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1.
The evaporation rate of water ice on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the ice layer. The thickness of the ice is governed principally by the solar flux which penetrates the ice layer and then is conducted back to the surface. These calculations differ from those of Lingenfelter et al. [(1968) Science161, 266–269] for putative lunar channels in including the effect of the atmosphere. Evaporation from the surface is governed by two physical phenomena: wind and free convection. In the former case, water vapor diffuses from the surface of the ice through a lamonar boundary layer and then is carried away by eddy diffusion above, provided by the wind. The latter case, in the absence of wind, is similar, except that the eddy diffusion is caused by the lower density of water vapor than the Martian atmosphere. For mean Martian insolations the evaporation rate above the ice is ～ 10?8 g cm?2 sec?1. Thus, even under present Martian conditions a flowing channel of liquid water will be covered with ice which evaporates sufficiently slowly that the water below can flow for hundreds of kilometers even with quite modest discharges. Evaporation rates are calculated for a wide range of frictional velocities, atmospheric pressures, and insolations and it seems clear that at least some subset of observed Martian channels may have formed as ice-choked rivers. Typical equilibrium thicknesses of such ice covers are ～ 10 to 30 m; typical surface temperatures are 210 to 235°K. Ice-covered channels or lakes on Mars today may be of substantial biological interest. Ice is a sufficiently poor conductor of heat that sunlight which penetrates it can cause melting to a depth of several meters or more. Because the obliquity of Mars can vary up to some 35°, the increased polar heating at such times seems able to cause subsurface melting of the ice caps to a depth which corresponds to the observed lamina thickness and may be responsible for the morphology of these polar features. 相似文献
2.
V. I. Aleshin 《Solar System Research》2004,38(6):434-440
The seasonal evolution of the H2O snow in the Martian polar caps and the dynamics of water vapor in the Martian atmosphere are studied. It is concluded that the variations of the H2O mass in the polar caps of Mars are determined by the soil thermal regime in the polar regions of the planet. The atmosphere affects water condensation and evaporation in the polar caps mainly by transferring water between the polar caps. The stability of the system implies the presence of a source of water vapor that compensates for the removal of water from the atmosphere due to permanent vapor condensation in the polar residual caps. The evaporation of the water ice that is present in the surface soil layers in the polar regions of the planet is considered as such a source. The annual growth of the water-ice mass in the residual polar caps is estimated. The latitudinal pattern of the seasonal distribution of water vapor in the atmosphere is obtained for the stable regime.Translated from Astronomicheskii Vestnik, Vol. 38, No. 6, 2004, pp. 497–503.Original Russian Text Copyright © 2004 by Aleshin. 相似文献
3.
Abstract— Although tenuous, the atmosphere of Mars affects the evolution of impact‐generated vapor. Early‐time vapor from a vertical impact expands symmetrically, directly transferring a small percentage of the initial kinetic energy of impact to the atmosphere. This energy, in turn, induces a hemispherical shock wave that propagates outward as an intense airblast (due to high‐speed expansion of vapor) followed by a thermal pulse of extreme atmospheric temperatures (from thermal energy of expansion). This study models the atmospheric response to such early‐time energy coupling using the CTH hydrocode written at Sandia National Laboratories. Results show that the surface surrounding a 10 km diameter crater (6 km “apparent” diameter) on Mars will be subjected to intense winds (?200 m/s) and extreme atmospheric temperatures. These elevated temperatures are sufficient to melt subsurface volatiles at a depth of several centimeters for an ice‐rich substrate. Ensuing surface signatures extend to distal locations (?4 apparent crater diameters for a case of 0.1% energy coupling) and include striations, thermally armored surfaces, and/or ejecta pedestals—all of which are exhibited surrounding the freshest high‐latitude craters on Mars. The combined effects of the atmospheric blast and thermal pulse, resulting in the generation of a crater‐centered erosion‐resistant armored surface, thus provide a new, very plausible formation model for high‐latitude Martian pedestal craters. 相似文献
4.
