Search

Measurements of CO2, Ar and N2 densities from the Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission (MAVEN) between 150 and 200 km altitude during 2015–2022 are analyzed to reveal diurnal (DW1), semidiurnal (SW2) and terdiurnal (TW3) solar‐synchronous tides in Mars thermosphere. Multi‐year‐mean tidal perturbations on a diurnal‐ and zonal‐mean background, corrected for solar flux variations, are reported as a function of latitude (48°S–48°N), altitude and solar longitude (Ls). The DW1, SW2 and TW3 amplitudes at for example, 180 km altitude are of order 90%–120%, 15%–20%, and ≲10% for CO2 and Ar, and roughly 2/3 these values for N2, the latter presumably due to the difference in molecular weight from the other species. Through examination of vertical phase progressions, DW1 is concluded to be mainly excited in situ, but SW2 and TW3 contain significant contributions from tides propagating upward from lower altitudes. By analogy with studies for Earth's thermosphere, the DW1 amplitudes and phases are thought to reflect the combined influences of thermal expansion and vertical winds. Points of agreement and disagreement with DW1, SW2, and TW3 amplitudes and phases derived from the Mars Climate Database are noted and interpreted. Key Points: Global‐scale solar‐synchronous tides are derived from Mars Atmosphere and Volatile Evolution Mission/Neutral Gas and Ion Mass Spectrometer measurements of CO2, Ar, and N2 at Mars, 150–200 kmThe diurnal tide originates mainly in situ; semidiurnal and terdiurnal tides show evidence of upward propagation from belowPoints of agreement and disagreement with the Mars Climate Database are noted and interpreted [ABSTRACT FROM AUTHOR]

In this paper, the non‐orographic gravity waves (GW) parameterization of the Mars Planetary Climate Model (PCM) previously implemented by Gilli et al. (2020, https://doi.org/10.1029/2018JE005873) is revisited and extended to the exobase (∼250 km). The simulations performed with the new scheme correct some known biases in the modeled thermal tide amplitudes and polar warming, improving the agreement with Mars Climate Sounder (MCS) observed thermal structures and tides below ∼100 km. Additionally, we find that the simulated densities above 150 km are compatible with NGIMS (Neutral Gas and Ion Mass Spectrometer) measured abundances. Large drag depositions ranging up to >∼950 m s−1 sol−1 are induced at altitude of 90–170 km due to the wave saturation (breaking) and depletion, leading to winds damped to magnitudes of ∼150–225 and ∼80 m s−1 in the zonal and meridional directions, respectively. Resulting temperature variations are ∼±10–30 K or 5%–10% at most latitudes except in the polar regions (where they can reach ∼±30–60 K). The results indicate that non‐orographic GW play a significant role in the dynamics of the middle‐upper atmosphere of Mars via the induced transfer of momentum and energy from the lower atmosphere. Plain Language Summary: Atmospheric gravity (buoyancy) waves are oscillations that result from flows over topography (orographic gravity waves (GW)) or perturbations caused by convective forcing, front systems, and jet streams (non‐orographic GW). In this paper, we model non‐orographic GW as a Gaussian wave packet, which is the sum of several monochromatic waves of random wavenumbers and frequencies. The wave packets are launched vertically from low altitudes (∼6 km), where the mean Mars Planetary Boundary Layer is located. We reproduce several features of the thermal structure and tides observed by the MCS by implementing our scheme to the Mars PCM. The scheme has a strong effect on the model's wind fields above an altitude of 35–40 km, transporting momentum from the source layers to higher layers, and even up to the thermosphere (altitude >∼100 km). The temperature and density variations generated by the scheme are comparable to the observations made by the Neutral Gas and Ion Mass Spectrometer. Our results demonstrate that non‐orographic GW play a crucial role in the momentum‐energy transport that affects the dynamics of the middle and upper atmosphere of Mars. Key Points: A stochastic parameterization of non‐orographic gravity waves is implemented up to the exobase (∼0–250 km)Simulation results are in very satisfying agreement with Mars Climate Sounder observed thermal structures and tidesThe simulated upper atmospheric densities are compatible with Neutral Gas and Ion Mass Spectrometer abundances [ABSTRACT FROM AUTHOR]

