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Observations show that the temperature above 100 km in Venus’ atmosphere intermittently falls below 100 K, when both H2O and CO2 become supersaturated. Profiles show temperatures can fall below 60 K at heights between 115-125 km, presumably as a result of large amplitude gravity waves. Cosmic dust particles entering the atmosphere are predicted to ablate between 110 and 125 km. This provides a source of metallic vapours (principally Mg and Fe atoms), which then form metal carbonate molecules known as meteoric smoke particles (MSPs). Because these molecules are highly polar, they are excellent nuclei for CO2- and H2O-ice particle formation.In this study we examine the feasibility and kinetics of CO2-ice cloud formation, using both classical nucleation theory (CNT) and bottom-up kinetic nucleation theory (KNT). For CNT, a dimensionless non-isothermal coefficient is included to reduce the nucleation rate of CO2 ice particles, since the atmospheric concentration of the nucleating species (CO2) comprises a significant fraction of the total atmosphere. For heterogeneous CNT on MSPs, a surface diffusion approach is used where molecules can diffuse on the surface to form a critical cluster for nucleation and the effect of dissipation of critical clusters is accounted for. Application of CNT shows that whereas homogeneous nucleation should be too slow for significant cloud formation, heterogeneous nucleation rates around 1 cm-3 s-1 for CO2 ice should be possible in the colder regions (< 80 K).For KNT, the rate coefficients for the sequential addition of CO2 molecules up to MgCO3(CO2)40 were calculated explicitly with Rice Ramsperger Kassel Markus (RRKM) theory, using a solution of the Master Equation based on the inverse Laplace transform method. The rates of dissociation of the clusters i.e. MgCO3(CO2)n+1 → MgCO3(CO2)n + CO2, were calculated by detailed balance. In order to explore the evolution of the CO2-ice clouds, a 1-dimensional model was constructed to describe the nucleation, growth, sedimentation and sublimation of the ice particles. The model is initiated with a vertical profile of atmospheric density and temperature determined using the Solar Occultation in the InfraRed (SOIR) instrument on a specified orbit of Venus Express, and then follows the fate of an MSP seed particle as it grows, sediments and finally sublimates on entering a warmer region. Two categories of cloud tend to be produced from the observed temperature profiles. The first peaks around 120 km with particles around 100-200 nm radius; and the second type persists for longer and peaks around 110 km, with particles that can exceed 2 μm in radius. Most clouds are predicted to occur at high latitudes (>70o). Using a probable underestimate of the MSP concentration (100 cm-3), the optical extinction of these clouds at 220 nm should be readily observable by the SOIR instrument. However, the clouds are short-lived because of rapid sedimentation (typically 300 s, the longest-lived around 1200 s), so that the detection of these ephemeral “hail showers” will be challenging.

Observational evidence shows the ubiquitous presence of short-lived halogens in the global atmosphere. This includes the biogenic contribution of organic very short-lived halocarbons as well as the abiotic source of inorganic halogens throughout heterogeneous recycling. All of these species are naturally emitted from the oceans, polar ice, and the biosphere, presenting a pronounced spatio-temporal source strength that controls the regional, vertical and seasonal distribution in the troposphere. In addition, anthropogenic emissions of reactive halogens, both organic and inorganic, have been identified in the atmosphere. Most notably, short-lived halogen emissions influence the oxidative capacity of the troposphere and consequently the concentration of ozone and methane. In this communication, we use the halogen version of CAM-Chem to evaluate how these interactions evolve across pre-industrial, present-day, and future climates under different halogen emission scenarios.

