The MAGO experiment for dust environment monitoring on the Martian surface

Among the main directions identified for future Martian exploration, the study of the properties of dust dispersed in the atmosphere, its cycle and the impact on climate are considered of primary relevance. Dust storms, dust devils and the dust “cycle” have been identified and studied by past remote and in situ experiments, but little quantitative information is available on these processes, so far. The airborne dust contributes to the determination of the dynamic and thermodynamic evolution of the atmosphere, including the large-scale circulation processes and its impact on the climate of Mars. Moreover, aeolian erosion, redistribution of dust on the surface and weathering processes are mostly known only qualitatively. In order to improve our knowledge of the airborne dust evolution and other atmospheric processes, it is mandatory to measure the amount, mass-size distribution and dynamical properties of solid particles in the Martian atmosphere as a function of time. In this context, there is clearly a need for the implementation of experiments dedicated to study directly atmospheric dust. The Martian atmospheric grain observer (MAGO) experiment is aimed at providing direct quantitative measurements of mass and size distributions of dust particles, a goal that has never been fully achieved so far. The instrument design combines three types of sensors to monitor in situ the dust mass flux (micro balance system, MBS) and single grain properties (grain detection system, GDS + impact sensor, IS). Technical solutions and science capabilities are discussed in this paper.     

Optical properties of dust and the opacity of the Martian atmosphere

Particulate component of the Mars atmosphere composed by micron-sized products of soil weathering and water ice clouds strongly affects the current climate of the planet. In the absence of a dust storm so-called permanent dust haze with τ ≈ 0.2 in the atmosphere of Mars determines its thermal structure. Dust loading varies substantially with the season and geographic location, and only the data of mapping instruments are adequate to characterize it, such as TES/MGS and IRTM/Viking. In spite of vast domain of collected data, no model is now capable to explain all observed spectral features of dust aerosol. Several mineralogical and microphysical models of the atmospheric dust have been proposed but they cannot explain the pronounced systematic differences between the IR data (τ = 0.05–0.2) and measurements from the surface (Viking landers, Pathfinder) which give the typical “clear” optical depth of τ ≈ 0.5 from one side, and ground-based observations in the UV–visible range showing much more transparent atmosphere, on the other side. Also the relationship between τ₉ and the visible optical depth is not well constrained experimentally so far. Future focused measurements are therefore necessary to study Martian aerosol.     

Numerical simulations of the regional characteristics of dust transport on Mars

Using a Martian general circulation model (GCM), regions favorable for expansion of dust storms on Mars are identified. Dust transport simulations for the northern fall provide global maps of dust expansibility. These global maps show that dust injected from certain areas in the northern mid-latitudes tends to spread widely within a few days. The high expansibility of dust in such areas results from thermal tides, baroclinic waves, and quasi-stationary disturbances. Dust injected into the vast regions around Tharsis and the Sirenum–Aonia regions also tends to spread extensively. However, dust expansion around these two regions largely depends on the local time of dust injection. On the other hand, dust injected at high latitudes in either hemisphere does not spread extensively. Such global maps indicating regions favorable for dust storm expansion are a clue to understanding the expansion processes and climatology of great dust storms on Mars.     

Thermal structure of the Martian atmosphere retrieved from the IR spectrometry in the 15 μm CO2 band: input to MIRA

This paper describes one of the sources of the data concerning the thermal structure of the Martian atmosphere, based on the thermal IR spectrometry method. It allows to investigate the Martian atmosphere below 55 km by retrieving the temperature profiles from the 15 μm CO₂ band. This approach enables to reach the vertical resolution of several kilometers and the temperature accuracy of several Kelvins. An aerosol abundance, which influences the temperature profile, is obtained from the continuum of the same spectrum parallel with the temperature profile and is taken into account in the temperature retrieval procedure in a self consistent way. Although this method has the limited vertical resolution, it possesses a significant advantage: the thermal IR spectrometry allows to monitor the temperature profiles with a good coverage both in space and local time. The Planetary Fourier spectrometer on board of Mars Express has the spectral range from 250 to 8000 cm⁻¹ and a high spectral resolution of about 2 cm⁻¹. Vertical temperature profiles retrieval is one of the main scientific goals of the experiment. The important data are expected to be obtained on the vertical thermal structure of the atmosphere, and its dependence on latitude, longitude, season, local time, clouds and dust loadings. These results should give a significant input in the future MIRA, being included in the Chapter “Structure of the atmosphere from the surface to 100 km”.     

