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1

A Few Highlights from Venus Monitoring Camera on Venus Express  

Science.gov (United States)

Venus is completely covered by a thick cloud layer whose upper part is composed of sulfuric acid and some unknown aerosols(1). The cloud tops are in fast retrograde rotation (super-rotation), but what is driving this super-rotation is unknown(2). Here we report observations of Venus with the Venus Monitoring Camera3 (VMC) on board the Venus Express spacecraft. Taking advantage of the VMC high resolution imaging and the polar orbit we investigate both global and small scale properties of these clouds, their temporal and latitudinal variations, and derive wind velocities. The Southern polar region is highly variable and can change dramatically on time scales as short as one day, perhaps arising from the injection of SO2 into the mesosphere. The convective cells in the vicinity of the sub-solar point are much smaller than previously inferred(4,5,6), which we interpret as indicating that they are confined to the upper cloud layer, contrary to previous conclusions(7,8), but consistent with more recent study(9). We will also report on surface observations with VMC. (1) Esposito, L.W. et al., in Venus, pp. 484-564, 1983, (2) Limaye, S. S., 2007, J. Geophys. Res., 112, 2007, (3) Markiewicz, W.J. et al., Planet. Space Sci., 55, 1701-1711, 2007, (4) Murray, B.C., et al., Science 183, 1307-1315 (1974), (5) Rossow, W.B. et al., J. Geophys. Res. 85, 8107-8128, 1980, (6) Covey, C.C. and G. Schubert, Nature, 290, 17-20, 1981, (7) Baker II, R.D. and G. Schubert, Nature, 355, 710-712, 1992, (8) Belton, M.J.S. et al., J. Atmos. Sci.. 33, 1394-1417, 1976, (9) Baker, R.D., G. Schubert, and P.W. Jones, J. Geophy. Res., 104, Issue E2, p. 3815-3832, 1999.

Markiewicz, Wojciech J.; Titov, D.; Keller, H.; Moissl, R.; Limaye, S.; Ignatiev, N.; Jaumann, R.; Michalik, H.; Thomas, N.

2008-09-01

2

Venus Express uurib Maa kurja kaksikut / ref. Triin Thalheim  

Index Scriptorium Estoniae

9. novembril startis Baikonuri kosmodroomilt Veenusele Euroopa Kosmoseagentuuri sond Venus Express, mis peaks planeedi atmosfääri sisenema aprillis. Teadlaste sõnul peab sondi saadetav info aitama mõista naaberplaneedi kliimat ja atmosfääri ning tooma selgust, kas Maa võib kunagi Veenuse sarnaseks muutuda. Lisaks joonis: Venus Express

2005-01-01

3

Vortex Organization and the Cloud Level Circulation from Venus Monitoring Camera Observations from Venus Express  

Science.gov (United States)

The Venus Monitoring Camera (VMC) has been observing Venus cloud cover at four wavelengths from the Venus Express spacecraft orbiting Venus since April 2006. The apocenter observations have enabled determination of the southern hemisphere cloud level flow by tracking cloud features using automated digital tracking between equator and mid-latitudes. Beyond about 45 degrees latitude, the cloud morphology and the moderately low resolution of the apocenter images makes cloud tracking very challenging and somewhat unreliable. Results from visual tracking have been presented by Moissl et al. (2009) The cloud tracking results show small temporal variations and the presence of solar thermal tides. At polar latitudes the organization of the cloud cover continues to be a hemispheric vortex centered over the pole. Both the VMC and the VIRTIS observations of the polar regions have shown occurrence of features that have been identified as signatures of dynamical instability (Limaye et al., 2009), which requires non-solid body rotation at high latitudes. The morphological evidence suggests that the high latitude measurements of cloud motions from the low spatial resolution imaging data (both VMC and VIRTIS, Sanchez-Lavega et al., 2008) should be interpreted with caution as they may not accurately reflect the meridional shear of the east-west component of the flow at high latitudes References Limaye et al., 2009, Vortex Circulation on Venus: Dynamical similarities with terrestrial hurricanes, Geophys. Res. Lett., doi:10.1029/2008GL036093, in press. Moissl et al., 2009, Venus cloud top winds from tracking UV features in Venus Monitoring Camera images, J. Geophys. Res., doi:10.1029/2008JE003117, in press. Sánchez-Lavega, A., et al. (2008), Variable winds on Venus mapped in three dimensions, Geophys. Res. Lett., 35, L13204, doi:10.1029/2008GL033817.

Limaye, S.; Markiewicz, W.; Titov, D.; Moissl, R.

2009-04-01

4

Low-frequency magnetic field fluctuations in Venus' solar wind interaction region: Venus Express observations  

Directory of Open Access Journals (Sweden)

Full Text Available We investigate wave properties of low-frequency magnetic field fluctuations in Venus' solar wind interaction region based on the measurements made on board the Venus Express spacecraft. The orbit geometry is very suitable to investigate the fluctuations in Venus' low-altitude magnetosheath and mid-magnetotail and provides an opportunity for a comparative study of low-frequency waves at Venus and Mars. The spatial distributions of the wave properties, in particular in the dayside and nightside magnetosheath as well as in the tail and mantle region, are similar to observations at Mars. As both planets do not have a global magnetic field, the interaction process of the solar wind with both planets is similar and leads to similar instabilities and wave structures. We focus on the spatial distribution of the wave intensity of the fluctuating magnetic field and detect an enhancement of the intensity in the dayside magnetosheath and a strong decrease towards the terminator. For a detailed investigation of the intensity distribution we adopt an analytical streamline model to describe the plasma flow around Venus. This allows displaying the evolution of the intensity along different streamlines. It is assumed that the waves are generated in the vicinity of the bow shock and are convected downstream with the turbulent magnetosheath flow. However, neither the different Mach numbers upstream and downstream of the bow shock, nor the variation of the cross sectional area and the flow velocity along the streamlines play probably an important role in order to explain the observed concentration of wave intensity in the dayside magnetosheath and the decay towards the nightside magnetosheath. But, the concept of freely evolving or decaying turbulence is in good qualitative agreement with the observations, as we observe a power law decay of the intensity along the streamlines. The observations support the assumption of wave convection through the magnetosheath, but reveal at the same time that wave sources may not only exist at the bow shock, but also in the magnetosheath.

L. Guicking; K.-H. Glassmeier; H.-U. Auster; M. Delva; U. Motschmann; Y. Narita; T. L. Zhang

2010-01-01

5

Limb Radius from Images taken by Venus Monitoring Camera on Venus Express  

Science.gov (United States)

Given the large number of images acquired from the VMC since the insertion of Venus Express in orbit in April 2006, it is now possible to measure the altitude of the visible cloud top (slant optical depth, ?slant = 1) from the images. Preliminary results were presented by Limaye et al. (2011) by determination of the ?slant location in the VMC images and using the observing geometry information to determine the altitude by first determining the image center very precisely.

Limaye, S. S.; Krauss, R. J.; Markiewicz, W. J.

2012-09-01

6

Neutral atmosphere composition from SOIR measurements on board Venus Express  

Science.gov (United States)

The SOIR instrument performs solar occultation measurements in the IR region (2.2 - 4.3 ?m) at a resolution of 0.12 cm-1, the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection [1,2]. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer with an emphasis on vertical distribution of the gases. Measurements of HDO, H2O, HCl, HF, CO and CO2 vertical profiles have been routinely performed, as well as those of their isotopologues [3,4]. We will discuss the improvements introduced in the analysis algorithm of the SOIR spectra. This discussion will be illustrated by presenting new results of retrievals of minor constituents of the Venus mesosphere, in terms of vertical profiles and geographical distribution. CO2 is the major constituent of the Venus atmosphere and was therefore observed in many solar occultations, leading to a good geographical coverage, although limited by the geometry of the orbit. Depending on the abundance of the absorbing isotopologue and on the intensity of the band measured, we will show that the SOIR instrument is able to furnish CO2 vertical profiles ranging typically from 65 to 150 km, reaching in some conditions 185 km altitude. This information is important in the frame of compiling, in collaboration with other teams, a new Venus Atmosphere Model. 1. A. Mahieux, S. Berkenbosch, R. Clairquin, D. Fussen, N. Mateshvili, E. Neefs, D. Nevejans, B. Ristic, A. C. Vandaele, V. Wilquet, D. Belyaev, A. Fedorova, O. Korablev, E. Villard, F. Montmessin and J.-L. Bertaux, "In-Flight performance and calibration of SPICAV SOIR on board Venus Express", Applied Optics 47 (13), 2252-65 (2008). 2. D. Nevejans, E. Neefs, E. Van Ransbeeck, S. Berkenbosch, R. Clairquin, L. De Vos, W. Moelans, S. Glorieux, A. Baeke, O. Korablev, I. Vinogradov, Y. Kalinnikov, B. Bach, J.-P. Dubois and E. Villard, "Compact high-resolution space-borne echelle grating spectrometer with AOTF based on order sorting for the infrared domain from 2.2 to 4.3 micrometer", Applied Optics 45 (21), 5191-5206 (2006). 3. A. Fedorova, O. Korablev, A. C. Vandaele, J.-L. Bertaux, D. Belyaev, A. Mahieux, E. Neefs, V. Wilquet, R. Drummond, F. Montmessin and E. Villard, "HDO and H2O vertical distribution and isotopic ratio in the Venus mesosphere by SOIR spectrometer on board Venus Express", JGR, doi:10.1029/2008JE003146 (2008). 4. A. C. Vandaele, M. De Mazière, R. Drummond, A. Mahieux, E. Neefs, V. Wilquet, D. Belyaev, A. Fedorova, O. Korablev, F. Montmessin and J.-L. Bertaux, "Composition of the Venus mesosphere measured by SOIR on board Venus Express", J. Geophysic. Res., doi:10.1029/2008JE003140 (2008).

