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The physics of the Mars PCM (previously LMD Mars GCM) has been improved : cloud nucleation now has a temperature-dependent scheme, latent heat of ground ice sublimation is computed and overall physical resolution is enhanced. Under these conditions, we find that retroactions of albedo and thermal inertia allow perennial deposition of ice outside the polar regions when increasing the obliquity of Mars from its present day value of 25° toward 35°, with accumulation rates compatibles with the formation of a "Latitude-Dependent Mantle" during the last high obliquity excursion.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made., HDO and the D/H ratio are essential to understand Mars past and present climate, in particular with regard to the evolution through ages of the Martian water cycle. We present here new modeling developments of the HDO cycle with the Laboratoire de Météorologie Dynamique Mars Global Climate Model (GCM). The present study aims at exploring the behavior of the D/H ratio cycle and its sensitivity to the modeling of water ice clouds and the formulation of the fractionation by condensation. Our GCM simulations are compared with observations provided by the Atmospheric Chemistry Suite (ACS) on board the ESA/Roscosmos Trace Gas Orbiter (TGO), and reveal that the model quite well reproduces the temperature and water vapor fields, which offers a good basis for representing the D/H ratio cycle. The comparison also emphasizes the importance of modeling the state of supersaturation, resulting from the microphysical processes of water ice clouds, to correctly account for the water vapor and the D/H ratio of the middle-to-upper atmosphere. This work comes jointly with a detailed comparison of the measured D/H profiles by TGO/ACS and the model outputs, conducted in the companion paper of Rossi et al. (2022, https://doi.org/10.1029/2022JE007201) (this issue). © 2022. The Authors., ExoMars is the space mission of ESA and Roscosmos. The ACS experiment is led by IKI Space Research Institute in Moscow. The project acknowledges funding by Roscosmos and CNES. Science operations of ACS are funded by Roscosmos and ESA. M.V. acknowledges support from the DIM ACAV labelled by the Ile-de-France region in support for the research (Domaine d’Intérêt Majeur, Astrophysique et Conditions d’Apparition de la Vie). L.R. acknowledges support from CNES. F. G.-G. is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00, and acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709).

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. © 2022. American Geophysical Union. All Rights Reserved., L.R. acknowledges support from CNES. F.G.-G. is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00, and acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). M.V. acknowledges support from the DIM ACAV labelled by the Ile-de-France region in support for the research (“Domaine d’Intérêt Majeur, Astrophysique et Conditions d’Apparition de la Vie).”

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 (ACS) onboard the ExoMars Trace Gas Orbiter (TGO). The data is selected near the northern summer solstice at solar longitude (LS) 75{\deg}-105{\deg} of Martian Year (MY) 35. The observations have a full local time coverage, which enables analyses of daily temperature anomalies. The observed zonal mean temperature is lower by 4-6K at ~100Pa, but higher towards the summer pole, compared to the 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 5K, 3K, and 2.5K, respectively, from tens to hundreds of Pa. The results generally agree well with the LMD Mars GCM, but with noticeable earlier phases of diurnal (~1h) and semi-diurnal (~3h) tides., Comment: 7 pages, 4 figures, accepted by GRL

Thermal tides are planetary-scale harmonic responses driven by diurnal solar forcing and influenced by planetary topography. Excited by solar heating absorbed by the atmosphere and energy exchange with surface, thermal tides grow in Martian atmosphere. These tides usually have large amplitudes due to the low heat capacity of Martian atmosphere, and dominate its diurnal variations. In this talk, we present results of the analysis of thermal tides in Martian atmosphere using temperature profiles retrieved using infrared spectra obtained by the Emirates Mars InfraRed Spectrometer (EMIRS) instrument onboard the Emirates Mars Mission (EMM) Hope spacecraft. The first set of data obtained during the mission science phase is selected, covering a solar longitude (LS) range 60° - 80° of Martian Year (MY) 36, which is a clear season without large dust storms. The novel orbit design of the spacecraft allows a full local time coverage to be reached within 10 Martian days, approximately ~5° of LS. It enables the analysis of diurnal temperature variations without the interference of seasonal changes, which was shown to be significant in previous studies. Wave mode decomposition is also applied to these diurnal variations, and amplitudes of other tide modes are derived. The results show good agreements with predictions derived using the Laboratoire de Météorologie Dynamique (LMD) Mars Global Circulation Model (GCM), except for a noticeable phase difference of the dominant diurnal thermal tide. This work provides valuable information on understanding diurnal variations in Martian atmosphere and inspires future advances of Mars GCMs.