Alberto G. Fairén 《Icarus》2010,208(1):165-48
Water on Mars has been explained by invoking controversial and mutually exclusive solutions based on warming the atmosphere with greenhouse gases (the “warm and wet” Mars) or on local thermal energy sources acting in a global freezing climate (the “cold and dry” Mars). Both have critical limitations and none has been definitively accepted as a compelling explanation for the presence of liquid water on Mars. Here is considered the hypothesis that cold, saline and acidic liquid solutions have been stable on the sub-zero surface of Mars for relatively extended periods of time, completing a hydrogeological cycle in a water-enriched but cold planet. Computer simulations have been developed to analyze the evaporation processes of a hypothetical martian fluid with a composition resulting from the acid weathering of basalt. This model is based on orbiter- and lander-observed surface mineralogy of Mars, and is consistent with the sequence and time of deposition of the different mineralogical units. The hydrological cycle would have been active only in periods of dense atmosphere, as having a minimum atmospheric pressure is essential for water to flow, and relatively high temperatures (over ∼245 K) are required to trigger evaporation and snowfall; minor episodes of limited liquid water on the surface could have occurred at lower temperatures (over ∼225 K). During times with a thin atmosphere and even lesser temperatures (under ∼225 K), only transient liquid water can potentially exist on most of the martian surface. Assuming that surface temperatures have always been maintained below 273 K, Mars can be considered a “cold and wet” planet for a substantial part of its geological history. 相似文献
5.
《Icarus》1987,72(1):95-127
The possibility that snowmelt could have provided liquid water for valley network formation early in the history of Mars is investigated using an optical-thermal model developed for dusty snowpacks at temperate latitudes. The heating of the postulated snow is assumed to be driven primarily by the absorption of solar radiation during clear sky conditions. Radiative heating rates are predicted as a function of depth and shown to be sensitive to the dust concentration and the size of the ice grains while the thermal conductivity is controlled by temperature, atmospheric pressure, and bulk density. Rates of metamorphism indicate that fresh fine-grained snow on Mars would evolve into moderately coarse snow during a single summer season. Results from global climate models are used to constrain the mean-annual surface temperatures for snow and the atmospheric exchange terms in the surface energy balance. Mean-annual temperatures within Martian snowpacks fail to reach the melting point for all atmospheric pressures below 1000 mbar despite a predicted temperature enhancement beneath the surface of the snowpacks. When seasonal and diurnal variations in the incident solar flux are included in the model, melting occurs at midday during the summer for a wide range of snow types and atmospheric pressures if the dust levels in the snow exceed 100 ppmw (parts per million by weight). The optimum dust concentration appears to be about 1000 ppmw. With this dust load, melting can occur in the upper few centimeters of a dense coarse-grained snow at atmospheric pressures as low as 7 mbar. Snowpack thickness and the thermal conductivity of the underlying substrate determine whether the generated snow-melt can penetrate to the snowpack base, survive basal ice formation, and subsequently become available for runoff. Under favorable conditions, liquid water becomes available for runoff at atmospheric pressures as low as 30 to 100 mbar if the substrate is composed of regolith, as is expected in the ancient cratered terrain of Mars. 相似文献
6.
Crofton B. Farmer 《Icarus》1976,28(2):279-289
The factors which affect fusion and evaporation of ice under a variety of Martian surface conditions are examined. It is found that a frost or ice deposit will pass through a transient liquid phase in temperate latitudes during summer, if the ice is partly or wholly dust covered. The barrier to free gaseous diffusion which the surface material presents is, under favorable (and definable) conditions, more than adequate to force the water to remain in the liquid state until its evaporation is complete. Furthermore, for a realistic range of regolith particle sizes and porosities, and depths of burial of the ice, the lifetime of the ice can be considerably longer than the duration of a single diurnal warming cycle. Current knowledge of the seosonal and diurnal behavior of the atmospheric vapor is summarized and discussed as it relates to the availability of surface ice at temperate latitudes. 相似文献
7.
Spectra of Mars from 100 to 360 cm?1 were obtained during three different observation periods from NASA's Kuiper Airborne Observatory. Also, a new thermal model was constructed for the surface of Mars, and synthetic spectra were computed from the models to compare with the observations. The models include the effects of a dusty atmosphere which absorbs, scatters, and reradiates energy. The synthetic spectra show significant effects on disk-averaged brigthness temperatures, as well as absorption features, due to silicate dust. The spectra of Mars, which are ratios of Mars to the Moon, do not fit the synthetic spectra unless the surface emissivities of Mars and the Moon have different dependencies on wavelenght. A possible explanation for this behavior is a difference in soil particle-size distributions between Mars and the Moon, with Mars being depleted in large particles compared to the Moon. Small particles are consistent with clay minerals which have been suggested elsewhere as constituents of the Martian surface. 相似文献
8.
