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Four surface stations (rovers Curiosity, Perseverance, and Zhurong, and the Insight platform) were operating on Mars along Martian Year 36 (7 February 2021 – 26 December 2022), all them equipped with a suite of meteorological sensors and cameras. In addition, eight orbiters are currently studying the planet from different perspectives and instruments. To help to interpret and put in context the meteorological measurements at the surface by these stations, we present here a study of the atmospheric disturbances, at the planetary and synoptic scales, based on images of Mars obtained from cameras onboard Mars Express and Mars Reconnaissance Orbiter [1, 2]. We report on the properties of the disturbances that evolved at the edge of the North Polar Cap (latitudes ~ 40°N to 70°N) during the springtime season in the northern hemisphere. These are dust storms and synoptic-scale cloud systems with arc, frontal, irregular and spiral shapes, typically growing from the baroclinic instabilities in the intense eastward jet present in this epoch of the Martian year. We also report on the evolution of the aphelion cloud belt (Ls ~ 0° – 180°), including among other phenomena the recurrent annular-double cyclone (Ls ~ 125°) and the cloud development at Hellas basin (Ls ~ 145° – 300°). Finally, we present an analysis of the dust storms that evolved at different latitudes, concentrating in particular in the regional storm that evolved over Perseverance in early January 2022. References[1] Sánchez-Lavega, A. et al., Icarus 299, 194-205 (2018)[2] Bell III, J. F. et al., J. Geophys. Res. Planets 114, E003315, 1-41 (2009)

Mars Express has the distinction of being one of the oldest operational spacecraft at Mars, with over 18 years since its injection into Martian orbit in December 2003. Designed for a nominal mission of one Martian year to survey the red planet, it is currently applying for its 9th mission extension. A recent technical review has concluded that Mars Express was technically fit to continue providing excellent science return for the 2023-25 and 2026-28 extension intervals. The spacecraft subsystems, scientific payload and ground segment are in overall good health, allowing continued smooth mission and science operations. The 3 lifetime-limiting elements of the spacecraft are the gyros, the batteries, and the fuel remaining onboard. The situation of the gyros has been improved by the successful implementation of a gyroless operations mode in May 2018 by the Mars Express teams at ESOC and ESAC. This difficult modification saved the mission and now allows an IMU duty cycle currently reduced to a monthly figure of about 3 to 4 % of the original usage. Mars Express can expect its gyro lifetime to be extended well beyond the 2025 timeframe. Studies performed in 2019 and 2020 have shown the spacecraft batteries to be much less degraded than had previously been assumed. The findings of these studies were substantiated in subsequent eclipse seasons. A new battery power model now used operationally allows for more flexibility in science planning particularly during eclipse seasons. The longest, most challenging eclipses of the mission were passed successfully in 2021. With shorter eclipse durations in the coming years the outlook is very favourable for continuing to operate the batteries well beyond 2030. The fuel situation remains satisfactory based on regularly actualised estimates and on a very low fuel consumption (assuming no safe modes; the last one was in 2011). The estimated ~3kg of usable hydrazine (with high confidence based on the Venus Express experience) left onboard can take the spacecraft mission operations to beyond 2030 with the current load of science operations. Planning and execution of science operations have been improved by upgrades to the mission operations run from the MOC at ESOC and to the Science Ground Segment operations done at ESAC near Madrid. More flexible, rationalised and in some cases even reduced constraints are now in place which enhance the capability of the spacecraft and its payload in performing scientific observations and data taking. Finally, new science opportunities are presenting themselves in the coming years, illustrated recently by the routine implementation of mutual radio occultations between Mars Express and the ExoMars Trace Gas Orbiter. This will greatly expand the number of atmospheric observations in the future. Automated dual-band radio science occultation observations have now been implemented at egress. The MARSIS subsurface radar is implementing two new promising modes of operation, one to investigate the subsurface at a better sampling rate and one to characterise Phobos, the largest Martian moon and future target for Japan’s MMX mission. Another proposed mission capability will be to perform active sounding of the local plasma environment using combined operation of the ASPERA particle detector and the MARSIS radar. MELACOM relay operations have increasingly taken place with regular Mars Surface Laboratory overflights and were also recently upgraded to implement CNSA’s Zhurong rover overflights and prepare for supporting the ExoMars rover mission as well as other NASA landed assets. These are only a limited set of examples of how Mars Express keeps delivering new and exciting science return. Interplanetary missions can operate over many years and learning how to use the technology in ways that were maybe not part of the original operational concept is an incredibly important ability. The above demonstrates that the Mars Express teams have been able throughout the mission’s many years of life to render Mars Express a better spacecraft now than at any time before, with in-flight upgrades that kept the mission flying. Those teams were able to make such changes thanks to: robust in-house control and support of the ESAC-run MAPPS planning software allowing for continuous improvement; Flight Control Team with enough skill and resources to modify and fully test the flight code; instrument teams with enough funding and support to allow for software updates/testing late in the mission. This might help younger and upcoming missions assemble the resources now so that they can attempt life-extending changes later. Combining a special set of payload instruments onboard Mars Express, very resilient spacecraft and payload health and a favourable orbit configuration, this makes for a still unique mission at Mars, very much complementary to newer orbiting elements with different capabilities. ESA is getting the most out of Mars Express and will continue to do so in the coming years, contributing to and enhancing the international cooperation at Mars.

