CARBON MONOXIDE IN THE ATMOSPHERES OF THE TERRESTRIAL PLANETS (VENUS, EARTH, MARS)

We summarize by noting the very different time scales for variations of CO in the upper atmospheres of Venus, the Earth, and Mars. The long diurnal period of Venus produces a very strong diurnal variation in mesospheric CO which is driven primarily by subsolar to antisolar circulation. CO in the terrestrial mesosphere shows strong seasonal variation which is apparently produced by seasonally driven meridional circulation. By contrast, if atmospheric CO does vary on Mars, it is most likely controlled by long-term changes in the chemistry and/or vertical mixing in the Martian atmosphere.