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At least 19 recordsLinked to original sources

PubMed1994

H2O-H2SO4 system in Venus' clouds and OCS, CO, and H2SO4 profiles in Venus' troposphere.

A coupled problem of diffusion and condensation is solved for the H2SO4-H2O system in Venus' cloud layer. The position of the lower cloud boundary and profiles of the H2O and H2SO4 vapor mixing ratios and of the H2O/H2SO4 ratio of sulfuric acid aerosol and its flux are calculated as functions of the column photochemical production rate of sulfuric acid, phi H2SO4. Variations of the lower cloud boundary are considered. Our basic model, which is constrained to yield fH2O (30 km) = 30 ppm (Pollack et al. 1993), predicts the position of the lower cloud boundary at 48.4 km coinciding with the mean Pioneer Venus value, the peak H2SO4 mixing ratio of 5.4 ppm, and the H2SO4 production rate phi H2SO4 = 2.2 x 10(12) cm-2 sec-1. The sulfur to sulfuric acid mass flux ratio in the clouds is 1 : 27 in this model, and the mass loading ratio may be larger than this value if sulfur particles are smaller than those of sulfuric acid. The model suggests that the extinction coefficient of sulfuric acid particles with radius 3.7 micrometers (mode 3) is equal to 0.3 km-1 in the middle cloud layer. The downward flux of CO is equal to 1.7 x 10(12) cm-2 sec-1 in this model. Our second model, which is constrained to yield fH2SO4 = 10 ppm at the lower cloud boundary, close to the value measured by the Magellan radiooccultations, predicts the position of this boundary to be at 46.5 km, which agrees with the Magellan data; fH2O(30 km) = 90 ppm, close to the data of Moroz et al. (1983) at this altitude; phi H2SO4 = 6.4 x 10(12) cm-2 sec-1; and phi co = 4.2 x 10(12) cm-2 sec-1. The S/H2SO4 flux mass ratio is 1 : 18, and the extinction coefficient of the mode 3 sulfuric acid particles is equal to 0.9 km-1 in the middle cloud layer. A strong gradient of the H2SO4 vapor mixing ratio near the bottom of the cloud layer drives a large upward flux of H2SO4, which condenses and forms the excessive downward flux of liquid sulfuric acid, which is larger by a factor of 4-7 than the flux in the middle cloud layer. This is the mechanism of formation of the lower cloud layer. Variations of the lower cloud layer are discussed. Our modeling of the OCS and CO profiles in the lower atmosphere measured by Pollack et al. (1993) provides a reasonable explanation of these data and shows that the rate coefficient of the reaction SO3 + CO --> CO2 + SO2 is equal to 10(-11) exp(-(13,100 +/- 1000)/T) cm3/s. The main channel of the reaction between SO3 and OCS is CO2 + (SO)2, and its rate coefficient is equal to 10(-11) exp(-(8900 +/- 500)T)cm3/s. In the conditions of Venus' lower atmosphere, (SO)2 is removed by the reaction (SO)2 + OCS --> CO + S2 + SO2. The model predicts an OCS mixing ratio of 28 ppm near the surface.

Atmosphere↗

PubMed1984

Water loss on Venus: the role of carbon monoxide.

The abundance of water on Venus is four to five orders of magnitude lower than on the Earth. This difference may reflect initial differences in the bulk volatile contents of the two planets, or may be the result of processes for massive water loss on Venus. A series of thermodynamic calculations are performed on the heterogeneous system C-O-H-N-S, varying C/H upward from its terrestrial value of 0.033 in order to evaluate the extent to which either of these two possibilities may account for the low water content on Venus. Relative abundances of 84 molecular gaseous species are computed as functions of temperature, total pressure, oxygen fugacity, and bulk C/H. As bulk C/H increases, the complement of atmospheric H2O decreases, but C/H would have to be raised to an improbably high value to account for the low water abundance on Venus by initial deficiency alone. Increasing C/H also results in a rapid increase in CO/H2O, however, and enhances water loss by the reaction CO + H2O = CO2 + H2 or by reaction of carbon monoxide with the free oxygen liberated by photodissociation of water. Other water loss mechanisms have relied on crustal FeO as an oxygen sink. Such mechanisms, however, should have operated on both Venus and the Earth and may be insufficient to account for the major differences in present H2O abundance between the two planets. Calculations performed in this study suggest that if the outgassed C/H on Venus was higher than on Earth by even less than a factor of 5, it would have been sufficient to make carbon monoxide competitive with FeO as a sink for oxygen. Together with the lower initial water abundance that follows from a higher C/H, water loss involving CO may have been a major factor in determining the present low abundance of water on Venus.