We assimilate atmospheric temperatures from the Emirates Mars Infrared Spectrometer on board the Emirates Mars Mission (EMM) into the Mars Planetary Climate Model at the start of EMM's early science phase (Mars Year 36 Ls = 57.34–92.90°). Mars data assimilation benefits significantly from EMM's unique near‐hemispheric observations, frequent repeated observations of the same location, and full diurnal cycle coverage. Our analysis verifies well against in‐sample temperature observations, and is 1–3 K warmer than Mars Climate Sounder observations. We identify a warm front in concurrent Emirates eXploration Imager observations by correlating an elongated water ice cloud with temperatures and winds in the analysis; the analysis winds are consistent with its observed motion. We also calculate the full horizontal wind diurnal cycle; the zonal flow is weaker and the meridional circulation is stronger than simulating the same time period using the model alone. Plain Language Summary: The Emirates Mars Mission (EMM) promises advances in our understanding of Mars' atmosphere similar to when geostationary satellites first observed Earth. Data assimilation is a process where we combine observations with an atmospheric simulation. Using it to study Mars will benefit from EMM's observations of the whole of one side of the planet, frequent repeated observations of the same location, and observations of the full day‐night cycle. We combined observations of Mars atmospheric temperatures with our model over 79 Martian days at the start of EMM's main study period. We were able to demonstrate what is possible with EMM that has not been possible before. In particular, we found a long water ice cloud near the north pole in separate visible and ultraviolet images made by EMM. By comparing the motion and structure of this cloud with our results, we found that this "warm front" also appears in our results, and we were able to deduce properties of the front that were not observed. We were also able to deduce how Martian winds change over the course of the day and night, by making use of EMM's temperature observations over the full day‐night period. Key Points: We assimilate atmospheric temperature profiles from Emirates Mars Mission‐Emirates Mars InfraRed Spectrometer (EMM‐EMIRS) over a 79‐sol period in Mars Year 36 shortly before northern summer solsticeEMIRS' near‐hemispheric spatial coverage is used to analyze complete weather systems; we deduce the structure and motion of a warm frontThe horizontal wind diurnal cycle is retrieved by assimilation based on EMM‐EMIRS' extended local time coverage of atmospheric temperatures [ABSTRACT FROM AUTHOR]

Observations by the Emirates eXploration Imager (EXI) on‐board the Emirates Mars Mission are used to characterize the diurnal, seasonal, and spatial behavior of aphelion cloud belt during Mars Year 36 LS ∼ 30°–190°. Building from previous work with the Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter, we retrieve water ice extinction optical depth (τice) with an uncertainty ±0.0232 (excluding particle size effects). We connect EXI and MARCI using radiance and τice. Zonal and meridional diurnal trends are analyzed over 6–18 hr Local True Solar Time. The retrievals show large morning‐evening asymmetries about a minimum near 12 hr. The latitudinal distributions in early morning are extensive and particularly striking near mid‐summer. Comparisons to the Mars Planetary Climate Model show reasonable agreement with basic diurnal behavior, but noticeable departures include too much water ice in early morning, the general latitudinal extent, and behavior at smaller scales like the volcanoes and other topographically distinct features. Plain Language Summary: Water ice clouds have important roles in the Martian atmosphere because they can influence weather and act as probes of important weather and climate processes. Using the camera on‐board the Emirates Mars Mission, water ice clouds are studied for the first time throughout the Martian day and year at scales of 10–20 km around the planet. We study a key cloud structure called the aphelion cloud belt (ACB) that encircles the planet at low latitudes during the northern hemisphere spring and summer seasons. Using the camera images from this period, we examine how the ACB structure changes from morning through evening and throughout these two seasons. We developed a computer program that converts the brightness of a pixel into a measure of the cloud thickness. We find that the ACB clouds are much thicker and wide‐spread in the early morning compared to other times of day; and are much more extant across the planet in the morning, particularly in mid‐summer. We also compare to weather prediction programs and find important differences that will help scientists improve Mars weather forecasts for future research and missions. Key Points: The Emirates eXploration Imager is used to retrieve ice extinction optical depth in Mars Year 36 during solar longitudes 30–190°Diurnal trends of the aphelion cloud belt are examined between 6 and 18 hr using both zonal and meridional maps, revealing new behaviorComparisons to the Mars Planetary Climate Model show reasonable agreement with broad structure, but important differences are noted [ABSTRACT FROM AUTHOR]