Mahieux, A.; Drummond, R.; Wilquet, V.; Vandaele, A. C.; Federova, A.; Belyaev, D.; Korablev, O.; Villard, E.; Montmessin, F.; Bertaux, J.-L.

2009-04-01

7

Cloud level winds from the Venus Express Monitoring Camera imaging  

Science.gov (United States)

Six years of continuous monitoring of Venus by European Space Agency's Venus Express orbiter provides an opportunity to study dynamics of the atmosphere our neighbor planet. Venus Monitoring Camera (VMC) on-board the orbiter has acquired the longest and the most complete so far set of ultra violet images of Venus. These images enable a study the cloud level circulation by tracking motion of the cloud features. The highly elliptical polar orbit of Venus Express provides optimal conditions for observations of the Southern hemisphere at varying spatial resolution. Out of the 2300 orbits of Venus Express over which the images used in the study cover about 10 Venus years. Out of these, we tracked cloud features in images obtained in 127 orbits by a manual cloud tracking technique and by a digital correlation method in 576 orbits. Total number of wind vectors derived in this work is 45,600 for the manual tracking and 391,600 for the digital method. This allowed us to determine the mean circulation, its long-term and diurnal trends, orbit-to-orbit variations and periodicities. We also present the first results of tracking features in the VMC near-IR images. In low latitudes the mean zonal wind at cloud tops (67 ± 2 km following: Rossow, W.B., Del Genio, A.T., Eichler, T. [1990]. J. Atmos. Sci. 47, 2053–2084) is about 90 m/s with a maximum of about 100 m/s at 40–50°S. Poleward of 50°S the average zonal wind speed decreases with latitude. The corresponding atmospheric rotation period at cloud tops has a maximum of about 5 days at equator, decreases to approximately 3 days in middle latitudes and stays almost constant poleward from 50°S. The mean poleward meridional wind slowly increases from zero value at the equator to about 10 m/s at 50°S and then decreases to zero at the pole. The error of an individual measurement is 7.5–30 m/s. Wind speeds of 70–80 m/s were derived from near-IR images at low latitudes. The VMC observations indicate a long term trend for the zonal wind speed at low latitudes to increase from 85 m/s in the beginning of the mission to 110 m/s by the middle of 2012. VMC UV observations also showed significant short term variations of the mean flow. The velocity difference between consecutive orbits in the region of mid-latitude jet could reach 30 m/s that likely indicates vacillation of the mean flow between jet-like regime and quasi-solid body rotation at mid-latitudes. Fourier analysis revealed periodicities in the zonal circulation at low latitudes. Within the equatorial region, up to 35°S, the zonal wind show an oscillation with a period of 4.1–5 days (4.83 days on average) that is close to the super-rotation period at the equator. The wave amplitude is 4–17 m/s and decreases with latitude, a feature of the Kelvin wave. The VMC observations showed a clear diurnal signature. A minimum in the zonal speed was found close to the noon (11–14 h) and maxima in the morning (8–9 h) and in the evening (16–17 h). The meridional component peaks in the early afternoon (13–15 h) at around 50°S latitude. The minimum of the meridional component is located at low latitudes in the morning (8–11 h). The horizontal divergence of the mean cloud motions associated with the diurnal pattern suggests upwelling motions in the morning at low latitudes and downwelling flow in the afternoon in the cold collar region.

Khatuntsev, I. V.; Patsaeva, M. V.; Titov, D. V.; Ignatiev, N. I.; Turin, A. V.; Limaye, S. S.; Markiewicz, W. J.; Almeida, M.; Roatsch, Th.; Moissl, R.

2013-09-01

8

Thermal zonal winds in the Venus mesosphere from the Venus Express temperature soundings  

Science.gov (United States)

The Venus mesosphere (60-100 km altitude) is a transition region characterized by extremely complex dynamics: strong retrograde zonal winds dominate in the troposphere and lower meso-sphere while a solar-antisolar circulation can be observed in the upper mesosphere. The super-rotation extends from the surface up to the cloud top (˜65 km altitude) with wind speeds of only a few meters per second near the surface and reaching a maximum value of ˜100 m s-1 at cloud top, corresponding to a rotation period of ˜4 Earth days (˜60 times faster than Venus itself). The solar-antisolar circulation is driven by the day-night contrast in solar heating, and occurs above 110 km altitude with speeds of 120 m s-1 . The processes responsible for maintain-ing the zonal super-rotation in the lower atmosphere and its transition to the solar-antisolar circulation in the upper atmosphere are still poorly understood (Schubert et al.,2007). Different techniques have been used to obtain direct observations of wind at various altitudes: tracking of clouds in ultraviolet (UV) and near infrared (NIR) images give information on wind speeds at the cloud top (Moissl et al., 2009; Sanchez-Lavega et al., 2008) and within the clouds (˜47 km, ˜61 km) (Sanchez-Lavega et al., 2008) while ground-based measurements of Doppler shifts in the CO2 band at 10 µm (Sornig et al., 2008) and in several CO millimiter lines (Rengel et al., 2008) provide wind speeds above the clouds up to ˜110 km altitude. The deep atmosphere from the surface up to the cloud top has been investigated through the Doppler tracking of descent probes and balloons (Counselman et al., 1980; Kerzhanovich and Limaye, 1985). In the mesosphere, between 45-85 km of altitude, where direct observations of wind are not possible, the zonal wind field can be derived from the vertical temperature structure using a special approximation of the thermal wind equation: based on cyclostrophic balance. Previous studies (Leovy, 1973; Newman et al., 1984) showed that on a slowly rotating planet, like Venus, strong zonal winds at the cloud top can be described by a cyclostrophic balance in which the equatorward component of centrifugal force is balanced by the meridional pressure gradient. This equation gives a possibility to reconstruct the zonal wind if the temperature field is known, together with a suitable boundary condition on u. Two experiments onboard Venus Express are sounding the temperature structure of the Venus mesosphere: VIRTIS sounds the Venus Southern hemisphere in the altitude range 65-90 km with a very good spatial and temporal coverage (Grassi et al., 2008) and the Northern hemi-sphere but with more limited coverage; VeRa observes both northern and southern hemispheres between 40-90 km altitude with a vertical resolution of ˜500 m (Tellmann et al., 2008). Here we present zonal thermal winds derived applying cyclostrophic balance from VIRTIS and VeRa temperature retrievals. The main features of the retrieved winds are: (1) a midlatitude jet with a maximum speed up to 140 ± 15 m s-1 which occurs around 50° S latitude at 70 km altitude; (2) the fast decrease of the wind speed from 60° S toward the pole; (3) the decrease of the wind speed with increasing height above the jet (Piccialli et al., 2008). Cyclostrophic winds show satisfactory agreement with the cloud-tracked winds derived from the Venus Monitoring Camera (VMC/VEx) UV images, although a disagreement is observed at the equator and near the pole due to the breakdown of the cyclostrophic approximation. From zonal thermal winds the Richardson number has been evaluated. In good agreement with previous studies (Allison et al., 1994), we have found that the atmosphere is dominated by convection from ˜45 km altitude up to the cloud top. A high value of Richardson number has been determined, cor-responding to the midlatitude jet and indicating a highly stable atmosphere. Verification of the necessary condition for barotropic instability implies that barotropic instability may occur on the poleward side of the midlatitude jet where pl

Piccialli, Arianna; Titov, Dmitri; Tellmann, Silvia; Migliorini, Alessandra; Read, Peter; Grassi, Davide; Paetzold, Martin; Haeusler, Bernd; Piccioni, Giuseppe; Drossart, Pierre

9

Whistler mode bursts in the Venus ionosphere due to lightning: Statistical properties using Venus Express magnetometer observations  

Science.gov (United States)

The Venus Express mission has completed over four years in polar orbit about Venus with periapsis altitudes as low as 180 km. On each orbit around periapsis the fluxgate magnetometer samples the magnetic field at 128 Hz. The data reveal short-lived bursts with peak-to-peak amplitudes up to 1.5 nT in the frequency range 42 to 60 Hz. These signals are whistler mode waves with burst durations of about 100 ms and Poynting vectors similar to terrestrial whistler mode signals generated by atmospheric lightning when detected in the ionosphere. We have examined the occurrence of these bursts as a function of background magnetic field strength, altitude, latitude and local time. The burst rates are highest for magnetic fields of 15-30 nT, at altitudes near 215 km, and at local times near the terminators. The characteristics of these signals are consistent with generation in the dynamic Venus atmosphere, entry into the ionosphere, propagation along the ionospheric magnetic field, and ultimately damping in the ionospheric plasma.

Daniels, J. T. M.; Russell, C. T.; Strangeway, R. J.; Wei, H. Y.; Zhang, T. L.

2012-04-01

10

In-flight performance and calibration of SPICAV SOIR onboard Venus Express.  

UK PubMed Central (United Kingdom)

Solar occultation in the infrared, part of the Spectoscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) instrument onboard Venus Express, combines an echelle grating spectrometer with an acousto-optic tunable filter (AOTF). It performs solar occultation measurements in the IR region at high spectral resolution. The wavelength range probed allows a detailed chemical inventory of Venus's atmosphere above the cloud layer, highlighting the vertical distribution of gases. A general description of the instrument and its in-flight performance is given. Different calibrations and data corrections are investigated, in particular the dark current and thermal background, the nonlinearity and pixel-to-pixel variability of the detector, the sensitivity of the instrument, the AOTF properties, and the spectral calibration and resolution.

