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
Atmosphere of Venus on the atmosphere between 65 and 85 km. The solar transit in 2004 enabled astronomers to gather a large amount of data useful not only in determining the composition of the upper atmosphere of Venus, but also in refining techniques used in searching for extrasolar planets. The atmosphere of mostly CO, absorbs near-infrared radiation, making it easy to observe. During the 2004 transit, the absorption in the atmosphere as a function of wavelength revealed the properties of the gases at that altitude. The Doppler shift of the gases also enabled wind patterns to be measured. A solar transit of Venus