Atmosphere↗

PubMed1991

[Our experience with the use of the new Bulgarian intrauterine contraceptive device, the Venus Cu 300 (preliminary report)].

A team of the family planning centre at the Research Institute of Obstetrics and Gynecology carried out a trial on a new Bulgarian intrauterine contraceptive device (ICD), produced by the firm Venus in the town of Varna: Venus Cu 300. This is a T-shaped device with horizontal arm of 30 mm, vertical arm of 34 mm, a copper thread with an area of 300 mm2 and two control threads. It is produced from PVC. Purity of copper is over 99.9% in the copper thread. The construction of Venus Cu 300 has the positive properties of other intrauterine contraceptive devices, used in our country during the last 15 years. 87 women have been followed in 320 cycles for a period of 6 months. A larger part of them are parous, mainly with one or two children. Venus Cu 300 has been used in seven nulliparas, presenting risk for frequent abortions. Three Venus Cu 300 have been placed immediately after abortion. No pregnancy occurs, which is explained by the careful choice of the patients. Extraction of ICD has been made only in one case due to medical causes: bleeding and pain. More abundant menstruation after ICD has been found in 11.5% of women, but there has been no need to extract ICD. Inferences are made that Venus Cu 300 is in every way equal to the known models of ICD, that the trial should include a larger group of women to accumulate data in dynamics, in order to improve Venus Cu 300 eventually.

Adult↗

PubMed1990

Observations of the microwave emission of Venus from 1.3 to 3.6 cm.

Laboratory measurements of Steffes (1986) have suggested that the intensity and shape of the microwave spectrum of Venus might be especially sensitive to the subcloud abundance of constituents such as SO2 and gaseous H2SO4. It was likewise suggested that some variations of the shape of the emission spectrum might occur between 1.5 and 3 cm (10 to 20 GHz), a wavelength range which had previously only been sparsely observed. As a result, coordinated observations of Venus emission were conducted at four wavelengths between 1.35 cm (22.2 GHz) and 3.6 cm (8.42 GHz) using the 43-m NRAO antenna at Green Bank, West Virginia, and the 64-m antenna at NASA's Deep Space Communication Complex, Goldstone, California. In this paper, we report the methodology and results of these observations, and compare the results with other observations and with calculated emission spectra. We conclude that the observed emission spectrum is consistent with an average subcloud abundance of gaseous H2SO4 in equatorial and midlatitude regions which is approximately 5 ppm. It is suggested that additional measurements of atmospheric microwave opacity be made with the Pioneer-Venus Orbiter Radio Occultation experiment to search for temporal and spatial variations in gaseous H2SO4 abundance in the Venus atmosphere. An upper limit for the subcloud abundance of SO2 is also determined.

Astronomy↗

PubMed2001

Non-detection at Venus of high-frequency radio signals characteristic of terrestrial lightning.

The detection of impulsive low-frequency (10 to 80 kHz) radio signals, and separate very-low-frequency (approximately 100 Hz) radio 'whistler' signals provided the first evidence for lightning in the atmosphere of Venus. Later, a small number of impulsive high-frequency (100 kHz to 5.6 MHz) radio signals, possibly due to lightning, were also detected. The existence of lightning at Venus has, however, remained controversial. Here we report the results of a search for high-frequency (0.125 to 16 MHz) radio signals during two close fly-bys of Venus by the Cassini spacecraft. Such signals are characteristic of terrestrial lightning, and are commonly heard on AM (amplitude-modulated) radios during thunderstorms. Although the instrument easily detected signals from terrestrial lightning during a later fly-by of Earth (at a global flash rate estimated to be 70 s(-1), which is consistent with the rate expected for terrestrial lightning), no similar signals were detected from Venus. If lightning exists in the venusian atmosphere, it is either extremely rare, or very different from terrestrial lightning.

Journal Article↗

PubMed2001

The four final rotation states of Venus.