Mahieux A; Berkenbosch S; Clairquin R; Fussen D; Mateshvili N; Neefs E; Nevejans D; Ristic B; Vandaele AC; Wilquet V; Belyaev D; Fedorova A; Korablev O; Villard E; Montmessin F; Bertaux JL

2008-05-01

11

In-flight performance and calibration of SPICAV SOIR onboard Venus Express.  

Science.gov (United States)

Solar occultation in the infrared, part of the Spectoscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) instrument onboard Venus Express, combines an echelle grating spectrometer with an acousto-optic tunable filter (AOTF). It performs solar occultation measurements in the IR region at high spectral resolution. The wavelength range probed allows a detailed chemical inventory of Venus's atmosphere above the cloud layer, highlighting the vertical distribution of gases. A general description of the instrument and its in-flight performance is given. Different calibrations and data corrections are investigated, in particular the dark current and thermal background, the nonlinearity and pixel-to-pixel variability of the detector, the sensitivity of the instrument, the AOTF properties, and the spectral calibration and resolution. PMID:18449289

Mahieux, Arnaud; Berkenbosch, Sophie; Clairquin, Roland; Fussen, Didier; Mateshvili, Nina; Neefs, Eddy; Nevejans, Dennis; Ristic, Bojan; Vandaele, Ann Carine; Wilquet, Valérie; Belyaev, Denis; Fedorova, Anna; Korablev, Oleg; Villard, Eric; Montmessin, Franck; Bertaux, Jean-Loup

2008-05-01

12

A solar storm observed from the Sun to Venus using the STEREO, Venus Express, and MESSENGER spacecraft  

Science.gov (United States)

The suite of SECCHI optical imaging instruments on the STEREO-A spacecraft is used to track a solar storm, consisting of several coronal mass ejections (CMEs) and other coronal loops, as it propagates from the Sun into the heliosphere during May 2007. The 3-D propagation path of the largest interplanetary CME (ICME) is determined from the observations made by the SECCHI Heliospheric Imager (HI) on STEREO-A (HI-1/2A). Two parts of the CME are tracked through the SECCHI images, a bright loop and a V-shaped feature located at the rear of the event. We show that these two structures could be the result of line-of-sight integration of the light scattered by electrons located on a single flux rope. In addition to being imaged by HI, the CME is observed simultaneously by the plasma and magnetic field experiments on the Venus Express and MESSENGER spacecraft. The imaged loop and V-shaped structure bound, as expected, the flux rope observed in situ. The SECCHI images reveal that the leading loop-like structure propagated faster than the V-shaped structure, and a decrease in in situ CME speed occurred during the passage of the flux rope. We interpret this as the result of the continuous radial expansion of the flux rope as it progressed outward through the interplanetary medium. An expansion speed in the radial direction of ˜30 km s-1 is obtained directly from the SECCHI-HI images and is in agreement with the difference in speed of the two structures observed in situ. This paper shows that the flux rope location can be determined from white light images, which could have important space weather applications.

Rouillard, A. P.; Davies, J. A.; Forsyth, R. J.; Savani, N. P.; Sheeley, N. R.; Thernisien, A.; Zhang, T.-L.; Howard, R. A.; Anderson, B.; Carr, C. M.; Tsang, S.; Lockwood, M.; Davis, C. J.; Harrison, R. A.; Bewsher, D.; Fränz, M.; Crothers, S. R.; Eyles, C. J.; Brown, D. S.; Whittaker, I.; Hapgood, M.; Coates, A. J.; Jones, G. H.; Grande, M.; Frahm, R. A.; Winningham, J. D.

2009-07-01

13

Return to Venus of AKATSUKI, the Japanese Venus Orbiter  

Science.gov (United States)

Japanese Venus Climate Orbiter 'AKATSUKI' (PLANET-C) was proposed in 2001 with strong support by international Venus science community and approved as an ISAS mission soon after the proposal. AKATSUKI and ESA's Venus Express complement each other in Venus climate study. Various coordinated observations using the two spacecraft have been planned. Also participating scientists from US have been selected. Its science target is to understand the climate of Venus. The mission life we expected was more than 2 Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles' expansion was confirmed. AKATSUKI was put into the 3-axis stabilized mode in the initial operation from Uchinoura station and the critical operation was finished at 20:00JST on the same day. The malfunction, which happened during the Venus Orbit Insertion (VOI) on7 Dec, 2010 is as follows. We set all commands on Dec. 5. Attitude control for Venus orbit insertion (VOI) was automatically done on Dec. 6. Orbital maneuver engine (OME) was fired 08:49 JST on Dec. 7. 1min. after firing the spacecraft went into the occultation region and we had no telemetry, but we expected to continuous firing for 12min. Recording on the spacecraft told us later that, unfortunately the firing continued just 152sec. and stopped. The reason of the malfunction of the OME was the blocking of check valve of the gas pressure line to push the fuel to the engine. We failed to make the spacecraft the Venus orbiter, and it is rotating the sun with the orbital period of 203 days. As the Venus orbit the sun with the period of 225 days, AKATSUKI has a chance to meet Venus again in 5 or 6 years depending on the orbit correction plan. Let us summarize the present situation of AKATSUKI. Most of the fuel still remains. But the condition of the propulsion system is unclear. ISAS is examining various scenarios of second Venus orbit insertion depending on the conditions of the check valve and the OME. Thermal condition during the extended cruise phase is severe. The solar flux (W/m2) to which the spacecraft is exposed from May 21, 2010 (Launch date) to the end of 2016. We expected about 2600W/m2 in the Venus orbit, but it is exposed to more than 3600W/m2 at perihelion (0.6AU from the sun). The temperatures of the instruments exposed to space gradually increased as the spacecraft approaching the perihelion. We tried to minimize the number of instruments whose temperatures exceed the allowed upper limits by letting a certain side of the spacecraft face to the sun. After passing the perihelion every instruments have been working normally. The degradation of the reflectivity of the outer film (MLI) during the extended cruise may influence the temperature tendency. Laboratory tests to evaluate the degradation are ongoing. We operate the test maneuver of the OME in September and hopefully the orbit maneuver in November, which leads the spacecraft close to Venus in 2015. We will report the result in the presentation.

Nakamura, M.; Iwagami, N.; Satoh, T.; Taguchi, M.; Watanabe, S.; Takahashi, Y.; Imamura, T.; Suzuki, M.; Ueno, M.; Yamazaki, A.; Fukuhara, T.; Yamada, M.; Ishii, N.; Ogohara, K.

2011-12-01

14

AKATSUKI status after the Venus orbit insertion  

Science.gov (United States)

Japanese Venus Climate Orbiter 'AKATSUKI' (PLANET-C) was successfully launched at 06:58:22JST on May 21, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles' expansion was confirmed. AKATSUKI was put into the 3-axis stabilized mode in the initial operation from Uchinoura station and the critical operation was finished at 20:00JST on the same day. AKATSUKI will arrive at Venus on Dec 7, 2010. From the orbit around Venus, it will take pictures of the distribution of clouds and minor gas components at different wavelength by 4 cameras. These data will be analyzed to study the meteorology on Venus, especially the mechanism of the super-rotation of Venusian atmosphere which is still the top mystery of the Venus science. Simultaneous observation with ESA's Venus Express is highly expected to study the Venusian atmosphere. We will present the present status of AKATSUKI after the Venus orbit insertion with the latest results from the cameras.

Nakamura, M.; Ishii, N.; Imamura, T.; Ueno, M.; Yamazaki, A.; Satoh, T.; Suzuki, M.; Iwagami, N.; Taguchi, M.; Watanabe, S.; Takahashi, Y.; Fukuhara, T.; Ohtsuki, S.; PLANET-C Project Team

2010-12-01

15

Science requirements and description of the 1 ?m camera onboard the Akatsuki Venus Orbiter  

Science.gov (United States)

The 1 ?m camera onboard the Japanese Venus Mission/Akatsuki scheduled to arrive at Venus in 2015 or 2016 is described. In addition to its scientific goals, the optical and mechanical designs, the calibration procedures, and some results of feasibility studies are presented. Those studies are about the source of the contrast in the dayside image, the resolution of the H2O detection on the nightside surface, and a possibility of finding an active volcano.

Iwagami, N.; Takagi, S.; Ohtsuki, S.; Ueno, M.; Uemizu, K.; Satoh, T.; Sakanoi, T.; Hashimoto, G. L.

2011-06-01

16

Venus - summary and review of science research activities 1983-87  

Energy Technology Data Exchange (ETDEWEB)

The geology, geomorphology, and atmosphere of Venus are characterized on the basis of observations obtained with the Soviet Venera 15 and 16 spacecraft (including two international Vega balloon experiments), the Pioneer Venus Orbiter, and the Arecibo radio telescope during the period 1983-1986. Features discussed include impact craters, evidence of tectonic and volcanic activity, the high average age of the Venusian surface (apparently over 1 Gyr, indicating resurfacing rates much lower than on earth), and atmospheric temperature differences across the equator. 85 references.

Saunders, R.S.

1987-03-01

17

Comparative analysis of airglow emissions in terrestrial planets, observed with VIRTIS-M instruments on board Rosetta and Venus Express  

Science.gov (United States)

Airglow emissions are optimal processes to investigate the chemistry and dynamics in planetary atmospheres. In this study, we focus on the O2 and OH airglow emissions in Venus, Earth, and Mars atmospheres, which are controlled by chemical reactions common to the three planets. By studying these phenomena on Venus, Earth, and Mars using similar instruments, we are able to derive information about their photochemistry and the physical conditions of the atmospheres, but also to constrain the dynamics responsible for transport of atomic oxygen, ozone and other minor species. After a review of the nightglow emissions observed in the Venus atmosphere, we analyze the O2 and OH airglow emissions in the Earth's atmosphere observed during the 3 swing-bys of our planet by the Rosetta spacecraft. We also report the detection of the O2 nightglow emission in the Mars atmosphere, observed in February 2007 during the Rosetta fly-by of the planet. The airglow characteristics are in agreement with the measurements obtained from sensors on board Mars Express.