Mars Express With almost two decades of Mars observation behind it, Mars Express remains a dependable and highly productive mission. Recent science highlights include (1) continued mapping of subsurface reflectors beneath the south polar layered ice deposits, and associated work to explain the cause of these reflections; (2) a global map of minerals on Mars with 200 m/px resolution, obtained from analysis of infrared spectra; (3) release of 50 m resolution Digital Elevation Models based on HRSC stereo topography for quadrangles covering an ever-increasing proportion of the global surface; (4) detailed characterization of the landing sites of the ESA, NASA and Chinese rovers; (5) a global climatology of ozone and water from both nadir and occultation observations and its relation to atmospheric dust; (6) transient atmospheric phenomena, such as a recurrent orographic cloud feature at Arsia Mons; (7) detailed investigation of the ionospheric structure, its variability, and coupling to the lower atmosphere; (8) continued monitoring of both the upstream solar wind conditions and of downstream escaping ions; (9) detailed study of Phobos during flybys at altitudes as low as 50 km. Spacecraft and instrument teams continue to implement new and improved observation modes. One example is new MARSIS instrument software which now allows raw data to be returned from much longer subsurface sounding passes, improving the search for basal reflectors beneath polar ice caps; another example is mutual radio occultation observations between Mars Express and ExoMars Trace Gas Orbiter, potentially providing vertical profiles of ionospheric electron content with good spatial and temporal coverage. ExoMars Trace Gas Orbiter TGO has now completed two full Martian years of observations. Highlights include (1) continuing non-detection of methane, with upper limits as low as 20 ppt by volume. Reconciling this continued non-detection by TGO with the background levels of several hundred ppt in Gale crater by MSL remains an enigma, stimulating further research. (2) detection of HCl, the first reported halogen-containing species in the atmosphere of Mars. (3) further detail of the transport of water to high altitudes, a critical step in the escape of water from Mars. (4) mapping of atomic hydrogen in the top 1-2 m of regolith, indicative of water ice and hydrated minerals, suggesting surprisingly high abundances of subsurface water ice in low latitude regions including one in central Valles Marineris; and (5) continued acquisition of 5 m colour imagery and digital elevation models over a wide range of terrain and target types, including landing site characterization. Future plans: Mission extension cases for both missions have been submitted for the years 2023-2025 and 2026-2028. The extension of the observations would allow several new and optimized observation types; in particular, it will allow many collaborative observation opportunities with other missions and with ground- and space-based observatories. Of particular note are joint observations with James Webb Space Telescope, for which dedicated observations of Mars are due to be conducted in 2022-2023. Science goals include mapping of the water D/H ratio, search for trace gases including methane, and mapping of thermospheric structure using 4.3 μm CO2 emission; the full-disk views provided by JWST are highly complementary to the vertical profiling and long temporal coverage provided by MEx and TGO.

