Using the Hubble Space Telescope/Space Telescope Imaging Spectrograph, ultraviolet (UV) extinction curves have been measured in M31 along 13 new sight lines, increasing the M31 sample to 17. This sample covers a wide area of M31, having galactocentric distances of 5–16 kpc, enabling the analysis of UV extinction curve variations over a large region of an external galaxy similar to the Milky Way with global galactic characteristics such as metallicity for the first time. No correlation is found between the extinction parameters and galactocentric distance, which might be expected if there is a radial metallicity gradient in M31. Most of the new UV extinction curves presented here are significantly different from the average extinction curves of the Milky Way, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC), but the average M31 extinction curve is similar to the average extinction curve in the 30 Dor region of the LMC. The wide range of extinction curves seen in each individual Local Group galaxy suggests that global galactic properties such as metallicity may be less important than the local environmental conditions, such as density, UV radiation field, and shocks along each sight line. The combined behavior of the Milky Way, LMC, SMC, and now M31 UV extinction curves supports the idea that there is a family of curves in the Local Group with overlapping dust grain properties between different galaxies.

We discuss and implement the physics of dust-gas non-equilibrium processes into 1-D radiative-convective and 3D climate models to assess at what altitude dust and gas temperatures in the Martian atmosphere diverge and to what extent it affects the thermal structure, dynamics, and transport capabilities of the upper atmosphere. As found in an earlier paper by Goldenson et al. (2008), we find (using a different approach) that dust and gas temperatures diverge above 40 km as collisions between dust particles and gas molecules are too infrequent to equilibrate these two components. With our 1-D model we show that when dust-gas non-equilibrium physics is included, gas temperatures above 40 km cool and heating rates are reduced. The magnitude of the effect depends mostly on the size and abundance of the dust particles and is proportional to each. With our 3-D model we show that this physics is important mainly during times of intense dust lifting events such as local rocket storms, or regional or global storms when dust quickly penetrates to high altitudes and particle sizes can be somewhat larger at least initially. During such times upper atmosphere temperatures cool, wind systems are weakened, and vertical and meridional transport is diminished when compared to simulation assuming thermal equilibrium.

Ozone plays a key role in both atmospheric and near-surface chemistry, as well as in UV absorption in planetary atmospheres. Here, we report observations of ozone from the surface of another planet, using the ozone detector included in the Mars Environmental Dynamics Analyzer (MEDA) Radiation and Dust Sensor (RDS) aboard NASA’s Mars 2020 mission, complementing previous space-based and ground-based observations from Earth. Measurements were acquired at Jezero Crater, Mars, at midday, retrieving an average ozone column abundance of 3.8 ± 2.3 μm-atm (1σ) around aphelion, which fell below uncertainties in northern summer. The retrieved column abundance is in reasonable agreement with previous space-based and ground-based observations from Earth. The measurements of total ozone column abundance around aphelion from Mars 2020 and other missions, together with vertical profile observations from orbit, indicate that ~90% of the observed ozone is confined below 20 km of altitude, the aphelion layer weakly contributing to the total column abundance. These ozone levels below 20 km are 3 to 4 times higher than those predicted by models, challenging current understanding of atmospheric chemistry and composition in the lower atmosphere of Mars. It may be possible that aerosols are reducing the destruction pathways of ozone and/or that unknown active chemistry in the near-surface atmosphere of Mars is at work. Both cases should strongly modify the oxidizing capacity in the lower atmosphere of Mars from current model predictions.

This dataset is simulation data from the NASA Ames Mars GCM, produced for the research article titled "Impact of a Bimodal Dust Distribution on the 2018 Martian Global Dust Storm with the NASA/Ames Mars Global Climate Model." It is presented in NetCDF format.

This study provides comprehensive intercomparisons of dust optical depths derived from Mars Climate Sounder on Mars Reconnaissance Orbiter with measurements from the orbiter instruments THEMIS on Mars Odyssey, CRISM on Mars Reconnaissance Orbiter, EMIRS on the Emirates Mars Mission, and from the surface-based instruments Pancam on the Spirit and Opportunity rovers and SSI on the Phoenix lander. We demonstrate good overall agreement between these dust optical depth datasets, in particular as these measurements were taken at different wavelengths (near IR to thermal IR) and with different measurement geometries (limb, downlooking from orbit, uplooking from the surface). To draw our conclusions, we use direct comparisons of co-located measurements from these instruments, plots of the dust optical depth differences averaged by latitude and Solar longitude, as well as modified Bland-Altman analysis that takes the measurement uncertainties into account. From the Bland-Altman analysis, we find that error estimates provided by the instruments reasonably represent the variability introduced by the two datasets but do not capture offsets. Based on our investigations, we propose potential physical causes such as surface reflectance factor estimation and thermal contrast, for some of the observed differences. We find a linear relation of the differences in dust optical depth between MCS and the other instruments with derived MCS water ice optical depth. Taking this relation into account, together with a constant parameter that accounts for general offsets between the datasets, significantly reduces differences.