Migliorini, A.; Piccioni, G.; Capaccioni, F.; Filacchione, G.; Tosi, F.; Gérard, J.-C.

2013-09-01

18

INPOP08, a 4-D planetary ephemeris: From asteroid and time-scale computations to ESA Mars Express and Venus Express contributions  

CERN Multimedia

The latest version of the planetary ephemerides developed at the Paris Observatory and at the Besancon Observatory is presented here. INPOP08 is a 4-dimension ephemeris since it provides to users positions and velocities of planets and the relation between TT and TDB. Investigations leading to improve the modeling of asteroids are described as well as the new sets of observations used for the fit of INPOP08. New observations provided by the European Space Agency (ESA) deduced from the tracking of the Mars Express (MEX) and Venus Express (VEX) missions are presented as well as the normal point deduced from the Cassini mission. We show the huge impact brought by these observations in the fit of INPOP08, especially in terms of Venus, Saturn and Earth-Moon barycenter orbits.

Fienga, A; Morley, T; Manche, H; Kuchynka, P; Poncin-Lafitte, C Le; Budnik, F; Gastineau, M; Somenzi, L

2009-01-01

19

PLANET-C: Venus Climate Orbiter Mission of Japan  

Science.gov (United States)

Venus is one of the most attractive targets in the solar system when we seek to understand the formation of the terrestrial environment. Venus is our nearest neighbor, and has a size very similar to the Earth's; however, previous spacecraft missions discovered an extremely dense (~90 bar) and dry CO[2] atmosphere with H[2]SO[4]-H[2]O clouds floating at high altitudes, and exotic volcanic features covering the whole planet. The abundant gaseous CO[2] brings about a high atmospheric temperature (~740 K) near the surface via greenhouse effect. The atmospheric circulation is also much different from the Earth's. The mechanisms which sustain such conditions are unclear and considered to be the keys to understand the origin of the terrestrial environment. In spite of the many previous missions that explored Venus, such as the Venera, Pioneer Venus, Vega and Magellan, most of the fundamental questions raised so far still remain unsolved. The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at understanding the atmospheric circulation of Venus. Meteorological data will be obtained by globally mapping clouds and minor constituents successively with 4 cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing vertical structures of the atmosphere with radio science technique. The equatorial elongated orbit with westward revolution fits the observations of the movement and temporal variation of the Venusian atmosphere which rotates westward. The systematic, continuous imaging observations will provide us with an unprecedented large dataset of the Venusian meteorology. 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. The spacecraft will be launched and arrive at Venus in 2010, and will perform 2 years of operation.

Ueno, M.; Nakamura, M.; Imamura, T.; Iwagami, N.; Satoh, T.; Watanabe, S.; Taguchi, M.; Takahashi, Y.; Suzuki, M.; Yamada, M.; Hashimoto, G.; Kasaba, Y.; Fukuhara, T.; Uemizu, K.; Abe, T.; Ishii, N.; Oyama, K.

2006-08-01

20

The structure of Venus' middle atmosphere and ionosphere.  

UK PubMed Central (United Kingdom)

The atmosphere and ionosphere of Venus have been studied in the past by spacecraft with remote sensing or in situ techniques. These early missions, however, have left us with questions about, for example, the atmospheric structure in the transition region from the upper troposphere to the lower mesosphere (50-90 km) and the remarkably variable structure of the ionosphere. Observations become increasingly difficult within and below the global cloud deck (<50 km altitude), where strong absorption greatly limits the available investigative spectrum to a few infrared windows and the radio range. Here we report radio-sounding results from the first Venus Express Radio Science (VeRa) occultation season. We determine the fine structure in temperatures at upper cloud-deck altitudes, detect a distinct day-night temperature difference in the southern middle atmosphere, and track day-to-day changes in Venus' ionosphere.

Pätzold M; Häusler B; Bird MK; Tellmann S; Mattei R; Asmar SW; Dehant V; Eidel W; Imamura T; Simpson RA; Tyler GL

2007-11-01

 
 
 
 
21

Limb Altitude and the Southern Hemispheric Vortex Observed by Venus Monitoring Camera on VEX Orbiter  

Science.gov (United States)

The Venus Monitoring Camera (VMC) on European Space Agency's Venus Express orbiter has been collecting almost daily images at four wavelengths (365, 550, 980 and 1050 nm) since June 2006 with a few gaps during solar conjunctions. These data provide a nearly continuous record of the southern vortex (Limaye at al. 2009) that spans the entire hemisphere and reveal a dynamic, constantly evolving structure and showing a range of dynamical instability features in the central region. These instability features are also seen in the near infrared observations from the VIRTIS instrument on Venus Express (Luz et al. 2011). Some similarities between the Venus hemispheric vortex and a tropical cyclone have been previously noted (Suomi and Limaye, 1981; Limaye et al., 2009; 2011) and more have been discovered from the VMC observations. While the details of the spatial structure of the vortex is easily observed from the imaging observations at ultraviolet (VMC) and near infrared wavelengths (VIRTIS), the vertical structure is more difficult to determine from Venus Express. Here we present inferences about the vertical level obtained from the visible limb of the planet in VMC images. The altitude of the limb has been measured using full or near full disk images and depicts the altitude of the Venus cloud cover which comprises the vortex circulation. By precisely locating the limb location by fitting each limb profile in the VMC images, the average latitudinal profile of the limb altitude has been estimated. Although the pixel size of the images used is ~ 30-45 km, the large number of images (> 25,000) provides a very large sample of limb altitude determinations at each latitude between the equator and about 60° S latitude enabling sub-pixel variations of the limb altitude. The latitudinal profile of the limb altitude is similar to that inferred from the near infrared observations from VIRTIS (Ignatiev et al., 2009; Cottini et al., 2012) - high in low latitudes and low in polar latitudes and is consistent with the vortex structure. References Cottini, V., N.I. Ignatiev, G. Piccioni, P. Drossart, D. Grassi, W.J. Markiewicz (2012), Water vapor near the cloud tops of Venus from Venus Express/VIRTIS dayside data, Icarus, 217, 561-569. Ignatiev, N.I., D. V. Titov, G. Piccioni, P. Drossart, W. J. Markiewicz, V. Cottini, Th. Roatsch, M. Almeida, and N. Manoel, (2009), Altimetry of the Venus cloud tops from the Venus Express observations, J. Geophys. Res., DOI: 10.1029/2008JE003320. Limaye, S.S., J.P. Kossin, C. Rozoff, G. Piccioni, D.V. Titov, W.K. Markiewicz (2009) Vortex circulation on Venus: dynamical similarities with terrestrial hurricanes, Geophys. Res.Lett., 36, L04204, doi:10.1029/2008GL036093. Limaye, S., R.J. Krauss, D. Santek and W. Markiewicz (2011), Global Cloud Organization and Motions on Venus from the Venus Monitoring Camera on Venus Express, EPSC Abstracts, Vol. 6, EPSC-DPS2011-1230, 2011.T@ Luz, D., et al., "Venus's Southern Polar Vortex Reveals Precessing Circulation", published online on Science Express, 7 April 2011. DOI:10.1126/science.1201629. Suomi, V. E., and S. S. Limaye (1978), Venus: Further evidence of vortex circulation, Science, 201, 1009- 1011.

Limaye, Sanjay; Krauss, Robert; Markiewicz, Wojciech

2013-04-01

22

Venus Atmospheric Maneuverable Platform (VAMP)  

Science.gov (United States)

We have explored a possible new approach to Venus upper atmosphere exploration by applying Northrop Grumman (non-NASA) development programs to the challenges associated with Venus upper atmosphere science missions. Our concept is a low ballistic coefficient (science payloads to explore the Venus upper atmosphere. In this presentation we report results from our ongoing study and plans for future analyses and prototyping. We discuss the overall mission architecture and concept of operations from launch through Venus arrival, orbit, entry, and atmospheric science operations. We present a strawman concept of VAMP, including ballistic coefficient, planform area, percent buoyancy, inflation gas, wing span, vehicle mass, power supply, propulsion, materials considerations, structural elements, subsystems, and packaging. The interaction between the VAMP vehicle and the supporting orbiter will also be discussed. In this context, we specifically focus upon four key factors impacting the design and performance of VAMP: 1. Feasibility of and options for the deployment of the vehicle in space 2. Entry into the Venus atmosphere, including descent profile, heat rate, total heat load, stagnation temperature, control, and entry into level flight 3. Characteristics of flight operations and performance in the Venus atmosphere: altitude range, latitude and longitude access, day/night performance, aircraft performance (aerodynamics, power required vs. power available, propulsion, speed, percent buoyancy), performance sensitivity to payload weight 4. Science payload accommodation, constraints, and opportunities We discuss interdependencies of the above factors and the manner in which the VAMP strawman’s characteristics affect the CONOPs and the science objectives. We show how these factors provide constraints as well as enable opportunities for novel long duration scientific studies of the Venus upper atmosphere that support VEXAG goals 2 and 3.

Shapiro Griffin, Kristen L.; Sokol, D.; Dailey, D.; Lee, G.; Polidan, R.