Iodine has the potential to cause stratospheric ozone depletion. However, there is still significant uncertainty concerning the magnitude of its effect, ranging from a few percent to 10% based on the literature studies. Moreover, these studies have only considered that up to 0.77±0.10 per trillion by volume (pptv) total inorganic iodine is entrained into the stratosphere from the surface emissions. Recently the first 12U CubeSat using the iodine electric propulsion was launched in November 2021 into an orbit at ~480 km. The system produces iodine ions after vaporizing solid iodine. Thus the launch of nanosatellites using iodine propulsion will inject gas-phase iodine species into the thermosphere, which upon re-entering the atmosphere could potentially cause depletion of the ozone layer and consequently impact climate. Here we use the 3-D Whole Atmospheric Community Climate Model (WACCM) to investigate stratospheric ozone depletion due to the launch of small satellites (e.g., CubeSats) with an iodine propulsion system and understand the potential risks caused to stratospheric ozone . We have separted the contribution to the stratospheric ozone depletion from the surface emissions of Iodine and its injection from the upper atmosphere. We have performed a number of model sensitivity runs with different additional scenarios of iodine injection at 120-140 km to explore the potential stratospheric ozone depletion from small satellites powered in this way. For the base case scenario in the current condition (for example year 2014), a steady-state nanosatellite launch rate of 20,000/year (e.g., 8 tons of I+ injected), the perturbation to the total column ozone is negligible. However, a 10 or 100-fold increase in the mass of iodine launched into near-Earth orbit will cause significant ozone depletion. This study quantifies the extent to which the injection of iodine into the thermosphere can deplete stratospheric ozone, which will be a useful guide for limiting the population of satellites with iodine propulsions systems in low Earth orbit. The impact of iodine for the extreme large ozone depletion years (for example, 2020) and future scenarios of the results will be also discussed.

Binary interactions have been proposed to explain a variety of circumstellar structures seen around evolved stars, including asymptotic giant branch (AGB) stars and planetary nebulae. Studies resolving the circumstellar envelopes of AGB stars have revealed spirals, discs and bipolar outflows, with shaping attributed to interactions with a companion. For the first time, we have used a combined chemical and dynamical analysis to reveal a highly eccentric and long-period orbit for W~Aquilae, a binary system containing an AGB star and a main sequence companion. Our results are based on anisotropic SiN emission, the first detections of NS and SiC towards an S-type star, and density structures observed in the CO emission. These features are all interpreted as having formed during periastron interactions. Our new method can yield stringent constraints on the orbital parameters of long-period binaries containing AGB stars, and establishes a template for future studies.

The Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been used to observe the Mg+ in the upper atmosphere of Mars since 2015. These observations reveal significant diurnal, seasonal and latitudinal variations. For example, a factor of two change in Mg+ occurs during the day at the equator and Mg+ above 100 km decreases across the globe during the Southern Hemisphere summertime. Possible causes include the influence of photo-chemistry, atmospheric dynamics and the injection rate of meteoric material. To delineate these sources of variability, a 3-dimensional model of the Martian Mg has been developed. The model is based on the Laboratoire de Météorologie Dynamique (LMD) Mars global circulation model (GCM), which is capable of simulating the seasonal cycles in the Martian atmosphere arising from changes in heating rates from orbital geometry and the distribution of dust in the lower atmosphere. The model solves for the dynamics and primary constituents of the atmosphere from the surface to the thermosphere. For this study, the chemistry has been augmented with neutral and ion chemistry for meteoric metals within a CO2 atmosphere, incorporating 7 neutral and 8 ionized Mg-containing species and an additional 42 neutral and ion-molecule reactions. The atmospheric input of meteoric material is specified from seasonal and latitudinal fits to new estimates of the deposition of the ablated metals in the atmosphere. Here we present the first detailed intercomparison of the MAVEN IUV Mg+ observations with simulated Mg+ from the LMD Mars GCM. Model variability is consistent with observations and indicates tropical variability is caused by a combination of photochemistry and vertical transport by atmospheric tides. Comparisons of simulations performed with variable and fixed meteoric input show that the high latitude variations are caused by both seasonal variation in ablation rates and the residual circulation. Finally, we show how Mg+ varies in relation to neutral Mg and the remaining Mg-containing species to determine how Mg+ may be used as a proxy for total Mg variability.