Bruce M. Jakosky 《Icarus》1983,55(1):19-39
The behavior of water vapor in the Mars atmosphere requires that there be a seasonally accessible nonatmospheric reservoir of water. Coupled models have been constructed which include exchange of water with the regolith and with the polar caps, and transport through the atmosphere due to its circulation. Comparison of the model results with the vapor observations and with other data regarding the physical nature of the surface allows constraints to be placed on the relative importance of each process. The models are capable of satisfactorily explaining the gross features of the observed behavior using plausible values for the regolith and atmosphere mixing terms. In the region between the polar caps, the regolith contributes as much water to the seasonal cycle of vapor as does transport in from the more-poleward regions, to within a factor of 2. Globally, 10–40% of the seasonal cycle of vapor results from exchange of water with the regolith, about 40% results from the behavior of the residual caps, and the remainder is due to exchange of water with the seasonal caps. It is difficult to determine the relative importance of the processes more precisely than this because both regolith and polar cap exchange of water act to first order in the same direction, producing the largest vapor abundance during the local summer. The system is ultimately regulated on the seasonal time scale by the polar caps, as the time to reach equilibrium between the atmosphere and regolith or between the polar atmosphere and the global atmosphere is much longer than the time for the polar caps to equilibrate with the local atmosphere. This same behavior will hold for longer time scales, with the polar caps being in equilibrium with the insolation as it changes on the obliquity time scale, and the atmosphere and regolith following along. 相似文献
9.
We report on new retrievals of water vapor column abundances from the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data. The new retrievals are from the TES nadir data taken above the ‘cold’ surface areas in the North polar region (Tsurf < 220 K, including seasonal frost and permanent ice cap) during spring and summer seasons, where retrievals were not performed initially. Retrievals are possible (with some modifications to the original algorithm) over cold surfaces overlaid by sufficiently warm atmosphere. The retrieved water vapor column abundances are compared to the column abundances observed by other spacecrafts in the Northern polar region during spring and summer and good agreement is found. We detect an annulus of water vapor growing above the edge of the retreating seasonal cap during spring. The formation of the vapor annulus is consistent with the previously proposed mechanism for water cycling in the polar region, according to which vapor released by frost sublimation during spring re-condenses on the retreating seasonal CO2 cap. The source of the vapor in the vapor annulus, according to this model, is the water frost on the surface of the CO2 at the retreating edge of the cap and the frost on the ground that is exposed by the retreating cap. Small contribution from regolith sources is possible too, but cannot be quantified based on the TES vapor data alone. Water vapor annulus exhibits interannual variability, which we attribute to variations in the atmospheric temperature. We propose that during spring and summer the water ice sublimation is retarded by high relative humidity of the local atmosphere, and that higher atmospheric temperatures lead to higher vapor column abundances by increasing the water holding capacity of the atmosphere. Since the atmospheric temperatures are strongly influenced by the atmospheric dust content, local dust storms may be controlling the release of vapor into the polar atmosphere. Water vapor abundances above the residual polar cap also exhibit noticeable interannual variability. In some years abundances above the cap are lower than the abundances outside of the cap, consistent with previous observations, while in the other years the abundances above the cap are higher or similar to abundances outside of the cap. We speculate that the differences may be due to weaker off-cap transport in the latter case, keeping more vapor closer to the source at the surface of the residual cap. Despite the large observed variability in water vapor column abundances in the Northern polar region during spring and summer, the latitudinal distribution of the vapor mass in the atmosphere is very similar during the summer season. If the variability in vapor abundances is caused by the variability of vapor sources across the residual cap then this would mean that they annually contribute relatively little vapor mass to significantly affect the vapor mass budget. Alternatively this may suggest that the vapor variability is caused by the variability of the polar atmospheric circulation. The new water vapor retrievals should be useful in tuning the Global Circulation Models of the martian water cycle. 相似文献
10.
