在火星上，季节性极冰盖消退后，由于火星表面和大气的低热导率，阴暗区域可能残留小型冰斑块，而这些斑块在夏季会受到直射阳光照射。这些斑块可能显著升温，我们在下文中通过普查 HiRISE 图像分析了液相如何可能在这些位置出现。研究分析了符合位置和季节选择标准的730幅图像，并识别出其中148幅含有较小冰斑块的图像。凭借其偏蓝颜色以及与局地地形阴影的强关联，可以将它们与云层或岩层和岩石较浅色调等其他明亮斑块区分开。这些区域位于南纬-40°至-60°的纬度带内，太阳经度范围为140°至200°。冰斑块直径介于1.5至300米之间；即使季节性极盖已经越过该区域，它们仍会在表面保留19至133个火星日。借助 The Mars Climate Database（MCD，火星气候数据库），我们模拟了22个分析区域的表面温度，并预测了 CO2 和 H2O 冰覆盖。模型判断表明，平均正午温度未达到水的熔点273 K，因此宏观尺度上出现液态水的可能性极低；不过，在层状冰与水冰之间仍可能形成冰的界面预熔层，即厚度仅数纳米的水层。
英文摘要：
On Mars it is possible that after the recession of the seasonal polar ice cap, small icy patches left behind in shady places due to the low thermal conductivity of the Martian surface and atmosphere, are met by direct sunlight during the summer. These patches might warm up substantially and we analyzed below how could a liquid phase emerge in these places, surveying HiRISE images. 730 images that fit the selection criteria of location and season were analyzed, and we identified 148 images with smaller ice patches on them. Their separation from other bright patches, like clouds or lighter shades of layers and rocks were possible by their bluish color and strong connection to local topographic shading. These areas range between 140° and 200° solar longitude in the latitude band between -40° and -60°. The diameter of the ice patches ranges between 1.5-300 meters, and they remain on the surface even after the seasonal polar cap has passed over the area for the duration range of 19-133 martian days.
With the help of The Mars Climate Database (MCD) we simulated the surface temperature and predicted CO2 and H2O ice cover at 22 analyzed areas. Judging by the models, the average noon temperature does not reach the melting point of water, which is 273 K, therefore the occurrence of liquid water on the macroscopic scale is highly unlikely, however there is a possibility that an interfacial premelting of ice (a few nanometers thick waterlayer) might form between the layered and the water ice.
Seasonal flows on warm slopes, or recurring slope lineae ("RSL"), have been presented as strong evidence for currently flowing water on Mars. This assumption was supported by a correlation between activity and warm temperatures, and by the spectral identification of hydrated salts. Here we first demonstrate that salts spectral identification is not robust, and that flow activity occurs on a wider range of seasons and slope orientations than previously thought, ruling out liquid water as a probable contributor. We then show that morphology, location and timing of flow activity is fully consiste…
We investigate the global seasonal variations of near-surface relative humidity and relevant attributes, like temperature and water vapor volume mixing ratio on Mars using calculations from modelled and measurement data. We focus on 2 am local time snapshots to eliminate daily effects related to differences in insolation, and to be able to compare calculations based on modelling data from the LMDZ GCM with the observations of MGS TES. We study the seasonal effects by examining four specific dates in the Martian year, the northern spring equinox, summer solstice, autumn equinox and winter solst…
Dark deposits visible from orbit appear in the Martian south polar region during the springtime. These are thought to form from explosive jets of carbon dioxide gas breaking through the thawing seasonal ice cap, carrying dust and dirt which is then deposited onto the ice as dark 'blotches', or blown by the surface winds into streaks or 'fans'. We investigate machine learning (ML) methods for automatically identifying these seasonal features in High Resolution Imaging Science Experiment (HiRISE) satellite imagery. We designed deep Convolutional Neural Networks (CNNs) that were trained and teste…