To accurately simulate the climate and the fate of volatiles for thousands to millions of years we must couple physical processes with very different timescale, ranging from clouds microphysics and atmospheric dynamics (represented in the GCM) to the evolution of lakes, glacier accumulation, and subsurface ice evolution. Given the diversity and the complexity of the Martian paleoclimates, we choose to use use an ambitious “asynchronous coupling” between the slow ice and water reservoirs models and the GCM. In practice our innovative Mars evolution model will use a horizontal grid identical to that of the GCM, and include the same representation of the micro-climate on slopes. In our case, we will run the Mars Evolution Model with a timestep of 50 to ~500 years, depending upon the dynamics of the modeled system (smaller timesteps must first be used so that the different volatile reservoirs reach a quasi-equilibrium, then the timestep will depends on the evolution of the forcing, which is slow in the case of obliquity, for instance) . At each timestep, the inputs from the atmosphere (e.g. mean precipitation, sublimation and evaporation, temperatures, dust deposition) will be obtained through a multi-annual run of the Global Climate model using the outcome of the Mars Evolution Model as initial state.First results about evolution of water ice and CO2 ice glacier will be presented.

Through today's observation of dry lakes, rives and large valley networks, we can assume liquid water abundantly flowed on Mars during the Noachian era, approximatively 4Gya. However, the climate that host this active water cycle is yet poorly understood. Recent modeling studies tried to reproduce the conditions that may have occured on the planet, trying to find an atmospheric process or composition that could solve the well known Faint Young Sun Paradox. Theses modeling studies, through the use of 3-dimensional Global Climate Models struggled to warm sufficiently the past climate of Mars, even considering different greenhouse gases, the role of clouds, meteoritic impact or even volcanism. However, the presence of H2 could be an interesting solution for a sustainable warming as some recent studies suggest (Turbet and Forget, 2021). Another recent study (Ito et al. 2020) suggested that H2O2 might be a convincing candidate but has to be in high supersaturation ratio in the atmosphere, even though it only used a simplified 1D model and relatively high supersaturation levels.We try here to explore the scenario of supersaturated water, that might be a specy able to provide a sufficient global warming under supersaturated conditions or through the formation of high altitude clouds. Through 1D and 3D modeling, we try to constrain the theoritical supersaturation level of H2O that will allow the warming of the climate above 273K. Our results suggest that in an atmosphere only composed of CO2 and H2O, water supersaturation can create a significant warming but only with with supersaturation levels in the lower layers of the atmosphere, although it can be seen as unrealistic. We describe in this work the effect of supersaturation on temperatures, clouds, and the water cycle of the simulated planet. Even if we do not tackle the question whether the supersaturation hypothesis is realistic or not, these results give a better understanding of what would be Early Mars' climate under such conditions.

In some high latitude craters, intriguing moraines are interpreted to have been deposited by CO2 ice glaciers, essentially frozen from when the local climate was colder (i.e., when Mars obliquity was low) [1]. This scenario has been little studied, but it suggests that the atmosphere could totally collapse into CO2 glaciers, leaving behind a residual atmosphere of only Ar and N2, but 20 times less dense than today [2]. However, these results are based on a radiative equilibrium that does not take into account all the dynamics of the atmosphere. Such periods of low obliquities generally last tens of thousands of years [3], making a complete simulation with a classical Global Circulation Model impossible. We will present the preliminary results of our climate simulations of Mars at low obliquity based on our new tool which is the Planetary Evolution Model developed at the LMD (Fig 1.). This model allows us to simulate the evolution of the climate, based on the LMD GCM, over long-time steps. Particular attention will be paid to the condensation of the atmosphere in the form of CO2 glaciers, and to the composition of the residual atmosphere.Fig 1. Principles of the Planetary Evolution Model References: [1] Kreslavsky and Head, Carbon dioxide glaciers on Mars: Products of recent low obliquity epochs(?). Icarus, 216:111–115, 2011.[2] Kreslavsky and Head. Mars at very low obliquity: Atmospheric collapse and the fate of volatiles. Geophysical Research Letters, 32(L12202), 2005.[3] Laskar, Correia, Gastineau, Joutel, Levrard, Robutel, Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343–364, 2004.Acknowledgments:This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No 835275).

