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Retrieving the optical depth of the Martian clouds ($\tau_\mathrm{cld}$) is a powerful way to monitor their spatial and temporal evolution. However, such retrievals from nadir imagery rely on several assumptions, including the vertical structure of the clouds in the atmosphere. Here we compare the results of cloud optical depth retrievals at 320 nm from the Emirates eXploration Imager (EXI) onboard the Emirates Mars Mission (EMM) "Hope" orbiter performed using a basic uniform cloud profile used in previous studies and using derived cloud profiles obtained from near-simultaneous Solar Occultation observations in the 3.1-3.4 $\mu$m spectral range from the Middle-Infrared channel of the Atmospheric Chemistry Suite (ACS) instrument onboard the ESA Trace Gas Orbiter (TGO). We show that the latitudinal dependence of the cloud vertical profiles can have a strong impact on the nadir retrievals; neglecting it can lead to a significant underestimation of $\tau_\mathrm{cld}$ in the polar regions (up to 25 % to 50 %, depending on the vertical distribution of the dust in the atmosphere) and to a lesser extent, to an overestimation of $\tau_\mathrm{cld}$ around the equator. We also discuss the impact of a vertically-dependent particle size profile, as previous studies have shown the presence of very small water ice particles at the top of the clouds. From this analysis, we provide recommendations for the improvement of water ice cloud parameterization in radiative transfer algorithms in nadir atmospheric retrievals.

In 2020, hydrogen chloride (HCl) in the gas phase was discovered in the atmosphere of Mars with the Atmospheric Chemistry Suite (ACS) onboard the Trace Gas Orbiter (TGO) mission (Korablev et al., 2021). Its volume mixing ratio (VMR) shows a seasonal increase of up to 5 ppbv during the perihelion season, followed by a sudden drop to undetectable levels, contradicting previous estimations of the HCl lifetime of several months. In the Earth's stratosphere, heterogeneous uptake of HCl onto water ice is known to be a major sink for this species. Modelling of associated chemistry involving heterogeneous reactions indicates that H2O ice becomes the most effective sink for HCl above 20 km with the characteristic time shorter than 12 hours. In this work, we use simultaneous measurements of water ice particles and HCl abundance obtained by the ACS instrument and show particular structures in the vertical profiles, forming detached layers of gas at the ice free altitudes ('ice-holes'). We demonstrate that the heterogeneous uptake of HCl onto water ice operates on Mars and is potentially a major mechanism regulating the HCl abundance in the atmosphere of Mars., Comment: 7 pages, 1 figure. Submitted to Icarus Notes

The middle infrared (MIR) channel of the Atmospheric Chemistry Suite (ACS) instrument onboard the ExoMars Trace Gas Orbiter (TGO) ESA-Roscosmos mission has performed Solar occultation measurements of the Martian atmosphere in the 2.3-4.2 $\mu$m spectral range since March 2018, which now covers two Martian Years (MY). We use the methodology previously developed for the study of the MY 34 Global Dust Storm (GDS) (Stcherbinine et al., 2020) to monitor the properties (effective radii, extinction, altitude) of the Martian water ice clouds over the first two Martian years covered by ACS-MIR. The observations encompass the period $L_s$ = 163{\deg} in MY 34 to $L_s$ = 181{\deg} in MY 36. We determine that the typical altitude of the clouds varies by 20 to 40 km between the summer and winter, with a maximum extension up to 80 km during summer in the midlatitudes. Similarly, we also note that for a limited temporal range, the altitude of the clouds also varies by 20 to 40 km between the polar regions and the midlatitudes. We also compare observations acquired during the MY 34 GDS to observations from the same period in MY 35, using that latter as a reference to characterize the effects of this GDS on the clouds' properties. In addition, we compare our retrievals with the predictions of the Mars Planetary Climate Model (PCM), which shows a reasonable agreement overall for the altitude of the clouds, although the model usually predicts lower altitudes for the top of the clouds.

We present a new implementation of the hydrological cycle scheme into a general circulation model of the Martian atmosphere. The model includes a semi-Lagrangian transport scheme for water vapor and ice, and accounts for microphysics of phase transitions between them. The hydrological scheme includes processes of saturation, nucleation, particle growth, sublimation and sedimentation under the assumption of a variable size distribution. The scheme has been implemented into the Max Planck Institute Martian general circulation model (MPI--MGCM) and tested assuming mono- and bimodal log-normal distributions of ice condensation nuclei. We present a comparison of the simulated annual variations, horizontal and vertical distributions of water vapor and ice clouds with the available observations from instruments onboard Mars orbiters. The accounting for bi-modality of aerosol particle distribution improves the simulations of the annual hydrological cycle, including predicted ice clouds mass, opacity, number density, particle radii. The increased number density and lower nucleation rates brings the simulated cloud opacities closer to observations. Simulations show a weak effect of the excess of small aerosol particles on the simulated water vapor distributions.