The springtime sublimation process of Mars' southern seasonal polar CO$_2$ ice cap features dark fan-shaped deposits appearing on the top of the thawing ice sheet. The fan material likely originates from the surface below the ice sheet, brought up via CO$_2$ jets breaking through the seasonal ice cap. Once the dust and dirt is released into the atmosphere, the material may be blown by the surface winds into the dark streaks visible from orbit. The location, size and direction of these fans record a number of parameters important to quantifying seasonal winds and sublimation activity, the most …
The InSight mission, featuring continuous high-frequency high-sensitivity pressure measurements, is in ideal position to study the active atmospheric turbulence of Mars. Data acquired during 1.25 Martian year allows us to study the seasonal evolution of turbulence and its diurnal cycle. We investigate vortices (abrupt pressure drops), local turbulence (frequency range 0.01-2 Hz) and non-local turbulence often caused by convection cells and plumes (frequency range 0.002-0.01 Hz). Contrary to non-local turbulence, local turbulence is strongly sensitive at all local times and seasons to the ambie…
We present results of simulations with the Max Planck Institute general circulation model (MPI-MGCM) implementing a hydrological cycle scheme. The simulations reveal a seasonal water "pump" mechanism responsible for the upward transport of water vapor. This mechanism occurs in high latitudes above 60$^\circ$ of the southern hemisphere at perihelion, when the upward branch of the meridional circulation is particularly strong. A combination of the mean vertical flux with variations induced by solar tides facilitates penetration of water across the "bottleneck" at approximately 60 km. The meridio…
We present the first systematic study of clouds observed during twilight on Mars. We analyze images obtained by the Visual Monitoring Camera (VMC) on Mars Express between 2007 and 2020. Using an automated retrieval algorithm we found 407 cases of clouds observed at twilight, in which the geometry of the observations allows to derive the minimum altitude, revealing that many of these clouds are in the mesosphere (above 40km and up to 90km). The majority of these mesospheric clouds were detected in mid-latitudes at local autumn and winter, a new trend only hinted at by previous studies. In parti…
Using the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), we map the temporal variability of water ice absorption bands over the near-polar ice mound in Louth crater, Mars. The absorption band depth of water ice at 1.5 microns can be used as a proxy for ice grain size and so sudden reductions can time any switches from ablation to condensation. A short period of deposition on the outer edge of the ice mound during late spring coincides with the disappearance of seasonal water frost from the surrounding regolith suggesting that this deposition is locally sourced. The outer unit at…
We investigate the feasibility and demonstrate the merits of using Mars Orbiter Laser Altimeter (MOLA) profiles to retrieve seasonal height variations of CO2 snow/ice cap in Mars' polar areas by applying a co-registration strategy. We present a prototype analysis on the research region of [85.75°S, 86.25°S, 300°E, 330°E] that is located on the residual south polar cap. Our method comprises the recomputation of MOLA footprint coordinates with an updated Mars Global Surveyor (MGS) ephemeris and a revised Mars rotation model. The reprocessed MOLA dataset at the South Pole of Mars (poleward of 78°…
We analyze Mars Climate Sounder temperature and aerosol data in the tropics to study atmospheric tides and their relation to the dust and water ice distributions. Our results from data covering Mars years (MY) 29-35 reveal that MY29 has large amplitude non-migrating thermal tides during southern hemisphere spring equinox that are not observed at the same local time in any other year. It is the nighttime temperatures that are most perturbed compared to other years, with strong temperature inversions at 35-55 km altitude. Analysis of data at different local times reveals that the temperatures an…