The scientific objectives of Mars Express (MEX) and ExoMars 2016 Trace Gas Orbiter (TGO) missions are very complementary, with increasing synergies among the science teams, in particular for the study of the atmosphere. In this contribution we summarize the coordination efforts to perform joint observations by the two European satellites around Mars until 2022, and the science opportunities for the expected mission extension until 2025.Since the start of the TGO science operations in April 2018 we have executed hundreds of coordinated observations of the Martian atmosphere, first reported in [1,2] and extended here to 2022. The science data obtained during these coordinated observations provide useful input for cross-calibration of the instruments, comparison of atmospheric vertical profiles, and potential for the study of the temperature, composition, meteorology and climate of Mars.Figure 1: Types of coordinated observations performed: MEX-TGO Sun Occultations (within 15min and distance These observations are routinely coordinated in collaboration between the Science Operations Centers (SOCs) of both missions [1, 3] and the instrument teams, in particular the spectrometers NOMAD and ACS onboard TGO [4,5] and SPICAM, OMEGA and PFS onboard MEX [6,7,8].The various types of joint observations are represented in Figure 1. First the joint solar occultations by the spectrometers SPICAM (MEX) and ACS-NOMAD (TGO) are performed quasi-simultaneously (The authors acknowledge the contributions of the European Space Agency, Roscomos, all National Agencies, research institutions and teams involved in the success of the Mars Express and ExoMars 2016 missions. ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos (Russia).References:[1] Cardesin Moinelo, A. et al: First year of coordinated science observations by Mars Express and ExoMars 2016 Trace Gas Orbiter, ICARUS 353, 2021[2] Cardesin Moinelo, A. et al: Atmospheric observations performed simultaneously in 2020-2021 by ESA’s Mars Express and Trace Gas Orbiter, European Planetary Science Congress, Vol. 15, EPSC2021-128, 2021[3] Geiger, B et al: Long Term Planning for the ExoMars Trace Gas Orbiter Mission: Opportunity Analysis and Observation Scheduling, Proceedings of SpaceOps Conference, 2018[4] Vandaele, A. C. et al: NOMAD, an Integrated Suite of Three Spectrometers for the ExoMars Trace Gas Mission: Technical Description, Science Objectives and Expected Performance, Space Sci Rev 214: 80. 2018[5] Korablev, O. et al: The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter Space Sci Rev 214: 7. 2018[6] Montmessin et al, SPICAM on Mars Express: A 10 year in-depth survey of the Martian atmosphere. Icarus, Volume 297, p. 195-216. 2017[7] Bibring, J.-P., et al., OMEGA: Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité, ESA SP-1240, pp. 3–16. 2004[8] Formisano V. et al: The Planetary Fourier Spectrometer (PFS) onboard the European Mars Express mission, Planetary and Space Science, Volume 53, Issue 10, p. 963-974. 2005[9] Svedhem H. et al: First results from the MEX – TGO Mutual Radio Occultation Experiment, European Planetary Science Congress, Vol. 15, Vol. 15, EPSC2021-719, 2021

Planetary protection (PP) is the scientific discipline that aims to keep the celestial bodies under study and the Earth free of biological and molecular contamination from samples that could have been brought back by space missions. Currently, this discipline is mainly focused on minimising the disturbance of planets and satellites in order to keep their environment pristine. The Committee on Space Research (COSPAR) is the body in charge of determining the good PP practices that the different space agencies must comply with [1]. These standards were developed taking into account, in particular, factors such as being located in the habitable zone, with the consequent possibility of the presence of liquid water and sufficient availability of energy on these celestial bodies. This means that the conditions of the environment could be compatible with some terrestrial microorganism, therefore, contamination could occur. For this reason, researchers from space organizations dedicated to the study of these bodies (who see contamination as a problem) should strictly follow the rules proposed by COSPAR, in order to avoid compromising future research. This paper presents the implementation of a planetary protection protocol in a hypothetical mission launched in 2030 by a student organisation called Uvigo Spacelab [2], which currently carries out missions in orbit around the Earth that do not require a PP protocol. The 2030 mission would aim to launch a lander and a rover to explore the surface of Mars, meaning that this mission falls into the proposed category IV with COSPAR so it would require a defined PP protocol and a change in the maintenance of facilities to keep biological contamination under control. For the elaboration of the protocol, firstly, a visit to the ESAC