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1.
Several arguments have been put forward suggesting that Venus has no place tectonics. We examine some of these arguments and suggest that because conditions on the surface of Venus are very different from those on Earth, the arguments should be reconsidered. We show that in the absence of an ocean, the differential hypsographic curve of Earth would probably have only one mode, like that for Venus. We show that the atmosphere of Venus is quite capable of erosion, provided that near-surface velocities are about 1 m · sec?1 or more, and that therefore the “oceanic” areas on Venus, should they exist, are probably covered with some thickness of sediment. If sedimentation on Venus is at all rapid, it is likely that subduction zones could be filled up and made unrecognizable topographically. Because Venus does not have an ocean, and because its surface temperature is much greater than that on Earth, ridge crests on Venus have a much smaller topographic expression than those on Earth. If significant sedimentation occurs they would be completely unrecognizable topographically. 相似文献
2.
The Venus ground-based image Active Archive is an online database designed to collect ground-based images of Venus in such a way that they are optimally useful for science. The Archive was built to support ESA's Venus Amateur Observing Project, which utilizes the capabilities of advanced amateur astronomers to collect filtered images of Venus in ultraviolet, visible and near-infrared light. These images complement the observations of the Venus Express spacecraft, which cannot continuously monitor the northern hemisphere of the planet due to its elliptical orbit with apocenter above the south pole. We present the first set of observations available in the Archive and assess the useability of the data set for scientific purposes. 相似文献
3.
The Chinese first reported the Crab Nebula supernova on 1054 July 5. Ecclesiastical documents from the near east reported it in April and May of 1054. More than 33 petroglyphs made by Native Americans in the US and Mexico are consistent with sightings both before and after conjunction with the Sun on 1054 May 27. We found a petroglyph showing the new star close to Venus and the Moon, which occurred on 1054 April 12 and April 13, respectively. Collins et al., using the four historical dates, derived a light curve that is like that of a Type Ia supernova. The only remaining problem with this identification is that this supernova was near maximum light for 85 d, which is unlike the behavior of any known supernova. 相似文献
4.
Anthony Mallama 《Icarus》2009,204(1):11-499
The empirically derived phase curves of terrestrial planets strongly distinguish between airless Mercury, cloud-covered Venus, and the intermediate case of Mars. The function for Mercury is steeply peaked near phase angle zero due to powerful backscattering from its surface, while that for Venus has 100 times less contrast and exhibits a brightness excess near 170° due to Mie scattering from droplets in the atmosphere. The phase curve of Mars falls between those of Mercury and Venus, and there are variations in luminosity due to the planet’s rotation, seasons, and atmospheric states. The phase function and geometric albedo of the Earth are estimated from published albedos values. The curves for Mercury, Venus and Mars are compared to that of the Earth as well as theoretical phase functions for giant planets. The parameters of these different phase functions can be used to characterize exoplanets. 相似文献
5.
We present a systematic survey for satellites of Venus using the Baade-Magellan 6.5 m telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile. In the outer portions of the Hill sphere the search was sensitive to a limiting red magnitude of about 20.4, which corresponds to satellites with radii of a few hundred meters when assuming an albedo of 0.1. In the very inner portions of the Hill sphere scattered light from Venus limited the detection to satellites of about a kilometer or larger. Although several main belt asteroids were found, no satellites (moons) of Venus were detected. 相似文献
6.
Valérie Wilquet Rachel Drummond Arnaud Mahieux Séverine Robert Ann Carine Vandaele Jean-Loup Bertaux 《Icarus》2012,217(2):875-881
The variability of the aerosol loading in the mesosphere of Venus is investigated from a large data set obtained with SOIR, a channel of the SPICAV instrument suite onboard Venus Express. Vertical profiles of the extinction due to light absorption by aerosols are retrieved from a spectral window around 3.0 μm recorded in many solar occultations (～200) from September 2006 to September 2010. For this period, the continuum of light absorption is analyzed in terms of spatial and temporal variations of the upper haze of Venus. It is shown that there is a high short-term (a few Earth days) and a long-term (～80 Earth days) variability of the extinction profiles within the data set. Latitudinal dependency of the aerosol loading is presented for the entire period considered and for shorter periods of time as well. 相似文献
7.