Polar vortices are common planetary flows that encircle the pole in the middle or high latitudes, and are observed on most of the solar systems' planetary atmospheres. The polar vortices on Earth, Mars, and Titan are dynamically related to the mean meridional circulation and exhibits a significant seasonal cycle. However, the polar vortex's characteristics vary between the three planets. To understand the mechanisms that influence the polar vortex's dynamics and dependence on planetary parameters, we use an idealized general circulation model with a seasonal cycle in which we varied the obliqu…
The Los Alamos National Laboratory designed and built Mars Odyssey Neutron Spectrometer (MONS) has been in excellent health operating from February 2002 to the present. MONS measures the neutron leakage albedo from galactic cosmic ray bombardment of Mars. These signals can indicate the presence of near-surface water deposits on Mars, and can also be used to study properties of the seasonal polar CO$_2$ ice caps. This work outlines a new analysis of the MONS data that results in new and extended time-series maps of MONS thermal and epithermal neutron data. The new data are compared to previous …
Temporary changes in precipitation may lead to sustained and severe drought or massive floods in different parts of the world. Knowing variation in precipitation can effectively help the water resources decision-makers in water resources management. Large-scale circulation drivers have a considerable impact on precipitation in different parts of the world. In this research, the impact of El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO) on seasonal precipitation over Iran was investigated. For this purpose, 103 synoptic stations with a…
Active dark flows known as recurring slope lineae have been observed on the warmest slopes of equatorial Mars. The morphology, composition and seasonality of the lineae suggest a role of liquid water in their formation. However, internal and atmospheric sources of water appear to be insufficient to sustain the observed slope activity. Experimental evidence suggests that under the low atmospheric pressure at the surface of Mars, gas can flow upwards through porous Martian soil due to thermal creep under surface regions heated by the Sun, and disturb small particles. Here we present numerical si…
Interannual observations and quantification of summertime H2O ice deposition on the Martian CO2 ice south polar cap
2004年，OMEGA（Observatoire pour l 'Mineralogie，l' Eau les Glaces et l 'Activite）在火星南极冰冠上观测到了水冰的光谱特征（Bibring等人，2004年）。三年后，欧米茄仪器被用来发现在南半球夏季沉积在极冠上的水冰（Langevin等人，2007年）。然而，这些水冰特征的时间和空间变化尚未被探索，这些水沉积物的起源仍然是一个重要的科学问题。为了研究这个问题，我们使用了火星勘测轨道飞行器（MRO）航天器上的火星紧凑型侦察成像光谱仪（CRISM）仪器在南半球夏季四个火星年期间的观测结果来寻找水冰量的变化。我们在下面报告说，对于我们观察到的冰帽，南部冰帽上的H2O冰特征的大小在整个夏天都在稳步上升，特别是在冰帽的西端。沉积的空间范围与目前对南极冰帽上水冰沉积的最佳模拟不一致（Montmessin等人，2007年）。水冰特征的增加很可能是由于大气中H2O冰的沉积造成的，并且一组不寻常的条件使得使用CRISM对这种传输通量的量化接近理想。我们计算了一个“最小表观”的沉积量对应于一个薄的H2O冰层的0.2毫米（70%的孔隙度）。这些冰的沉积量占火星大气水总量的0.6%-6%。我们将我们的“最小表观”量化与以前的估计进行比较。这种沉积过程也可能对南部二氧化碳冰帽的形成和稳定性产生影响，因此在现代火星的气候收支中发挥着重要作…
On the Possibility of Melting Water Ice during the Recent Past of Mars: Application to the Formation of Gullies
Sorbonne Université, Centre National de la Recherche Scientifique (CNRS), École Polytechnique, École Normale Supérieure (ENS)（索邦大学、法国国家科学研究中心（CNRS）、巴黎综合理工学院、法兰西公学院）
We present an analysis of all currently available ground-based imaging of Neptune in the mid-infrared. Dating between 2003 and 2020, the images reveal changes in Neptune's mid-infrared ($\sim 8-25μ$m) emission over time in the years surrounding Neptune's 2005 southern summer solstice. Images sensitive to stratospheric ethane ($\sim12μ$m), methane ($\sim8μ$m), and CH$_3$D ($\sim9μ$m) display significant sub-seasonal temporal variation on regional and global scales. Comparison with H$_2$ S(1) hydrogen-quadrupole ($\sim17.035μ$m) spectra suggests these changes are primarily related to stratospher…
Surveying the ice condensation period at southern polar Mars using a CNN