Cosmic dust consists of mineral grains that are held together by a refractory organic "glue", and it has been proposed that loss of the organics during atmospheric entry can lead to the fragmentation of dust particles into sub-micron sized fragments (Campbell-Brown 2019). If this happens, there are several important implications in the Earth’s atmosphere: 1) slow-moving particles may be undetectable by radar, so that the total dust input could be considerably larger than current estimate of around 30 tonnes per day that is required to explain the measured vertical fluxes of Na and Fe atoms in the mesosphere, and the accumulation rate of cosmic spherules and unmelted micrometeorites at the surface (Carrillo-Sánchez et al. 2020, Rojas et al. 2021); 2) meteoritic fragments may freeze stratospheric droplets in the polar lower stratosphere, producing polar stratospheric clouds that cause ozone depletion (James et al. 2018); and 3) the anomalously large measured accumulation rates of meteoritic material in polar ice cores may be better explained (Brooke et al. 2017). Meteoritic fragmentation may also supply nuclei for the formation of ice clouds in other planetary atmospheres, such as Mars (Plane et al. 2018). At Leeds we have developed a new experimental system for studying the pyrolysis of the refractory organic constituents in cosmic dust during atmospheric entry (Bones et al. 2022). The pyrolysis kinetics of meteoritic fragments was measured by mass spectrometric detection of CO2 at temperatures between 625 and 1300 K. The complex time-resolved kinetic behaviour is consistent with two organic components – one significantly more refractory than the other, probably corresponding to the insoluble and soluble organic fractions, respectively (Alexander et al. 2017). The measured temperature-dependent pyrolysis rates were then incorporated into the Leeds Chemical Ablation Model (CABMOD) (Vondrak et al. 2008), which demonstrates that organic pyrolysis should be detectable using high performance large aperture radars (Bones et al. 2022). Atomic force microscopy was used to show that although the residual meteoritic particles became more brittle after organic pyrolysis, they will nevertheless withstand stresses that are at least 3 orders of magnitude higher than would be encountered during atmospheric entry. This suggests that most small cosmic dust particles (radius < 100 μm) will not fragment during entry into the atmosphere as a result of organic pyrolysis (Bones et al. 2022). However, a subset of slow-moving, low density particles with a large organic component, as observed in fresh cometary particles such as those in the coma of comet 67/P (Mannel et al. 2019), could fragment into sub-micron meteoritic particles that would survive entry. In fact, meteoritic fragments with a size distribution peaking around radius = 250 nm have been observed in the Arctic polar vortex (Schneider et al. 2021). Experiments in our laboratory show that meteoritic fragments, as well the nanometre-sized meteoric smoke particles which form from the condensation of metallic vapours produced by meteoric ablation in the upper mesosphere, are very effective ice nuclei. On Earth, these particles can facilitate the freezing of polar stratospheric cloud droplets, and may also play a role in the freezing of clouds in the middle atmospheres of Mars and Venus. Alexander C.M.O., Cody G.D., De Gregorio B.T., Nittler L.R., Stroud R.M., 2017, Chemie Der Erde-Geochemistry, 77, 227 Bones D.L., Sánchez J.D.C., Connell S.D.A., Kulak A.N., Mann G.W., Plane J.M.C., 2022, Earth Space Sci., 9, art. no.: e2021EA001884 Brooke J.S.A., Feng W.H., Carrillo-Sanchez J.D., Mann G.W., James A.D., Bardeen C.G., Plane J.M.C., 2017, J. Geophys. Res.-Atmos., 122, 11112 Campbell-Brown M.D., 2019, Planet. Space Sci., 169, 1 Carrillo-Sánchez J.D., Gómez-Martín J.C., Bones D.L., Nesvorný D., Pokorný P., Benna M., Flynn G.J., Plane J.M.C., 2020, Icarus, 335, art. no.: 113395 James A.D., Brooke J.S.A., Mangan T.P., Whale T.F., Plane J.M.C., Murray B.J., 2018, Atmos. Chem. Phys., 18, 4519 Mannel T., et al., 2019, Astron. Astrophys., 630, art. no.: A26 Plane J.M.C., Carrillo-Sanchez J.D., Mangan T.P., Crismani M.M.J., Schneider N.M., Maattanen A., 2018, J. Geophys. Res.-Planets, 123, 695 Rojas J., et al., 2021, Earth Planet. Sci. Lett., 560, art. no.: 116794 Schneider J., et al., 2021, Atmos. Chem. Phys., 21, 989 Vondrak T., Plane J.M.C., Broadley S., Janches D., 2008, Atmos. Chem. Phys. , 8, 7015