Temperature profiles retrieved using the first set of data of the Emirates Mars InfraRed Spectrometer obtained during the science phase of the Emirates Mars Mission are used for the analysis of migrating thermal tides in the Martian atmosphere. The selected data cover a solar longitude (LS) range of 60°–90° of Martian Year 36. The novel orbit design of the Hope Probe leads to a good geographic and local time coverage that significantly improves the analysis. Wave mode decomposition suggests dominant diurnal tide and important semi‐diurnal tide with maximal amplitudes of 6 and 2 K, respectively, as well as the existence of ∼0.5 K ter‐diurnal tide. The results agree well with predictions by the Mars Planetary Climate Model, but the observed diurnal tide has an earlier phase (3 hr), and the semi‐diurnal tide has an unexpectedly large wavelength (∼200 km). Plain Language Summary: As a result of its small thickness, the Martian atmosphere experiences large temperature variations within each Martian day due to the incoming sunlight. Such rapid and large temperature variations excite waves propagating in the Martian atmosphere that highly influence winds, cloud formation, and dust transport. In this work, we use the atmospheric temperature measurements derived using observations obtained by an infrared spectrometer onboard the Hope Probe to analyze the diurnal temperature variations and the excited waves. The novel design of the spacecraft's orbit provides good data coverage in location and time, leading to the success of detailed analyses of the waves that propagate in the Martian atmosphere synchronously with the movement of the Sun, among which a new wave mode with a period of one third of a Martian day is detected. We compare the results with predictions provided by numerical simulations, and they show good agreements in the wave strengths, but the observed waves have different wavelengths and phases. Key Points: Migrating thermal tides in the Martian atmosphere are analyzed using the first set of Emirates Mars Mission/Emirates Mars InfraRed Spectrometer observationsThe observed amplitudes of diurnal and semi‐diurnal tides agree well with model predictions, but with different phases and wavelengthsTer‐diurnal tide is detected with an amplitude of ∼0.5 K, due to the observations covering the full range of local times [ABSTRACT FROM AUTHOR]

We assimilate atmospheric temperature profiles and column dust optical depth observations from the ExoMars Trace Gas Orbiter Atmospheric Chemistry Suite thermal infrared channel (TIRVIM) into the Mars Planetary Climate Model. The assimilation period is Mars Year 34 Ls = 182.3°–211.4°, covering the onset and peak of the 2018 global dust storm. We assimilated observations using the Local Ensemble Transform Kalman Filter with 36 ensemble members and adaptive inflation; our nominal configuration assimilated TIRVIM temperature profiles to update temperature and dust profiles, followed by dust column optical depths to update the total column dust abundance. The observation operator for temperature used the averaging kernels and prior profile from the TIRVIM retrievals. We verified our analyses against in‐sample TIRVIM observations and independent Mars Climate Sounder (MCS) temperature and dust density‐scaled opacity profiles. When dust observations were assimilated, the root‐mean‐square temperature error verified against MCS fell by 50% during the onset period of the storm, compared with assimilating temperature alone. At the peak of the storm the analysis reproduced the location and magnitude of the peak in the nighttime MCS dust distribution, along with the surface pressure diurnal cycle measured by Curiosity with a bias of less than 10 Pa. The analysis winds showed that, at the peak of the storm, the meridional circulation strengthened, a 125 m s−1 asymmetry developed in the midlatitude zonal jets, the diurnal tide weakened near the equator and strengthened to 10–15 K at midlatitudes, and the semi‐diurnal tide strengthened almost everywhere, particularly in the equatorial lower atmosphere. Plain Language Summary: ExoMars Trace Gas Orbiter has been in low orbit around Mars since early 2018. During 2018 a large amount of dust was lifted from Mars' surface into the atmosphere. This eventually obscured most of the planet, forming a global dust storm. These storms have a large effect on the temperature and weather in Mars' atmosphere. We used observations from the spacecraft's thermal infrared instrument. This measures how much light comes from the atmosphere and surface at wavelengths where heat is emitted, and can be used to work out the atmospheric temperature and dust content at different times of day. We combined these observations with a numerical model of Mars' atmosphere, considering uncertainties in the measured atmospheric properties and the modeled atmosphere. We compared our results with temperature and dust observations made by Mars Climate Sounder on board Mars Reconnaissance Orbiter. Including dust observations was better than just using temperature observations. While the dust storm was raging, north‐south wind speeds increased, the strong eastward wind in the northern hemisphere became much stronger than in the southern hemisphere, and differences between day and night became larger. Our results mean we can better understand aspects of Mars' atmosphere throughout the daily cycle. Key Points: We assimilate temperature and dust observations from ExoMars Trace Gas Orbiter‐Atmospheric Chemistry Suite‐TIRVIM during the MY34 global dust storm (GDS)The analysis verifies well against independent Mars Climate Sounder temperature and dust profiles, and Curiosity pressure measurementsAt the peak of the GDS the winds strengthen, the diurnal tide migrates poleward, and the semi‐diurnal tide strengthens [ABSTRACT FROM AUTHOR]