The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite onboard the ExoMars Trace Gas Orbiter (TGO) is composed of three spectrometers. In this work, we will use the UVIS channel in occultation mode. An aerosol climatology had been produced covering the second half of MY 34 up to the end of MY 36. Aerosols are an important part of the Martian atmosphere and have a strong relationship with the atmospheric temperature. They are composed of dust, H2O ice, and CO2 ice. Dust is the main aerosol and has a significant contribution to the radiative transfer budget, as it absorbs solar radiation, leading to local heating of the atmosphere. Dust is confined to lower altitudes during the aphelion season and can reach higher altitudes during the perihelion, especially during dust storms that frequently arise on Mars during this period. The ice clouds are more present during the aphelion when the temperature is colder and follow a seasonal pattern. Several types of clouds can be found throughout the year, contrary to the dust they reflect the sunlight and cool locally the atmosphere. Using only the spectral range of UVIS dust, H2O ice, and CO2 ice cannot be differentiated because the three aerosols have similar spectral features in the UV-visible. Dust represents most of the aerosols present in the atmosphere, therefore only dust refractive indices are used in this work. Detection of CO2 and water ice will be investigated in future work using the infrared channel of NOMAD. Nevertheless, we presented a way of indirectly recognizing the composition of the aerosols using indirect parameters such as the temperature or comparison with other datasets.It is possible to distinguish the particle size between 0.1 to 0.8 µm with confidence. When the particles are larger it is not possible to retrieve the precise size. In conclusion we present a climatology of Martian aerosols, including vertical extinction profiles as well as vertical profiles of particle size distributions. The seasonal cycle of the dust is observed and recurring structures over different Martian years such as dust storms or ice clouds are detected. We also present a comparison with water vapor profiles and aerosol profiles during regional dust storms, we showed that the water vapor during the storm could condense to water ice due to the presence of dust condensation nuclei at high altitudes. The thermal and dynamical structure of the atmosphere, and chemical species are all sensitive to the aerosol’s abundance and size.

We performed retrievals of dust and water-ice optical depths at select times spanning Mars years (MYs) 33 through 36. We used data taken by the Imaging Ultraviolet Spectrograph (IUVS) instrument aboard the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, whose precessing orbit allowed IUVS to image the diurnal evolution of water-ice clouds at local times throughout this MY range where they have not been studied. We created a radiative-transfer retrieval algorithm and used it to simultaneously fit the dust and water-ice optical depth of each usable spectrum in IUVS apoapse data for the majority of the MAVEN mission. We compared our results to other datasets to ensure our retrievals produced plausible values and discuss potential reasons for discrepancies. We obtained global climate model (GCM) simulations from two state-of-the-art models and compared our results to both sets of simulations. We show that there are significant differences between our water-ice retrievals and both sets of simulations, both in the spatial cloud patterns and column-integrated optical depths. We discuss the different approaches both models used for simulating these clouds and the implications for accurately modeling these clouds in future GCM work.

The distribution of Mars ozone (O3) is well established; however, our knowledge on the dayside diurnal variation of O3 is limited. We present measurements of Mars O3 column abundances, spanning Mars Year (MY) 34 to the end of MY 36, by the Ultraviolet and VIsible Spectrometer (UVIS), part of the Nadir and Occultation for MArs Discovery (NOMAD) instrument, aboard the ExoMars Trace Gas Orbiter. UVIS provides the capability to measure dayside diurnal variations of O3 and for the first time, a characterization of the dayside diurnal variations of O3 is attempted. The observed O3 climatology for Mars Years (MY) 34-36 follows the established seasonal trends observed through previous O3 measurements. At aphelion, the equatorial O3 distribution is observed to be strongly correlated with the water ice distribution. We show that the early dust storm in MY 35 resulted in a near-global reduction in O3 during northern spring and the O3 abundances remained 14% lower in northern summer compared to MY36. Strong latitudinal and longitudinal variation was observed in the diurnal behavior of O3 around the northern summer solstice. In areas with a weak O3 upper layer, O3 column abundance peaks in the mid-morning, driven by changes in the near-surface O3 layer. In regions with greater O3 column abundances, O3 is observed to gradually increase throughout the day. This is consistent with the expected diurnal trend of O3 above the hygropause and suggests that in these areas an upper O3 layer persists throughout the Martian day. Ozone, a highly reactive gas, plays an important role in the chemical cycles of both carbon and hydrogen on Mars. As ozone is tightly correlated to the presence of the difficult to detect odd hydrogen species, measurement of the ozone distribution can provide vital insight into the Martian photochemistry. We present the ozone abundances measured by the UVIS spectrometer aboard the ExoMars Trace Gas Orbiter, spanning Mars years (MYs) 34-36 and attempt to characterize the daily variations in ozone. The ozone follows the expected seasonal trends, with the highest ozone abundances observed at polar regions in the spring, autumn and winter seasons of both hemispheres and very little ozone during southern summer, outside the northern polar latitudes. An enhancement in equatorial ozone during northern summer is observed, with MY 35 showing lower ozone abundances compared to MY 36, likely the effect of an early dust storm in MY 35 or the long-term impact of the MY 34 global dust storm. In both years, the O3 distribution in northern summer appears to closely follow the water ice distribution and the observed daily cycle in ozone is shown to be highly sensitive to the presence of a high altitude ozone layer. Dayside O3 column abundances on Mars between MY 34 (LS = 150 degrees) and MY 36 have been obtained using the NOMAD-UVIS instrument Ozone is strongly correlated with the presence of water ice clouds in the aphelion season Differences between observed and modeled ozone diurnal variations points toward an under/overestimation of water ice condensation