In 1761, the Russian polymath Mikhail Vasilievich Lomonosov (1711–1765) discovered the atmosphere of Venus during its transit over the Sun’s disc. In this paper we report on experimental reenactments of Lomonosov’s discovery with antique refractors during the transit of Venus June 5–6, 2012. We conclude that Lomonosov’s telescope was fully adequate to the task of detecting the arc of light around Venus off the Sun’s disc during ingress or egress provided proper experimental techniques as described by Lomonosov in his 1761 report are employed. 相似文献
8.
A Monte Carlo program by Thomason and Krider has been adapted to the Venus cloud geometry and optical properties. If lightning flashes occur within or just below the clouds, the fraction of photons of visible light escaping to space is 0.1–0.4, depending on the location of the flash. For flashes near the surface, only one blue photon in 104 was found to escape; about 5% of the red ones are transmitted. Failure of the Pioneer Venus Orbiter to unambiguously detect optical lightning signals from space is not due to attenuation by the atmosphere and clouds. In any case, lightning is not acceptable as an explanation for ashen light. 相似文献
9.
《Planetary and Space Science》2007,55(12):1831-1842
The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at understanding the atmospheric circulation of Venus. Meteorological information will be obtained by globally mapping clouds and minor constituents successively with four cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science technique. The equatorial elongated orbit with westward revolution fits the observation of the movement and temporal variation of the atmosphere which as a whole rotates westward. The systematic, continuous imaging observations will provide us with an unprecedented large data set of the Venusian atmospheric dynamics. Additional targets of the mission are the exploration of the ground surface and the observation of zodiacal light. The mission will complement the ESA's Venus Express, which also explores the Venusian environment with different approaches. 相似文献
10.
The observed density of Venus is about 2% smaller than would be expected if Venus were a twin planet of the Earth, possessing an identical internal composition and structure. In principle, this could be explained by a process of physical segregation of metal particles from silicate particles in the solar nebula prior to accretion, so that Venus accreted from relatively metal-depleted material. However, this model encounters severe difficulties in explaining the nature of the physical segregation process and also the detailed chemical composition of the Earth's mantle. Two alternative hypotheses are examined, both of which attempt to explain the density difference in terms of chemical fractionation processes. Both of these hypotheses assume that the relative abundances of the major elements Fe, Si, Mg, Al, and Ca are similar in both planets. According to the first hypothesis, a larger proportion of the total iron in Venus is present as iron oxide in the mantle, so that the core-to-mantle ratio is smaller than in the Earth. This model implies that Venus is more oxidized than the Earth, with its lower intrinsic density (i.e., corrected to equivalent pressures and temperatures) due to the larger amount of oxygen present. The difference between oxidation states is attributed to differing degrees of accretional heating arising from the relatively smaller mass of Venus. On the other hand, the second hypothesis maintains that Venus is more reduced than the Earth, with its mantle essentially devoid of oxidized iron. The difference intrinsic densities is attributed to the Earth accreting at a lower temperature than Venus as a result of the Earth's greater distance from the center of the nebula. As a result, large amounts of sulfur accreted on the Earth but not on Venus. The sulfur, which entered the core, is believed to have increased the mean density of the Earth because of its relatively high atomic weight. The hypothesis also implies that most of the Earth's potassium, because of its chalcophile properties, entered the core.These hypotheses are evaluated in the light of existing data. The second hypothesis leads to an intrinsic density for Venus which is only 0.4% smaller than that of the Earth. This difference is much smaller than is believed to exist. A wide range of chemical evidence is found to be unfavorable to this second hypothesis, but to be consistent with the interpretation that Venus is more oxidized than the Earth, as required by the first hypothesis. 相似文献
11.
M.V. Keldysh 《Icarus》1977,30(4):605-625
In October 1975 the Venera 9 and 10 space vehicles reached Venus. Two landers separated from the spacecraft and soft-landed on the illuminated side of the planet while their remaining orbiters were inserted into highly elliptical orbits, with pericenters at about 7600 km. These flights became a very important step in the Soviet program of Venus exploration. For the first time two panoramas of the Venus surface were returned to the Earth. Both landers and orbiters were equipped with various scientific instruments for studying the structure and dynamics of the atmosphere, physical properties and structure of the clouds, light attenuation in the atmosphere and illumination properties of the surface at the landing sites, and the composition, structure, and interaction processes in the Venus upper atmosphere and environment. The experiments were of complex character due to the simultaneous measurements from landers and orbiters, while the orbiters delivered very important information provided by systematic observations of the planet with great time and space coverage. In this report the principal characteristics of the flights, construction of the spacecraft, instrumentation, and scheme of landing on the surface are described. The preliminary results of the measurements obtained and their tentative interpretation are discussed. 相似文献
12.