Since the discovery of atmospheric Mg+ at Mars in 2015 by the Mars Atmosphere and Volatile Evolution (MAVEN) mission, there have been almost continuous observations of this meteoric ion layer in a variety of seasons, local times, and latitudes. Here we present the most comprehensive set of observations of the persistent metal ion layer at Mars, constructing the first grand composite maps of a metallic ion species. These maps demonstrate that Mg+ appears in almost all conditions when illuminated, with peak values varying between 100 and 500 cm-3, dependent on season and local time. There exists significant latitudinal variation within a given season, indicating that Mg+ is not simply an inert tracer, but instead may be influenced by the meteoric input distribution and/or atmospheric dynamics and chemistry. Geographic maps of latitude and longitude indicate that Mg+ may be influenced by atmospheric tides, and there is no apparent correlation with remnant crustal magnetic fields. This work also presents counter-intuitive results, such as a reduction of Mg+ ions in the northern hemisphere during Northern Winter in an apparent correlation with dust aerosols.

It is evident that a variety of metals are deposited in the Earth’s mesosphere and lower thermosphere (MLT, ~70-120 km) through meteoric ablation when the cosmic dust particles enter the atmosphere at high entry velocity (11-72 km/s). However, it is still unclear how much and accuarate cosmic dust enters the atmosphere of Mars (though the estimation of global dust input would be a few tons per sol) and what is the difference comparing to Earth’s atmosphere (which has a 1-2 order global input range from different estimations). We have developed global atmospheric meteoric models of Na, Fe, K, Mg, Ni, Ca, Al, Si, P, S etc) into the Whole Atmosphere Community Climate Model (WACCM) and its vertical extensions to 600 km (WACCM-X) from US National Center for Atmospheric Research (NCAR, termed WACCM-metals), which simulate well the metal layers compared with the available lidar/rocket/satellite measurements. New observations of some metals for the Martian atmosphere (i.e., Mg+ observations from IUVS (Imaging UV Spectrometer) and Mg+, Na+ and Fe+ from NGIMS (Neutral Gas Ion Mass Spectrometer)) instruments on NASA’s Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft are available from 2014. Therefore, we have incorporated the chemistry of three metals (Mg, Na and Fe) in the Laboratoire de Météorologie Dynamique (LMD) Mars global circulation model (termed as LMD-Mars-Metals), following similar work we have done for the Earth’s atmosphere. The model has been developed by combining three components: the state-of-the-art LMD-Mars model covering the whole atmosphere from the surface to the upper thermosphere (up to ~ 2 x10-8 Pa or 240 km), a description of the neutral and ion-molecule chemistry of Mg, Fe and Na in the Martian atmosphere (where the high CO2 abundance produces a rather different chemistry from the terrestrial atmosphere), and a treatment of injection of the metals into the atmosphere from the ablation of cosmic dust particles. The LMD-Mars model contains a detailed treatment of atmospheric physics, dynamics and chemistry from the lower atmosphere to the ionosphere. The model also includes molecular diffusion and considers the chemistry of the C, O, H and N families and major photochemical ion species in the upper atmosphere, as well as improved treatments of the day-to-day variability of the UV solar flux and 15 mm CO2 cooling under non-local thermodynamic equilibrium conditions. We have incorporated the chemistries of Mg, Fe and Na into LMD-Mars because these metals have different chemistries which control the characteristic features of their ionized and neutral layers in the Martian atmosphere. The Mg chemistry adds 7 neutral and 8 ionized Mg-containing species, connected by 42 neutral and ion-molecule reactions. The corresponding Fe chemistry has 39 reactions with 14 Fe-containing species. Na chemistry adds 7 neutral and only 2 ionized Na-containing species, with 32 reactions. The injection rate of these metals as a function of latitude, solar longitude at different pressure levels is pre-calculated from the Leeds Chemical Ablation Model (CABMOD) combined with an astronomical model which predicts the dust from Jupiter Family and Long Period comets, as well as the asteroid belt, in the inner solar system. The model has been evaluated against by Mg+, Na+ and Fe+ observations from IUVS and NGIMS measurements. The comparison of these metal layers between Earth’s and Mar’s atmospheres will be discussed, which allows us to understand the meteor astronomy, chemistry and transport processes that control the different metal layers in the upper atmosphere on different planets.