2013-10-01

23

Venus volcanism  

Energy Technology Data Exchange (ETDEWEB)

Eruption styles and processes on the planets are known to be strongly influenced by such factors as gravity, temperature, and atmospheric characteristics. The ascent and eruption of magma on Venus in the current Venus environment must take into account the influence of the extreme surface temperatures (650-750 K) and pressures (40-100 bars) on these processes. Conditions on Venus will reduce the subsurface exsolution of volatiles and lead to a reduction of the possible range of explosive interactions with the atmosphere. Pyroclastic eruptions will be severely inhibited and continuous magma disruption by gas bubble growth may not occur at all unless the exsolved magma volatile content exceeds several weight percent. Recent US and USSR spacecraft missions and Earth-based radar observations are beginning to provide a view of the range of Venus volcanic features, including domes, cones, calderas, shields, and flows. The nature of many lava flows suggests that numerous eruptions have effusion rates exceeding common terrestrial rates and lying more in the range inferred for lunar basaltic flood eruptions (10/sup 4/-10/sup 5/m/sup 3//s). Shield volcanoes are often wide but are low (<2 km elevation) relative to those on Mars and the Earth. Volcano height depends in part on the depth of origin of the magma and the density contrast between the lava and the rocks between the source and the surface, both of which may be different on Venus. Correlations between volcanic style and tectonic structure are emerging.

Head, J.W.

1985-01-01

24

The Venus environment  

Energy Technology Data Exchange (ETDEWEB)

Attention is given to noble gases in planetary atmospheres, the photochemistry of the stratosphere of Venus, the chemistry of metastable species in the Venusian ionosphere, the Venus ionosphere at grazing incidence of solar radiation, disappearing ionospheres on the nightside of Venus, and the observed composition of the ionosphere of Venus. Other investigations considered are concerned with the predicted electrical conductivity between 0 and 80 km in the Venusian atmosphere, sulfuric acid vapor and other cloud-related gases in the Venus atmosphere, the composition and vertical structure of the lower cloud deck on Venus, amorphous sulfur as the ultraviolet absorber on Venus, and polarization studies of the Venus UV contrasts. A description is provided of topics related to temporal variability of ultraviolet cloud features in the Venus stratosphere, zonal mean circulation at the cloud level on Venus, the influence of thermospheric winds on exospheric hydrogen on Venus, and an analysis of Venus gravity data.

1982-08-01

25

Venus reconsidered.  

UK PubMed Central (United Kingdom)

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.

Kaula WM

1995-12-01

26

Transient Structures and Stream Interaction Regions in the Solar Wind: Results from EISCAT Interplanetary Scintillation, STEREO HI and Venus Express ASPERA-4 Measurements  

CERN Document Server

We discuss the detection and evolution of a complex series of transient and quasi-static solar wind structures in the days following the well-known comet 2P / Encke tail disconnection event in April 2007. The evolution of transient solar wind structures ranging in size from 106 km was characterized using one-minute time resolution observation of Interplanetary Scintillation (IPS) made using the European Incoherent SCA Tter (EISCA T) radar system. Simultaneously, the global structure and evolution of these features was characterized by the Heliospheric Imagers (HI) on the Solar TERrestrial RElations Observatory (STEREO) spacecraft, placing the IPS observations in context. Of particular interest was the observation of one transient in the slow wind apparently being swept up and entrained by a Stream Interaction Region (SIR). The SIR itself was later detected in-situ at Venus by the Analyser of Space Plasma and Energetic Atoms (ASPERA-4) instrument on the Venus Express (VEX) spacecraft. The availability of such...

Dorrian, Gareth; Davies, Jackie; Rouillard, Alexi; Fallows, Richard; Whittaker, Ian; Brown, Daniel; Harrison, Richard; Davis, Chris; Grande, Manuel; 10.1007/s11207-010-9599-z

2012-01-01

27

Japanese Venus Climate Orbiter in 2010  

Science.gov (United States)

Venus Climate Orbiter (VCO"FProject Code Planet-C) is the first Japanese Venus orbiter to be launched in 2010. It aims at studying the atmospheric dynamics of Venus. In this talk we will report its engineering aspect to meet its science purposes, and also present the present status of the VCO development. We have finished the Proto-Model integration test of major components of VCO in December 2007. In March 2008, we finished the CDR for the phase-up (to Phase D). The flight model development will be finalized by 2009 and the final integration test will be done during whole 2009.

Nakamura, M.; Ishii, N.; Satoh, T.; Abe, T.; Imamura, T.; Suzuki, M.; Ueno, M.

2008-12-01

28

Morphology and dynamics of the Venus upper cloud layer  

Science.gov (United States)

Venus is completely covered by a thick cloud layer whose upper part is composed of sulfuric acid and some unknown aerosols1. The cloud tops are in fast retrograde rotation (super-rotation), but what is driving this super-rotation is unknown2. Here we report observations of Venus with the Venus Monitoring Camera3 (VMC) on board the Venus Express spacecraft. Taking advantage of the VMC high resolution imaging and the polar orbit we investigate both global and small scale properties of these clouds, their temporal and latitudinal variations, and derive wind velocities. The Southern polar region is highly variable and can change dramatically on time scales as short as one day, perhaps arising from the injection of SO2 into the mesosphere. The convective cells in the vicinity of the sub-solar point are much smaller than previously inferred4,5,6, which we interpret as indicating that they are confined to the upper cloud layer, contrary to previous conclusions7,8, but consistent with more recent study9. (1) Esposito, L.W. et al., in Venus, pp. 484-564, 1983, (2) Limaye, S. S., 2007, J. Geophys. Res., 112, 2007, (3) Markiewicz, W.J. et al., Planet. Space Sci., 55, 1701-1711, 2007, (4) Murray, B.C., et al., Science 183, 1307-1315 (1974), (5) Rossow, W.B. et al., J. Geophys. Res. 85, 8107-8128, 1980, (6) Covey, C.C. and G. Schubert, Nature, 290, 17-20, 1981, (7) Baker II, R.D. and G. Schubert, Nature, 355, 710-712, 1992, (8) Belton, M.J.S. et al., J. Atmos. Sci.. 33, 1394-1417, 1976, (9) Baker, R.D., G. Schubert, and P.W. Jones, J. Geophy. Res., 104, Issue E2, p. 3815-3832, 1999.

Markiewicz, Wojciech; Titov, Dmitri; Limaye, Sanjay; Moissl, Richard; Ignatiev, Nikolay; Basilevsky, A. T.; Shalygin, E. V.; Kreslavsky, M. A.; Khatuntsev, Igor; Keller, Horst Uwe; Jaumann, Ralf; Thomas, Nicolas; Michalik, Harald

29

Venus' 5577 Å Oxygen Green Line: An Auroral Process?  

Science.gov (United States)

Venus' oxygen green line at 5577 Å is a highly variable feature on the Venusian nightside. It was first seen in 1999 by Slanger et al. (Science 291, 463, 2001) and found to be stronger than the terrestrial green line. It subsequently decreased in strength and was undetectable after 2004. It was seen again in 2012 by Gray et al. (Icarus, submitted, 2013) after a coronal mass ejection (CME) impacted Venus in April 2012 and after an X-flare and CME impact in July 2012. They found that for every detection from 1999 - 2004, a high energy flare, CME, or strong solar wind stream occurred within one week prior to each observation. For observations where the green line was not detected, there were no solar flares or CMEs. They propose that solar flares and/or CMEs are responsible for green line emission. The process for emission is still unknown, but they suggest two possibilities. First, increased levels of EUV photons from flares may increase photodissocation of dayside molecules, which are then transported to the nightside, to a large enough level where green line emission becomes detectable. Second, electron precipitation from solar flares and CMEs may have a high enough energy and density to penetrate deep in atmosphere (electron density profiles on the Venusian nightside, obtained by the Venus Radio Science Experiment on Venus Express, before and after solar flares and CMEs. Here we present the result of these comparisons. This research is funded by NASA's Earth and Space Science Fellowship, NNX12AM70H.

Gray, Candace L.; Chanover, N.; Slanger, T.; Molaverdikhani, K.; Häusler, B.; Tellmann, S.; Peter, K.

2013-10-01

30

Statistical study of solar wind ion precipitation on Venus  

Science.gov (United States)

Solar wind ions are known to precipitate onto the atmosphere of Mars. The large gyroradii of hot particles in the magnetosheath compared to the size of the induced magnetosphere/magnetic barrier make it possible for the ions to gyrate through the barrier. Venus interacts with the solar wind in a similar way and an induced magnetosphere is formed around the planet. However, the scale-sizes are different and precipitation of solar ions onto the atmosphere of Venus is not frequently occurring. We use ion data from ASPERA-4 on Venus Express to investigate how often precipitation of protons and alpha-particles occurs on Venus. With a statistical approach we also estimate the net inflow of solar wind ions onto the ionosphere of Venus. We highlight the differences between solar wind ion precipitation at Mars and Venus and suggest possible explanations for the observed differences.