Observations of the South Polar Residual Cap suggest a possible erosion of the cap, leading to an increase of the global mass of the atmosphere. We test this assumption by making the first comparison between Viking 1 and InSight surface pressure data, which were recorded 40 years apart. Such a comparison also allows us to determine changes in the dynamics of the seasonal ice caps between these two periods. To do so, we first had to recalibrate the InSight pressure data because of their unexpected sensitivity to the sensor temperature. Then, we had to design a procedure to compare distant pressure measurements. We propose two surface pressure interpolation methods at the local and global scale to do the comparison. The comparison of Viking and InSight seasonal surface pressure variations does not show changes larger than +-8 Pa in the CO2 cycle. Such conclusions are supported by an analysis of Mars Science Laboratory (MSL) pressure data. Further comparisons with images of the south seasonal cap taken by the Viking 2 orbiter and MARCI camera do not display significant changes in the dynamics of this cap over a 40 year period. Only a possible larger extension of the North Cap after the global storm of MY 34 is observed, but the physical mechanisms behind this anomaly are not well determined. Finally, the first comparison of MSL and InSight pressure data suggests a pressure deficit at Gale crater during southern summer, possibly resulting from a large presence of dust suspended within the crater.

Introduction: For many years we have been working on the modeling of the martian water cycle in the Laboratoire de Météorologie Dynamique martian Global Climate Model [1,2,3,4]. This has been challenging because of destabilizing feedbacks such as the coupling between temperatures, water vapour, clouds, and temperature changes induced by radiatively active water clouds [2]. It is interesting to accurately model Mars’s water cycle not only to understand present day Mars but also to simulate past climate changes induced by obliquity and orbital variations. This study is partly motivated by the ERC Mars Through Time project which notably aims at modeling recent ( Sensitivity to the physical timestep: The standard physical timestep used in [1] was 15 martian minutes, subsequently reduced to 7.5 minutes. The water cycle shows a significant sensitivity to the physical timestep. This is because the dust and water physics and transport are strongly coupled with boundary layer parametrization radiative transfert, and cloud microphysics. Cloud microphysics uses a dedicated subtimestep for computing efficiency, but the diversity of processes involved bind us to increase physical resolution altogether. We will discuss the influence of an even smaller physical timestep to the water cycle, and the distinct effect of the dynamical timestep. Temperature-dependant water contact parameter: The water “contact parameter” controls the effective fraction of nuclei activated for water condensation. The higher it is, the more water ice nucleation is favored and water-ice clouds form. Experimental data and literature [8] tend to show a strong dependence of the contact parameter with temperature. However, GCMs usually use constant water contact parameter. We find that using a simple linear fit from [8], albeit oversimplifying the bimodal behavior between low and high temperatures, attenuates the thickness of the northern polar hood during the second part of the year while allowing for a thick aphelion cloud belt, which was a key modeling issue in the LMD GCM (Navarro et al. 2014). Latent heat of ground ice sublimation: The latent heat of ground water ice sublimation had been neglected in our climate model, because of the low amount of water and thus energy flux involved. The sublimation of water was hitherto simply computed using surface temperature and water vapor equilibrium. Preliminary studies of martian climates at higher obliquities have shown that the energy fluxes involved may become of prime importance, as accounting for the latent heat of ground ice strongly inhibits the summer sublimation of the polar caps. Its calculation in a GCM requires an implicit numerical scheme to properly account for the coupling between temperature and sublimation during the GCM timestep. We show that the latent heat of ground ice sublimation has a minor influence on the global present-day water-cycle but may be considered for specific phenomenons such as the perenniality of crater-induced water ice ejectas [8]. Differentiation of perennial ice albedo and water frost albedo: Through sublimation, the northern polar cap around summer solstice is the dominant atmospheric source of water vapor in our GCM. It shows a strong dependence of summer surface temperature with albedo and thus sublimation [2]. While acceptable water ice albedos range from 0.3 to 0.5 on Mars [9], monitoring the northern polar cap show that the start and end of sublimation phases are correlated with albedo variations [10]. The outlier region of the polar cap is actually the main source of sublimation in the GCM, while the central cap is a cold trap where water vapor condenses into frost. The albedo of perennial water ice and frost, previously identical, are now separated in our GCM to take into account the fact that fresh frosts can exhibit higher albedos which tend to slow down their sublimation . Future enhancements may include a time-varying frost albedo, as it changes with the evolution of ice particules size (metamorphism) and dust accumulation, and thus represent more accurately the insolation on the northern polar cap during summer. These processes may play a key role in paleoclimate studies. Conclusion: Because of the intricate complexity of the feedbacks between dynamics, dust and water transport and cloud microphysics, increasing the temporal resolution in the GCM is mandatory. We have addressed the disruptions it causes to our reference water cycle simulation by taking into account previously neglected physical processes, which allow for a satisfying agreement with TES and SPICAM datasets (figure 1). Figure 1: Reference simulation (MY26) compared to TES data for water vapor column and cloud opacity at 2 PM. References: [1] Montmessin et al. (2004), Journal of Geophysical Research: Planets, 109(E10). [2] Navarro et al. (2014), Journal of Geophysical Research: Planets, 119(7), 1479-1495. [3] Pottier et al. (2017), Icarus, 291, 82-106. [4] Vals (2019), Doctoral dissertation, UPMC. [5] Smith (2004), Icarus, 167(1), 148-165. [6] Maltagliati et al. (2011), Science, 333(6051), 1868-1871. [7] Fedorova et al. (2020), Journal of Geophysical Research: Planets, e2020JE006616. [7] Määttänen et al. (2014), GeoResJ, 3, 46-55. [8] Byrne et al. (2009), Science, 325(5948), 1674-1676. [9] Wilson et al. (2007), Geophysical Research Letters, 34(2). [10] Hale, A. S. et al. (2005), Icarus, 174(2), 502-512.

Thermal tides in Martian atmosphere from ACS/TIRVIM Siteng Fan1 (sfan@lmd.ipsl.fr), Sandrine Guerlet1, Francois Forget1, Antoine Bierjon1, Ehouarn Millour1, Nikolay Ignatiev2, Alexey Shakun2, Alexey Grigoriev2, Alexander Trokhimovskiy2, Franck Montmessin3, Oleg Korablev2 1: LMD/IPSL, Sorbonne Université, PSL Research University, École Normale Supérieure, École Polytechnique, CNRS, Paris, France 2: Space Research Institute (IKI), Moscow, Russia 3: LATMOS/IPSL, Guyancourt, France Abstract Atmospheric thermal tides are planetary-scale temperature oscillations driven by diurnal solar forcing. On Mars, they dominate the temperature variations and winds throughout the thin atmosphere due to its low heat capacity. Given the short timescales of tide modes, which are typically equal or shorter than a Martian day, analyses of these tides require observations with large spatial coverage and high local time resolution. Observations from the TIRVIM Fourier-spectrometer, part of the Atmospheric Chemistry Suite (ACS) onboard ExoMars Trace Gas Orbiter (TGO), provide data meeting such requirement. Here we report the spatial- and temporal-dependent temperature profiles of Martian atmosphere retrieved from TIRVIM nadir data. Amplitudes and phases of thermal tide modes are obtained, and their influence on the thermal structure of Martian atmosphere is estimated using numerical simulations, The LMD Mars Global Circulation Model (GCM). Introduction Diurnal thermal forcing by solar radiation excites temperature oscillations in Martian atmosphere through direct sunlight absorption and heat exchange with Mars surface (Gierasch & Goody 1968). Influenced by surface topography, the varying solar forcing produces harmonic responses in the Martian atmosphere, thermal tides (Zurek 1976). Some modes of the tides can vertically propagate to upper altitudes with amplitudes growing exponentially with decreasing air density, which therefore influences the atmospheric circulation. The existence of such temperature and the related pressure variations has been observed by many Mars landers and orbiters (e.g., Hess et al., 1977, Banfield et