THERMOSPHERIC ODD NITROGEN

The photochemistry of NO, N(2D) and N(4S) and results of recent space measurements of their density distribution are discussed. In particular, the role of the reaction between metastable N(2D) atoms and O2 as a source of O(1D) is discussed in the light of laboratory and aeronomical observations. Global satellite measurements are compared with results of two- and three-dimensional models including transport. The possibility of explaining the odd nitrogen observations gathered in the Venusian and Martian thermospheres with the current understanding of the terrestrial models adapted ti CO2- rich atmospheres is examined. It is concluded that the understanding of the processes governing the distribution of odd nitrogen in terrestrial planets is generally satisfactory, although several aspects require further quantitative investigation.