Venus rotates very slowly on its axis in a retrograde direction, opposite to that of most other bodies in the Solar System. To explain this peculiar observation, it has been generally believed that in the past its rotational axis was itself rotated to 180 degrees as a result of core-mantle friction inside the planet, together with atmospheric tides. But such a change has to assume a high initial obliquity (the angle between the planet's equator and the plane of the orbital motion). Chaotic evolution, however, allows the spin axis to flip for a large set of initial conditions. Here we show that independent of uncertainties in the models, terrestrial planets with dense atmosphere like Venus can evolve into one of only four possible rotation states. Moreover, we find that most initial conditions will drive the planet towards the configuration at present seen at Venus, albeit through two very different evolutionary paths. The first is the generally accepted view whereby the spin axis flips direction. But we have also found that it is possible for Venus to begin with prograde rotation (the same direction as the other planets) yet then develop retrograde rotation while the obliquity goes towards zero: a rotation of the spin axis is not necessary in this case.

Journal Article↗

PubMed1987

Venus, the goddess of fertility, numerologically 15 in Babylon and the origin of the Chinese system of 8 designs, called Pa-Kua.

In Babylonia, numerology was invented and Venus, as the goddess of fertility, was first depicted as a 6-cornered star. But, numerologically she was designated 15. As a 6-cornered star, its make-up shows two opposite triangles interpenetrated. This was changed to two squares fused into one where geometrically the shape became a square. It created 9 cells which were so numbered that the numbers counted in any row gave the sum 15. Venus thus became a Magic Square of 15. Geometrically it was a Magic Square, but numerologically it was 15. In the make-up the squares were two and opposites. As goddess of fertility she especially helped the pregnant to an easy delivery. Some 8 variants of the Magic Square, with different arrangements of numbers, represented 4 cosmic elements and 4 cosmic qualities. The Magic Squares, which represented elements, had the numbers 1, 3, 5 and 8 near one another forming a miniature square by themselves. A Magic Square representing a quality did not have the numbers 1, 3, 5 and 8, as a consolidated unit. This explains the importance of the numbers 1, 3, 5 and 8, a mystery which had remained unsolved. Venus was also the star of copper. When copper technology migrated from Babylon to China, the occult science associated with Venus also reached China. Here the 8 Magic Squares were translated into a system of whole and broken lines, called Pa-Kua, meaning 8 designs.(ABSTRACT TRUNCATED AT 250 WORDS)

China↗

PubMed1996

The 825-1110 angstroms EUV spectrum of Venus.

On 15 August 1994 we launched the EUVS sounding rocket payload to observe the 825-1110 angstrom region of Venus's far ultraviolet airglow spectrum. The EUVS telescope/spectrograph obtained good data at five times higher spectral resolution than was previously available in the far ultraviolet. We present these data and compare our results to those obtained by the Galileo UVS and Venera 11/12 UV spectrophotometers. We identify several new spectral emission features, including both singly ionized nitrogen and molecular nitrogen in Venus's spectrum. We also see evidence for electron-impact-induced emission from CO. Finally, the EUVS data indicate that the "Ar" emissions detected in Venus's far ultraviolet spectrum by Venera 11/12 spectrophotometers are in fact not due to argon, thus eliminating the discrepancy between in situ and remote sensing measurements.

Astronomy↗

PubMed1988

Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus.

A one-dimensional climate model is used to study the response of an Earth-like atmosphere to large increases in solar flux. For fully saturated, cloud-free conditions, the critical solar flux at which a runaway greenhouse occurs, that is, the oceans evaporate entirely, is found to be 1.4 times the present flux at Earth's orbit (S0). This value is close to the flux expected at Venus' orbit early in solar system history. Is is nearly independent of the amount of CO2 present in the atmosphere, but is sensitive to the H2O absorption coefficient in the 8- to 12-micrometers window region. Clouds should tend to depress the surface temperature on a warm, moist planet; thus, Venus may originally have had oceans if its initial water endowment was close to that of Earth. It lost them early in its history, however, because of rapid photodissociation of water vapor followed by escape of hydrogen to space. The critical solar flux above which water is rapidly lost could be as low as 1.1S0. The surface temperature of a runaway greenhouse atmosphere containing a full ocean's worth of water would have been in excess of 1500 degrees K--above the solidus for silicate rocks. The presence of such a steam atmosphere during accretion may have significantly influenced the early thermal evolution of both Earth and Venus.

