We report the gravity wave (GW) statistics accumulated over two Martian years from the second half of Martian Year 34 (MY34) to the middle of MY36 (May 2018 - February 2022). The observations were performed by the middle- and near-infrared (MIR and NIR, respectively) spectrometers of Atmospheric Chemistry Suite (ACS) on board ExoMars Trace Gas Orbiter (TGO). Temperature profiles obtained independently of both channels during simultaneous measurements show a good agreement, thus providing verification and additional confidence in the data. GW parameters such as temperature fluctuations, potential energy per unit mass, and wave drag are retrieved at altitudes up to 160 km from the MIR channel and up to 100 km from the NIR channel. We present seasonal, intraday and latitude distributions of the wave potential energy and drag, serving to represent the wave activity and impact on the dynamics. A comparison of data obtained during the global dust storm (GDS) of MY34 with the corresponding period of MY35 without a storm reveals a reduction of GW activity in mid-latitudes in agreement with previous observations, and enhancement in the polar regions of both hemispheres, which was predicted by theoretical studies using simulations with a high-resolution circulation model. Seasonal variations of the derived GW activity can be linked to changes in the solar tide.

Temperature and density in the upper Martian atmosphere, above ~100 km, are key diagnostic parameters to study processes of the species’ escape, investigate the impact of solar activity, model the atmospheric circulation, and plan spacecraft descent or aerobraking maneuvers. In this paper, we report vertical profiling of carbon dioxide (CO2) density and temperature from the Atmospheric Chemistry Suite (ACS) solar occultations onboard the ExoMars Trace Gas Orbiter (TGO). A strong CO2 absorption band near 2.7 μm observed by the middle infrared spectrometric channel (ACS MIR) allows the retrieval of the atmospheric thermal structure in a large altitude range, from 20 to 180 km. We present the latitudinal and seasonal climatology of the thermal structure for 1.5 Martian years (MYs), from the middle of MY 34 to the end of MY 35. The results show the variability of distinct atmospheric layers, such as a mesopause (derived from 70 to 150 km) and homopause, changing from 80-90 km at aphelion to 100-110 km at perihelion. Some short-term homopause fluctuations are also observed depending on the dust activity.