Annual solar UV exposure and biological effective dose rates on the Martian surface.

The ultraviolet (UV) environment of Mars has been investigated to gain an understanding of the variation of exposure throughout a Martian year, and link this flux to biological effects and possible survival of organisms at the Martian surface. To gain an idea of how the solar UV radiation varies between different regions, including planned landing sites of two future Mars surface missions, we modelled the total solar UV surface flux throughout one Martian year for two different dust scenarios. To understand the degree of solar UV stress on micro-organisms and/or molecules essential for life on the surface of Mars, we also calculated the biologically effective dose (BED) for T7 and Uracil in relevant wavelength regions at the Martian surface as a function of season and latitude, and discuss the biological survival rates in the presence of Martian solar UV radiation. High T7/Uracil BED ratios indicate that even at high latitudes where the UV flux is significantly reduced, the radiation environment is still hostile for life due to the persisting UV-C component of the flux.     

Ablation and chemistry of meteoric materials in the atmosphere of Titan

We compute the input of meteoric materials expected on Titan, and integrate this dust model with an ablation model and a comprehensive chemical model, investigating the effects on the atmosphere and surface. We find that a water deposition of 10-100 times the expected interplanetary dust flux /7/, or a recent large impact, is required to produce the observed CO₂ abundance /2/. Ionisation due to meteoric activity is not likely to be higher than that due to other sources.     

火星大气模型参数对MSL气动特性的影响

火星大气与地球大气截然不同,飞行器在进入火星时气动特性不同于地球再入. 大气模型的差异主要表现为气体组份、密度和温度等物理参数. 针对火星进入器MSL在进入-下降-着陆过程中的高超声速进入段,利用三维并行程序求解耦合真实气体模型的流体动力学Navier-Stokes方程,分析MSL进入火星大气时大气模型参数对进入器气动特性的影响. 结果表明,通过与海盗号飞行数据的对比,验证了所采用的火星气体模型和计算方法,且其与NASA的 LAURA代码气动特性计算结果也较为一致;大气模型气体性质,即CO₂环境对进入器阻力系数和俯仰力矩系数影响较大,利用空气得到的计算和实验数据必须考虑CO₂效应;密度增大促进了化学非平衡效应,但对进入器气动特性基本没有影响;温度升高大大增强了化学非平衡效应,而对进入器气动特性影响较小.     

Martian Buildings: Design loading

Multiplanetary life has been studied by scientists as a way to supply energy or sustain human life in the future. Mars is likely to be man’s first destination, colonization using onsite structural construction would be one of the main options. The first step to designing a reliable building is to know the applied structural loads and to have an accurate design load combination. Due to lack of complete knowledge, short span of recorded data, Martian environment, and hazardous environment that Martian structures face, constructed Martian structures should behave appropriately under the highest likely live, dead and environmental loads either simultaneously or as a worst-case scenario. The present study evaluated and calculated probable Martian structural loads, including live, internal pressure, snow, gravity (dead), dust accumulation, thermal stress, wind, marsquake, asteroid, and meteoroid impact loads and their effects. Information was gathered from previous studies and valid data from Martian landers, rovers and orbiters. Wind loads were calculated based on the over 6.5 years of data recorded by Vikings 1 and 2, temperature and winds for InSight (TWINS) sensor. A wind shear exponent and wind profile have been proposed for a Martian flat terrain construction site. Marsquake lateral loads, frequency content and seismicity were assessed using data from the seismic experiment for interior structure (SEIS) and the Viking 2 seismometer. Considering the high influx of micrometeoroids, their penetration distance, impact loads and their effects on structures were calculated. The annual probability of an asteroid impact on a settlement was assessed for a 30-year mission. A load map for Martian residential buildings that considers the worst-case scenario in which a Martian structure should be designed based on them has been proposed.     