Introduction: The spatial and temporal variation of ozone (O3) is key to understanding ongoing atmospheric processes and transport in the martian atmosphere[1]. As a photochemically active species, O3 has been used to validate the photochemistry of short lived species and, by extension, the water vapour cycle [2,3,4,5] and as a tracer to track the global circulation[6].The Ultraviolet and Visible Spectrometer (UVIS) instrument[7], a channel of the NOMAD spectrometer suite[8], has been in orbit around Mars for over two years with near continuous nadir observations through the latter half of Mars Year(MY) 34 through to MY36. The UVIS observations provide high resolution spatial and temporal maps of O3 column abundance and provides observations at different local times.A retrieval procedure was developed, using spectral measurements over the Hartley band to obtain the O3 column abundances. The radiative transfer simulation is performed using the discrete ordinates DISORT package[9] and we employ the ‘front-end’ routines (DISORT_MULTI) developed by Mike Wolff, for studies of the martian atmosphere [1,10,11]Results: In this work we present the geographic and seasonal distribution of O3 in the martian atmosphere as measured by UVIS between LS = 148 and 360° in Mars Year 34 (April 2018 to March 2019). Seasonally the O3 distribution is consistent, with low O3 abundances in equatorial regions and higher O3 abundances at higher latitudes in the winter season. As the martian atmosphere cools through northern spring between Ls = 350°(MY34) and Ls = 90°(MY35), due to the reduced solar insolation, we observed a steady increase in equatorial O3, coinciding with the onset of the aphelion cloud belt. The equatorial O3 peaks near the northern winter solstice Ls = 90°, associated with the cooler and dryer atmosphere of the martian aphelion season before reducing again as the atmosphere warms and more water vapour enters the atmosphere.Ozone entrapment[1] is observed in large impact basins, such as the Hellas Basin and to a lesser extent Argyre Planitia. Ozone abundances measured within Hellas can be an order of magnitude higher than the surrounding regions with abundances of 20 µm-atm observed within Hellas compared to 2-5 µm-atm in the surrounding area at aphelion. Ozone entrapment is still observed during the perihelion season, with abundances within Hellas being 5-10 µm-atm.The UVIS dataset provides comprehensive seasonal coverage between latitudes ~74° N and 74° S and samples multiple local times at a giving location enabling unprecedented detail in the O3 diurnal cycle.References:[1] Clancy, R. T, et al. Icarus 266 (2016). [2] Lefèvre, F, et al. Nature 454.7207 (2008). [3] Montmessin, F and Lefèvre, F. Nature Geoscience 6.11 (2013). [4] Holmes, J,A. et al. Icarus 302 (2018). [5] Daerden, F., et al. Icarus 326 (2019). [6] Holmes, J,A. et al. Icarus 282 (2017). [7] Patel, M, R., et al. Applied Optics 56.10 (2017). [8] Neefs, Eddy, et al. Applied Optics 54.28 (2015). [9] Stamnes, Knut, et al. Applied Optics 27.12 (1988). [10] Wolff, M, J., et al. Icarus 208.1 (2010). [11] Wolff, M, J., et al. Icarus 332 (2019).

IntroductionRecently, [1] characterized the relation between ozone and water vapor using SPICAM simultaneous measurements of O3 and H2O column densities covering four Martian years. They found that O3 and H2O columns are clearly anti-correlated at high latitudes while being uncorrelated at low latitudes.In our study, we take advantage of the NOMAD capability to measure simultaneous vertical profiles of ozone and water vapor to characterize the O3 – H2O relationship at different altitude ranges and latitudes. 1. Ozone and water vapor profile retrievalsNOMAD (Nadir and Occultation for MArs Discovery) is a spectrometer composed of 3 channels: 1) a solar occultation channel (SO) operating in the infrared (2.3-4.3 μm); 2) a second infrared channel LNO (2.3-3.8 μm) capable of doing nadir, as well as solar occultation and limb; and 3) an ultraviolet/visible channel UVIS (200-650 nm) that can work in the three observation modes [2,3].The UVIS channel has a spectral resolution