Nadine G. Barlow 《Meteoritics & planetary science》2006,41(10):1425-1436
Abstract— Mars Global Surveyor (MGS) and Mars Odyssey data are being used to revise the Catalog of Large Martian Impact Craters. Analysis of data in the revised catalog provides new details on the distribution and morphologic details of 6795 impact craters in the northern hemisphere of Mars. This report focuses on the ejecta morphologies and central pit characteristics of these craters. The results indicate that single‐layer ejecta (SLE) morphology is most consistent with impact into an ice‐rich target. Double‐layer ejecta (DLE) and multiple‐layer ejecta (MLE) craters also likely form in volatile‐rich materials, but the interaction of the ejecta curtain and target‐produced vapor with the thin Martian atmosphere may be responsible for the large runout distances of these ejecta. Pancake craters appear to be a modified form of double‐layer craters where the thin outer layer has been destroyed or is unobservable at present resolutions. Pedestal craters are proposed to form in an icerich mantle deposited during high obliquity periods from which the ice has subsequently sublimated. Central pits likely form by the release of vapor produced by impact into ice‐soil mixed targets. Therefore, results from the present study are consistent with target volatiles playing a dominant role in the formation of crater morphologies found in the Martian northern hemisphere. 相似文献
11.
Tetsuya Tokano 《Icarus》2003,164(1):50-78
In an effort to test and to understand the global hydrogen distribution in the shallow subsurface of Mars retrieved by the Mars Odyssey gamma-ray spectrometer, the present state and movement of water are investigated by a coupled global subsurface-atmosphere water cycle model. It was found that the observed global subsurface hydrogen distribution is largely consistent with the modeled global water cycle, so a large fraction of hydrogen is likely to exist as water, at low and mid latitudes in the form of adsorbed water. Under the present climate the water content in the shallow subsurface becomes higher in the northern hemisphere than in the southern hemisphere as a result of global water cycle, regardless of the initial water distribution in the soil or adsorptive capacity. The higher annual maximum soil temperature in the south, stronger net northward transport of atmospheric water vapor, and the emission of vapor from the northern residual polar cap in northern summer contribute to this hemispheric asymmetry. The generally higher adsorptive capacity of clay minerals in the northern plains may further increase this bias. The longitudinal inhomogeneity is caused by several factors, such as thermal inertia, adsorptive capacity, and atmospheric surface pressure. The water abundance is locally high in low thermal inertia regions (e.g., Arabia Terra) and at deep places where the surface pressure is high (e.g., Hellas); it is low in soil with a low adsorptive capacity (e.g., Tharsis) and high thermal inertia regions (e.g., Solis Planum). Most of the soil humidity near the surface at low and mid latitudes may originate from the atmosphere. The model implies that the upper soil layer should be largely ice-free because otherwise an excessive sublimation and vapor emission into the atmosphere in warm seasons would violate the observational constraints. Moreover, the more uniform latitudinal variation of the observed hydrogen abundance near the surface compared to that of deeper layers is indicative of the presence of adsorbed water instead of ground ice because the adsorbed water content does not as steeply depend on latitude as the ground ice stability. Concerning the regolith mineralogy, montmorillonite can much better account for the observed water cycle than palagonite. While the presence of permanent ground ice appears likely in the polar region below a thin layer, large seasonal cycle of phase change between pore ice and adsorbed water may be possible. Regolith adsorption/desorption is neither negligible nor crucial for the seasonal atmospheric water cycle, but the surface-atmosphere coupling is a major prerequisite for the long-term evolution of subsurface water distribution. 相似文献
12.
Solar System Research - Within the framework of this work, using a three-dimensional numerical model of the general circulation of the Martian atmosphere MAOAM (Martian Atmosphere: Observation and... 相似文献
13.
Philip B. James 《Icarus》1985,64(2):249-264
The Martian CO2 cycle, which includes the seasonal condensation and subsequent sublimation of up to 30% of the planet's atmosphere, produces meridional winds due to the consequent mass flux of CO2. These winds currently display strong seasonal and hemispheric asymmetries due to the large asymmetries in the distribution of insolation on Mars. It is proposed that asymmetric meridional advection of water vapor on the planet due to these CO2 condensation winds is capable of explaining the observed dessication of Mars' south polar region at the current time. A simple model for water vapor transport is used to verify this hypothesis and to speculate on the effects of changes in orbital parameters on the seasonal water cycle. 相似文献
14.