The D/H ratio and its implications on the atmospheric escape, make it an essential observable to study the current and past inventory of water on Mars. With the arrival of the Trace Gas Orbiter around Mars, new measurements of the D/H ratio are now available and require tools to interpret the observations and understand the HDO cycle. We here present simulations of an updated version of the Laboratoire de Météorologie Dynamique Mars Global Climate Model which includes HDO and in particular the fractionation processes it undergoes. We compare our model simulations with the HDO observations in solar occultation from the Atmospheric Chemistry Suite mid‐infrared channel on board the Trace Gas Orbiter (Alday et al., 2021; https://doi.org/10.5281/ZENODO.5100448). The model successfully reproduces the general trends of the D/H ratio, indicating that the main physical processes are captured by theory. A consistent simulation of condensation processes is found to be key in the representation of the D/H ratio. Improvements in the representation of clouds and on the water cycle will help improving the representation of the HDO cycle and better help extrapolate back in times the conditions of water escape on Mars. Plain Language Summary: Understanding how the Martian climate affects the isotopic ratio of water is key to understand the history of water on the planet. We use a general circulation model to simulate the cycle of HDO, an isotope of water, in the atmosphere of Mars. We compare our model results with spacecraft observations from the Atmospheric Chemistry Suite spectrometer on board the Trace Gas Orbiter, currently in orbit around Mars. Our model provides a good qualitative agreement with the observations. We find that the condensation of water vapor into ice is a critical process for determining the isotopic ratio of the vapor phase. Key Points: We simulated the HDO cycle on Mars using a 3D Global Climate ModelGCM simulations were compared with solar occultations from Atmospheric Chemistry Suite on board the Trace Gas OrbiterA good representation of the condensation processes is key to reproduce the observed D/H ratio [ABSTRACT FROM AUTHOR]

