共查询到20条相似文献，搜索用时 93 毫秒
1.
H. Levy 《Planetary and Space Science》1973,21(4):575-591
Altitude profiles for the number densities of NO, NO2, NO3, N2O5, HNO2, CH3O, CH3O2, H2CO, OH, and HO2 are calculated as a function of time of day with a steady-state photochemical model in which the altitude profiles for the number densities of H2O, CH4, H2, CO, O3, and the sum of NO and NO2 are fixed at values appropriate to a summer latitude of 34°. Average daily profiles are calculated for the long-lived species, HNO3, H2O2, and CH3O2H.The major nitrogen compound HNO3 may have a number density approaching 5 × 1011 molecules cm?3 at the surface, although an effective loss path due to collisions with particulates could greatly reduce this value.The number density of OH remains relatively unchanged in the first 6 km and reaches 1 × 107 molecules cm?3 at noon, while the number density of HO2 decreases throughout the lower troposphere from its noontime value of 8 × 108 molecules cm?3 at the surface.H2O2 and H2CO both have number densities in the ppb range in the lower troposphere.Owing to decreasing temperature and water concentration, the production of radicals and their steady-state number densities decrease with altitude, reaching a noontime minimum of 1 × 108 molecules cm?3 for OH and 3 × 107 molecules cm?3 for HO2 at the tropopause. The related minor species show even sharper decreases with increasing altitude.The primary path for interconverting OH and HO2 serves as the major sink for CO and leads to a tropospheric lifetime for CO of ~0.1 yr.Another reaction cycle, the oxidation of CH4, is quite important in the lower troposphere and leads to the production of H2CO along with the destruction of CH4 for which a tropospheric lifetime of ~2 yr is estimated.The destruction of H2CO that was produced in the CH4 oxidation cycle provides the major source of CO and H2 in the atmosphere. 相似文献
2.
Joel S. Levine 《Icarus》1976,28(2):165-169
The presence of 28% argon on Mars as calculated by Levine and Riegler and indirectly inferred from Soviet Mars-6 lander data has important implications for the outgassing history of H2O, CO2, and N2 on Mars. Even if the terrestrial volatile outgassing ratio is only approximately valid for Mars, then large quantities of H2O [of the order of 105 gcm?2 (about 108 more H2O than is currently present in the Martian atmosphere)] and about 104 gcm?2 of CO2 (about 103 times more CO2 than found at present in the Martian atmosphere) and some 450 gcm?2 of N2 may have outgassed over the history of Mars. 相似文献
3.
The rise of atmospheric O3 as a function of the evolution of O2 has been investigated using a one-dimensional steady-state photochemical model based on the chemistry and photochemistry of Ox(O3, O, O(1D)), N2O, NOx(NO, NO2, HNO3), H2O, and HOx(H, OH, HO2, H2O2) including the effect of vertical eddy transport on the species distribution. The total O3 column density was found to maximize for an O2 level of 10?1 present atmospheric level (PAL) and exceeded the present total O3 column by about 40%. For that level of O2, surface and tropospheric O3 densities exceeded those of the present atmosphere by about an order of magnitude. Surface and tropospheric OH densities of the paleoatmosphere exceeded those of the present atmosphere by orders of magnitude. We also found that in the O2-deficient paleoatmosphere, N2O (even at present atmospheric levels) produces much less NOx than it does in the present atmosphere. 相似文献
4.