The most detailed information on the seasonal evolution of water vapor distribution in the Martian atmosphere was obtained by the Mars Atmospheric Water Detector (MAWD), which was a five-channel spectrometer operating aboard the Viking 1 and 2 spacecraft in 1977–1980, and from the very recent observations by the Thermal Emission Spectrometer (TES) on the Mars Global Surveyor spacecraft. The TES results show a considerably larger amount of water vapor near the perihelion of Mars (summer in the southern hemisphere) than the estimates based on the MAWD data for this season, which is characterized by the development of global dust storms. The TES and MAWD instruments operated in different spectral regions (20–50 m and 1.38 m, respectively), and this could result in the aforementioned difference because of the effect of aerosol scattering on the intensity of the H2O bands, which becomes significant at short wavelengths. We considered the effect of aerosol scattering on the water vapor content measured in the 1.38-m band, taking into account the different geometries of observations, and restored the H2O content from the MAWD data with allowance for multiple scattering. We obtained a seasonal and spatial distribution of water vapor that showed better agreement with the TES data and, thus, indicated the stability of the hydrological cycle on Mars. Periodic structures, which could possibly be associated with the influence of the stationary planetary waves, are reliably revealed in the zonal distribution of the atmospheric water vapor. The seasonal variability of the wave structures correlates with variations of the latitude gradient of water vapor. This could indicate that wave processes contribute considerably to the meridional water transport in the Martian atmosphere.Translated from Astronomicheskii Vestnik, Vol. 38, No. 6, 2004, pp. 483–496.Original Russian Text Copyright © 2004 by Fedorova, Rodin, Baklanova. 相似文献
15.
Lakes on Mars were formed under periglacial to glacial climates. Extreme conditions prevailed including freezing temperatures, low atmospheric pressure, high evaporation/sublimation rates, and liquid water reservoirs locked in aquifers below a thick cryosphere. Although many of the Martian paleolakes display evidence of a short period of activity consistent with these conditions, others display clear evidence of lifetimes ranging from 104 to 105 years. The discovery of young seeping processes in impact craters and pole-facing valley slopes along with young volcanic activity raise questions about the conditions and limitations of liquid water flow and potential lacustrine activity today on Mars. Current climate models show that in today's conditions there exist regions on Mars of sols above the triple point and below boiling point of water that could provide hydrogeological conditions comparable to these of the Antarctic Dry Valley lakes (with the exception of the atmosphere pressure). The locations of the most recent Martian paleolakes are correlated with these regions. Throughout the history of Mars, lakes generated diversified environments, which could have provided potential habitats for life. The recent discovery of young energy sources from volcanism and the potential for liquid water reinforces the possibility of extant life on Mars, and suggests recent ponds and ancient paleolakes as primary targets for rover and sample return missions. 相似文献
16.
Aaron P. Wilson Matthew J. Genge Agata M. Krzesi&#x;ska Andrew G. Tomkins 《Meteoritics & planetary science》2019,54(9):1-19
The atmospheric entry heating of micrometeorites (MMs) can significantly alter their pre‐existing mineralogy, texture, and organic material. The degree of heating depends predominantly on the gravity and atmospheric density of the planet on which they fall. For particles falling on Earth, the alteration can be significant, leading to the destruction of much of the pre‐entry organics; however, the weaker gravity and thinner atmosphere of Mars enhance the survival of MMs and increase the fraction of particles that preserve organic material. This paper investigates the entry heating of MMs on the Earth and Mars in order to examine the MM population on each planet and give insights into the survival of extraterrestrial organic material. The results show that particles reaching the surface of Mars experience a lower peak temperature compared to Earth and, therefore, experience less evaporative mass loss. Of the particles which reach the surface, 68.2% remain unmelted on Mars compared to only 22.8% on Earth. Due to evaporative mass loss, unmelted particles that reach the surface of Earth are restricted to sizes <70 μm whereas particles >475 μm survive unmelted on Mars. Approximately 10% of particles experience temperatures below ~800 K, that is, the sublimation temperature of refractory organics found in MMs. On Earth, this fraction is significantly lower with less than 1% expected to remain below this temperature. Lower peak temperatures coupled with the larger sizes of particles surviving without significant heating on Mars suggest a much higher fraction of organic material surviving to the Martian surface. 相似文献
17.
