Carbon offset production flows to regions or industries that have a lower price of carbon—unless carbon can be purchased from that area, which offsets effectively permit, equalizing the price. Carbon offsets may represent six primary categories of greenhouse gases: carbon dioxide (), methane (CH), nitrous oxide (NO), perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF). Carbon offsets have several common features: In 2009, 8.2 billion metric tons of carbon dioxide equivalent changed hands worldwide, up 68 per cent from 2008, according to the study by carbon-market research firm Point Carbon, of Washington and Oslo. But at EUR94 billion, or about $135 billion,
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