facilities in Madrid was carried out, in order to personally meet researchers and projects in the aerospace area. On the other hand, a visit was also made to the INTA-CAB facilities, in order to see a cleanroom dedicated to planetary protection and receive training in astrobiology and PP from experts who worked for the Raman Laser Spectrometer (RLS) project [3], with the purpose to complete and reinforce the knowledge acquired from the bibliographic resources consulted. This learning was then applied by performing a microbiological sampling prior to the start of the mission, following a NASA sampling method, in order to quantify the accumulated bioburden in the ISO 7 cleanroom of Uvigo Spacelab. At the same time, another cleanroom with the same classification but dedicated to semiconductor and biomedical device processing at the CINTECX [4], was quantified under the same sampling method in order to compare the bioburden incorporated in the ISO 7 rooms with engineering activities. Finally, the rules and improvements to be implemented to ensure compliance with the pre-launch bioburden, which is established by the PP standards for this type of mission were drafted. References: [1] COSPAR Panel on Planetary Protection, 2020. COSPAR Policy on Planetary Protection. Space Res. Today 208, August 2020, Pages 10-22. https://doi.org/10.1016/j.srt.2020.07.009 [2] Rull, et al. The Raman Laser Spectrometer for the ExoMars Rover Mission to Mars. Astrobiology.Jul 2017.627-654. http://doi.org/10.1089/ast.2016.1567 [3] UVigo Spacelab: https://uvigospacelab.space/ [4] CINTECX Centro de Investigación en Tecnologías, Energía y Procesos Industriales de la Universidad de Vigo http://cintecx.uvigo.es/ Keywords: Astrobiology, Planetary Protection, Cleanrooms, COSPAR.

Planetary protection (PP) is the scientific discipline that aims to keep the celestial bodies under study and the Earth free of biological and molecular contamination from samples that could have been brought back by space missions. We present here a research collaboration between the University of Vigo, ESA and INTA/CAB to analyse, adapt and test standard Planetary Protection (PP) protocols to avoid biological contamination during the development of future Mars exploration instrumentation. This project is based on the standard PP requirements, procedures and techniques currently used for Mars science instruments, in particular for the Raman Laser Spectrometer (RLS) developed at INTA/CAB for the ESA ExoMars mission. The goal of the project is to compile, adapt and test these procedures in the current instrumentation facilities at the University of Vigo, so they could be used for the development of science payload in a potential future mission to Mars surface. We will summarize in this contribution the standard requirements and procedures followed by ExoMars RLS team (biological contamination prevention, monitoring and cleaning methods) and how these techniques can be adapted to the University, including the preliminary study of various samples taken at the UVigo SpaceLab and CINTECX FA3 lab facilities to assess the current state of biological contamination., This study has been supported by the ESA Science Faculty at ESAC, INTA/CAB RLS team, UVigo SpaceLab, CINTECX FA3 group and the Faculty of Biology of the University of Vigo.

International audience; Mars ExpressWith almost two decades of Mars observation behind it, Mars Express remains a dependable and highly productive mission.Recent science highlights include (1) continued mapping of subsurface reflectors beneath the south polar layered ice deposits, and associated work to explain the cause of these reflections; (2) a global map of minerals on Mars with 200 m/px resolution, obtained from analysis of infrared spectra; (3) release of 50 m resolution Digital Elevation Models based on HRSC stereo topography for quadrangles covering an ever-increasing proportion of the global surface; (4) detailed characterization of the landing sites of the ESA, NASA and Chinese rovers; (5) a global climatology of ozone and water from both nadir and occultation observations and its relation to atmospheric dust; (6) transient atmospheric phenomena, such as a recurrent orographic cloud feature at Arsia Mons; (7) detailed investigation of the ionospheric structure, its variability, and coupling to the lower atmosphere; (8) continued monitoring of both the upstream solar wind conditions and of downstream escaping ions; (9) detailed study of Phobos during flybys at altitudes as low as 50 km.Spacecraft and instrument teams continue to implement new and improved observation modes. One example is new MARSIS instrument software which now allows raw data to be returned from much longer subsurface sounding passes, improving the search for basal reflectors beneath polar ice caps; another example is mutual radio occultation observations between Mars Express and ExoMars Trace Gas Orbiter, potentially providing vertical profiles