Climatology and first-order composition estimates of mesospheric clouds from Mars Climate Sounder limb spectra

► We detect mesospheric aerosol layers in limb-spectra from Mars Climate Sounder. ► Aphelion season layers are mostly equatorial, high altitude and cold. ► Layers in perihelion season are mostly mid-latitude, lower altitude and warmer. ► Layers are spectrally similar to H2O or CO2-ice. ► Temperatures proximal to some aphelion layers are close to the CO2 frost point.