Nine plates of the 7820 Å CO2 band were taken in 1971. A curve-of-growth analysis of the CO2 lines indicates a rotational temperature of 241 ± 2°K, with an average slope to the curve of growth of 0.60 ± 0.03. The Venus phase angle ranged from 7.2 to 10.7°. The equivalent widths of the 1971 data fall on a smooth curve fit through the 1969 data for this band; there does not appear to be any discontinuity in the phase curve at small phase angles. 相似文献
13.
In the light of the wide applications of a series of ephemerides developed by the Jet Propulsion Laboratory (JPL) of the National Aeronautics and Space Administration (NASA) of the USA to many aspects like the deep-space navigation and interplanetary exploration, it is necessary to make comparisons of their contents, applicable ranges, realizations and maintenances. In view of the fact that the explorations of the Venus and Mars are expected to carry out in China, their dynamical models and the adopted observational data are analysis by taking the DE405, DE421 and DE423 to be the examples. From the evaluations of the accuracies and performances of the above-mentioned ephemerides of different editions, their effects on the probes orbiting around the Venus or Mars are emphatically discussed, and a suggestion is given for their use that as far as the Venus missions are concerned, the use of the DE423 is recommend, and that the use of the DE421 or DE423 is recommended for the Mars Missions. 相似文献
14.
《Planetary and Space Science》2006,54(13-14):1336-1343
The Venus Express mission is scheduled for launch in 2005. Among many other instruments, it carries a magnetometer to investigate the Venus plasma environment. Although Venus has no intrinsic magnetic moment, magnetic field measurements are essential in studying the solar wind interaction with Venus. Our current understanding of the solar wind interaction with Venus is mainly from the long lasting Pioneer Venus Orbiter (PVO) observations. In this paper, we briefly describe the magnetic field experiment of the Venus Express mission. We compare Venus Express mission with PVO mission with respect to the solar wind interaction with Venus. Then we discuss what we will achieve with the upcoming Venus Express mission. 相似文献
15.
A fundamental question in exobiology remains the degree to which habitats on Venus, past and present, were, or are suitable for life. This has relevance for assessing the exobiological potential of extrasolar Venus-like greenhouse planets. In this paper the parameters of the Venusian surface and atmosphere are considered and the biochemical adaptations required to survive them are explored in the light of new information on microbial adaptations to extreme environments. Neither the pressure (9.5 MPa) nor the high carbon dioxide concentrations (97%) represent a critical constraint to the evolution of life on the surface or in the atmosphere. The most significant constraints to life on the surface are the lack of liquid water and the temperature (464°C). In the lower and middle cloud layers of Venus, temperatures drop and water availability increases, generating a more biologically favorable environment. However, acidity and the problem of osmoregulation in hygroscopic sulfuric acid clouds become extreme and probably life-limiting. If it is assumed that these constraints can be overcome, considerations on the survival of acidophilic sulfate-reducing chemoautotrophs suspended as aerosols in such an environment show that Venus does come close to possessing a habitable niche. Conditions on the surface and in the atmosphere may have been greatly ameliorated on early Venus and may also be ameliorated on extrasolar planets with early Venus-like characteristics where temperatures are less extreme and liquid water is available. 相似文献
16.
The ESA/Venus Express mission spent more than 8 years in orbit around Venus to extensively study its atmosphere, ionosphere and plasma environment and unveil new aspects of its surface. Extensive reviews of the work of Venus Express are underway, to cover in-depth studies of the new face of Venus revealed by Venus Express and ground-based concurrent observations. This paper intends to give a summarized and wide overview of some of the outstanding results in all the science areas studied by the mission. This paper will first review the main aspects of the mission and its instrumental payload. Then, a selection of results will be reviewed from the outermost layers interacting with the Solar wind, down to the surface of Venus. As Venus Express is already considered by space agencies as a pathfinder for the future of Venus exploration, perspectives for future missions will be given, which will have to study Venus not only from orbital view, but also down to the surface to solve the many remaining mysteries of the sister planet of the Earth. 相似文献
17.
