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The Thermal InfraRed channel in honor of professor Vassili Ivanovich Moroz (TIRVIM) of the Atmospheric Chemistry Suite onboard ExoMars Trace Gas Orbiter has continuously monitored the Martian atmosphere from 13 March 2018 until 2 December 2019, covering almost a complete Martian Year (MY). In the nadir mode of observations, infrared spectra obtained by TIRVIM in the spectral range 600–1,300 cm−1permit retrievals of vertical temperature profiles from the surface up to 60 km of altitude, surface temperatures and column aerosol optical depths. Here we report the retrieved atmospheric thermal structure and the column dust content during the global dust storm (GDS) of MY 34 monitored from Ls= 182.2° to Ls= 211.8° (Solar Longitude), capturing the evolution of the GDS and the response of the atmospheric thermal structure to the changing dust loading. The global storm caused asymmetric atmosphere heating, predominantly in the southern hemisphere, and changed diurnal contrast of atmospheric thermal structure. We also observe a reduced diurnal contrast of surface temperatures at the peak of the GDS. The thermal radiation emitted by Mars in the spectral range 7.7–16.7 μm was measured by the Atmospheric Chemistry Suite Thermal InfraRed channel in honor of professor Vassili Ivanovich Moroz (ACS TIRVIM) onboard ExoMars Trace Gas Orbiter. The nadir spectra carry information about the temperature of the atmosphere at different altitudes thanks to a deep CO2absorption present around 15 μm. Also, the dust loading can be found from the 9‐μm silicate absorption, and the surface temperature can be estimated at 7 μm where the atmosphere is mostly transparent. We follow the evolution of these parameters during the strong global dust storm of Martian Year (MY) 34 (2018). The peculiarity of the ACS TIRVIM data set is the exceptionally dense coverage providing a new look at this otherwise well‐studied dust event. Atmospheric thermal structure and dust content on Mars are retrieved from Atmospheric Chemistry Suite Thermal InfraRed channel nadir measurements in the spectral range 7.7–16.7 μmThe 2018 global dust storm covered the entire planet and caused an asymmetric heating of the atmosphere with a hotter southern hemisphereWe observe a reduced diurnal contrast of surface temperatures and a changed contrast of atmospheric thermal structure during the storm Atmospheric thermal structure and dust content on Mars are retrieved from Atmospheric Chemistry Suite Thermal InfraRed channel nadir measurements in the spectral range 7.7–16.7 μm The 2018 global dust storm covered the entire planet and caused an asymmetric heating of the atmosphere with a hotter southern hemisphere We observe a reduced diurnal contrast of surface temperatures and a changed contrast of atmospheric thermal structure during the storm

The properties of Martian aerosols are an integral part of the planetary climatology. Global dust storms (GDS) significantly alter spatial and vertical distributions of dust and water ice aerosols and their microphysical properties. We explored the 2018/Martian year 34 GDS with the Atmospheric Chemistry Suite instrument onboard the ESA‐Roscosmos Trace Gas Orbiter mission. Solar occultation observations of thermal infrared and near infrared channels in the 0.7–6 μm spectral range with >103signal‐to‐noise ratio are used to constrain the vertical dependence and the temporal evolution of the particle properties of water ice and dust (effective radius, effective variance, number density, and mass loading) before the 2018 GDS and during its onset and decay phases. In most of the observations, the particle size of dust and water ice decreases with altitude. The effective radius of dust and water ice particles ranges in 0.1−3.5 μm and 0.1–5.5 μm, respectively. The largest aerosol particles (> 2.5 μm for dust and > 3.5 μm for water ice) are present below 10 km before the onset and during the GDS decay phase. During the peak of the GDS, dust reached altitudes of 85 km; the most frequently observed effective radius is 1–2 μm with 0.1–1 cm−3number density and 0.1 effective variance. Detached layers of water ice composed of 0.1–1 μm particles are systematically observed at 50–100 km during this period. Below, at 0–50 km, we see the dust mixed with the main water ice layer comprising 1–4 μm particles. Suspended in the air, mineral dust and water ice particles play a key role in thermal balance and circulation of the atmosphere of Mars and its climate. In that context, global dust storms are rare but powerful events that significantly alter spatial and vertical distributions of dust and water ice particles and their properties. The most recent event, which occurred in the summer of 2018, was monitored by the Atmospheric Chemistry Suite instrument onboard the ESA‐Roscosmos Trace Gas Orbiter mission. Solar occultation observations carried out in the visible and the middle infrared spectral ranges enabled monitoring of dust and water ice particles properties such as size, number of particles and their mass per unit volume, and the width of their size distribution during the evolution of the storm. Dust was lifted to 85 km, while water ice clouds were observed at even higher altitudes, up to 100 km. Atmospheric Chemistry Suite solar occultations in the 0.7–6 μm spectral range separate microphysical properties of dust and water ice aerosols in Martian atmosphereThe observed particle radius ranges from 0.1 to 3.5 μm for dust and from 0.1 to 5.5 μm for water ice clouds, with the largest particles found below 10 kmWater ice clouds with 0.1–1 μm particles reached altitudes up to 100 km during the peak of the 2018 global dust storm Atmospheric Chemistry Suite solar occultations in the 0.7–6 μm spectral range separate microphysical properties of dust and water ice aerosols in Martian atmosphere The observed particle radius ranges from 0.1 to 3.5 μm for dust and from 0.1 to 5.5 μm for water ice clouds, with the largest particles found below 10 km Water ice clouds with 0.1–1 μm particles reached altitudes up to 100 km during the peak of the 2018 global dust storm