Introduction: We have currently accumulated over 25 years of continuous satellite data on Martian dust and, generally, on the weather of the Red Planet. By utilizing data from instruments operating in the thermal infrared such as the Thermal Emission Spectrometer (TES, onboard the Mars Global Surveyor satellite), Thermal Emission Imaging System (THEMIS, onboard Mars Odyssey), and Mars Climate Sounder (MCS, onboard the Mars Reconnaissance Orbiter), we have been able to reconstruct diurnal maps of column dust optical depth (CDOD) spanning more than 13 Martian years (MY) from 1999 to the present day [1, 2, 3, 4, 5]. Two types of maps exist: ‘gridded maps’ (the mesh is regular but values are missing where there are no observations) and ‘kriged maps’ (interpolated from the gridded maps using kriging to produce complete maps). These longitude-latitude maps are used as 'dust scenario' in the Mars Climate Database [6], among many other applications. They are routinely updated and made publicly available in NetCDF or FITS formats (see the links to the datasets in the acknowledgments section).Recent developments: The daily CDOD maps covering MY 24 through part of MY 27 have been recently improved by using revised retrievals of column dust optical depths from TES observations (refer to the link in the acknowledgments section for accessing this updated dataset). The top four panels of Figure 1 (MY 24, 25, 26, 27) show zonal means of these improved CDOD maps normalized to 610 Pa (MY 27 zonal mean is actually a combination of revised TES-based maps and previous THEMIS-based maps).The arrival of the Emirates Mars Mission (EMM) 'Hope' spacecraft in a low-inclination, high-altitude orbit around Mars has enabled simultaneous monitoring of the full disk of the Martian atmosphere. The CDOD retrievals from the Emirates Mars InfraRed Spectrometer (EMIRS) observations significantly enhance the quality of our dust maps, enabling for the first time quasi-continuous monitoring of storms over multiple local times [7]. The bottom two panels of Figure 1 show zonal means of, respectively, MCS-based maps and EMIRS-based maps for MY 36. Work is in progress to 1) understand the differences, and 2) integrate CDOD information from both MCS and EMIRS to produce combined daily maps.Moreover, the availability of visible images from the EMM/Emirates Exploration Imager (EXI) on one side [8], and retrievals of CDOD in the visible from TES Emission Phase Function (EPF) observations on the other (refer to the link in the acknowledgments section for access to this novel dataset), enables cross-comparison and validation of the daily gridded dust maps with an unprecedented level of detail.Figure 1: Zonal means of CDOD normalized to 610 Pa for 13 Martian years. The top four panels (MY 24, 25, 26, 27) show zonal means of improved maps using revised TES retrievals. The bottom two panels show zonal means of, respectively, MCS-based maps and EMIRS-based maps for MY 36.Tracking of dust events: From the daily CDOD maps, it is possible to identify large-scale dust events (“storms”) reaching regional and planetary scales, follow their evolution, and create statistics of their main characteristics such as trajectory, area, and optical depth (see an example in Figures 2 to 5). A new development in progress is the identification and tracking of large-scale dust events using unsupervised machine learning algorithms [9].A key outcome of this work is the production of a catalog of historic large-scale dust events, which can be routinely updated with new events as new dust maps become available. An important aspect of creating a catalog of dust events is the precise determination of their occurring time. While a Mars calendar based on solar longitude works for many applications, it does not work well for daily maps produced at a discrete number of sols per year. Therefore, we choose to use a sol-based calendar as described in [1, Appendix A]. Each Martian year has either 669 or 668 sols, following a 5-year cycle. The beginning and end of a year is always at midnight at the prime meridian, hence a new year in our sol-based calendar does not necessarily start at LS=0° (see Figure 6).Figure 2: Sol-by-sol identification and tracking of the evolution of a dust sequence (“storm”) in MY 36 between LS=309° and LS=318° from daily EMIRS-based CDOD maps normalized to 610 Pa. The rest of the daily maps is visible in the transparent background.Figure 3: Plot of the trajectory of the centroid of the dust event shown in Figure 2. Figure 4: Plot of the time evolution of the area of the dust event shown in Figure 2.Figure 5: Plot of the time evolution of the average and 1-σ envelope of the CDOD normalized to 610 Pa for the dust event shown in Figure 2.Figure 6: This table shows the Earth UTC dates and Mars solar longitudes of the beginning of Martian years 1 through 38 in our sol-based calendar (see also [1]).Acknowledgments: LM acknowledges support from CNES and ESA MCD project. BKG was supported by UAE University Grant G00003407. Work at the Jet Propulsion Laboratory, California Institute of Technology, is supported by NASA.The multi-annual dataset of daily gridded and kriged maps v2.x for MY24 through MY36 is available on the MCD webpage (NetCDF format) at https://www-mars.lmd.jussieu.fr/mars/dust_climatology/ and on the VESPA repository (FITS format) at https://bit.ly/3QMFfIf (shortened link)The latest v3.0 of the daily gridded maps for MY24 through part of MY27, together with corresponding TES CDOD retrievals in the infrared and in the visible, are available on the NASA PDS (atmosphere node) at:https://atmos.nmsu.edu/data_and_services/atmospheres_data/MARS/montabone.htmlReferences:[1] L. Montabone et al., 2015, doi: 10.1016/j.icarus.2014.12.034.[2] L. Montabone et al., 2020, doi: 10.1029/2019JE006111.[3] M. D. Smith, 2009, doi: [10.1016/j.icarus.2009.03.027[4] M. D. Smith, 2004, doi: 10.1016/j.icarus.2003.09.010[5] A. Kleinboehl et al., 2009, doi: 10.1029/2009JE003358[6] E. Millour et al., EPSC2022-786, https://doi.org/10.5194/epsc2022-786, 2022.[7] Smith et al, 2022, doi : 10.1029/2022GL099636[8] B. K. Guha et al., 2023, doi: 10.1029/2023JE008156[9] T. Lombard & L. Montabone, 10th International Conference on Mars, 2024