The photochemistry of the stratosphere of Venus was modeled using an updated and expanded chemical scheme, combined with the results of recent observations and laboratory studies. We examined three models, with H2 mixing ratio equal to 2 × 10?5, 5 × 10?7, and 1 × 10?13, respectively. All models satisfactorily account for the observations of CO, O2, O2(1Δ), and SO2 in the stratosphere, but only the last one may be able to account for the diurnal behavior of mesospheric CO and the uv albedo. Oxygen, derived from CO2 photolysis, is primarily consumed by CO2 recombination and oxidation of SO2 to H2SO4. Photolysis of HCl in the upper stratosphere provides a major source of odd hydrogen and free chlorine radicals, essential for the catalytic oxidation of CO. Oxidation of SO2 by O occurs in the lower stratosphere. In the high-H2 model (model A) the OO bond is broken mainly by S + O2 and SO + HO2. In the low-H2 models additional reactions for breaking the OO bond must be invoked: NO + HO2 in model B and ClCO + O2 in model C. It is shown that lightning in the lower atmosphere could provide as much as 30 ppb of NOx in the stratosphere. Our modeling reveals a number of intriguing similarities, previously unsuspected, between the chemistry of the stratosphere of Venus and that of the Earth. Photochemistry may have played a major role in the evolution of the atmosphere. The current atmosphere, as described by our preferred model, is characterized by an extreme deficiency of hydrogen species, having probably lost the equivalent of 102–103 times the present hydrogen content. 相似文献
5.
William C. Maguire 《Icarus》1977,32(1):85-97
The Mariner 9 infrared spectrometer obtained data over a large part of Mars for almost a year beginning late in 1971. Mars' infrared emission spectrum was measured from 200 to 2000 cm?1 with an apodized resolution of 2.4 cm?1. No significant deviation from terrestrial ratios of carbon (12C/13C) or oxygen (16O/18O; 16O/17O) isotopes was observed on Mars. The 12C/13C isotopic ratio was found to be terrestrial with an uncertainty of 15%. Upper limits have been calculated for several minor constituents. With an effective noise equivalent radiance of 1.2 × 10?9 W cm?2 sr?1/cm?1, new upper limits in centimeter-atmospheres of 2 × 10?5 for C2H2, 4 × 10?3 for C2H4, 3 × 10?3 for C2H6, 2 × 10?4 for CH4, 1 × 10?3 for N2O, 1 × 10?4 for NO2, 4 × 10?5 for NH3, 1 × 10?3 for PH3, 7 × 10?4 for SO2, and 1 × 10?4 for OCS have been derived. 相似文献
6.
A thermodynamical analysis of the multicomponent system SiTiAlFeMnMgCaNaKPCHO open with respect to CO2, CO, H2O was carried out. Hydration and carbonatization processes are proposed to be geochemical consequences of the hypothesis of quasi-equilibrium conditions between the troposphere and crustal surface rocks. The probable rock-forming hydrated mineral phases are represented by epidote, glaucophane, tremolite, phlogopite, and annite; the carbonatization results in existence of calcite and dolomite as rock-forming minerals of weathered alkaline lavas. The surface rocks are assumed to have high ferric/ferrous iron ratios. The wollastonite equilibrium is rejected as a buffering chemical reaction. Hydrated minerals could be stable at least up to 5-km depths and contribute about 0.1 × 1024 g of H2O whereas about (0.7–0.8) × 1024 g of H2O would be consumed in ferrous iron oxidation with concomitant hydrogen dissipation. The distribution of H2O in the outer planetary shells is possibly a function of their temperatures. 相似文献
7.
Absorption cross sections have been calculated for molecular oxygen as a function of wavelength over the domain for temperatures between 190 and 400°K. The spectrum has been divided into 19 wavelength intervals and opacity distribution functions have been constructed for each interval. Atmospheric photodissociation rates of O2, O3, CO2, H2O, H2O2, NO2 and HNO3 are presented. 相似文献
8.