Thermal tides in the Martian atmosphere are analyzed using temperature profiles retrieved from nadir observations obtained by the TIRVIM Fourier‐spectrometer, part of the Atmospheric Chemistry Suite onboard the ExoMars Trace Gas Orbiter. The data is selected near the northern summer solstice at solar longitude (LS) 75°–105° of Martian Year 35. The observations have a full local time coverage, which enables analyses of daily temperature anomalies. The observed zonal mean temperature is lower by 4–6 K at ∼100 Pa, but higher toward the summer pole, compared to the Laboratoire de Météorologie Dynamique (LMD) Mars General Circulation Model (GCM). Wave mode decomposition shows dominant diurnal tide and important semi‐diurnal tide and diurnal Kelvin wave, with maximal amplitudes of 5, 3, and 2.5 K, respectively, from tens to hundreds of Pa. The results generally agree well with the LMD Mars GCM, but with noticeable earlier phases of diurnal (∼1 hr) and semi‐diurnal (∼3 hr) tides. Plain Language Summary: Unlike the Earth, daily temperature variation on Mars is as large as tens of degrees because of its thin atmosphere. The sunlight absorbed by the Martian surface and dust in the atmosphere leads to dramatic temperature increase in the lower atmosphere during daytime. Such large and regular changes can trigger temperature waves, and some modes of them can propagate into higher altitudes, where they become the major factor controlling the daily temperature variation. In this work, temperature profiles obtained using thermal‐infrared spectra are analyzed. Zonal mean temperature is compared with numerical simulations of the Martian atmosphere. Different types of the wave modes are computed through decomposition. Results from the observation agree well with model prediction when the observation mechanisms are taken into consideration. Estimation of the strength of these waves can be improved in the future with improved design of observation strategies. Key Points: Thermal tides in the Martian atmosphere are investigated using temperature profiles retrieved from TIRVIM nadir observationsDiurnal tide dominates daily temperature variations; semi‐diurnal tide and diurnal Kelvin wave are also importantObservations agree well with numerical simulations, but suggest phases of diurnal and semi‐diurnal tides earlier than predicted [ABSTRACT FROM AUTHOR]

The deuterium to hydrogen (D/H) ratio is commonly used to investigate the history of water on Mars, yet the mechanisms controlling present‐day HDO behavior are poorly understood. Significant variations of the D/H ratio were first predicted on the basis of a 3D global climate model, which were later confirmed by ground‐based observations. This behavior, consisting of lower HDO/H2O ratios in the colder regions of Mars, is related to the isotopic fractionation occurring at condensation. We leverage this previous effort and present an updated implementation, using the modern version of the model, that remains in agreement with the older version. We explore the impact of the global dust storm (GDS) that occurred during Martian year 34 (MY34) on HDO. Our simulations indicate that HDO is on average 40% more abundant at 100 km during the MY34 GDS year than during a regular year, with likely large consequences for the escape flux of water that year. Plain Language Summary: HDO, the semi‐heavy isotope of water, when compared to water, is a good indicator of how much water has been escaping from the atmosphere of Mars over the ages. Ultimately, it can be used to estimate the past reservoir of water available on Mars in its early youth. Because HDO has a slightly higher molecular mass compared to H2O, condensation induces an enrichment of HDO in the ice phase compared with the vapor phase. This subsequently causes spatial and temporal variations of the deuterium to hydrogen ratio. We use a global circulation model to simulate the HDO cycle in the atmosphere. Our model is an upgrade of the previous model presented in Montmessin et al. (2005, Journal of Geophysical Research, 110(E3), E10004. doi:10.1029/2004JE002357). We then simulate the effect of the global dust storm that affected Mars during the summer of 2018, and show that it should have had a strong impact on the vertical distribution of HDO, allowing it to reach higher altitudes. Such simulations are intended to be compared with observations from the Trace Gas Orbiter, currently in orbit around Mars. Key Points: We reimplemented the HDO cycle in a more recent version of the Laboratoire de Météorologie Dynamique Mars global climate modelWe reproduce the observed gradient of the deuterium to hydrogen ratio between cold and warm regionsThe global dust storm of Martian year 34 has a strong effect on the vertical distribution of HDO [ABSTRACT FROM AUTHOR]

We report a new water‐ice cloud feature observed during the Mars year 34 global dust storm: twilight cloud bands that routinely formed just past the evening terminator. We use images taken by the MAVEN/IUVS instrument. These bands were often latitudinally continuous, spanning over 6,000 km and were present between 18:00 and 19:00 local time. They were present for nearly the entire time IUVS imaged the evening terminator and often reached altitudes of at least 40 to 50 km during the mature phase of the storm. We compare these observations to LMD global climate model simulations. The simulations generally contain the temporal and spatial extents of the bands seen in IUVS data throughout the storm, but there are some discrepancies. We infer that these clouds formed as a result of semidiurnal thermal tides. Plain Language Summary: Water‐ice clouds and dust are among the most common particles in the Martian atmosphere, but the effect of global dust storms on cloud formation is largely unknown. We observed cloud bands that repeatedly formed near dusk during the Mars year 34 global dust storm. We saw these bands throughout the storm at locations all across the planet. We investigate this feature by using a global climate model, which predicted the formation of these cloud bands as a result of rapidly changing temperatures. The simulations of the bands contain several features seen in our observations, but not all. Key Points: We observed a new cloud formation phenomenon just after sunset during the Mars year 34 global dust storm in MAVEN/IUVS imagesGlobal climate model simulations are able to reproduce several but not all aspects of our observationsThese twilight clouds formed due to semidiurnal thermal tides [ABSTRACT FROM AUTHOR]

