Atmosphere of Mars slowly decreased to very low concentrations, with no layer detectable above 35 km. The reporting scientists think that the observed polar ozone layers are the result of the same atmospheric circulation pattern that creates a distinct oxygen emission identified in the polar night and also present in Earth's atmosphere. This circulation takes the form of a huge Hadley cell in which warmer air rises and travels toward the south pole before cooling and sinking at higher latitudes. Mars is on a quite elliptical orbit and has a large axial tilt, which causes extreme seasonal variations in temperature amongst the northern
Extraterrestrial atmosphere exoplanet known to have a relatively cloud-free atmosphere and, as well, the first time molecules of any kind have been found, specifically water vapor, on such a relatively small exoplanet. The presence of molecular oxygen () may be detectable by ground-based telescopes, and it can be produced by geophysical processes, as well as a byproduct of photosynthesis by life forms, so although encouraging, is not a reliable biosignature. In fact, planets with high concentration of in their atmosphere may be uninhabitable. Abiogenesis in the presence of massive amounts of atmospheric oxygen could be difficult because early organisms relied on the