of ionospheric electron content with good spatial and temporal coverage. ExoMars Trace Gas Orbiter TGO has now completed two full Martian years of observations.Highlights include (1) continuing non-detection of methane, with upper limits as low as 20 ppt by volume. Reconciling this continued non-detection by TGO with the background levels of several hundred ppt in Gale crater by MSL remains an enigma, stimulating further research. (2) detection of HCl, the first reported halogen-containing species in the atmosphere of Mars. (3) further detail of the transport of water to high altitudes, a critical step in the escape of water from Mars. (4) mapping of atomic hydrogen in the top 1-2 m of regolith, indicative of water ice and hydrated minerals, suggesting surprisingly high abundances of subsurface water ice in low latitude regions including one in central Valles Marineris; and (5) continued acquisition of 5 m colour imagery and digital elevation models over a wide range of terrain and target types, including landing site characterization. Future plans: Mission extension cases for both missions have been submitted for the years 2023-2025 and 2026-2028. The extension of the observations would allow several new and optimized observation types; in particular, it will allow many collaborative observation opportunities with other missions and with ground- and space-based observatories. Of particular note are joint observations with James Webb Space Telescope, for which dedicated observations of Mars are due to be conducted in 2022-2023. Science goals include mapping of the water D/H ratio, search for trace gases including methane, and mapping of thermospheric structure using 4.3 μm CO2 emission; the full-disk views provided by JWST are highly complementary to the vertical profiling and long temporal coverage provided by MEx and TGO.

To date, Mars’s weather has been monitored mainly from spacecraft in polar or quasi-polar orbits, which sample only a narrow range of local times, or several local times over multiple sols with discontinuous spatial coverage (Fig.1). When observations have been made and/or analyzed at different local times, a high magnitude of diurnal variability often has been found [see e.g. 1 to 5]. The significance of diurnal meteorological variability at Mars argues for orbital observations that span the diurnal cycle. The rapid dynamics of meteorological phenomena such as dust storms (typical timescale of a few hours) and water/CO2 ice clouds (typical timescale of half an hour or less), together with their spatial extension (up to the planetary scale for dust events) and duration/repeatability, argues for continuous and simultaneous observations across the planet (Fig.1). As it happened for the study of meteorology on Earth in the 1970s, now is the right time to introduce monitoring to the observation paradigm for the martian atmosphere, so far almost exclusively focused on mapping. The Emirates Mars Mission (EMM), which entered Mars’s orbit in February 2021, is the first orbiter fully dedicated to the study of its climate. Thanks to its high, eccentric, low inclination orbit, it is also the first satellite that can reasonably observe the evolution of meteorological phenomena over multiple local times simultaneously, thus operating the transition from the mapping to the monitoring paradigm. Although unique so far, EMM alone cannot provide what has been identified as a high priority requirement to improve the spatiotemporal coverage of existing data and to enable future human exploration missions, i.e. global, continuous, and simultaneous monitoring, leading to forecasting of meteorological phenomena [6]. Quasi-global monitoring (excluding the polar regions) can be achieved by a constellation of areostationary platforms, i.e. satellites in equatorial, circular orbits in which the orbital period of the satellite matches the rotational period of Mars. The minimum number required for covering all equatorial longitudes is three [7]. The required number to cover all longitudes in a continuous latitude band extending from nearly 80°S to nearly 80°N with some large overlapping in longitude is four (Fig.2). If the areostationary constellation is coupled with at least one satellite in low polar orbit, the continuous (high cadence) and simultaneous (all locations at once) monitoring becomes nearly global [8]. Areostationary observations would revolutionize Mars weather forecasting as geostationary satellite imagery did for Earth weather forecasting in the 1970s. The quasi-global, continuous, and simultaneous view that observations from an areostationary network provide would allow forecast initialization from atmospheric states that properly account for teleconnections, large-scale weather and dust events, tides, and other diurnally varying, global-scale phenomena (Fig. 3). Operational monitoring coupled to modelling will enable forecasting, allowing to take preventive actions and minimize