ELTE Institute of Physics（罗兰大学物理研究所）；Wigner RCP（维格纳研究中心）；Konkoly Thege Miklos Astronomical Institute, HUN-REN Research Centre for Astronomy and Earth Sciences（匈牙利科学院天文与地球科学研究中心孔科利-泰格·米克洛什天文研究所）；Luleå University of Technology（吕勒奥理工大学）；CSFK, MTA Centre of Excellence（匈牙利科学院卓越中心）
Sedimentary deposits characterized by the Mars Science Laboratory Curiosity rover provide evidence that Gale crater, Mars intermittently hosted a fluvio-lacustrine environment during the Hesperian. However, estimates of the CO2 content of the atmosphere at the time the sediments in Gale crater were deposited are far less than needed by any climate model to maintain temperatures warm enough for sustained open water lake conditions due to the low solar energy input available at that time. We incrementally test the existence of open water conditions using energy balance calculations for the globa…
Flowing water and brine have been proposed to cause seasonally reappearing dark streaks called recurring slope lineae (RSL) on steep warm slopes on Mars, along with other formation mechanisms that do not involve water. This study aims to examine whether the evaporation of water vapor from the RSL, whether from fresh water or brine, is detectable by observing water vapor and/or clouds. In this study, we summarize the possible rate and duration of water-vapor emission from RSL in different scenarios, simulate how the emitted water vapor behaves in a global climate model, and discuss the detectab…
The Mars Reconnaissance Orbiter (MRO) spacecraft has been in orbit around Mars since March 2006. The Context Camera (CTX) on MRO has returned over 100,000 images of the planet at approximately 5-6 meters per pixel, providing nearly global coverage. During that time, Mars has gone through nearly 7 of its own years, changing solar distance from 1.38 to 1.67 AU and the corresponding solar flux by 45% due to its orbital eccentricity. Seasonal effects and transient phenomena affect atmospheric transparency. Combined with an aging detector, CTX images are difficult to mosaic seamlessly, for all of t…
We analyse the potential vorticity of Saturn's polar regions, as it is a fundamental dynamical tracer that enables us to improve our understanding of the dynamics of these regions and their seasonal variability. In particular, we present zonally averaged quasi-geostrophic potential vorticity maps between 68° planetographic latitude and the poles at altitudes between 500 mbar and 1mbar for three different epochs: (i) June 2013 (early northern summer) for the north polar region, (ii) December 2008 (late northern winter) for both polar regions and (iii) October 2006 (southern summer) for the sout…
A multi-decade record of ground-based mid-infrared (7-25 $μ$m) images of Saturn is used to explore seasonal and non-seasonal variability in thermal emission over more than a Saturnian year (1984-2022). Thermal emission measured by 3-m and 8-m-class observatories compares favourably with synthetic images based on both Cassini-derived temperature records and the predictions of radiative climate models. 8-m class facilities are capable of resolving thermal contrasts on the scale of Saturn's belts, zones, polar hexagon, and polar cyclones, superimposed onto large-scale seasonal asymmetries. Season…
Feasibility assessment of optical communications between ground and satellite on Mars through the simulation of atmospheric effects on signal quality leading to a proposal for a new communications network architecture during extreme weather
Carbon dioxide (CO$_2$) ice clouds have been routinely observed in the middle atmosphere of Mars. However, there are still uncertainties concerning physical mechanisms that control their altitude, geographical, and seasonal distributions. Using the Max Planck Institute Martian General Circulation Model (MPI-MGCM), incorporating a state-of-the-art whole atmosphere subgrid-scale gravity wave parameterization [Yiğit et al., 2008], we demonstrate that internal gravity waves generated by lower atmospheric weather processes have wide reaching impact on the Martian climate. Globally, GWs cool the upp…
