  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 CO2. This process does not
appear to have been evaluated for CO, although the density of CO exceeds that
of CO2 in the upper atmospheres of these planets. In this paper electron
cooling rates for CO are calculated and compared with existing rates for CO2.
It is found that electron cooling by CO becomes more significant than by CO2
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
