Trace gas Trace gas The most abundant gases in the atmosphere are nitrogen (78.1%), oxygen (20.9%), and argon (0.934%). Combined, oxygen, argon, and nitrogen make up 99.934% of the gases in the atmosphere (not including water vapor). The other gases that are not part of the 99.934% of the atmosphere are called trace gases. The abundance of a trace gas can range from a few parts per trillion (ppt) by volume to several hundred parts per million by volume (ppmv). When a trace gas is added into the atmosphere, that process is called a "source". There are two possible types of sources
Gas torus Gas torus A gas torus is a toroidal cloud of gas or plasma that encircles a planet. In the Solar System, gas tori tend to be produced by the interaction of a satellite's atmosphere with the magnetic field of a planet. The most famous example of this is the Io plasma torus, which is produced by the ionization of roughly 1 ton per second of oxygen and sulfur from the tenuous atmosphere of Jupiter's volcanic moon Io. Before being ionized, these particles are part of a neutral torus, also centered on the orbit of Io. Energetic particle observations also suggest