Using ab initio calculated potential energy and electric dipole moment functions, absolute radiative transition probabilities between the rovibronic Renner-Teller states of the electronic ground state X-2 Pi(g) of CO2+ have been evaluated. The rovibronic eigenstates were obtained (up to 6500 cm(-1) and J <= 13/2) from variational calculations including the Renner-Teller and spin-orbit angular momentum couplings. The absolute intensities for the rovibrational states of the neutral CO2 electronic ground state, calculated by a similar approach, are found to be in excellent agreement with experimental data. For CO2+ the presented results are expected to have similar accuracy. It is found that the overtone intensities of the antisymmetric stretching mode of CO2+ are of similar magnitude as the fundamental transitions, in contrast with CO2. The theoretically generated IR-emission spectrum is compared with the limb spectrum of the Mars atmosphere, measured by the Thermal Emission Spectrometer on Mars Global Surveyor. (C) 2007 Elsevier Ltd. All rights reserved.