al. 2000, Lee et al. 2009, Kleinböhl et al. 2013, Forbes et al. 2020), but observations are still lacking for comprehensive studies as large spatial coverage and high temporal resolution are required to study such planetary-scale diurnal/sub-diurnal variations. Methodology and Results We analyze the thermal tides using temperature structures retrieved from TIRVIM nadir data. TIRVIM is a thermal infrared Fourier-spectrometer, as part of the ACS instrument onboard the ESA-Roscosmos mission ExoMars TGO (Korablev et al., 2018, Svedhem et al. 2020). TGO is on a non-solar-synchronous orbit with a period of 2 hours, so observations obtained at nadir viewing geometry could cover a wide range of local time due to the short orbital period and orbit drifting (Capderou & Forget, 2004, Figure 1). A full diurnal cycle can be sampled between 74°N and 74°S within ~55 solar days (sols), which is equivalent to ~30° in solar longitude (Ls). Binning data within this range results in data covering most local time in a specific Martian month with little seasonal variations. TIRVIM operated from April 2018 to December 2019, nearly one Martian year (MY) from MY34 Ls134° to MY35 Ls 115°, and provides ~1.5 million thermal infrared nadir-viewing spectra with decent data quality. Despite some degeneracy, we retrieved temperature profiles together with dust and water ice from these spectra (Guerlet et al. 2018). Each profile covers a vertical range from ~2-3km above Mars surface to ~50-55km (~1-2Pa) with a vertical resolution of ~1 scale height (10km). Full coverage of local time is obtained for the first time on sub-seasonal scales (Figure 1), which makes it possible to evaluate thermal tides in Martian atmosphere with details and resolve the harmonic aliasing introduced by solar-synchronous observations, e.g., observations at 3am and 3pm local time by the Mars Climate Sounder (MCS, Lee et al. 2009). A preliminary result of the thermal structure on the Martian southern hemisphere near MY35 spring equinox (Ls=90°) is shown in Figure 2a. We binned the data between Ls 75° to 105° so that most of the local time is covered. No dust storms are identified during this period. The selected bin size of latitude is 3° and that of the local time is 1 hour. Temperature profiles are also zonal averages, so only migrating tides are shown. The diurnal temperature difference structure shows diurnal and semi-diurnal cycles at lower and middle atmosphere, respectively, with “apparent” amplitudes of ~7K. Due to the degeneracy introduced by vertically distributed sensitivity response functions of TIRVIM thermal infrared spectra, the retrieved temperature profiles are vertically smoothed (Guerlet et al. 2018). Suggested by the LMD Mars GCM (Forget et al. 1999), amplitudes of these tides are 2-3 times larger (Figure 2b), as smoothing them with the same response functions gives similar diurnal temperature difference structure (Figure 2c). A priori in the temperature profile retrieval makes a difference in extracting the diurnal temperature anomaly at low pressure level due to small weights in the convolution kernels (Figure 2b and 2c), which requires further investigation with GCMs. Figure 1. Spatial-temporal coverage of ACS/TIRVIM observations. Data from 20 orbits are shown for the purpose of illustration, with colors denoting the local time. Figure 2. (a) Diurnal temperature anomaly derived using ACS/TIRVIM observations. The data is binned between MY35 Ls 75° and 105°, and between 10.5°S and 13.5°S in latitude. (b) Result of the LMD Mars GCM. The model result has the same spatial-temporal sampling weight as observations. (c) Same as (b), but vertically convolved with the averaging kernels of TIRVIM. References Banfield, D., Conrath, B., Pearl, J. C., et al. (2000). JGR, 105, 9521. Capderou, M., & Forget, F. (2004). P&SS, 52, 789. Forbes, J. M., Zhang, X., Forget, F., et al. (2020). JGR: Space Physics, 125, e28140. Forget, F., Hourdin, F., Fournier, R., et al. (1999). JGR, 104, 24155. Gierasch, P., & Goody, R. (1968). P&SS, 16, 615. Guerlet, S., Ignatiev, N., Fouchet, T., et al. (2018). EPSC, 2018-223. Hess, S. L., Henry, R. M., Leovy, C. B., et al. (1977). JGR, 82, 4559. KleinböHl, A., John Wilson, R., Kass, D., et al. (2013). GRL, 40, 1952. Korablev, O., Montmessin, F., Trokhimovskiy, A., et al. (2018). SSW, 214, 7. Lee, C., Lawson, W. G., Richardson, M. I., et al. (2009). JGR: Planets, 114, E03005. Svedhem, H., Korablev, O., Mitrofanov, I., et al. (2020). EPSC, 2020-802. Zurek, R. W. (1976). JAS, 33, 321.