A two-qubit Heisenberg XYZ model with Dzyaloshinsky-Moriya (DM) and Kaplan-Shekhtman-Entin-Wohlman--Aharony (KSEA) interactions is considered at thermal equilibrium. Analytical formulas are derived for the local quantum uncertainty (LQU) and local quantum Fisher information (LQFI). Using the available expressions for the entropic quantum discord, we perform a comparative study of these measures of nonclassical correlation. Our analysis showed the following: all three measures of quantum correlation have similar qualitative and even quantitative behavior on temperature for different values of system parameters, there are regions in the parameter space which correspondent to a local increase of correlations with increasing temperature, and sudden changes in the behavior of quantum correlations occur at certain values of the interaction parameters., Comment: 21 pages, 7 figures (24 eps files)

The ExoMars Trace Gas Orbiter (TGO) was sent to Mars in March 2016 to search for trace gases diagnostic of active geological or biogenic processes. We report the first observation of the spectral features of Martian ozone (O3) in the mid-infrared range using the Atmospheric Chemistry Suite (ACS) Mid-InfaRed (MIR) channel, a cross-dispersion spectrometer operating in solar occultation mode with the finest spectral resolution of any remote sensing mission to Mars. Observations of ozone were made at high northern latitudes (>65N) prior to the onset of the 2018 global dust storm (Ls = 163-193). During this fast transition phase between summer and winter ozone distribution, the O3 volume mixing ratio observed is 100-200 ppbv near 20 km. These amounts are consistent with past observations made at the edge of the southern polar vortex in the ultraviolet range. The observed spectral signature of ozone at 3000-3060 cm-1 directly overlaps with the spectral range of the methane (CH4) nu3 vibration-rotation band, and it, along with a newly discovered CO2 band in the same region, may interfere with measurements of methane abundance., Comment: 7 pages, 6 figures

The Atmospheric Chemistry Suite (ACS) instrument onboard the ExoMars Trace Gas Orbiter (TGO) ESA-Roscosmos mission began science operations in March 2018. ACS Mid InfraRed (MIR) channel notably provides solar occultation observations of the martian atmosphere in the 2.3 - 4.2 $\mu$m spectral range. Here we use these observations to characterize water ice clouds before and during the MY 34 Global Dust Storm (GDS). We developed a method to detect water ice clouds with mean particle size $\leq$ 2 $\mu$m, and applied it to observations gathered between $L_s=165^\circ$ and $L_s=243^\circ$. We observe a shift in water ice clouds maximum altitudes from about 60 km before the GDS to above 90 km during the storm. These very high altitude, small-sized ($r_\mathrm{eff} \leq 0.3$ $\mu$m) water ice clouds are more frequent during MY34 compared to non-GDS years at the same season. Particle size frequently decreases with altitude, both locally within a given profile and globally in the whole dataset. We observe that the maximum altitude at which a given size is observed can increase during the GDS by several tens of km for certain sizes. We notably notice some large water ice particles ($r_\mathrm{eff}\geq1.5$ $\mu$m) at surprisingly high altitudes during the GDS (50 - 70 km). These results suggest that GDS can significantly impact the formation and properties of high altitude water ice clouds as compared to the usual perihelion dust activity.

This paper is devoted to the multiple-quantum (MQ) NMR spectroscopy in nanopores filled by a gas of spin-carrying molecules (s=1/2) in a strong external magnetic field. It turned out that the high symmetry of the spin system in nanopores yields a possibility to overcome the problem of the exponential growth of the Hilbert space dimension with an increase in the number of spins and to investigate MQ NMR dynamics in systems consisting of several hundred spins. We investigate the dependence of the MQ coherence intensities on their order (the profile of the MQ coherence intensities) for a spin system governed by the standard MQ NMR Hamiltonian (the nonsecular two-quantum/two-spin Hamiltonian) together with the second order correction of the average Hamiltonian theory. It is shown that the profile depends on the value of this correction and varies from the exponential to the logarithmic one., Comment: 7 pages, 3 figures