The search for nitrogen compounds on the surface of Mars

Nitrogen is an essential element for life. Specifically, “fixed nitrogen” (i.e., NH₃, NH₄⁺, NO_x, or N that is chemically bound to either inorganic or organic molecules and is releasable by hydrolysis to NH₃ or NH₄⁺) is the form of nitrogen useful to living organisms. To date no direct analysis of Martian soil nitrogen content, or content of fixed nitrogen compounds has been done. Consequently, the planet's total inventory of nitrogen is unknown. What is known is that the N₂ content of the present-day Martian atmosphere is 0.2 mbar. It has been hypothesized that early in Mars' history (3 to 4 billion years ago) the Martian atmosphere contained much more N₂ than it does today. The values of N₂ proposed for this early Martian atmosphere, however, are not well constrained and range from 3 to 300 mbar of N₂. If the early atmosphere of Mars did contain much more N₂ than it does today the question to be answered is, Where did it go? The two main processes that could have removed it rapidly from the atmosphere include: 1) nonthermal escape of N-atoms to space; and 2) burial within the regolith as nitrates and nitrites. Nitrate will be stable in the highly oxidized surface soil of Mars, and will tend to accumulate in the soil. Such accumulations are observed in certain desert environments on Earth. Some NH₄⁺---N may also be fixed and stabilized in the soil by inclusion as a structural cation in the crystal lattices of certain phyllosilicates replacing K. Analysis of the Martian soil for traces of NO₃⁻ and NH₄⁺ during future missions will supply important information regarding the nitrogen abundance on Mars, its past climate as well as its potential for the evolution of life.     

Optical properties of the Martian atmosphere and radiative heat exchange

Optical properties of the Martian atmosphere and its radiative heat exchange have been investigated. The role of the greenhouse effect mechanism in evolution of the Martian climate has been studied.     

Martian cloud systems: Current knowledge and future observations

In this paper we summarise the current understanding of Martian condensate and dust clouds. The paper is particularly concerned with the spatial, temporal and seasonal characteristics of the clouds. The condensate clouds are composed of water and ice particles and occasionally CO₂ particles. Dust clouds are composed of material from the surface and redistributed over the planet through the weather systems. The apparent lack of annual reproductivity of these dust storms forms a major unresolved problem. We discuss in this paper the types of observations needed in future space missions, in particular the requirements for the NASA Mars Geochemical Climatology Orbiter Mission planned for the end of this decade.     

Planetary protection and the search for life beneath the surface of Mars.

The search for traces of extinct and extant life on Mars will be extended to beneath the surface of the planet. Current data from Mars missions suggesting the presence of liquid water early in Mars' history and mathematical modeling of the fate of water on Mars imply that liquid water may exist deep beneath the surface of Mars. This leads to the hypothesis that life may exist deep beneath the Martian surface. One possible scenario to look for life on Mars involves a series of unmanned missions culminating with a manned mission drilling deep into the Martian subsurface (approximately 3Km), collecting samples, and conducting preliminary analyses to select samples for return to earth. This mission must address both forward and back contamination issues, and falls under planetary protection category V. Planetary protection issues to be addressed include provisions stating that the inevitable deposition of earth microbes by humans should be minimized and localized, and that earth microbes and organic material must not contaminate the Martian subsurface. This requires that the drilling equipment be sterilized prior to use. Further, the collection, containment and retrieval of the sample must be conducted such that the crew is protected and that any materials returning to earth are contained (i.e., physically and biologically isolated) and the chain of connection with Mars is broken.     

