particles which, when they collide with the terrain, erode the relief and leave deposits (eolian processes).