Upper Atmosphere Of Venus Research Articles

Atomic chlorine on Venus

The possible presence of atomic chlorine in the upper atmosphere of Venus is examined. It is suggested that a Cl abundance as low as 2 ppm will be readily detectable in far ultraviolet via 1351.7 and 1335.7 Å emissions of neutral Cl atoms. These transitions can be resonantly excited by the bright solar emission line of C+, at 1335.7 Å. It is particularly interesting to investigate atomic chlorine since the bright 1356 Å emission feature which was reported by Rottman and Moos (1973) in the Venus spectra could not be explained without requiring high concentrations of atomic oxygen. From these data, a spectroscopic upper limit of 10−4 is deduced for the mixing ratio of Cl atoms at 125 km altitude. Although we cannot justify such a large mixing ratio, it may not be unreasonable considering the uncertainties in the present understanding of chlorine photochemistry on Venus.

Ultraviolet Observations of Venus from Mariner 10: Preliminary Results

An objective grating spectrometer on Mariner 10 has measured air-glow in the wavelength range 200 to 1700 angstroms. The data reveal the presence of significant concentrations of hydrogen, helium, carbon, and oxygen atoms in the upper atmosphere of Venus. A preliminary analysis of the hydrogen data indicates an exospheric temperature of 400 degrees K. There is evidence for intense air-glow emission at wavelengths longward of 1350 angstroms; the nature of this emission is unclear, but the radiation is spatially extensive and detectable on both day and night sides of the planet.

O i and H i Emissions from the Upper Atmosphere of Venus

Venus upper atmospheric UV spectra from rocket- borne telescope spectrophotometer, considering O I and H I emission features

Calculations of CO2 Energy Levels: The Ã1B2 State

The Ã1B2 state of CO2, identified by Dixon (1963) as the upper level of the ‘carbon monoxide flame bands’, must be of importance in the upper atmospheres of Venus and Mars. New calculations of the high vibrational levels of the ground state, which lead to improved fits of the observed vibration-rotation bands, confirm Dixon's analysis, except that the numbering must be lowered by two, and fix the energy of the v = 0, K = 0 level of 1B2 at 45210 ± 10 cm−1 = 5.605 eV.

An estimate of the present-day deep-mantle degassing rate from data on the atmosphere of Venus

We argue that the present rate of escape of hydrogen from the upper atmosphere of Venus establishes an upper limit for the rate of degassing of water from the interior of the planet. This upper limit is 2.4×109 grams of water per year. If we assume that this value holds also for deep-mantle degassing from the earth, we find that the rate is insufficient, by five orders of magnitude, to supply the water at the earth's surface in 4.5×109 years. An early episode of greatly enhanced degassing appears to be required.

Carbon atoms in the upper atmosphere of Venus

The detection of carbon atoms in the upper atmosphere of Venus is reported on the basis of an extension of a previously reported analysis of low-resolution spectra of the solar-illuminated atmosphere of Venus. It is demonstrated that the previously reported anomalously high albedo for λλ > 1500 A ̊ can be explained by invoking the presence of a 14 kR (kilorayleigh) CI signal at 1667 Å. It is possible to check the validity of this conclusion on a future Venus fly by mission which employs a scanning spectrometer operating in this spectral region. Furthermore, if it is valid to extrapolate these results to the case of Mars the vacuum ultraviolet spectra acquired by the Mariner 6 and 7 missions should include this spectral feature as well as some of the more intense bands of the CO 4th positive system.

Estimate of radiogenic He4and Ar40concentration in the Cytherean atmosphere

Mixing ratios of 2 × 10−4 and 1 × 10−4 for He4 and Ar40, respectively, in a 100% Co2 Mariner 5 model of the Cytherean lower atmosphere are derived by assuming that the He4 and Ar40 are secondary in origin and result entirely from radioactive disintegration with subsequent outgassing from the planet. Production rates on Venus are assumed equal to those for the earth. Thermal escape of He4 is shown to be negligible, and other loss mechanisms are assumed unimportant. Concentration of these gases in the upper atmosphere of Venus are calculated from the mixing ratios and a turbopause at 6180 km radius. The He4 concentration in the upper atmosphere is a factor of 10 larger than the minimum value estimated by McElroy and Strobel [1969] to account for the observed nighttime ionosphere and is about a factor of 4 larger than that suggested by Whitten [1969] to explain the observed daytime ionosphere. This degree of agreement among three separate approaches strengthens the possibility that He4 is a dominant constituent in the upper atmosphere of Venus and also implies that loss of He4 on Venus by plasma expansion is unimportant. He4 will be the dominant constituent out to a radius of about 7600 km if H2 is present at the upper limit suggested by McElroy and Hunten [1969] and out to a radius of about 8700 km if H2 is negligible.

The Ashen Light: An auroral phenomenon on Venus

We have collected and analyzed 129 visual observations of the Ashen Light, the luminous glow on the dark side of Venus, made between 1954 and 1962. Spectroscopic and photometric studies attempting to detect dark side emission on Venus are reviewed and discussed in light of the visual occurrence of the glow. We have found a general increase in the geomagnetic index coinciding with the occurrence of the Ashen Light at times of inferior conjunction of Venus, which suggests that the Ashen Light is an auroral phenomena due to solar particle bombardment on the dark side of Venus. This possibility is explored in terms of the nature and characteristics of the visual Ashen Light observations and in terms of the recent Mariner V and Venera-4 data on the upper atmosphere of Venus.