W.A. Baum 《Planetary and Space Science》1973,21(9):1511-1519
Day-to-day and hour-to-hour changes in the large-scale atmospheric and surface features of the planets can now be studied more effectively than previously possible. Since 1969 a network of observatories has obtained almost uninterrupted photographic coverage during all apparitions of Jupiter and Mars, plus some of Venus. Patrol films and catalogues are available to the scientific community. Recent or current analyses include the distribution and motion of clouds on Mars, the development and decay of Martian dust storms, the seasonal, diurnal and random fluctuations in contrast between adjacent light and dark regions on Mars, the detection of vertical shear in the Jovian atmosphere, the longitudinal oscillation of the Red Spot, the dependence of rotation period on xenographic latitude and on time, the eruption and spread of SEB disturbances, and the retrograde circulation of the Venus cloud deck. 相似文献
18.
Magnetic flux ropes are created in the ionosphere of Venus and Mars during the interaction of the solar wind with their ionospheres and also at Titan during the interaction of the Saturnian magnetospheric plasma flow with Titan’s ionosphere. The flux ropes at Venus and Mars were extensively studied from Pioneer Venus Orbiter and Mars Global Surveyor observations respectively during solar maximum. Based on the statistical properties of the observed flux ropes at Venus and Mars, the formation of a flux rope in the ionosphere is thought first to arise near the boundary between the magnetic barrier and the ionosphere and later to sink into the lower ionosphere. Venus flux ropes are also observed during solar minimum by Venus Express and the observations of developing and mature flux ropes are consistent with the proposed mechanism. With the knowledge of flux rope structure in the Venus ionosphere, the twisted fields in the lower ionosphere of Titan from Cassini observations are studied and are found to resemble the Venus flux ropes. 相似文献
19.
M.Ya. Marov V.S. Avduevsky N.F. Borodin A.P. Ekonomov V.V. Kerzhanovich V.P. Lysov B.Ye. Moshkin M.K. Rozhdestvensky O.L. Ryabov 《Icarus》1973,20(4):407-421
The Venera 8 descent module measured pressure, temperature, winds and illumination as a function of altitude in its landing on July 22, 1972, just beyond the terminator in the illuminated hemisphere of Venus. The surface temperature and pressure is 741 ± 7°K and 93 ± 1.5kgcm?2, consistent with early Venera observations and showing either no diurnal variation or insignificant diurnal variation in temperature and pressure in the vicinity of the morning terminator. The atmosphere is adiabatic down to the surface. The horizontal wind speed is low near the surface, about 35m/sec between 20 and 40km altitude, and increasing rapidly above 48km altitude to 100–140m/sec, consistent with the 4-day retrograde rotation of the ultraviolet clouds. The illumination at the center of the day hemisphere of Venus is calculated to be about 1% of the solar flux at the top of the atmosphere, consistent with greenhouse models and high enough to permit photography of the Venus surface by future missions. The attenuation below 35km altitude is explained by Rayleigh scattering with no atmospheric aerosols; above 35km there must be substantial extinction of incident light. 相似文献
20.
《Planetary and Space Science》2007,55(12):1636-1652
Venus Express is the first European mission to planet Venus. The mission aims at a comprehensive investigation of Venus atmosphere and plasma environment and will address some important aspects of the surface physics from orbit. In particular, Venus Express will focus on the structure, composition, and dynamics of the Venus atmosphere, escape processes and interaction of the atmosphere with the solar wind and so to provide answers to the many questions that still remain unanswered in these fields. Venus Express will enable a breakthrough in Venus science after a long period of silence since the period of intense exploration in the 1970s and the 1980s.The payload consists of seven instruments. Five of them were inherited from the Mars Express and Rosetta projects while two instruments were designed and built specifically for Venus Express. The suite of spectrometers and imaging instruments, together with the radio-science experiment, and the plasma package make up an optimised payload well capable of addressing the mission goals to sufficient depth. Several of the instruments will make specific use of the spectral windows at infrared wavelengths in order to study the atmosphere in three dimensions. The spacecraft is based on the Mars Express design with minor modifications mainly needed to cope with the thermal environment around Venus, and so a very cost-effective mission has been realised in an exceptionally short time.The spacecraft was launched on 9 November 2005 from Baikonur, Kazakhstan, by a Russian Soyuz-Fregat launcher and arrived at Venus on 11 April 2006. Venus Express will carry out observations of the planet from a highly elliptic polar orbit with a 24-h period. In 3 Earth years (4 Venus sidereal days) of operations, it will return about 2 Tbit of scientific data.Telecommunications with the Earth is performed by the new ESA ground station in Cebreros, Spain, while a nearly identical ground station in New Norcia, Australia, supports the radio-science investigations. 相似文献