The Emirates eXploration Imager (EXI) onboard the Emirates Mars Mission (EMM) is a dual-telescope camera system capable of observing various Martian atmospheric phenomena. The spacecraft's unique orbit allows the EXI to capture full disk views of Mars at a time step of hours or less, with a resolution of similar to 2-4 km per pixel (in the nadir-looking direction) in both visible and UV channels. Leveraging these unparalleled observations, we conducted a comprehensive analysis of dust storms for Martian year (MY) 36, in alignment with EMM's scientific goals. This study involved the compilation of a dust storm database covering one MY using EMM-EXI images. This database contains essential information such as the start and end times of dust storms, their areal extent, and the latitude and longitude of the centroid. Furthermore, we devote significant attention to characterizing sub-diurnal variability, a facet not previously emphasized, by meticulously tracking dust storm evolution across multiple local times. Our analysis also delves into the origins, pathways, and morphological attributes of these dust storms. Overall, we catalog a total of 98 dust storms until the end of MY 36 (excluding the polar cap edge dust storms) since the beginning of the EMM science phase, and discuss their diurnal, seasonal, and spatial variability while comparing with some previously published findings. Additionally, we address the potential impact of EMM's coverage on the variability of these dust storms, drawing insights from a well-established multi-year database prepared from the observations of the Mars Color Imager onboard the Mars Reconnaissance Orbiter. The Emirates Mars Mission (EMM) uses a camera called the Emirates eXploration Imager (EXI) to take pictures of Mars. The EMM spacecraft moves in a unique way that allows the EXI to take pictures of the whole planet multiple times a day. We used the EXI images to learn about dust storms during one Martian year. We created a database with information about when dust storms started and ended, how big they were, and where they occurred on the planet. We found 98 dust storms during this time and compared the findings with previously published results. We observed a strong influence of the atmospheric thermal tides on the occurrence of dust storms over different times of the day, with the peak phases for the large storms mostly between 10 and 16 hr. We observed four different clusters and two pauses in the distribution of dust storms between the southern and northern spring seasons. Finally, we assess the EMM coverage bias on the frequency of dust storms observed with the help of already-established findings from another Mars mission. Overall, this study helps us understand more about dust storms on Mars and how they behave over times of a day or seasons. Emirates Mars Mission (EMM)- Emirates eXploration Imager (EXI) can capture full disk views of Mars at a time step of hours or less We created a dust storm database based on EMM-EXI images for Martian year 36 at the beginning of the EMM science phase Significant attention is given to characterizing the sub-diurnal variability of the storms, which is not previously emphasized

Aerosols are an important part of the Martian atmosphere. They are composed of dust, H2O ice, and CO2 ice. Dust is the main aerosol and has a significant contribution to the radiative transfer budget, as it absorbs solar radiation, leading to local heating of the atmosphere. Dust is confined to lower altitudes during the aphelion season and can reach higher altitudes during the perihelion, especially during dust storms that frequently arise on Mars during this period. The seasonal behavior of the dust will lead to temperature variations in the atmosphere that are important, especially for modelers. Ice clouds are more present during the aphelion when the temperature is colder and follow a seasonal pattern. Different types of clouds can be found throughout the year and contrary to dust, they reflect sunlight and locally cool the atmosphere.The thermal and dynamical structure of the atmosphere, as well as the distribution of chemical species are sensitive to the aerosol’s abundance and size.The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite onboard the ExoMars Trace Gas Orbiter (TGO) is composed of three spectrometers. In this work, we will use the UVIS and SO channels in occultation mode. Both channels are respectively in the UV-Visible (200-650 nm) and infrared (2.3-4.3 µm).We first developed a methodology to compute extinction and particle sizes with the UVIS channel. The climatology produced allowed us to study aerosols along different seasons and latitudes between the second half of Martian Year (MY) 34 up to the end of MY 36 (figure 1).Using only the spectral range of UVIS in occultation, dust, H2O ice, and CO2 ice cannot be differentiated because the three aerosols have similar extinction features. To model the extinction cross-section, we assume spherical symmetry and use a Mie scattering code (Bohren, et al., 1998). We use the commonly used log-normal size distribution with the parameterization of (Hansen, et al., 1974).We show that with UVIS it is possible to distinguish size between 0.1 to 0.8 µm with confidence. When the particles are larger, it is not possible to retrieve the precise size, as the spectra does not possess any absorption bands.With the addition of the infrared channel, NOMAD SO, we can broaden the sensitivity with respect to particle size and can retrieve the composition of the aerosols. H2O ice, CO2 ice, and dust possess different signatures in the IR (figure 2) and it is possible to differentiate them with confidence. The combination of both UVIS and SO greatly improves the retrieval of particle size as it allows us to have more sensitivity for larger particles.Several works have already published climatologies of aerosols with NOMAD. Liuzzi et al., (2019) study water ice cloud and dust particles with the SO channel during MY34 and the beginning of Martian year 35.They were able to discriminate the aerosols and study the presence and evolution of water ice clouds during dust storms. Stolzenbach et al., (2023) also made a similar study , also using SO, from MY 34 to MY 35. Both works were able to study in detail the size distribution during dust events.Streeter et al (2022), used the UVIS channel to produce a climatology of aerosols between MY34 to the end of MY35. They derived extinction vertical profiles but not the size of the particles. Using a model, they were also able to study the presence of water ice clouds and dust in the atmosphere.By the combination of previous work’s results, and the methodology developed for the UVIS channel, we aim to create a new climatology covering from MY34 to the end of MY 36. This new data set will use information contained in the UV and IR channels allowing us to have greater constraints on size and composition of the aerosols. We will be able to study in detail the evolution and occurrence of detached layers during several seasons and latitudes. Figure 1: Extinction vertical profiles with the UVIS channel as a function of LS for the northern ([30°,70°] Lat, Top panel), equatorial ([-30°,30°] Lat, Middle panel), and southern latitude ([-70°,-30°] Lat, Bottom panel) regions for Martian Years 34, 35, and 36. The extinction is taken as the average between 320 and 360 nm. Shaded regions denote periods where there are no observations due to orbital geometry, while the white regions are where the spectrum is rejected. Both sunset and sunrise occultations are averaged in this figure. Figure 2: Example of SO extinction spectra (in red) showing the absorption due to water ice (in orange) with other aerosols here for comparison.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on the Mars Reconnaissance Orbiter (MRO) collected hyperspectral images of the Martian surface and atmosphere from September 27, 2006, through May 7, 2022. Over that time, nearly twenty scientific investigations were completed, most of which arose as a result of the findings from previous investigations. Two review papers published in 2009 (Murchie et al., 2009a, b) described the initial two-year investigation during MRO's Primary Science Phase, its key findings, and the CRISM data products that were developed and released to the community through that time. Here we describe the conduct and evolution of the CRISM investigation since then, which includes MRO's Extended Science Phase and first five Extended Missions. We document the physical changes in the instrument as it aged, including capabilities that were lost as well as new modes of operation not initially envisioned; the new science questions that were investigated and their key findings; anatomy of the extensive collection of data products that have been released to the Planetary Data System; the "final" radiometric calibration; high-order derived products produced from high-resolution targeted observations and global mapping campaigns; and data processing and analysis tools which have been developed and released by the CRISM team.