Atmosphere↗

PubMed1992

Possible cometary origin of heavy noble gases in the atmospheres of Venus, Earth and Mars

Models that trace the origin of noble gases in the atmospheres of the terrestrial planets (Venus, Earth and Mars) to the 'planetary component' in chondritic meteorites confront several problems. The 'missing' xenon in the atmospheres of Mars and Earth is one of the most obvious; this gas is not hidden or trapped in surface materials. On Venus, the absolute abundances of neon and argon per gram of rock are higher even than those in carbonaceous chondrites, whereas the relative abundances of argon and krypton are closer to solar than to chondritic values (there is only an upper limit on xenon). Pepin has developed a model that emphasizes hydrodynamic escape of early, massive hydrogen atmospheres to explain the abundances and isotope ratios of noble gases on all three planets. We have previously suggested that the unusual abundances of heavy noble gases on Venus might be explained by the impact of a low-temperature comet. Further consideration of the probable history of the martian atmosphere, the noble-gas data from the (Mars-derived) SNC meteorites and laboratory experiments on the trapping of noble gases in ice lead us to propose here that the noble gases in the atmospheres of all of the terrestrial planets are dominated by a mixture of an internal component and contribution from impacting icy planetesimals (comets). If true, this hypothesis illustrates the importance of impacts in determining the volatile inventories of these planets.

Argon↗

PubMed2005

Venus, Mars, and the ices on Mercury and the moon: astrobiological implications and proposed mission designs.

Venus and Mars likely had liquid water bodies on their surface early in the Solar System history. The surfaces of Venus and Mars are presently not a suitable habitat for life, but reservoirs of liquid water remain in the atmosphere of Venus and the subsurface of Mars, and with it also the possibility of microbial life. Microbial organisms may have adapted to live in these ecological niches by the evolutionary force of directional selection. Missions to our neighboring planets should therefore be planned to explore these potentially life-containing refuges and return samples for analysis. Sample return missions should also include ice samples from Mercury and the Moon, which may contain information about the biogenic material that catalyzed the early evolution of life on Earth (or elsewhere). To obtain such information, science-driven exploration is necessary through varying degrees of mission operation autonomy. A hierarchical mission design is envisioned that includes spaceborne (orbital), atmosphere (airborne), surface (mobile such as rover and stationary such as lander or sensor), and subsurface (e.g., ground-penetrating radar, drilling, etc.) agents working in concert to allow for sufficient mission safety and redundancy, to perform extensive and challenging reconnaissance, and to lead to a thorough search for evidence of life and habitability.

Atmosphere↗

PubMed1991

Deuterium on Venus: observations from Earth.

Absorption lines of HDO and H2O have been detected in a 0.23-wave number resolution spectrum of the dark side of Venus in the interval 2.34 to 2.43 micrometers, where the atmosphere is sounded in the altitude range from 32 to 42 kilometers (8 to 3 bars). The resulting value of the deuterium-to-hydrogen ratio (D/H) is 120 +/- 40 times the telluric ratio, providing unequivocal confirmation of in situ Pioneer Venus mass spectrometer measurements that were in apparent conflict with an upper limit set from International Ultraviolet Explorer spectra. The 100-fold enrichment of the D/H ratio on Venus compared to Earth is thus a fundamental constraint on models for its atmospheric evolution.

Atmosphere↗

PubMed1995

Venus reconsidered.

The Magellan imagery shows that Venus has a crater abundance equivalent to a surface age of 300 million to 500 million years and a crater distribution close to random. Hence, the tectonics of Venus must be quiescent compared to those of Earth in the last few 100 million years. The main debate is whether the decline in tectonic activity on Venus is closer to monotonic or episodic, with enhanced tectonism and volcanism yet to come. The former hypothesis implies that most radioactive heat sources have been differentiated upward; the latter, that they have remained at depth. The low level of activity in the last few 100 million years inferred from imagery favors the monotonic hypothesis; some chemical evidence, particularly the low abundance of radiogenic argon, favors the episodic. A problem for both hypotheses is the rapid decline of thermal and tectonic activity some 300 million to 500 million years ago. The nature of the convective instabilities that caused the decline, and their propagation, are unclear.

Elements↗

PubMed1964

The atmospheres of Mars, Venus and Jupiter.

The general properties of the atmospheres of Mars, Venus and Jupiter are reviewed. The evolutionary processes of planetary atmospheres are outlined as an introduction to a detailed discussion of the structure of the atmospheres of other planets. The most recent observational results indicate that the surface pressure on Mars could be as low as 20 mb, and the amount of CO2 may have a mixing ratio as high as 25% by volume. For Venus, the Mariner II results suggest that the surface temperature may actually be of the order of 600 degrees K. Also there are indications that the surface pressure on Venus could be approximately 100 atm., with the atmosphere mainly composed of N2. In the case of Jupiter, recent theoretical investigations of the atmosphere below the clouds suggest, that there may be regions in the atmosphere of very high density and pressure but at relatively low temperature, creating conditions possibly favorable to the occurrence of complex organic reactions.