H. Böhringer D.W. Fahey F.C. Fehsenfeld E.E. Ferguson 《Planetary and Space Science》1983,31(2):185-191
We have investigated the role of several ion-molecule reactions in the conversion of N2O5 to HNO3. In the proposed conversion, an N2O5 molecule would react with an H2O molecule clustered to an inert ion to produce two HNO3 molecules. Subsequent clustering of an H2O molecule to the inert ion would make the reaction catalytic. If such an ion-catalysed conversion of N2O5 to HNO3 occurs, it would probably play a role in the stratospheric chemistry at high latitudes in winter. In this paper we present reaction rate constant measurements made in a flowing afterglow apparatus for hydrated H3O+, H+(CH3CN)m (m = 1, 2, 3), and several negative ions reacting with N2O5. Slow rate constants were found for these ions for hydration levels that are predominant in the stratosphere. With the known stratospheric ion density, these slow rate constants preclude significant N2O5 conversion by ion-molecule reactions. 相似文献
9.
H. Böhringer M. Durup-Ferguson E.E. Ferguson D.W. Fahey 《Planetary and Space Science》1983,31(4):483-487
New experimental techniques have yielded several thermal energy vibrational quenching rate constants for O2+(v). Rates for quenching of O2+(v = 1) by O2, N2, Ar, CO2, H2, and CH4 are 3(?10), 2(?12), 1(?12), 1(?10), 2.5(?12), and 6(?10) cm3s?1 at 300 K. The quenching is somewhat faster for O2+(v = 2). The triatomic ions CO2+, NO2+, N2O+, SO2+, and H2O+ are all vibrationally deexcited with an efficiency greater than 10?3 in Ar or Ne collisions. A theoretical rationalization of the experimental results leads to the prediction that vibrational quenching in planetary atmospheres will generally be efficient, k > 1(?12) cm3s?1 for almost all ion and neutral gas pairs. 相似文献
10.
A.A. Viggiano F. Arnold D.W. Fahey F.C. Fehsenfeld E.E. Ferguson 《Planetary and Space Science》1982,30(5):499-506
The results of a rocket-borne mass spectrometer measurement indicate that large concentrations of negative ions exist above the bottom of the atmospheric atomic oxygen layer. A large majority of these ions have a mass greater than 100 amu. In addition, an ion at mass 76 was observed with concentrations too large to be CO4?. In order to explain these features, a number of reactions involving silicon oxide negative ions have been measured in a flowing afterglow system. The ion SiO3? is produced by reaction of O3?, and CO3?, with SiO. The SiO3? ion is extremely stable and does not react measurably with NO, NO2, CO, CO2, O3 or O. Since meteoroid ablation produces a large silicon input into the atmosphere, it appears possible that the ions observed at mass 76 may be SiO3?. Possible production mechanisms for this ion as well as the heavy ions are discussed. 相似文献
11.
G. Kockarts 《Planetary and Space Science》1976,24(6):589-604
The penetration in the terrestrial atmosphere of solar radiation corresponding to the spectral range of the Schumann-Runge bands of molecular oxygen is analyzed between 1750 and 2050 Å. The variation of the absorption cross section with temperature is taken into account and it is shown that average O2 absorption cross sections cannot lead to correct photodissociation coefficients. Reduction factors are defined in order to simplify the computation of the molecular oxygen photodissociation and to permit a simple determination of the photodissociation coefficients of any minor constituent with smoothly varying absorption cross section. Examples are given for O2, H2O, CO2, N2O, HNO3 and H2O2. Numerical approximations are developed for three types of spectral subdivisions: Schumann-Runge band intervals, 500 cm?1 and 10 Å intervals. The approximations are valid from the lower thermosphere down to the stratosphere and they can be applied for a wide range of atmospheric models and solar zenith distances. 相似文献
12.