The Martian atmosphere (from the surface up to the outer layers) is a very dynamic system, quickly responding to strong radiative forcing coming from the absorption of solar radiation from dust particles lofted during dust storms. So far, such dynamical phenomena at short time scales and large spatial scales have been observed mainly from spacecraft in polar or quasi-polar orbits, which cannot provide continuous and simultaneous observations over fixed, large regions. This limitation can be bypassed using spacecraft in equatorial, circular, planet-synchronous (i.e. areostationary) orbit at an altitude of 17,031.5 km above the Martian surface. Besides their possible use as communication relays for ground-based assets, for space weather monitoring (they orbit outside Mars' bow shock), and for the study of surface properties (e.g. thermal inertia and albedo), the unique scientific advantages of areostationary satellites for weather monitoring are comparable to those provided by geostationary satellites. These platforms greatly increase the temporal resolution and coverage of single events, and are ideally suited for data assimilation in global climate models. Thanks to NASA PSDS3 program, we have elaborated a mission concept to put a low-cost, low-weight, ESPA-class SmallSat in areostationary orbit, which is capable of supporting various tank sizes in order to provide a wide range of ΔV for three different Mars arrival scenarios. ExoTerra Resource LLC adapted its "Electrically Propelled Interplanetary CubeSat" bus as part of the mission design. Despite the optimization of the flight trajectories and the use of machine learning algorithms to prioritize data downlink, the conclusions of the concept study clearly point towards the current challenges represented by propulsion, communication, and possibly radiation tolerance for scientific SmallSat missions to Mars. Such conclusions are generally common among all low-cost interplanetary SmallSat concepts. Furthermore, a single areostationary satellite is enough to provide a full-disk view to monitor regional dust storms and water ice clouds at specific locations, but cannot provide the global coverage required to understand extreme phenomena such as Martian planetary-scale dust events. For this reason, we have recently started to study a more advanced mission concept involving the use of at least three areostationary satellites. This new study is carried out in collaboration with the Jet Propulsion Laboratory within the scope of a wider NASA-funded project (PMCS program) looking at a constellation concept. The challenge is to keep the areostationary satellite configuration within the ESPA class limits, in order to take advantage of possible future rideshare opportunities.

