Carbon dioxide equivalent of carbon dioxide. Equivalent (e) is the concentration of that would cause the same level of radiative forcing as a given type and concentration of greenhouse gas. Examples of such greenhouse gases are methane, perfluorocarbons, and nitrous oxide. e is expressed as parts per million by volume, ppmv. Carbon dioxide equivalent Carbon dioxide equivalent (CDE) and equivalent carbon dioxide (e and eq) are two related but distinct measures for describing how much global warming a given type and amount of greenhouse gas may cause, using the functionally equivalent amount or concentration of carbon dioxide () as the reference. Carbon dioxide
ExoMars Trace Gas Orbiter be a strong indication that biological processes are involved. However, if methane is found in the presence of gases such as sulfur dioxide (), that would be an indication that the methane is a byproduct of geological processes. The nature of the methane source requires measurements of a suite of trace gases in order to characterise potential biochemical and geochemical processes at work. The orbiter has very high sensitivity to (at least) the following molecules and their isotopomers: water (), hydroperoxyl (), nitrogen dioxide (), nitrous oxide (), methane (), acetylene (), ethylene (), ethane (), formaldehyde (), hydrogen cyanide