Electron cooling by carbon monoxide in the atmospheres of Mars and Venus

Electron cooling, in which free electrons lose energy to vibrational excitation of gases, has been identified as a significant process in the atmospheres of Mars and Venus for electron impact on CO 2 . This process does not appear to have been evaluated for CO, although the density of CO exceeds that of CO 2 in the upper atmospheres of these planets. In this paper electron cooling rates for CO are calculated and compared with existing rates for CO 2 . It is found that electron cooling by CO becomes more significant than by CO 2 above altitudes of about 300 km on Mars and about 168 km on Venus. The sensitivity of the calculated cooling rates to different measurements of the integral cross sections for electron-impact vibrational excitation of CO is also investigated. PACS Codes : 34.80.Gs, 96.12.Jt