Mesospheric CO 2 ice clouds on Mars observed by Planetary Fourier Spectrometer onboard Mars Express

•We investigated Martian mesospheric CO2 ice clouds using MEx/PFS observations.•The spatial and seasonal distributions are consistent with previous reports.•The main CO2 scattering peak was found between 4.240 and 4.265 μm.•We report the first detection of an occasional secondary peak at 4.28 μm.•The spectral features cannot be simulated using Mie theory.