AbstractThe SuperCam instrument on the NASA Perseverance rover [1,2] is equipped with a microphone which, for the first time, has recorded sounds from Mars. These sounds include shockwaves from the laser-induce breakdown spectroscopy technique, the Ingenuity rotorcraft and the ambient Martian atmosphere [3,4]. Each of these offers a unique dataset to study Martian atmospheric dynamics at high frequencies. In this abstract we present preliminary results on studying the relationship between the wind and the sounds recorded from the microphone.1. The SuperCam microphoneThe microphone is a Knowles Electret condenser microphone model EK-23132 [1,2,5]. It can record at sampling rates of 25kHz or 100kHz for up to 167s. The nominal bandwidth is 100Hz-10kHz but lower frequencies can be retrieved. It is located on the SuperCam mast unit 2.1m above the ground and is aligned with the camera. This means that the microphone can be made to point in different azimuths and elevations.2. Wind speed estimation from the microphoneThe microphone records the atmospheric pressure at high frequencies. This dynamic pressure is linked to the winds on Mars [5,6]. In a pre-landing analogue study in a wind tunnel, Chide et al. 2021 [5] found that the root mean square (RMS) of the pressure signal is correlated to the wind speed. It was shown that the RMS value from the microphone in the bandwidth of 100-500Hz is proportional to the square of the wind speed. This frequency band was seen to not be extremely sensitive to the wind incidence azimuth but there is some uncertainty, especially for higher wind speeds.We can calculate the RMS envelope over the recording. The square root of this envelope is then proportional to wind speed and can be used as a relative estimate. Figure 1 shows initial results from an afternoon recording on Sol 38 of the mission.Figure 1: Microphone data from Sol 38. Top panel: microphone signal, Middle panel: spectrogram of microphone data, Bottom panel: square root of RMS envelope for 100-500Hz bandwidth.A cross-calibration will be performed with the Mars environmental dynamic analyser (MEDA) wind sensor [7]. This will enable us to obtain an absolute wind speed determination with the microphone. The mast will also be rotated during the cross-calibration to help capture recordings for a variety of wind speed incidence azimuths and thus also determine the sensitivity to wind direction including the identification of vortex shedding [5]. Moreover, a variation of the mast elevation may lead to the determination of vertical wind speeds.The relationship could also be sensitive to other effects, such as the atmospheric stability. To this end, we aim to track diurnal and seasonal variation, along with temperature and static pressure conditions.3. Wind speed variation - gustinessThe microphone recordings yield an estimate of the Martian wind speed. The so far obtained relative wind speed estimates can be used for an analysis of the wind gustiness, that is, the wind speed variation with respect to its mean. This has been explored for Phoenix, Viking and InSight data [6,8] with a gustiness metric defined as the wind speed standard deviation, σw, over the mean wind speed, μw, asnormalised gustiness = σw/μw.The gustiness metric was applied to several microphone recordings around Noon and 16:00 local true solar time (LTST). These results indicate that the later afternoons are more turbulent than midday, where some acquisitions contain very little wind. However, the noon recordings can contain infrequent very large gusts, including the largest so far observed by the microphone. This information was utilised early on in the mission to aid the understanding of potential flight conditions for the rotorcraft Ingenuity.4. ConclusionsWe have introduced how the microphone data are related to the Martian wind. It enables an estimation of the Martian wind speed and the ability to examine the high frequency content of wind gusts. This is important for the understanding of the dynamic pressure spectrum on Mars [3]. The microphone will record the high frequency portion of this dynamic pressure spectrum shedding light on the dissipative regime in Martian turbulence. The variability of the relationship to wind speed and the distribution of gustiness provides a study of high frequency Martian atmospheric dynamics, valuable for studying the Martian planetary boundary layer (PBL). References[1] Wiens et al., SSR, 2021;[2] Maurice et al., SSR, 2021;[3] Murdoch et al., EPSC, 2021[4] Chide et al., EPSC, 2021;[5] Chide et al., ICARUS, 2021;[6] Murdoch et al., SSR, 2017;[7] Rodriguez-Manfredi et al., SSR, 2021;[8] Spiga et al., JGR, 202

New analyses of thermal infrared spectra obtained from the Emirates Mars Infrared Spectrometer (EMIRS) allow for retrieval of water-ice cloud effective radius, reff,ice, in the lower atmosphere of Mars across spatial, seasonal, and daytime diurnal scales. Using a one Martian-year observational dataset the mean retrieved reff,ice is 3.1 mu m (standard deviation, a = 1.5 mu m) for an assumed effective variance, veff,ice = 0.1, and with most individual values between 1 and 10 mu m. Sensitivity analyses show the uncertainty associated with reff,ice is largely inversely proportional to water-ice cloud optical depth, tau ice. As a result, our retrieval is generally applicable to water-ice clouds with tau ice of at least -0.02 to 0.08 at 825 cm-1. Seasonal results show mean reff,ice values of 4.3 mu m (a = 1.9 mu m) during aphelion season (Ls = 40 degrees-140 degrees), associated with larger particle sizes in the aphelion cloud belt (ACB), and 2.5 mu m (a = 0.8 mu m) during perihelion season (Ls = 225 degrees-360 degrees). Diurnal analyses between roughly 06:00 and 20:00 local true solar time indicate the largest variability occurs in ACB clouds, with effective radii tending to be smaller during midday (zonal-mean reff,ice of 4-5 mu m) as compared to the mornings and afternoons (zonal-mean reff,ice of 6-7 mu m). Relatively large spatial gradients in reff,ice within the ACB are observed, including a seasonal mean reff,ice of -8 mu m in the Tharsis region and regions in the southern mid-latitudes with seasonal mean reff,ice of -2 mu m. Spatial variability in reff,ice tends to be smaller throughout the rest of the year, though with some similar patterns. This includes several time periods between regional dust storms when a low-latitude band of water-ice clouds formed in the afternoons near Tharsis, which grew in both optical depth and effective radius to maxima in the early evenings. Lastly, changes in reff,ice are found to be generally positively correlated with changes in tau ice and negatively correlated with estimated cloud height, though reff,ice distributions also show this to be a more complex relationship than simple averages might suggest.