V.A. Krasnopolsky 《Planetary and Space Science》1983,31(11):1363-1369
In an updating of energy characteristics of lightnings on Venus obtained from Venera-9 and -10 optical observations, the flash energy is given as 8 × 108 J and the mean energy release of lightnings is 1 erg cm?2 s which is 25 times as high as that on the Earth. Lightnings were observed in the cloud layer. The stroke rate in the near-surface atmosphere is less than 5 s?1 over the entire planet if the light energy of the stroke exceeds 4 × 105 J and less than 15 s?1 for (1–4) × 105 J.The average NO production due to lightnings equals 5 × 108 cm?2 s?1, the atomic nitrogen production is equal to 7 × 109 cm?2s?1,the N flux toward the nightside is 3.2 × 109 cm?2s?1, the number densities [N] = 3 × 107cm?3 and [NO] = 1.8 × 106cm?3 at 135 km. Almost all NO molecules in the upper atmosphere vanish interacting with N and the resulting NO flux at 90-80 km equals 5 × 105cm?2s?1, which is negligibly small as compared with lightning production. If the predissociation at 80–90 km is regarded as the single sink of NO, its mixing ratio, fNO, is 4 × 10?8, for the case of a surface sink fNO = 0.8 × 10?9 at 50 km. Excess amounts, , may exist in the thunderstorm region. 相似文献
13.
Robert L. Huguenin 《Icarus》1976,28(2):203-212
Photostimulated oxidation weathering irreversibly removes both oxygen and hydrogen from the atmosphere at a rate of 108 to 1011 cm?2sec?1. This corresponds to a net loss of 1025 to 1028 molecules cm?2 (102 to 105 g cm?2 of H2O, assuming a uniform rate over geologic time. Additional H2O is removed through hydration of Fe2O3 and clay minerals, but the loss is reversible and the extent of regolith storage is uncertain. CO2 is irreversibly removed from the atmosphere through the formation of CaCO3 at a rate of 107?1010cm?2sec?1. Over geologic time this corresponds to a net loss of 1024?1027 molecules cm?2 (101?104g cm?2) of CO2. Previously, it was proposed that exospheric escape was the principal irreversible volatile sink, amounting to only 102g cm?2 of H2O and 100g cm?2 of CO2 over geologic time. A recent tentative identification of abundant argon on Mars suggests that the planet may have degassed up to 105g cm?2 of H2O and 104g cm?2 of CO2. If the amounts of H2O and CO2 removed by photostimulated oxidation are close to the upper limits proposed here, it is possible that chemical weathering may have had a major effect on limiting the supply of H2O and CO2 trapped in the regolith and polar caps. 相似文献
14.
The calculation of number densities of CO2, H2O and N2 photolysis products was carried out for the Martian atmosphere at heights up to 60 km. The ozone distributed in the atmosphere as a layer of 10 km width with [O3] max = 2.5 × 109 cm3 at height of 35 km which agree well with the results of u.v. observations on the evening terminator from the Mars-5 satellite. The calculated densities of O2, CO and H2O are also in good agreement with the measured data. The eddy diffusion coefficient is equal to 3 × 106 in the troposphere (h ? 30 km) and 108 cm2 s?1 above 40 km. The dependence of the total ozone content on water vapour amount in the atmosphere is considered; the hypothesis about the influence of water ice aerosol on the ozone formation is proposed to explain the high concentrations of ozone in the morning. 相似文献
15.
《Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science》2001,26(7):527-532
The nitrogen isotope ratio of middle atmosphere nitrogen oxide is predicted as a function of altitude. Nitrogen oxides originate photochemically either from stratospheric nitrous oxide reacting with O(1D) or in the mesosphere and thermosphere from direct dissociation of N2 and ionization-initiated reactions involving O2 and N2. During its formation process, N2O acquires a nitrogen isotopic composition of N isotopes different than N2. Photodissociation within the stratosphere also modifies the proportion of isotopes. Reaction of stratospheric NO with O3 produces NO2, which when photodissociated yields NO depleted in 15N relative to NO2 in laboratory air. The value of δ15NO in the stratosphere is −100‰. In the altitude region between 50 and 65 km, NO is transformed into NO2 and then returned to NO by reaction of NO2 with O and by NO2 photodissociation. These reactions determine the isotopic makeup of NO. Above 65 km, nitric oxide is produced by local ionization processes and gas phase photochemical reactions involving N2 and excited O2. These processes determine the isotopic composition of NO in the upper mesosphere and thermosphere. Here δ15NO is 0‰. Air transported into the mesosphere above 65 km will reflect the NO isotopic values of the region below, while mesospheric NO transported below 65 km will not be distinguishable from NO originating in the stratosphere. 相似文献
16.