Sterilisation properties of the Mars surface and atmospheric environment.

The radiative and chemical conditions at the surface and in the lower Martian atmosphere are computed at various latitudes and seasons combining a 2D photochemical model and radiation simulations. In most situations, the solar UV B and C radiations reach the surface however, suspended dust and, in polar cases, ozone can constitute an effective UV shield. The daytime and night time concentrations of the sterilizing oxidants: OH, H2O2 and O3 are determined, as well as the concentration of the substances which could influence the metabolism of microorganisms. The possible habitats of a remaining Mar's life as well as the possibilities of contamination by resistant earth life forms will be described.     

Studies in the search for life on Mars.

The ability of living organisms to survive extraterrestrial conditions has implications for the origins of life in the solar system. We have therefore studied the survival of viruses, bacteria, yeast, and fungi under simulated Martian conditions. The environment on Mars was simulated by low temperature, proton irradiation, ultraviolet irradiation, and simulated Martian atmosphere (CO2 95.46%, N2 2.7%, water vapor 0.03%) in a special cryostat. After exposure to these conditions, tobacco mosaic virus and spores of Bacillus, Aspergillus, Clostridium, and some species of coccus showed significant survival.     

A new Mars radiation environment model with visualization.

A new model for the radiation environment to be found on the planet Mars due to Galactic Cosmic Rays (OCR) has been developed at the NASA Langley Research Center. Solar modulated primary particles rescaled for Mars conditions are transported through the Martian atmosphere, with temporal properties modeled with variable timescales, down to the surface, with altitude and backscattering patterns taken into account. The Martian atmosphere has been modeled by using the Mars Global Reference Atmospheric Model--version 2001 (Mars-GRAM 2001). The altitude to compute the atmospheric thickness profile has been determined by using a model for the topography based on the data provided by the Mars Orbiter Laser Altimeter (MOLA) instrument on board the Mars Global Surveyor (MGS) spacecraft. The Mars surface composition has been modeled based on averages over the measurements obtained from orbiting spacecraft and at various landing sites, taking into account the possible volatile inventory (e.g., CO2 ice, H2O ice) along with its time variation throughout the Martian year. Particle transport has been performed with the HZETRN heavy ion code. The Mars Radiation Environment Model has been made available worldwide through the Space Ionizing Radiation Effects and Shielding Tools (SIREST) website, a project of NASA Langley Research Center.     

Evolution of the Martian water cycle.

The current Martian water cycle is extremely asymmetric, with large amounts of vapor subliming off a permanent north polar water ice cap in northern summer, but with no apparent major source of water vapor in the southern hemisphere. Detailed simulations of this process with a three-dimensional circulation model indicate that the summertime interhemispheric exchange (Hadley cell) is very much stronger than transport by eddies in other seasons. As a result, water ice would be distributed globally were it not for the buffering action of regolith soil adsorption which limits the net flux of water vapor off the north polar cap to amounts that are insignificant even on the scale of thousands of years. It has been suggested that the polar layered deposits are the result of exchange on these long time scales, driven by changes in Martian orbital parameters. We therefore are conducting simulations to test the effect of varied orbital parameters on the Martian water cycle. We find that when the perihelion summer pole is charged with a polar water ice cap, large quantities of water are quickly transfered to the aphelion summer pole, setting up an annual cycle that resembles the present one. Thus, the adsorptivity of the Martian regolith may be in the narrow range where it can limit net transport from the aphelion but not the perihelion pole.     

火星大气环境模拟装置设计及仿真分析研究

对火星表面大气环境特性进行了研究,通过选取合适的计算方法并结合FLUENT流体有限元计算软件对火星表面稀薄气体内部环流进行了模拟仿真分析,提出了以动量源模拟风扇段内流的仿真方法,并进行了可行性讨论。进一步实现了针对圆柱形模拟装置多工况下的内部气体流场稳态和非稳态计算仿真,并对计算结果进行了分析讨论,为火星大气环境模拟装置的设计提供了技术支持和参考。     

The implantation of life on Mars: feasibility and motivation.