risks. It will take several attempts to optimize an operational monitoring and forecasting system, primarily because extreme events such as dust storms attaining the planetary scale occur at irregular times. It is thus essential to send precursor missions aimed at developing the operative infrastructure well in advance of the first human mission. Areostationary platforms do not only offer advantages in meteorology. Satellites in areostationary orbit would spend nearly 75% of their time outside the bow shock of Mars, offering monitoring of the upstream solar wind at an unobstructed vantage point (Fig. 4). The high distance of an areostationary orbit from Mars could also allow for globally mapping the escape of atmospheric species in response to changes in upstream drivers, a task only partially fulfilled by EMM. Last but not the least, areostationary relay satellites could advance telecommunication capabilities for future robotic and human Mars missions far beyond current capabilities [9 to 11]. They are also ideal to support the communication requirements of a future generation of small, low-cost Mars science orbiters and be part of a Global Navigation Satellite System (GNSS), which would greatly improve mission safety and reliability for sustainable, long-term exploration [12]. See [7] for more information on the benefits and applications of satellites in areostationary orbit. Furthermore, the architecture of the constellation, and recent advancements on on-board computational capabilities, would enable significant degrees of autonomy, such as coordination of observations, event-driven operations, and goal-based monitoring. In order to fully shift paradigm from mapping to monitoring, therefore, we have developed a mission concept to send a constellation of at least three satellites in the second half of the current decade, place them in an areostationary orbit, and monitor atmospheric and space weather over the course of at least two Martian years. We name our concept MACAWS, which stands for "Monitoring Areostationary Constellation for Atmosphere and Weather in Space" (Fig. 5). The nature and objectives of this novel mission lend themselves to the use of SmallSats to reduce costs and accept higher risks, while maximizing impact. The scientific and operational achievements of this precursor mission will directly feed into the subsequent planning of larger-scale monitoring constellations. The stated goal of MACAWS is to be a low-cost, precursor, orbital mission to monitor atmospheric and space weather events continuously and simultaneously at most locations on the planet and in the upstream solar wind, in preparation for the human exploration of Mars. The scientific payload, mission architecture, and ConOps are defined accordingly (Fig. 6). The planned outcomes are a better scientific understanding of the dynamics of such events, and the development of an operational forecasting system in order to reduce the risks for humans when in orbit around Mars or on the ground. REFERENCES [1] Glenar+ 2003 Icarus 161 297, https://doi.org/10.1016/S0019-1035(02)00046-5 [2] Zent+ 2016 JGR Plan. 121 626, https://doi.org/10.1002/2015JE004933 [3] Wolkenberg & Giuranna 2020 Icarus 113823, https://doi.org/10.1016/j.icarus.2020.113823 [4] Kleinboehl+ 2020 JGR Plan., e2019JE006115, https://doi.org/10.1029/2019JE006115 [5] Montabone+ 2020 JGR Plan., e2019JE006111, https://doi.org/10.1029/2019JE006111 [6] Banfield+ 2020 MEPAG Science Goals, https://mepag.jpl.nasa.gov/reports/MEPAGGoals_2020_MainText_Final.pdf [7] Montabone+ 2020 White Paper PSA Decadal Survey, https://bitly.com/areowhitepaper [8] Lillis+2021, Planet. Sci. J., in press [9] Breidenthal+2018 SpaceOps Conf. 2426, https://doi.org/10.2514/6.2018-2426 [10] Edwards+2016 Proc. IEEE Aerosp. Conf., https://doi.org/10.1109/AERO.2016.7500680 [11] Lock+2016 Proc. IEEE Aerosp. 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In 2018 a regional dust storm on Mars has evolved to a global scope, becoming one of the largest dust storms ever observed. These rare and unpredictable events are poorly known. A key factor for its evolution is the role played by the Martian winds. Measuring winds on Mars is a real challenge for remote observations but a global dust storm offers to us a unique opportunity thanks to an innovative technique to measure the Doppler effect of solar Fraunhofer lines back-scattered on the Mars dust cloud. A high spectral resolution is required to resolve the solar lines and to allow us to measure with precision the line shifts due to aerosol motion and in this manner retrieve the related wind map. We used dedicated ground-based observations made with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the European Southern Observatory's Very Large Telescope (VLT) facility in Chile. This instrument's high resolution (R ~100000) allows for the dust cloud velocity to be measured, by computing the Doppler shift induced in the Fraunhofer lines (λ of 420-1100 nm) in the solar radiation that is back-scattered in the dust suspended in the Martian atmosphere, by the motion of that same dust particles, with an average error of approximately 5 ms-1. The processes that allow for the development of global dust storms are poorly understood. Furthermore, the cut-off mechanisms that spur the end of these storms are also without consensus and may even vary from storm to storm. During such events dust can be lifted to heights above 50 km across all latitudes and longitudes, increasing the optical depth along the dust layer in atmospheric suspension and increasing the heat absorbed at each altitude covered by dust [1,2]. Global dust storms are complex stochastic events that can drastically alter the atmospheric dynamics [3,4]. These storms usually develop in the southern hemisphere during southern Summer and Spring ( Ls ≈ 180º - 360º), however, the 2018 storm started developing in the northern hemisphere on Ls ≈ 185º. Our understanding of both the initiation and decline of global dust storms is only marginal, nevertheless we do know that such events probably originate from the superimposition of three circulation components: the Hadley cell, thermal tides and topographically controlled circulations. This mechanism was suggested by Leovy (1973) [5] and relies on the seasonally increased insolation and dust loading coupled with the above-mentioned components to allow certain storms to become global at the planetary scale. The decay of dust storms is even more obscure as the cause for the halting of the dust lifting hasn't been unambiguously identified. Either the depletion of surface dust available for lifting shuts off the lifting events (which requires replenishment of the surface dust sources) or the decrease in intensity of the various components allows for the surface wind stress to drop below the required threshold for dust lifting [6,7]. Mars' atmosphere is highly transparent in the visible and ultraviolet ranges and the back-scattered radiation in those wavelength ranges in the atmosphere is negligible which precludes the application of the Doppler velocimetry method that we developed and fine-tuned for the case of Venus [8,9,10,11,12]. However, during global dust storms, the opacity of the atmosphere increases and allows for the scattering of enough light in the suspended dust in the middle atmosphere for the application of our Doppler method in an effective way. The adaptation of our Doppler velocimetry method took in account the geometry of our observations. Spherical geometry was used to locate the observations within the planet, as seen from Earth at the time of each observation, and to compute the de-projection of the radial Doppler velocities from the observer's line-of-sight, for each point of the slit and for each exposure. The rotation velocity's contribution to the overall Doppler shift was removed by computing and subtracting the rotation velocity at each point on Mars sensed by the spectroscopic slit. Furthermore, the contributions made to the total shift by the Young effect were evaluated and deemed negligible under the specific geometry of our observations. The scope of this work is to study the dynamical behaviour of Mars’ middle atmosphere during a global dust storm using ground-based observations made with the high-resolution spectrograph UVES at ESO’s Very Large Telescope and Doppler velocimetry methods, for the first time, to complement observations of orbiter instruments. The success and validation of the application of this method to the atmosphere of Mars may provide a new tool to investigate the Martian atmosphere during dust storms. We intent is to contribute for a better understanding of the atmosphere's dynamics during planet encircling dust events. We measured the wind velocity and its spatial variability, through high resolution spectroscopy and Doppler velocimetry. The main goal of this research line is therefore, to provide wind measurements using visible Fraunhofer lines scattered at Mars’ dust hazes, which allows spatial wind variability studies and will make possible to obtain a latitudinal profile of the wind along the cited global dust storm and a wind map of the dust storm as a function of the latitude and local time over the planet as seen from Earth. Acknowledgements: We acknowledge support from the Portuguese Fundação Para a Ciência e a Tecnologia ref. PTDC/FIS-AST/29942/2017 References: [1] Vandaele, et al., Nature, 568, 2019. [2] Stone, S., et al. Science, Vol. 370, 2020. [3] Zurek, R., and Martin, L., JGR, 98, 1993. [4] Haberle, R.M., Science, 234, 1986. [5] Leovy, C. Journal of Atmospheric Sciences, 30, 1973. [6] Kahre, M., et al., Cambridge University Press, 2017. [7] Pollack, J., JGR, 1979. [8] Machado, P., et al., Icarus, 2012. [9] Machado, et al. Icarus, 285, 2014. [10] Machado, et al. Icarus, 2017. [11] Machado P., et al., Atmosphere, 2021. [12] Gonçalves R., et al., Icarus, vol 335, 2020.