A simultaneous night-time observation of NO3 and 03 has been made by means of a balloon-borne spectrophotometer pointing at the rising planet Venus. The spectrum recorded between 642 and 672 nm makes it possible to determine the NO3 and O3 absorptions in the 662 nm band and the Chappuis bands, respectively. The NO3 vertical distribution is deduced, and is found to reach a peak of (3.4 ± 0.4) 107 molecules cm?3at 35 km. Such an observational result can be interpreted in terms of a theoretical profile deduced from a one-dimension time-dependant photochemical model which takes account of the night-time stratospheric NO2, NO3 and N2O5 constituents and the latest kinetic and photochemical data for the rate constants. 相似文献
17.
Following our recently published measurements of the rate coefficients for mutual neutralization, α, of the ionospherically important reactions NO+ + NO2?(α1) and NO+ + NO3?(α2) carried out in ion-ion flowing afterglow plasmas at 300 K, we have determined the mutual neutralization rates for the water cluster ion H3O+ · (H2O)3 with a mixture of several negative ions which are known to exist in the D region. The α coefficients for these cluster ion reactions do not differ significantly from alpha;1 and α2, all of these reactions having α ?6 × 10?8 cm3/sec which is significantly smaller than values usually adopted in ionospheric calculations. Current information on the ionic composition of the D region and the implications of the present results to de-ionization rate calculations are discussed. 相似文献
18.
Excitation functions for collision-induced dissociation reactions of CO 3? and NO3? to give O? and the corresponding neutral species have been studied using an in-line tandem mass spectrometer. When these ions were prepared from certain gaseous mixtures, larger cross-sections and lower thresholds were observed for the dissociation processes than those found for the same ions in their apparent ground states. These observations suggest the existence of long-lived excited states of CO3?1 and NO3?1. The heats of formation of these excited ionic states were determined to be ?4.8 ± 0.1 and ?0.3 ± 0.2 eV for CO3?1 and NO3?1, respectively. Possible implications of these findings with respect to the D -region negative ion reaction scheme are discussed. 相似文献
19.
For the first time, a model of the daytime disturbed D-region is presented which is consistent with experimental solar proton event (SPE) data, that of the 2–5 November, 1969 event in particular. Sunset electron concentration profiles also are shown to be quite compatible with the experimental results, but computed sunrise electron concentrations are found to rise faster with solar elevation than do the measurements. In the daytime, O2?, O?, CO4? and CO3? ions apparently do not retain electrons in contrast to NO2? and NO3? ions. Hydration of the latter two species is probably unimportant since photodetachment and/or photodissociation of these ions are insignificant processes even when they are unattached to water molecules. Difficulties at sunrise are thought to arise most likely from our omission of hydration processes for negative ions, the pre-sunrise negative ion populations undoubtedly having the highest diurnal hydration level. Sunset ozone computations using the latest chemistry are shown to match the data except for some problem at the highest altitude, near 70 km, for the earlier, more disturbed, of the two experimental profiles. 相似文献
20.
The effects of collision-induced absorption on the far infrared spectrum of Titan have been investigated. After a review of the procedure for the theoretical calculation of the N2 translation-rotational spectrum, new results for the temperature range of 70 to 120°K are reported. These are used as input data for a simple atmospheric model in order to compute the far infrared radiance, brightness temperature, and spectral limb function. This source of opacity alone is not capable of explaining the Voyager results. When the collision-induced methane is included, the results are in closer agreement in the range between 200 and 300 cm?1, suggesting that a more complete treatment of collision-induced absorption including particularly CH4N2, N2H2, and H2H2 results, may provide sufficient opacity to reduce or obviate the need for opacities due to clouds or aerosols in order to explain the observed spectra. 相似文献