The NOMAD instrument suite on the ESA-Roskosmos ExoMars Trace Gas Orbiter (TGO) observes the physical and chemical composition of the Martian atmosphere with highly resolved vertical profiles and nadir sounding in the IR and UV-vis domains. Vertically resolved profiles of, amongst other species, water vapor, HDO, ozone, CO, CO2, oxygen airglow, dust and clouds were obtained for more than one Martian year [1-5]. During its first year of operations, NOMAD witnessed the 2018 Global Dust Storm (GDS) during its onset, peak and decline. The redistribution of water vapor to high altitudes and latitudes observed during the GDS was explained using the GEM-Mars General Circulation Model (GCM) [6-8]. The GCM was driven by the dust optical depths for Mars Year 34 provided by [9]. The photolysis products of water vapor are a major driver for the atmospheric chemistry on Mars. As water vapor is redistributed over the atmosphere, it is expected to have considerable impact on many other species. GEM-Mars contains routines for atmospheric chemistry and here we present some results of the simulated impact of the GDS on atmospheric chemistry and on several of the observed species. GEM-Mars now also includes the simulation of HDO and the fractionation of water vapor upon cloud formation. The simulations will be compared with the vertical profiles of the D/H ratio obtained from NOMAD observations. The impact of the GDS on D/H can be estimated from these simulations. References [1] Vandaele, A. C. et al. (2019), Nature, 568, 7753, 521-525, doi: 10.1038/s41586-019-1097-3.[2] Aoki, S. et al. (2019), J. Geophys. Res.: Planets, 124, 3482–3497. https://doi.org/10.1029/2019JE006109[3] Gérard et al. (2020), Nature Astronomy, https://doi.org/10.1038/s41550-020-1123-2[4] Villanueva et al., submitted.[5] Korablev et al., 2020, in rev.[6] Neary, L. and F. Daerden (2018), Icarus, 300, 458–476, https://doi.org/10.1016/j.icarus.2017.09.028[7] Daerden, F. et al. (2019), Icarus, 326, 197-224, doi: 10.1016/j.icarus.2019.02.030.[8] Neary, L. et al. (2020), Geophys. Res. Lett., 47, e2019GL084354. https://doi.org/10.1029/2019GL084354[9] Montabone, L. et al. (2019), J. Geophys. Res.: Planets. doi: 10.1029/2019JE006111. 2.11.0.

The Emirates Mars Mission (EMM) has a unique opportunity to observe the surface of Deimos, the smaller and outermost of the two moons of Mars. The origins of both Phobos and Deimos remain debated largely due to lack of available observations. The elliptical orbit of the EMM spacecraft, designed to provide comprehensive coverage of the martian atmosphere, allows for campaigns to periodically observe the moon. The slight adjustment of the orbit to move into a resonance with Deimos permits nominal science to continue. The campaign began in August of 2022 by undertaking a series of maneuvers to enable several flybys each stepping in and progressively attaining a closer distance to Deimos. Here, we will present the images collected by EXI of the targeted flyby (e.g., the flyby wherein the spacecraft achieves its closest distance to the moon). Observations for each flyby will include an initial image set at the start of the approach (red/green/blue/320 nm/260 nm), red images will be acquired at 1 min intervals during the approach, and when the spacecraft is at the closest point to Deimos a red/green/blue image set at full resolution, as well as a 320 nm image binned at 2×2 pixels, will be acquired. As the spacecraft leaves Deimos, the reverse observation strategy will be employed. These observations will help constrain the short-wavelength spectral properties and further characterize the geomorphology of this relatively understudied martian moon.

The EXI instrument onboard the Emirates Mars Mission (EMM) spacecraft has been operating for a full Martian year. Using the elliptical orbit, EXI has observed the atmosphere and surface of Mars at both regional and global scales while providing a unique diurnal sampling. This diurnal coverage is available over much of the planet on a time scale of approximately ten days. The observations are typically taken in both the ultraviolet and visible: 260, 320, 437, 546, and 635 nm, with an effective spatial resolution of 2–4 km per native pixel. This presentation will provide an overview of EXI’s on-orbit activities and performance during the first Mars year of science operations, a summary of the diurnal behavior of seasonal trends in water ice clouds, and some examples of the combined analysis of EXI and Emirates Mars InfraRed Spectrometer (EMIRS) observations. More specifically, we will cover the following: The multiple types of observational modes employed, statistics of the images obtained and available in the EMM Science Data Center, and the radiometric performance of the camera as measured by the standard star observation program. The diurnal trends are associated with the seasonal behavior of water ice clouds through a Martian year, including the aphelion and perihelion seasons. The advantages and challenges of combining the EXI and EMIRS observations for atmospheric and surface studies, where the Instantaneous Field of View differs by one-to-two orders of magnitude. Funding for the development of the EMM mission was provided by the UAE government and to co-authors outside of the UAE by the Mohammed bin Rashid Space Center (MBRSC).