Stenberg, Gabriella; Nilsson, Hans; Barabash, Stas; Futaana, Yoshifumi; Fedorov, Andrei

2013-04-01

31

High Temperature Mechanisms for Venus Exploration  

Science.gov (United States)

Future Venus missions, including New Frontiers Venus In-Situ Explorer and three Flagship Missions - Venus Geophysical Network, Venus Mobile Explorer and Venus Surface Sample Return all focus on searching for evidence of past climate change both on the surface and in the atmospheric composition as well as in the interior dynamics of the planet. In order to achieve these goals and objectives, many key technologies need to be developed for the Venus extreme environment. These key technologies include sample acquisition systems and other high-temperature mechanisms and mobility systems capable of extended operation when directly exposed to the Venus surface or lower atmosphere environment. Honeybee Robotics has developed two types of high temperature motors, the materials and components in both motors were selected based on the requirement to survive temperatures above a minimum of 460° C, at earth atmosphere. The prototype Switched Reluctance Motor (SRM) has been operated non-continuously for over 20 hours at Venus-like conditions (460° C temperature, mostly CO2 gas environment) and it remains functional. A drilling system, actuated by two SRMs was tested in Venus-like conditions, 460° C temperature and mostly CO2 gas environment, for more than 15 hours. The drill successfully completed three tests by drilling into chalk up to 6 inches deep in each test. A first generation Brushless DC (BLDC) Motor and high temperature resolver were also tested and the feasibility of the designs was demonstrated by the extended operation of both devices under Venus-like condition. Further development of the BLDC motor and resolver continues and these devices will, ultimately, be integrated into the development of a high temperature sample acquisition scoop and high temperature joint (awarded SBIR Phase II in October, 2007). Both the SR and BLDC motors will undergo extensive testing at Venus temperature and pressure (TRL6) and are expected to be mission ready before the next New Frontiers AO release. Scalable high temperature motor, resolver and bearing developments allow for creation of long lasting sample acquisition systems, booms, robot arms and even mobility systems that operate outside of an environment-controlled landed platform on the surface of Venus. The SR and BLDC motors are no longer expected to limit the life of Venus surface operations. With the accompanying high temperature bearing and other mechanisms development, surface operations will be limited only by available power. Therefore, the motor and resolver's capability to survive for hours (and potentially longer) in the environment is a major benefit to future Venus science missions and they also allow time for communication ground loops to optimize sample target selection and the possibility for acquiring multiple samples from the surface. The extreme temperature motors, resolver and other high temperature mechanisms therefore revolutionize the exploration of Venus.

Ji, Jerri; Narine, Roop; Kumar, Nishant; Singh, Sase; Gorevan, Steven

32

Exploring the Planets: Venus  

Science.gov (United States)

This site contains most of the up-to-date information known about the planet Venus, including mean distance from Sun, length of year, rotation period, mean orbital velocity, inclination of axis, average temperature (day and night), and diameter. Many discoveries about Venus have been made using Earth-based radio telescopes, however the images of Venus in this exhibit were collected by the Magellan spacecraft. Magellan used radar to produce the first high-resolution global map of Venus. Since Venus has no water erosion and little wind, volcanic eruptions are a major force reshaping the landscape. Geologic forces at work beneath the crust create mountains, rifts, and patterns of fractures, while the sluggish winds sculpt the surface in subtler ways but many mysteries remain. This site includes numerous images of the planet.

33

Salt tectonics on Venus  

Energy Technology Data Exchange (ETDEWEB)

The discovery of a surprisingly high deuterium/hydrogen ratio on Venus immediately led to the speculation that Venus may have once had a volume of surface water comparable to that of the terrestrial oceans. The authors propose that the evaporation of this putative ocean may have yielded residual salt deposits that formed various terrain features depicted in Venera 15 and 16 radar images. By analogy with models for the total evaporation of the terrestrial oceans, evaporite deposits on Venus should be at least tens to hundreds of meters thick. From photogeologic evidence and in-situ chemical analyses, it appears that the salt plains were later buried by lava flows. On Earth, salt diapirism leads to the formation of salt domes, anticlines, and elongated salt intrusions - features having dimensions of roughly 1 to 100 km. Due to the rapid erosion of salt by water, surface evaporite landforms are only common in dry regions such as the Zagros Mountains of Iran, where salt plugs and glaciers exist. Venus is far drier than Iran; extruded salt should be preserved, although the high surface temperature (470/sup 0/C) would probably stimulate rapid salt flow. Venus possesses a variety of circular landforms, tens to hundreds of kilometers wide, which could be either megasalt domes or salt intrusions colonizing impact craters. Additionally, arcurate bands seen in the Maxwell area of Venus could be salt intrusions formed in a region of tectonic stress. These large structures may not be salt features; nonetheless, salt features should exist on Venus.

Wood, C.A.; Amsbury, D.

1986-05-01

34

Venus sky light polarization  

Energy Technology Data Exchange (ETDEWEB)

The computations of the polarization degree and intensity of radiation near the Venus surface are described. A purely gaseous plane layer with physical parameters corresponding to those of the lower 20 km of the Venus atmosphere has been chosen as a model of the subcloud atmosphere. It is shown that the radiation field near the surface is practically determined only by the amount of absorbing components in the lower atmospheric layers. The conclusion is drawn that simultaneous polarimetric and photometric experiments should make it possible to determine the absorbing components in the Venus atmosphere, such as water vapour and finely dispersed aerosol.

Loskutov, V.M.; Minin, I.N.; Selyakov, K.I.

1984-10-01

35

Magellan Mission to Venus  

Science.gov (United States)

The Magellan Mission to Venus Home is now available at NASA's Jet Propulsion Lab. The Magellan mission ended with a dramatic plunge into the atmosphere of Venus, the first time an operating spacecraft has ever been intentionally crashed into a planet. On October 11, 1994, Magellan's thrusters were fired in four sequences to lower its orbit into the atmosphere of Venus for its final experiment -- to gather data on Venus' high atmosphere. Within two days after these maneuvers, the spacecraft became caught in the atmosphere and plunged to the surface. Although most of Magellan will be vaporized during the fiery descent, some sections of the spacecraft will probably hit the planet's surface. The latest updates on Magellan's status -- as well as a comprehensive gallery of images and information from the five-year mission -- are available on the home page.

36

Astrobiology and Venus exploration  

Science.gov (United States)

For hundreds of years prior to the space age, Venus was considered among the most likely homes for extraterrestrial life. Since planetary exploration began, Venus has not been considered a promising target for Astrobiological exploration. However, Venus should be central to such an exploration program for several reasons. At present Venus is the only other Earth-sized terrestrial planet that we know of, and certainly the only one we will have the opportunity to explore in the foreseeable future. Understanding the divergence of Earth and Venus is central to understanding the limits of habitability in the inner regions of habitable zones around solar-type stars. Thus Venus presents us with a unique opportunity for putting the bulk properties, evolution and ongoing geochemical processes of Earth in a wider context. Many geological and meteorological processes otherwise active only on Earth at present are currently active on Venus. Active volcanism most likely affects the climate and chemical equilibrium state of the atmosphere and surface, and maintains the global cloud cover. Further, if we think beyond the specifics of a particular chemical system required to build complexity and heredity, we can ask what general properties a planet must possess in order to be considered a possible candidate for life. The answers might include an atmosphere with signs of flagrant chemical disequilibrium and active, internally driven cycling of volatile elements between the surface, atmosphere and interior. At present, the two planets we know of which possess these characteristics are Earth and Venus. Venus almost surely once had warm, habitable oceans. The evaporation of these oceans, and subsequent escape of hydrogen, most likely resulted in an oxygenated atmosphere. The duration of this phase is poorly understood, but during this time the terrestrial planets were not isolated. Rather, due to frequent impact transport, they represented a continuous environment for early microbial life. Life, once established in the early oceans of Venus, may have migrated to the clouds which, on present day Venus, may represent a habitable niche. Though highly acidic, this aqueous environment enjoys moderate temperatures, surroundings far from chemical equilibrium, and potentially useful radiation fluxes. Observations of unusual chemistry in the clouds, and particle populations that are not well characterized, suggest that this environment must be explored much more fully before biology can be ruled out. A sulfur-based metabolism for cloud-based life on Venus has recently been proposed (Schulze-Makuch et al., 2004). While speculative, these arguments, along with the discovery of terrestrial extremophile organisms that point toward the plausibility of survival in the Venusian clouds, establish the credibility of astrobiological exploration of Venus. Arguments for the possible existence of life on Mars or Europa are, by convention and repetition, seen as more mainstream than arguments for life elsewhere, but their logical status is similar to plausibility arguments for life on Venus. With the launch of COROT in 2006 and Kepler in 2008 the demographics of Earth-sized planets in our galaxy should finally become known. Future plans for a Terrestrial Planet Finder or Darwin-type space-based spectrograph should provide the capability of studying the atmospheric composition and other properties of terrestrial planets. One of the prime rationales for building such instruments is the possibility of identifying habitable planets or providing more generalized observational constraints on the habitable zones of stellar systems. Given the prevalence of CO2 dominated atmospheres in our own solar system, it is quite likely that a large fraction of these will be Venus-like in composition and evolutionary history. We will be observing these planets at random times in their evolution. In analogy with our own solar system, it is just as likely that we will find representatives of early Venus and early Earth type planets from the first 2 billion years of their evolution as i

Grinspoon, David H.; Bullock, Mark A.

37

The galileo venus encounter.  

UK PubMed Central (United Kingdom)

The Galileo spacecraft passed Venus on its way to Jupiter on 10 February 1990, less than 4 months after launch from Earth aboard the shuttle Atlantis. Because Galileo's instruments were selected for broad-based planetary exploration, the spacecraft was able to obtain a wide range of measurements during the Venus encounter. Together with ground-based observations conducted during the encounter, these observations have yielded more accurate information about the planet's plasma environment, cloud patterns, and the possible existence of lightning.

Johnson TV; Yeates CM; Young R; Dunne J

1991-09-01

38

Mercury, Venus, and Earth!  

Science.gov (United States)

You will compare and contrast Mercury, Venus, and Earth. While looking at these different websites, use the information to fill in your handout of a column chart and on the back answer the questions you are asked on here. First view this website and record on your chart the distance from the sun Mercury,Venus, and Earth are. Now, learn about Mercury! What is the surface ...