Moving Flame Experiment with Liquid Mercury: Possible Implications for the Venus Atmosphere

A bunsen flame rotated under a cylindrical annulus filled with liquid mercury forces the liquid mercury to rotate in a direction counter to that of the rotating flame. The rate of rotation of the liquid is several times greater than that of the flame. This observation may provide an explanation for the high velocities of apparent cloud formations in the upper atmosphere of Venus.

Structure of the Venus and Mars atmospheres

Models of the Venus atmosphere are presented and compared with observations obtained from Mariner 5. Best agreement is found if it is assumed that the Venus atmosphere, at all heights, consists of pure CO2. The modeling procedures are used to obtain upper limits to the abundance of N2 and O. It is concluded that the N2 mixing ratio should not exceed 10%. Atomic oxygen should be a minor constituent, at least for altitudes less than about 200 km. Possible variations of the upper Venus atmosphere with solar activity are discussed briefly. It is shown from the theoretical discussion that the exospheric temperature may vary from a solar minimum value of about 600°K to a solar maximum value of about 1000°K. Attention is directed to apparent similarities between the upper atmospheres of Venus and Mars. The modeling procedures, which satisfactorily account for the Venus observations, are applied to Mars. A simple photochemical theory gives results in poor agreement with the Martian ionosphere as observed by Mariner 4. Possible reasons for the discrepancy are discussed.

Further examination of the hydrogen content in the upper atmosphere of Venus

In a recent paper, Earth et al. [1968] computed the molecular hydrogen concentration in the upper atmosphere of Venus from the component of the Lyman-alpha emission attributed to photodissociation of molecular hydrogen as measured by Mariner 5. The outcome of these computations, as seen in Figure 3 of Barth et al. [1968], resulted in part from the assumptions of a molecular hydrogen density of 2.8 × 109 molecules cm−3 at a planetocentric distance of 6500 km, with an isothermal region of temperature 650°K above this level. As a consequence, the optical thickness of molecular hydrogen at 6500 km, based upon the photoionization cross sections of Lee et al. [1952], would result in significant ultraviolet energy in the wavelength region below 804 A being absorbed above 6500 km. Correspondingly, the rapid settling of the heavy CO2 molecule in the lower thermosphere would severely limit the effectiveness of CO2 as a cooling agent at these high altitudes. Under such circumstances, it is difficult to understand both the isothermal region above 6500 km and the relatively low exospheric temperature of Venus. To verify these points the author reconstructed the upper atmosphere of Venus by solving numerically the heat conduction equation in conjunction with separate diffusion equations for each constituent similar to the method outlined in Chamberlain [1962], Chamberlain et al. [1966], and McGovern [1967].

The Upper Atmosphere of Venus in Light of the Mariner 5 Measurements

Abstract Models for the Venus atmosphere and ionosphere are presented and compared with data obtained in the S-band occultation experiment on Mariner 5. Good agreement is found between model and experiment if the Venus atmosphere is composed of essentially pure CO2. An upper limit of about 10% is derived for the N2 mixing rate. It is argued that atomic oxygen is a minor constituent in the upper atmosphere of Venus.

Interpretation of Mariner 5 and Venera 4 Data on the Upper Atmosphere of Venus

Abstract Calculations have been completed on the structure of the ionosphere of Venus. Comparisons between these calculations and the results of the Mariner 5 and Venera 4 flights yield the following information on the structure of the Venus upper atmosphere: the ionosphere of Venus is of the F1 type; no more than 2% of the CO2 in the Venus ionosphere is dissociated; the relative abundance of N2 is ≤10%, in rough agreement with the Venus 4 limit of 7%; the exospheric temperature is 700±100K, the uncertainty in this result reflecting uncertainties in the CO2 vibrational deactivation coefficient and beating efficiency.

The Upper Atmosphere of Venus: A Review

Abstract The implications of recent data on Venus obtained by Mariner 5, Venera 4 and ground based observations for the aeronomy of Venus is received. The theoretical thermal structure model of McElroy based on a pure CO2 atmosphere is in good agreement with the temperature deduced from the hydrogen distribution obtained by Mariner 5. No credible mechanism has been devised to recombine CO and O to CO2 in the upper atmosphere. It is suggested that O2 is formed but that CO and O2 recombine to CO2 in the dense atmosphere far enough above the cloud tops to agree with abundance measurements. Serious difficulties exist for the H2 model of the upper atmosphere. It is suggested that deuterium can account for the anomalous Lyman α glow observed by Mariner 5 without implying a large D/H planetary ratio. Other problems such as the maintenance of the ionosphere at night and the escape of water are discussed.

The Recombination mechanism of CO and O in the upper atmospheres of venus amd mars

The recombination mechanism between CO and O produced by the photodissociation of CO 2 in the upper atmospheres of Venus and Mars is discussed in detail. It is concluded that the rapid recombination of CO and O( 1D) through CO 2 formation may be excluded.