Environmental conditions on Mars are extremely hostile, and would be destructive to any organisms which might arrive there unprotected to-day. However, it is a biocompatible planet. Its unalterable astrophysical parameters would allow the maintenance of a much thicker, warmer carbon dioxide atmosphere than that which currently exists. Though very cold (averaging about -60 degrees C), highly oxidizing and desiccated, Mars may possess substantial quantities of the materials needed to support life--in particular, water and carbon dioxide. A general scenario for implanting life on Mars would include three main phases: (1) robotic and human exploration to determine whether sufficiently large and accessible volatile inventories are available; (2) planetary engineering designed to warm the planet, release liquid water and produce a thick carbon dioxide atmosphere; and (3) if no indigenous Martian organisms emerge as liquid water becomes available, a program of biological engineering designed to construct and implant pioneering microbial communities able to proliferate in the newly clement, though still anaerobic, Martian environment. The process of establishing an ecosystem, or biosphere, on a lifeless planet is best termed 'ecopoiesis.' This new word, derived from Greek, means 'the making of an abode for life.' It is by no means clear whether ecopoiesis on Mars is scientifically possible or technologically achievable. Thus we urge that it be one of the objectives of space research during the next century to assess the feasibility of ecopoiesis on Mars.     

Atmospheric dynamics on Venus and Mars

New results from Pioneer Orbiter observations indicate a continued vortex organization of the cloud level atmosphere in either hemisphere, centered over respective poles. Significant changes in the magnitude of the cloud level zonal circulation over a period of several years have been detected. A strong signature of the solar tidal circulation has been detected in the atmospheric circulation with the lowest speeds occurring in equatorial latitudes about 20° upstream of the sub-solar point. Finally, a solar-locked persistent spatial structure has been discovered in the variance of the ultraviolet brightness measured from brightness normalized images of Venus. Vega balloons (drifting at about 53 km altitude near 7°N and 7°S latitudes) have also provided some unique observations of atmospheric circulation, significant among them being the strong vertical motions, the zonality of their drift speeds as well as a significant temperature difference between the two balloons. The temperature difference which amounts to 6.5°K on average is currently being interpreted as a temperature variation with longitude or time.

Diagnostic modelling efforts towards simulating the atmospheric circulation on Venus are continuing and have provided some clues about the processes that maintain them but have not yet been successful in explaining the superrotation of the atmosphere.

Knowledge of the Martian atmospheric dynamics on the other hand is still limited by lack of adequate observations. Numerical modelling of the Martian atmosphere continues to provide most of the information about the atmospheric circulation. The situation regarding the paucity of observations should improve with the completion of the proposed Mars Observer mission. The low circular polar orbit planned provides an excellent opportunity to study the Martian atmosphere.     

Electric discharge in the Martian atmosphere,Paschen curves and implications for future missions

Electric discharge between two electrically charged surfaces occurs at a well-defined, gas-dependent combination of atmospheric pressure and the distance between those two surfaces, as described by Paschen’s law. The understanding of when the discharge will occur in the conditions present on Mars is essential for designing space-flight hardware that will operate on the Martian surface as well as understanding electrical discharge processes occurring in the Martian atmosphere. Here, we present experimentally measured Paschen curves for a gas mixture representative of the Martian atmosphere and compare our results to breakdown voltages of carbon dioxide, nitrogen, and helium as measured with our system and from the literature. We will discuss possible implications for instrument development as well as implications for processes in the Martian atmosphere. The DC voltage at which electric discharge occurred between two stainless steel spheres was measured at pressures from 10⁻² to 100 torr in all gases. We measured a minimum voltage for discharge in the Mars ambient atmosphere of 410 ± 10 V at 0.3 torr cm. As an application, the breakdown properties of space-qualified, electrical wires to be used in the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) were studied.