Background In situ probe measurements and remote sensing have revealed that Venus has a highly organised cloud system. Comparisons between models of the expected spectra and observations reveal unexplained absorption in the near-UV to blue region of the spectrum. While many candidates for this “unknown absorber” have been proposed over the years, none have been conclusively demonstrated to match the physical and optical behaviour observed (Pérez-Hoyos et al., 2018, JGR Planets, 123). One such candidate is ferric chloride (Krasnopolsky, 2017, Icarus, 286; Zasova et al., 1981, ASR, 1). Attempts to reliably determine its suitability have been hampered by the scarcity of representative spectra available. Absorbance spectra generally used in the literature are measured in ethyl acetate (Aoshima et al., 2013, Polymer Chemistry, 4), and therefore may not be representative of the absorption produced by ferric chloride in the Venusian clouds. In addition to the absorption spectrum produced, the behaviour of absorber candidates must also be considered, including their rates and locations of production and loss, transport mechanisms, and lifetimes in the atmosphere. While much of this behaviour must be examined in atmospheric models, laboratory studies to establish reaction pathways and measure rates are needed to provide as much quantitative data as possible for model development. Method and results Literature spectra for ferric chloride employ UV-visible spectrometry using ethyl acetate as a solvent. We present absorption spectra of ferric chloride in sulphuric acid. This change of solvent produces an environment more closely aligned to that on Venus, where ferric chloride, if present, may exist as an impurity in the micron-sized sulphuric acid cloud droplets (Petrova, 2018, Icarus, 306). In addition, mass spectrometry was used to investigate the kinetics and products of reactions of ferric chloride that could occur in the Venusian atmosphere. Behaviour predicted by these experiments can then be included in atmospheric models to test the lifetime and transport of ferric chloride and its reaction products in the atmosphere. Conclusions The unknown absorption was first observed close to 100 years ago, yet the mystery of its cause remains unsolved. More representative spectra of ferric chloride and a greater understanding of its behaviour in the atmosphere of Venus are critical to advancing the identification of the unknown absorber. As the absorber is located towards the top of the clouds and absorbs in the near-UV to blue region, it is responsible for large amounts of absorption of incident sunlight, and therefore has a significant impact on the Venusian energy budget. Accurate atmospheric modelling of the planet therefore requires an understanding of the absorber which can only be achieved once it has been conclusively identified.

Interplanetary dust particles, liberated from the surfaces of comets and asteroids, are ubiquitous in interplanetary space within the solar system. These particles travel at orbital velocities and ablate upon entry into planetary atmospheres, where they are the sole explanation for high altitude atmospheric metal layers. On Earth, such layers inform us of the dynamics of the upper atmosphere, and we use the abundance of relative species to investigate the origin of these particles from various potential sources (Jupiter family comets, asteroids, etc.). Since the discovery of atmospheric Mg+ at Mars in 2015, there have been almost continuous observations of this layer in a variety of seasons, local times, and latitudes. Here we present the most comprehensive set of observations of the persistent metal ion layer at Mars, constructing the first grand average maps of metal ions species. Such maps can be compared to current and future modeling efforts, which attempt to track mesospheric transport, chemistry and interplanetary dust particle sources. This work confirms some previous model predictions and observations, such as the relatively long lifetime of Mg+, but also presents counter-intuitive results, such as a paucity of Mg+ ions in the northern hemisphere during Northern Winter in an apparent correlation with dust aerosols. Previous discrepancies between model predictions and metal ion observations led to the development of a novel nucleation scheme for mesospheric clouds, and we revisit these ideas on a global and seasonally varying scale. Overall, this represents the broadest investigation of meteoric metal ions, summarizes the first order behavior and outlines new model challenges for the future.