We report observations by the Mars Climate Sounder showing strong diurnal variations in temperature and the vertical dust distribution during the 2018 (Mars Year 34) global dust event. The temperature field shows weak diurnal tidal activity at equatorial latitudes but a strong diurnal tide in middle to high latitudes with a maximum amplitude of 29 K in the lower atmosphere of the south polar region. The diurnal variability of dust is small in the equatorial region and increases toward higher latitudes. At middle and low latitudes, comparable dust amounts are found about 5–10 km higher in the atmosphere on the dayside than on the nightside. The dust reaches the highest altitudes in the late afternoon and is found at the lowest altitudes in the late night. In the southern high latitudes a persistent cold air mass with low dust content is identified on the nightside of the planet centered at 3–6 a.m. local time. The observed variations are well represented by model simulations with the Laboratoire de Météorologie Dynamique General Circulation Model. Comparisons between data and model results suggest that the diurnal variations in the dust are largely driven by the meridional circulation exhibiting diurnal tidal variations. The model results show that the compact air mass in the south polar region has a high potential vorticity, supporting its interpretation as a remnant of the southern polar vortex, which is forced toward the nightside of the planet due to the enhanced diurnal tide during the global dust event. Plain Language Summary: One of the most distinctive features of the Martian atmosphere are global dust storms, one of which occurred in 2018. We report on observations of the vertical structure of atmospheric temperature and dust by the Mars Climate Sounder onboard Mars Reconnaissance Orbiter. Strong differences between day and night are found in both temperature and dust vertical structure. The strongest temperature variations are observed in the south polar atmosphere, with temperature differences up to 58 °C/136 °F between day and night. Comparable dust amounts are found 5–10 km (3–6 miles) higher in the atmosphere on the dayside than on the nightside at central and equatorial latitudes. In the southern polar region a persistent cold body of air with low dust is identified on the nightside of the planet. The observations are compared with the results from a global atmospheric computer model. The observed temperature and dust distribution and their variations over the Martian day are well represented by the model. The diurnal variations in the dust are largely driven by diurnal changes in the large‐scale atmospheric circulation. The compact body of air in the south polar region is forced to the nightside by this altered circulation but does not dissipate for several months. Key Points: The Mars Climate Sounder observes strong diurnal variations in the vertical distribution of dust during the 2018 global dust stormDust diurnal variability at low and middle latitudes is largely related to the meridional circulation exhibiting diurnal tidal variationsDiurnal variations at south polar latitudes are related to a remnant of the polar vortex confined to the nightside of the planet [ABSTRACT FROM AUTHOR]