Introduction: Remnants of glacial and periglacial geomorphological features are visible up to mid-latitudes on Mars. Notably, an out-of-equilibrium “latitude-dependant mantle” extends to 30° latitude in both hemispheres [1]. These patches were likely deposited as snowfall in the recent past (less than ~2Myr) in response to climate change driven by shift in obliquity, similar to Earth glacial/interglacial periods [2]. However, martian climate models usually struggle to reproduce environmental conditions required to form LDM under recent paleoclimatic orbital forcing. We present a new set of simulations with refined description of surface and sub-surface water processes and their relevance regarding the deposition and above all stability of large ice patches up to mid-latitudes in both martian hemispheres. Water-ice clouds in recent paleoclimates: As present-day martian atmosphere is extremely dry, water ice clouds have second-order effects in global climate models [6]. Modeling higher obliquity episodes, ie shifts from 25° up to 35°, atmospheric humidity is enhanced by polar warming and water-ice cloud become a key element of martian climate [7,8]. Their radiative effect strongly warms the atmosphere, amplifies meridional circulation and water transport toward tropical latitudes. Previous work showed that radiatively active water-ice clouds allow for the transportation and deposition of water ice patches up to mid-latitudes [7]. However, these deposits can only be perennial under extreme atmospheric dust scenarios, in order to limit summertime sublimation. Frost and ice albedo: Surface water ice has a typical albedo of 0.35 in our present-day Mars model [9]. Mid-latitude ice patches resulting from an intensified water cycle at higher obliquity would rather have a 0.7 albedo, due to less dust content and fresh snowfall. By limiting solar heating, this albedo parametrization favors the persistence of mid-latitude ice throughout summer. Latent heat of sublimation: The latent heat of water sublimation has been neglected in present-day climate models, because of the low amount of water and thus energy flux involved. The sublimation of water was hitherto simply computed using surface temperature and water vapor equilibrium. Similarly to the frost albedo effect, taking into account the latent heat of water becomes relevant when the water cycle, and thus the energy flux involved, is intensified at higher obliquity. It also favors the year-long persistence of mid-latitude ice by adding an energy cost to sublimation, which decreases surface heating. Nudging subsurface thermal inertia: Martian soil’s thermal inertia is driven by the presence of subsurface perennial water ice, regulated by long-term equilibrium with water vapor [10]. This equilibrium is modified with the water cycle at higher obliquity. Instead of waiting for natural equilibrium to occur, we artificially accelerate the relocation of subsurface water ice, and accordingly increase subsurface thermal inertia. Subsurface ice inventory is computed each year using annual mean water vapor, as proposed in [10]. Conclusions with idealized orbital forcing: The recent excursions to 35° obliquity are thought to be the main drivers of martian glaciations. We use our new parametrizations along with idealized orbital forcing, that is a 35° obliquity and a null-excentricity, to show that the effect of water-ice clouds, frost albedo and latent heat of sublimation allow for the preservation of mid-latitude ice deposits when equilibrium is reached. In the last ~2 Myr on Mars, obliquity has reached 35° a dozen times, for approximately 1000 years each time [11]. Under our idealized hypothesis, the accumulation rate is compatible with hundreds of meters thick latitude-dependent mantle of ice-rich deposits. References: [1] Head, J. W., J. F. Mustard, M. A., Kreslavsky, R. E. Milliken, and D. R. Marchant (2003), Nature, 426 (6968), 797–802. [2] Forget, F., Byrne, S., Head, J. W., Mischna, M. A., & Schörghofer, N. (2017), The Atmosphere and Climate of Mars, Haberle et al. Editors, Cambridge University Press [3] Forget, F., Haberle, R. M., Montmessin, F., Levrard, B., & Head, J. W. (2006), 311(5759), 368-371. [4] Levrard, B., Forget, F., Montmessin, F and Laskar, J. (2004), Nature, 431 (7012), 1072-1075. [5] Madeleine, J. B., Forget, F., Head, J. W., Levrard, B., Montmessin, F., & Millour, E. (2009), Icarus, 203(2), 390-405. [6] Madeleine, J. B., Forget, F., Millour, E., Navarro, T., & Spiga, A. (2012), GRL, 39(23).[7] Madeleine, J. B., Head, J. W., Forget, F., Navarro, T., Millour, E., Spiga, A., ... & Dickson, J. L. (2014), GRL, 41(14), 4873-4879. [8] Kahre, M. A., Haberle, R. M., Hollingsworth, J. L. and Wilson, R. J. (2019), Ninth International Conference on Mars, held 22-25 July, 2019 in Pasadena, California. LPI Contribution No. 2089, id.6303. [9] Navarro, T., Madeleine, J. B., Forget, F., Spiga, A., Millour, E., Montmessin, F., & Määttänen, A. (2014), JGR: Planets, 119(7), 1479-1495. [10] Schorghofer, N. (2007). Theory of ground ice stability in sublimation environments. Physical Review E, 75(4), 041201. [11] Laskar, J., Correia, A. C. M., Gastineau, M., Joutel, F., Levrard, B., & Robutel, P. (2004), Icarus, 170(2), 343-364.