Sulfur hexafluoride (SF6) and carbon tetrafluoride (CF4) are inert gases in the atmosphere that can absorb infrared radiation and affect the climate. They have lifetimes up to 1278 years for SF6 and 50000 years for CF4. The International Panel on Climate Change lists the two as part of the most influential long-lived, well-mixed greenhouse gases, with SF6 having the highest identified global warming potential. Both gases have anthropogenic major sources. SF6 is used as an insulating gas in the electrical power industry, and CF4 is a by-product of aluminum manufacturing. In this study, we question whether atmospheric electricity significantly influences the atmospheric concentrations of these molecules. We aim to investigate SF6 and CF4 decomposition within streamers at different altitudes in the atmosphere, and then estimate the global occurrence rate of such streamers and their impact. To accomplish this, we simulate positive streamers in synthetic air that contains a small concentration of the two gases. From our simulations, we identify relations between streamer properties and the amounts of SF6 and CF4 destroyed, which can be used to estimate the rates of chemical processes in observed streamer events.

Molecular and metallic ions are vastly unexplored in near-Earth space because only a few terrestrial missions have been equipped with dedicated instrumentation to separate these molecular and metallic ions, within only a limited energy range (cold ions of < 50 eV and energetic ions of ~100 keV). Nevertheless, existing data from past and on-going missions including those not designed for the required mass separation are capable of detecting many of these ions with available tools, although severe limitations exist (sensitivity and energy range in addition to mass resolution and mass range). By combining these patchy and incomplete data, we found several features that indicate sources of these heavy ions.(1) Combination of Kaguya and Cluster/RAPID during high flux events of solar wind heavy ions suggests that the Moon can be a substantial source for low charge-state metallic ions in the magnetosphere when the Moon is located upstream of the Earth. This interpretation is consistent with Geotail/STICS statistics of increased flux of low charge-state heavy ions near new-Moon for medium activity (Kp=2-4).(2) The major route of molecular ion supply ((3) A case study of lidar data during high flux events of solar wind heavy ions suggests that upward expansion of Na signal can be associated with molecular ion escape to the magnetosphere that is also observed by Cluster/RAPID and e-POP/IRM, although this expansion can be related to a major magnetic storm rather than solar wind event.

A dual-wavelength resonance fluorescence lidar facility, operating at 341 and 589 nm, was used to observe simultaneously the Ni and Na layers in the upper atmosphere over Yanqing station, Beijing (40.41°N, 116.01°E). Lidar measurements were performed on 126 nights (1090 hr in total) from April 2019 to March 2020 and April 2021 to August 2021, so that the full seasonal cycle of the Ni layer was observed for the first time. The Ni and Na layers exhibit a similar annual cycle, increasing by a factor of ∼3 from a mid-summer minimum to a midwinter maximum. The annual mean column densities of Ni and Na are 3.1 × 108 and 2.5 × 109 cm−2, respectively, giving a mean Na:Ni ratio of 8.1, which is significantly larger than their CI chondritic ratio of 1.2. This is explained by the more efficient ablation of Na from cosmic dust particles by a factor of 3, and the more rapid neutralization of Na+ between 90 and 100 km, where the measured Na+:Ni+ ratio is only 2.2. The Ni layer peak occurs around 84 km, 8 km below that of Na. These features are simulated satisfactorily by the Whole Atmosphere Community Climate Model (WACCM) and are explained by significant differences in the neutral chemistry of the two metals below 90 km and their ion-molecule chemistry between 90 and 100 km.