The hydration of the martian regolith at decimeter depth scales varies regionally, suggestive of geologically sustained processes, independent of diurnal soil-atmosphere exchange. A combination of factors, including residual hydration from ancient processes in the hydrosphere/cryosphere, seasonal exchange between the crust and atmosphere in the martian critical zone, or structural water in minerals or salts sourced via hydrothermal processes can contribute to such lateral changes in bulk regolith hydration. Here, we consider the theoretical extent of regolith hydration from explosive volcanic eruptions and subsequent hydration. While magmatic degassing has previously been considered as a contributing factor to regolith hydration, the relationship between hydrated regolith and the depositional footprint of volcanic eruption columns and associated atmospheric dispersal remains poorly known. We run simulations of eruptions in an ancient atmosphere over a martian year to account for seasonality and produce theoretical ash deposition maps which are then input into a geographic weighted regression model to predict hydrated regolith. We find that ash deposited via explosive volcanism can help explain certain patterns of hydration enrichment in the martian regolith, including those near Apollinaris Patera Arabia Terra, and Sabea Terra. While the global patterns of regolith hydration cannot be explained by one process alone, we found that hydrated ash likely contributed to hydrated regolith at a commensurable level to other leading hydration mechanisms. The surface of Mars is blanketed by a pervasive layer of regolith, a mixture of unconsolidated sediment of multiple grainsizes that range from very fine dust to larger pebbles. This regolith contains significant amounts of water that are stored in the chemical bonds that make up the individual regolith grains. The amount of water bound in the regolith is spatially inconsistent throughout the planet; some areas contain more water, while others contain less. Several different geologic processes have likely contributed to these inconsistencies, including volcanic processes. While gentle volcanic outgassing has already been considered, here we specifically looked at how explosive volcanism and the associated spreading of volcanic ash in the martian atmosphere may have contributed to hydrated regolith patterns. By using multiple numerical simulations, we found that explosive volcanism likely contributed to certain patterns of hydration in the regolith along with other geologic processes. • There is a pathway between explosive volcanism and hydrated regolith. • Ancient explosive volcanism contributed to hydrated regolith patterns. • Areas near Apollinaris Patera, Arabia Terra, and Terra Sabaea show best fit between deposited ash and regolith hydration. [ABSTRACT FROM AUTHOR]

The entry, descent and landing of Schiaparelli, the ExoMars Entry, descent and landing Demonstrator Module (EDM), offered a rare (once-per-mission) opportunity for in situ investigations of the martian environment over a wide altitude range. The aim of the ExoMars AMELIA experiment was to exploit the Entry, Descent and Landing System (EDLS) engineering measurements for scientific investigations of Mars' atmosphere and surface. Here we present the simulations, modelling and the planned investigations prior to the Entry, Descent and Landing (EDL) event that took place on 19th October 2016. Despite the unfortunate conclusion of the Schiaparelli mission, flight data recorded during the entry and the descent until the loss of signal, have been recovered. These flight data, although limited and affected by transmission interruptions and malfunctions, are essential for investigating the anomaly and validating the EDL operation, but can also contribute towards the partial achievement of AMELIA science objectives. [ABSTRACT FROM AUTHOR]

The InSight spacecraft landed in the flat regions of Elysium Planitia on November 26th 2018. The instruments on board InSight make it capable of acting as a meteorological station at the surface of Mars. A pressure sensor (PS), two temperature and wind sensor booms (TWINS), along with the InSight FluxGate (IFG) magnetometer, form the Auxiliary Sensor Payload Suite (APSS). This is complemented by capabilities to measure surface brightness temperature by the radiometer in the Heat-Flow and Physical Properties Package (HP3) suite, to explore the impact of atmospheric processes on seismic measurements by SEIS, and to use InSight cameras to estimate atmospheric opacity (notably caused by suspended dust particles) and other atmospheric phenomena such as clouds and dust devils. We will discuss results drawn from atmospheric measurements on board InSight over the first two months of operation, highlighting new perspectives permitted by the high-frequency, continuous nature of the InSight acquisitions. Surface pressure measurements record global-to-local atmospheric phenomena: CO2 condensation (annual), dust cycle and storms (seasonal), baroclinic waves (weekly), thermal tides (daily), gravity waves (thousands of seconds), convective cells (hundreds of seconds), convective vortices (tens of seconds, leading to dust devils if dust particles are transported in the vortex). Two main large-scale wind regimes were expected from Global Climate Modeling at the InSight landing site during a typical year: towards the northwest in northern spring and summer, then in the opposite direction in southern summer. Existing in-situ measurements on Mars and Large-Eddy Simulations indicate that daytime convective vortices and cells not only impact pressure, but also temperature and winds; the nighttime atmosphere on Mars is comparatively much less turbulent and dominated by shear-driven turbulence, in contrast to the buoyancy-driven turbulence active in daytime. All such existing measurements and model predictions will be compared and challenged with InSight measurements. Seismic signatures associated with atmospheric phenomena will also be discussed, with a particular emphasis on the knowledge gained by the unprecedented measurements performed by InSight's seismometers. [ABSTRACT FROM AUTHOR]