Earth-based observations of Mars atmospheric water vapor, made from McDonald Observatory, are presented for the 1975–1976, 1977–1978, and 1983 apparitions. Comparisons are made with near-simultaneous spacecraft measurements made from the Viking Orbiter MarsAtmospheric Water Detection experiment during 1976–1978 and with previous Earth-based measurements (made since 1964). Differences occur between the behavior in the different years, and may be related to the Mars climate. Measurements during the southern summer in 1969 indicate a factor of three times as much water as is present at this same season in other years.This difference may have resulted from the sublimation of water from the south polar residual cap upon removal of most or all of the CO2 ice present; sublimation of all the CO2 ice during some years could be a result of a greater thermal load being placed on the cap due to the presence of differing amounts of atmospheric dust. If substantiated, the water vapor variability will turn out to be a very sensitive indicator of yearly variability in the Martian climate. 相似文献
18.
Benton C. Clark 《Icarus》1978,34(3):645-665
Converging lines of evidence suggest that a significant portion of the Martian surface fines may consist of salts and smectite clays. Salts can form stoichiometric hydrates as well as eutectic solutions with depressed freezing points; clays contain bound water of constitution and adsorb significant quantities of water from the vapor phase. The formation of ice may be suppressed by these minerals in some regions on Mars, and their presence in abundance would imply important consequences for atmospheric and geologic processes and the prospects for exobiology. 相似文献
19.
David Andrew Fisher 《Icarus》2007,187(2):430-441
A time varying stable isotope model for the D/H history of Mars water cycle is developed with variable atmosphere, space loss rate, ground and ice cap flux rates. It considers coupled ground reservoirs and traces D/H in the air and reservoirs secularly and over obliquity cycles. The various flux rates are prescribed time variables that simulate surface flux, and solar driven space loss rates. Predicted bulk averages for the ice cap, ground ice reservoirs and atmosphere span the observed ranges reported by Mumma et al. [Mumma, M.J., Novak, R.E., DiSanti, M.A., Bonev, B., Dello Russo, N., Magee-Sauer, K., 2003. The Martian Atmosphere. Conference Reports of “Sixth International Conference on Mars Atmosphere,” No. 3186]. When the dominant obliquity cycle variations are scaled so that the model delivers present seasonal variations, the present long term bulk D/H average for the ice cap is ∼+2.7 (equivalent to +1700‰ in δ(D) wrt SMOW). The obliquity driven D/H cycle in the ice cap's layers varies between 3 and 6. The smaller more accessible reservoirs have larger bulk averages with the smallest being able to reach D/H values over 9 within ∼105 years. Small hypothetical solar activity driven variations in the escape rate to space and in the fractionation constant [Krasnopolsky, V.A., Feldman, P.D., 2001. Science 294, 1914-1917] for the escape process can produce a “solar wiggle” whose D/H amplitude can reach 0.1 (δ(D) amplitude of 100‰). Because of the temporal variability, a single modern measured atmospheric D/H ratio at a particular Ls cannot tell very much about the total water inventory of Mars. A bulk average for the Northern Ice Cap and better still a dated vertical profile of D/H from the ice cap would, however, go a long way towards illuminating the “modern” water history of Mars. The age and stability of the Northern Ice Cap and the D/H history locked in the layering is discussed. An ice cap that is very young and exchanges its mass through the atmosphere often will necessarily have a large D/H. 相似文献
20.
James R. C. Garry Inge Loes ten Kate Zita Martins Per Nrnberg Pascale Ehrenfreund 《Meteoritics & planetary science》2006,41(3):391-405
Abstract— We have investigated the native amino acid composition of two analogs of Martian soil, JSC Mars‐1 and Salten Skov. A Mars simulation chamber has been built and used to expose samples of these analogs to temperature and lighting conditions similar to those found at low latitudes on the Martian surface. The effects of the simulated conditions have been examined using high‐performance liquid chromatography (HPLC). Exposure to energetic ultraviolet (UV) light in vacuum appears to cause a modest increase in the concentration of certain amino acids within the materials, which is interpreted as resulting from the degradation of microorganisms. The influence of low temperatures shows that the accretion of condensed water on the soils leads to the destruction of amino acids, supporting the idea that reactive chemical processes involving H2O are at work within the Martian soil. We discuss the influence of UV radiation, low temperatures, and gaseous CO2 on the intrinsic amino acid composition of Martian soil analogs and describe, with the help of a simple model, how these studies fit within the framework of life detection on Mars and the practical tasks of choosing and using Martian regolith analogs in planetary research. 相似文献