Atmosphere↗

PubMed2005

Transgenic frogs expressing the highly fluorescent protein venus under the control of a strong mammalian promoter suitable for monitoring living cells.

To easily monitor living cells and organisms, we have created a transgenic Xenopus line expressing Venus, a brighter variant of yellow fluorescent protein, under the control of the CMV enhancer/chicken beta-actin (CAG) promoter. The established line exhibited high fluorescent intensity not only in most tissues of tadpoles to adult frogs but also in germ cells of both sexes, which enabled three-dimensional imaging of fluorescing organs from images of the serial slices of the transgenic animals. Furthermore, by using this transgenic line, we generated chimeric animals by brain implantation and importantly, we found that the brain grafts survived and expressed Venus in recipients after development, highlighting the boundary between fluorescent and nonfluorescent areas in live animals. Thus, Venus-expressing transgenic frogs, tadpoles, and embryos would facilitate their use in many applications, including the tracing of the fluorescent cells after tissue/organ transplantation.

Aging↗

PubMed2003

The Venus effect: people's understanding of mirror reflections in paintings.

We propose the term 'Venus effect' for a common phenomenon in picture perception. It occurs when a picture shows an actor and a mirror that are not placed along the observer's line of sight, for instance a Venus admiring herself in a small mirror, and when the actor's reflection in the mirror is visible to the observer. In this situation, observers tend to report, incorrectly, that Venus is also seeing herself in the mirror in the same location as the observer. We discuss this using famous paintings as examples.

Adult↗

PubMed2003

Phyto-oestrogen levels in foods: the design and construction of the VENUS database.

The objective of the Vegetal Estrogens in Nutrition and the Skeleton (VENUS) project was to evaluate existing data on dietary exposure to compounds with oestrogenic and anti-oestrogenic effects present in plant foods as constituents or contaminants, and to identify and disseminate in vitro and in vivo methodologies to analyse the effects of such compounds on bone. To permit the assessment of exposure to isoflavones in European populations (Italy, the UK, Ireland, The Netherlands), the VENUS database of phyto-oestrogen levels in foods was established. Data on the isoflavone (genistein and daidzein) content of 791 foods, including almost 300 foods commonly consumed in Europe, were collected. Levels of coumestrol, formononetin and biochanin A in a limited number of foods were also included. Lignan levels (secoisolariciresinol and matairesinol) in 158 foods were incorporated into the database, which also contains information on the references sourced for the compositional data, on the analytical methods used by each author and on the number of foods analysed in each reference. The VENUS database was constructed in Microsoft Access 2000, which is widely available as part of Microsoft Office Professional. This paper outlines the procedures used for the selection and evaluation of existing literature data for incorporation into the database. In addition, the design of the database is described, along with the data entry and quality control procedures used in its construction. Limitations of the data are discussed and guidelines for its use are provided.

Database Management Systems↗

PubMed2001

Very Early Nimodipine Use in Stroke (VENUS): a randomized, double-blind, placebo-controlled trial.

BACKGROUND AND PURPOSE: The Very Early Nimodipine Use in Stroke (VENUS) trial was designed to test the hypothesis that early treatment with nimodipine has a positive effect on survival and functional outcome after stroke. This was suggested in a previous meta-analysis on the use of nimodipine in stroke. However, in a recent Cochrane review we were unable to reproduce these positive results. This led to the early termination of VENUS after an interim analysis. METHODS: In this randomized, double-blind, placebo-controlled trial, treatment was started by general practitioners or neurologists within 6 hours after stroke onset (oral nimodipine 30 mg QID or identical placebo, for 10 days). Main analyses included comparisons of the primary end point (poor outcome, defined as death or dependency after 3 months) and secondary end points (neurological status and blood pressure 24 hours after inclusion, mortality after 10 days, and adverse events) between treatment groups. Subgroup analyses (on final diagnosis and based on the per-protocol data set) were performed. RESULTS: At trial termination, after inclusion of 454 patients (225 nimodipine, 229 placebo), no effect of nimodipine was found. After 3 months of follow-up, 32% (n=71) of patients in the nimodipine group had a poor outcome compared with 27% (n=62) in the placebo group (relative risk, 1.2; 95% CI, 0.9 to 1.6). A treatment effect was not found for secondary outcomes and in the subgroup analyses. CONCLUSIONS: The results of VENUS do not support the hypothesis of a beneficial effect of early nimodipine in stroke patients.

Acute Disease↗