The ExoMars Trace Gas Orbiter (TGO), a mission by ESA and Roscosmos, was launched inMarch 2016 and reached its final, near-circular 400 km orbit around Mars in March, 2018. Onboard TGO, the Atmospheric Chemistry Suite (ACS) is a set of three spectrometers includinga thermal-infrared channel, TIRVIM. This Fourier-transform spectrometer covers the range600–6000 cm−1 (1.7–17μm) with a spectral resolution of 1.2 cm−1. We focus here on nadirobservations in the range 600-1300 cm−1, which covers absorption by CO2 (centered at 667cm−1), water ice clouds (centered at 820 cm−1) and dust (centered at 1100 cm−1).The advantage of the TIRVIM data set over previous instruments comes from theTGO orbit, which is not sun-synchronous and was designed to sample a completedaily cycle every 55 days. Hence, TIRVIM has the capacity to uniquely study boththe diurnal and seasonal variability of the thermal structure, dust and ice cloudopacity. We have developed a radiative transfer model coupled to a retrieval algorithm thatexploits TIRVIM spectra to simultaneously retrieve vertical profiles of the temperature from 5 to 45 km, surface temperature, and integrated optical depth of dust and water ice clouds.This algorithm was tested and validated against synthetic observations generated undervarious conditions (local time, seasons, latitude, aerosol load,...). We have thenapplied this algorithm to the first 45 days of TIRVIM data acquired in March-April,2018. The retrieved temperature profiles have been validated against thousandsof co-located measurements acquired by the Mars Climate Sounder around 3amand 3pm, a limb-viewing radiometer onboard Mars Reconnaissance Orbiter. Theagreement between the two data sets is very satisfactory. In particular, the amplitudeof the diurnal thermal tide as seen by MCS is very well captured by TIRVIM atpressures greater than 10 Pa. However, TIRVIM underestimates it in the range 1–10 Pa,which is due to a much poorer vertical resolution in this region (as expected froma nadir-viewing sounder). We will present these results with an emphasis on thediurnal cycle of the atmospheric temperature and the aerosols load, along withcomparisons with predictions from the LMD Mars GCM. Analysis of TIRVIM dataacquired during the dust storm in June-July 2018 is in progress and will also bepresented. Acknowledgements: The ACS experiment is led by IKI in Moscow. We acknowledgesupport by CNES and Roscosmos. [ABSTRACT FROM AUTHOR]

The ExoMars Trace Gas Orbiter (TGO), a collaborative project between the European Space Agency and Roscosmos, was successfully inserted into Mars orbit on 19 October 2016, and reached its final science orbit on 7 April 2018. TGO began taking observations as part of commissioning operations in March 2018.At the Laboratoire de Météorologie Dynamique (LMD) we are responsible for data assimilation of observations from the Atmospheric Chemistry Suite (ACS) thermal infrared instrument (TIRVIM) on board TGO. This instrument measures vertical profiles of temperature as well as dust and water ice integrated content, at various local times, latitudes and seasons.Here we report on assimilation of the first six weeks of TIRVIM observations into the LMD Mars General Circulation Model (GCM), using the Local Ensemble Transform Kalman Filter (LETKF) technique. The LETKF is an ensemble-based assimilation scheme where we typically use 16 ensemble members and multiplicative inflation to adjust the background ensemble error covariance. The assimilation focuses on atmospheric temperatures retrieved from nadir thermal emission spectra taken between 2018 March 13 and 2018 April 28. These have been calibrated and then retrieved using a line-by-line radiative transfer model. The observations cover various local times of day with full coverage in longitude every 7-10 days, over +/- 75 degree latitude, with vertical coverage between 5-45 km altitude.We shall report on the differences between the assimilation and a free-running model, particularly at local times of day that have not been observed prior to TGO. We shall also report on progress combining assimilation of ACS observations with profiles from Mars Climate Sounder on board NASA's Mars Reconnaissance Orbiter, to fill in anticipated gaps in the ACS observational record and to sample the local time of day more fully. [ABSTRACT FROM AUTHOR]