Here we report a global model of meteoric metals including Mg, Fe and Na in the Laboratoire de Météorologie Dynamique (LMD) Mars global circulation model (termed as LMD-Mars-Metals), following on similar work as we have done for the Earth’s atmosphere. The model has been developed by combining three components: the state-of-the-art LMD-Mars model covering the whole atmosphere from the surface to the upper thermosphere (up to ~ 2 x10-8 Pa or 240 km), a description of the neutral and ion-molecule chemistry of Mg, Fe and Na in the Martian atmosphere (where the high CO2 abundance produces a rather different chemistry from the terrestrial atmosphere), and a treatment of injection of the metals into the atmosphere as a result of the ablation of cosmic dust particles. The LMD-Mars model contains a detailed treatment of atmospheric physics, dynamics and chemistry from the lower atmosphere to the ionosphere. The model also includes molecular diffusion and considers the chemistry of the C, O, H and N families and major photochemical ion species in the upper atmosphere, as well as improved treatments of the day-to-day variability of the UV solar flux and 15 mm CO2 cooling under non-local thermodynamic equilibrium conditions. So far, we have incorporated the chemistries of Mg, Fe and Na into LMD-Mars because these metals have different chemistries which control the characteristic features of their ionized and neutral layers in the Martian atmosphere. The Mg chemistry has 4 neutral and 6 ionized Mg-containing species, connected by 25 neutral and ion-molecule reactions. The corresponding Fe chemistry has 39 reactions with 14 Fe-containing species. Na chemistry has 7 neutral and only 2 ionized Na-containing species, with 32 reactions. The injection rate of these metals as a function of height is pre-calculated from the Leeds Chemical Ablation Model (CABMOD) combined with an astronomical model which predicts the dust from Jupiter Family and Long Period comets, as well as the asteroid belt, in the inner solar system. The LMD-Mars-Metals model has been run for several full Martian years under different surface dust scenarios to investigate the impact of high atmospheric dust loadings on the modelled metal layers. The model has been evaluated against Mg+ observations from IUVS (Imaging UV Spectrometer) and NGIMS (Neutral Gas Ion Mass Spectrometer) instruments on NASA’s Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft. We have also carried out other sensitivity experiments with different seasonality/altitude/latitudinal varying of Meteoric Input Function (MIF) of these metals in the model. These sensitivity results will be discussed.

Field observations of IO3− and HIO3−-containing cluster anions by chemical ionization–atmospheric pressure interface–time-of-flight mass spectrometry (CI-API-ToF-MS) have been reported1. These observations, which employ nitrate (NO3−) reagent ions for reaction with the analytes, have been interpreted as resulting from atmospheric gas-phase iodic acid (HOIO2) and molecular cluster formation via HOIO2 addition steps. CI-API-ToF-MS chamber measurements with alternative ionization schemes have also reported signals that could be attributed to gas-phase HOIO and HOIO2. However, well-established chemical kinetics and thermochemistry do not indicate any straightforward route to gas-phase iodine oxyacids and HOIO2 particle formation in the atmosphere. This does not only hinder the ability of chemical models for linking iodine emissions and particle formation, but also calls into question the interpretation of these CI-API-ToF-MS measurements. It has been proposed that water plays an important role in generating gas phase and HOIO2-containing molecular clusters, but recent flow tube experiments have established extremely low upper limits to the rate constants of possible reactions between iodine oxides (IOx and IxOy) and water. In this presentation, we discuss experimental and theoretical kinetics and thermochemistry of proposed routes to gas-phase HOIO and HOIO2 in the atmosphere as well as potential ion-molecule reactions turning iodine oxides into IO3- ions in the CI-API-ToF-MS inlet. We show that there is an important ambiguity in the interpretation of IO3- and other signals observed with CI instruments as a result of barrierless reactions between IxOy and the reagent ions. Experiments for solving this ambiguity and reconciling conflicting results are proposed.

We examine long-term energetic heavy ion measurements including three planets' magnetospheres, focusing on Fe ions (specifically, but not exclusively, Fe+) in and near Earth's magnetosphere. We com...

A Comparison of the Mid-latitude Nickel and Sodium Layers in the Mesosphere: Observations and Modeling by Jing Jiao1, Wuhu Feng2,3, Fang Wu1,4, Fuju Wu1,4, Haoran Zheng1, Lifang Du1, Guotao Yang1,* and John Plane2,* 1State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China. 2School of Chemistry, University of Leeds, Leeds LS2 9JT, UK. 3National Centre for Atmospheric Science, University of Leeds, Leeds LS2 9PH, UK. 4University of Chinese Academy of Sciences, Beijing 100049, China The repository contains the data used in the above paper.