Bschiffer

2009-10-21

39

Limb imaging of the Venus O2 visible nightglow with the Venus Monitoring Camera  

CERN Document Server

We investigated the Venus O2 visible nightglow with imagery from the Venus Monitoring Camera on Venus Express. Drawing from data collected between April 2007 and January 2011, we study the global distribution of this emission, discovered in the late 70s by the Venera 9 and 10 missions. The inferred limb-viewing intensities are on the order of 150 kiloRayleighs at the lower latitudes and seem to drop somewhat towards the poles. The emission is generally stable, although there are episodes when the intensities rise up to 500 kR. We compare a set of Venus Monitoring Camera observations with coincident measurements of the O2 nightglow at 1.27 {\\mu}m made with the Visible and Infrared Thermal Imaging Spectrometer, also on Venus Express. From the evidence gathered in this and past works, we suggest a direct correlation between the instantaneous emissions from the two O2 nightglow systems. Possible implications regarding the uncertain origin of the atomic oxygen green line at 557.7 nm are noted.

Muñoz, A García; Sánchez-Lavega, A; Markiewicz, W J; Titov, D V; Witasse, O; Opitz, A

2013-01-01

40

Magellan: The Unveiling of Venus.  

Science.gov (United States)

In the late 1970s and early 1980s, the United States and the Soviet Union sent the Pioneer Venus and Venera spacecraft, respectively, to study Venus more closely and to image its surface with radar. These missions have answered many questions about Venus,...

1989-01-01

 
 
 
 
41

Overview of Venus orbiter, Akatsuki  

Science.gov (United States)

The Akatsuki spacecraft of Japan was launched on May 21, 2010. The spacecraft planned to enter a Venus-encircling near-equatorial orbit in December 7, 2010; however, the Venus orbit insertion maneuver has failed, and at present the spacecraft is orbiting the Sun. There is a possibility of conducting an orbit insertion maneuver again several years later. The main goal of the mission is to understand the Venusian atmospheric dynamics and cloud physics, with the explorations of the ground surface and the interplanetary dust also being the themes. The angular motion of the spacecraft is roughly synchronized with the zonal flow near the cloud base for roughly 20 hours centered at the apoapsis. Seen from this portion of the orbit, cloud features below the spacecraft continue to be observed over 20 hours, and thus the precise determination of atmospheric motions is possible. The onboard science instruments sense multiple height levels of the atmosphere to model the three-dimensional structure and dynamics. The lower clouds, the lower atmosphere and the surface are imaged by utilizing near-infrared windows. The cloud top structure is mapped by using scattered ultraviolet radiation and thermal infrared radiation. Lightning discharge is searched for by high speed sampling of lightning flashes. Night airglow is observed at visible wavelengths. Radio occultation complements the imaging observations principally by determining the vertical temperature structure.

Nakamura, M.; Imamura, T.; Ishii, N.; Abe, T.; Satoh, T.; Suzuki, M.; Ueno, M.; Yamazaki, A.; Iwagami, N.; Watanabe, S.; Taguchi, M.; Fukuhara, T.; Takahashi, Y.; Yamada, M.; Hoshino, N.; Ohtsuki, S.; Uemizu, K.; Hashimoto, G. L.; Takagi, M.; Matsuda, Y.; Ogohara, K.; Sato, N.; Kasaba, Y.; Kouyama, T.; Hirata, N.; Nakamura, R.; Yamamoto, Y.; Okada, N.; Horinouchi, T.; Yamamoto, M.; Hayashi, Y.

2011-05-01

42

Sox10-Venus mice: a new tool for real-time labeling of neural crest lineage cells and oligodendrocytes  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background While several mouse strains have recently been developed for tracing neural crest or oligodendrocyte lineages, each strain has inherent limitations. The connection between human SOX10 mutations and neural crest cell pathogenesis led us to focus on the Sox10 gene, which is critical for neural crest development. We generated Sox10-Venus BAC transgenic mice to monitor Sox10 expression in both normal development and in pathological processes. Results Tissue fluorescence distinguished neural crest progeny cells and oligodendrocytes in the Sox10-Venus mouse embryo. Immunohistochemical analysis confirmed that Venus expression was restricted to cells expressing endogenous Sox10. Time-lapse imaging of various tissues in Sox10-Venus mice demonstrated that Venus expression could be visualized at the single-cell level in vivo due to the intense, focused Venus fluorescence. In the adult Sox10-Venus mouse, several types of mature and immature oligodendrocytes along with Schwann cells were clearly labeled with Venus, both before and after spinal cord injury. Conclusions In the newly-developed Sox10-Venus transgenic mouse, Venus fluorescence faithfully mirrors endogenous Sox10 expression and allows for in vivo imaging of live cells at the single-cell level. This Sox10-Venus mouse will thus be a useful tool for studying neural crest cells or oligodendrocytes, both in development and in pathological processes.

Shibata Shinsuke; Yasuda Akimasa; Renault-Mihara Francois; Suyama Satoshi; Katoh Hiroyuki; Inoue Takayoshi; Inoue Yukiko U; Nagoshi Narihito; Sato Momoka; Nakamura Masaya; Akazawa Chihiro; Okano Hideyuki

2010-01-01

43

The clouds of Venus  

International Nuclear Information System (INIS)

[en] The current state of knowledge of the Venusian clouds is reviewed. The visible clouds of Venus are shown to be quite similar to low level terrestrial hazes of strong anthropogenic influence. Possible nucleation and particle growth mechanisms are presented. The Pioneer Venus experiments that emphasize cloud measurements are described and their expected findings are discussed in detail. The results of these experiments should define the cloud particle composition, microphysics, thermal and radiative heat budget, rough dynamical features and horizontal and vertical variations in these and other parameters. This information should be sufficient to initialize cloud models which can be used to explain the cloud formation, decay, and particle life cycle. (Auth.)

1977-01-01

44

The European Space Agency's Planetary Science Archive (PSA)  

Science.gov (United States)

The Planetary Science Archive (PSA), available at http://archives.esac.esa.int/psa, represents the central repository for all science data returned by ESA's planetary missions. PSA provides support for data producers and end users of the data, aiming to maximize its long-term usability and access after the mission itself is complete. The repository contains data from all of ESA's planetary explorers, from Giotto through to the ongoing Mars Express, Venus Express and Rosetta missions.

Heather, D.; Barthelemy, M.; Szumlas, M.; Arviset, C.; Osuna, P.

2012-09-01

45

Mercury and Venus  

Science.gov (United States)

Students explore Mercury and Venus, the first and second planets nearest the Sun. They learn about the planets' characteristics, including their differences from Earth. Students also learn how engineers are involved in the study of planets by designing equipment and spacecraft to go where it is too dangerous for humans.

Integrated Teaching And Learning Program

46

Present Status of Janaese Venus Climate Orbiter  

Science.gov (United States)

The start of the Japanese Venus Exploration program was in 2001, and last year (2006) we moved it to Phase C after PDR in August.We would like to report the present status of our Venus Climate Orbiter. Planet-C is the project name in ISAS/JAXA. The launch vehicle is changed from M-V to H-IIA. It will be launched from Tanegashima Space Center (TNSC) in Kagoshima. With this modification, we changed some minor design of the spacecraft and the total weight is slightly heavier than before, but the basic design has not been modified. The launch window will be kept in summer in 2010 and it will arrive at Venus in December 2010. The spacecraft will be directly put into the interplanetary orbit. Now we are preparing the Mechanical and Thermal engineering Model (MTM) which will end in middle of 2007 and will shake it and do the thermal vacuum test. Later this model will be modified to the flight model and the final integration test will be in 2009 which takes 1 year. Development of all the science instruments are going well. The first integration test of science instruments will be in August this year. We can report the results of it in the meeting.

Nakamura, M.; Imamura, T.; Ishii, N.; Satoh, T.; Abe, T.; Ueno, M.; Suzuki, M.; Yamazaki, A.

2007-08-01

47

Transit Observations of Venus's Atmosphere in 2012 from Terrestrial and Space Telescopes as Exoplanet Analogs  

Science.gov (United States)

We extensively observed the 8 June 2012 transit of Venus from several sites on Earth; we provide this interim status report about this and about two subsequent ToVs observed from space. From Haleakala Obs., we observed the entire June transit over almost 7 h with a coronagraph of the Venus Twilight Experiment B filter) and with a RED Epic camera to compare with simultaneous data from ESA's Venus Express, to study the Cytherean mesosphere; from Kitt Peak, we have near-IR spectropolarimetry at 1.6 µm from the aureole and during the disk crossing that compare well with carbon dioxide spectral models; from Sac Peak/IBIS we have high-resolution imaging of the Cytherean aureole for 22 min, starting even before 1st contact; from Big Bear, we have high-resolution imaging of Venus's atmosphere and the black-drop effect through 2nd contact; and we had 8 other coronagraphs around the world. For the Sept 21 ToV as seen from Jupiter, we had 14 orbits of HST to use Jupiter's clouds as a reflecting surface to search for an 0.01% diminution in light and a differential drop that would result from Venus's atmosphere by observing in both IR/UV, for which we have 170 HST exposures. As of this writing, preliminary data reduction indicates that variations in Jovian clouds and the two periods of Jupiter's rotation will be too great to allow extraction of the transit signal. For the December 20 ToV as seen from Saturn, we had 22 hours of observing time with VIMS on Cassini, for which we are looking for a signal of the 10-hr transit in total solar irradiance and of Venus's atmosphere in IR as an exoplanet-transit analog. Our Maui & Sac Peak expedition was sponsored by National Geographic Society's Committee for Research and Exploration; HST data reduction by NASA: HST-GO-13067. Some of the funds for the carbon dioxide filter for Sac Peak provided by NASA through AAS's Small Research Grant Program. We thank Rob Ratkowski of Haleakala Amateur Astronomers; Rob Lucas, Aram Friedman, Eric Pilger, Stan Truitt, and Steve Bisque/Software Bisque for Haleakala support/operations; Vasyl Yurchyshyn and Joseph Gangestad '06 of The Aerospace Corp. at Big Bear Solar Obs; LMSAL and Hinode science/operations team.

Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Penn, M. J.; Jaeggli, S. A.; Galayda, E.; Reardon, K. P.; Widemann, T.; Tanga, P.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson, P. D.; Dantowitz, R.

2013-06-01

48

Perspectives of the bistatic radar and occultation studying of the Venus atmosphere and surface  

Science.gov (United States)

Studying the physical properties of Venus surface and subsurface structures is an important direction in the space research. The first aim of this contribution is to present some results of reanalysis of the bistatic radar and occultation experiments provided using Venera-9, 10 and 15, 16 satellites. Comparison is made with Magellan and Venus Express bistatic radar missions. Bistatic radio images of the Venus surface is compared with monostatic radio images obtained by the Soviet and USA orbiters. The second aim consists in introducing new methods for investigation of the layered structure of the Venus atmosphere and measuring parameters of Venus surface and subsurface structures using the bistatic radar technology. The first bistatic radar measurements with spatial resolution ~ 10-20 km have been carried out during autumn of 1975 year in the five Venus equatorial regions using the Venera-9 and 10 satellites. Small roughness and, in general, plain character of relief in the investigated regions have been revealed. In 1983, the satellites Venera 15 and 16 have carried out new bistatic radar experiments with spatial resolution in the interval 5 - 10 km. New information on the large-scale topography and roughness of small-scale relief has been obtained in Northern polar areas of the planet. Some features have been detected. 1. The significant variations of the reflectivity ~ 2-4 times were found in the first region. The second area of reflectivity magnitude was far below (by three - four times) the previously measured values in the equatorial regions of Venus. These significant reflectivity variations may be related to changes in the conductivity of the ground. 2. Extremely small values roughness with rms of slopes ~ 0.20 were recorded in the northern area. 3. Both the bending angle and the reflection coefficient were determined in the experiment from the measured frequency difference between the direct and the reflected signals as a function of time, using the orbital data. New methods developed by analysis of the experimental data obtained using high-stability radio fields of the Earth's navigational satellites are introduced. For investigations of the layered structures of the Venus atmosphere a new eikonal acceleration/intensity technique is proposed. This technique allows: (1) one frequency high-precision measuring the total absorption of radio waves in the atmosphere; (2) estimating vertical gradients of the refractivity, and determining the height, slope, and horizontal displacement of the atmospheric and ionospheric layers; (3) a criterion is introduced for identification of the internal waves in the Venus atmosphere. To obtain the information on the planetary subsurface structure up to depth 1 km it is necessary to use radio waves in the Low Frequency (LF), Medium Frequency (MF), or High Frequency (HF) bands with wavelength from 1 m up 300 m. The depth of radio sounding is proportional to the wavelength, the intensity of the radio-emission source, and depends on the conductivity of the ground. The bistatic subsurface remote sensing of the planet can be achieved using powerful Earth based transmitters, and/or sporadic radio emission of the Sun and other space radio sources. The work was partly supported by Program 22 of Presidium of Russian Academy of Sciences.

Pavelyev, Alexander; Gubenko, Vladimir; Matyugov, Stanislav; Yakovlev, Oleg

2013-04-01

49

Tectonics and composition of Venus  

Energy Technology Data Exchange (ETDEWEB)

The uncompressed density of Venus is a few percent less than the Earth. The high upper mantle temperature of Venus deepens the eclogite stability field and inserts a partial melt field. A thick basaltic crust is therefore likely. The anomalous density of Venus relative to the progression from Mercury to Mars may therefore have a tectonic rather than a cosmochemical explanation. There may be no need to invoke differences in composition or oxidization state.

Anderson, D.L.

1980-01-01

50

Magellan unveils Venus  

Energy Technology Data Exchange (ETDEWEB)

Images obtained after an eight month Venusian year, during which the radar mapper Magellan surveyed nearly all of Venus, are described. It is observed that, instead of rigid plates moving as on earth, Venus appears covered with plumes of hot upwellings that dome out over hundreds or thousands of kilometers, feeding a continuous volcanic resurfacing of the planet. Although the Venusian surface is changing relatively rapidly by vulcanism and tectonic processes, the Magellan images make it clear that erosion is very slow. It is seen that some of the lava flows are highly fluid, etching narrow channels for hundreds of kilometers through the crust. Magellan also revealed some peculiarly Venusian formations, the tesserated areas where ridges and faults crosshatch the region into large blocks.

Lerner, E.J.

1991-07-01

51

Venus nightside ionospheric holes  

Science.gov (United States)

Pioneer Venus Orbiter (PVO) measured the ionosphere and atmosphere of Venus for 13 years 10 months yielding a rich data set of archived data from a complement of instruments. One particularly striking feature seen was the occurrence of deep localized nightside ionization depletions commonly called holes. A number of theories have been put forth to explain their observed characteristics, but there is still no consensus on their source. A possibly related phenomenon in the Venus nightside ionosphere is the occurrence of "disappearing" or severely disturbed ionospheres characterized by deep, widespread plasma depletions in almost the entire nightside. This paper reexamines the holes and "disappearing ionospheres" and other characteristics of the nightside ionosphere during solar maximum using a more extensive database than earlier studies. The hole locations, occurrences, and dependencies on solar wind dynamic pressure (Psw) are analyzed, and a comparison is made with earlier studies. It is shown that there is no Psw threshold for holes to occur and at Psw values greater than ˜9 nPa, hole occurrence decreases while the occurrence of severely disturbed orbits increases, suggesting that holes may evolve into severely disturbed orbits. Other characteristics of the nightside are shown to be influenced by solar wind pressure to varying degrees; for example, the density integrated along the orbit path below the ionopause, and the median density at low altitudes exhibit strong inverse correlation with Psw, while the peak density is nearly independent of Psw.

Hoegy, Walter R.; Grebowsky, Joseph M.

2010-12-01

52

Status of the VENUS ECR ion source  

International Nuclear Information System (INIS)

[en] The status and future developments of the 28-GHz VENUS (Versatile ECR for Nuclear Science) Electron Cyclotron Resonance (ECR) ion source after the two years repair are presented. The fully superconducting ECR ion source VENUS serves as prototype injector for the Facility for Rare Isotope Beams (FRIB) project at Michigan State University (MSU) as well as injector ion source for the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory (LBNL). As such the source has produced many record beams of high charge state ions as well as high-intensity, medium charge state ions. As the FRIB project has now entered the preliminary design phase, LBNL is involved in the design of two new VENUS-like ECR injector ion sources for the FRIB facility. This paper will review the design changes for the FRIB injector, which will allow the installation of the FRIB injector source on a 100 kV platform. In support of the FRIB ion sources design systematic measurements of the heat load due to Bremsstrahlung from the plasma for different magnetic fields have been performed and are presented. Finally, a possible future upgrade path for the FRIB injector using an advanced Nb3Sn magnet structure is described. The paper is followed by the slides of the presentation. (authors)

2012-01-01

53

The VENUS detector at TRISTAN  

International Nuclear Information System (INIS)

The design of the VENUS detector is described. In this paper, emphasis is placed on the central tracking chamber and the electromagnetic shower calorimeters. Referring to computer simulations and test measurements with prototypes, the expected performance of our detector system is discussed. The contents are, for the most part, taken from the VENUS proposal /2/. (author).

1983-01-01

54

From CERN to VENUS Express  

CERN Multimedia

Participants in the 'Schweizer Jugendforscht' projects at CERN under the supervision of Günther Dissertori, professor at the Swiss Federal Institute of Technology (ETH Zürich) and other members of ETH Zürich, Werner Lustermann and Michael Dittmar. In Switzerland, as in many other countries, this year has seen a long list of activities, celebrating the centenary of Einstein's 'Annus mirabilis'. Having formerly employed Einstein, the Swiss Federal Institute of Intellectual Property in Bern made its contribution by sponsoring a special 'study week' for young high-school students, under the tutorship of 'Schweizer Jugendforscht', an organisation which supports the scientific activities of very talented young people. The organisers chose 'Mission to Jupiter's Moon, Europa' as the general theme for this study week. From 2 to 8 October 2005 several groups of students (between 16 and 19 years old) had to investigate some mission-related questions, ranging from the choice of the orbit and different ways of explor...

2005-01-01

55

Science, religious tolerance and freedom of expression  

Directory of Open Access Journals (Sweden)

Full Text Available In this article we offer a perspective on the immense number of problems and challenges confronting humanity in our common biosphere. As our human population grows and urbanization increases globally, billions of humans with diverse beliefs and opinions are living in large urban areas without the basic needs of life. The way forward in our biosphere is not violence and disrespect. It is working to maintain and improve our common biosphere and solve our common global problems. Religion and religious believers will need science, so humans can survive and sustain our biosphere.

Jack T. Trevors; Milton H. Saier, jr.

2010-01-01

56

Plasma vortices, lateral forcing, and the superrotating Venus atmosphere  

Science.gov (United States)

New observations from Venus Express (VEX) show the existence of a large-scale vortex-like ion flow pattern in the Venus plasma tail. The flow pattern is characterized by besides a dominating antisunward flow, also a lateral flow component of solar wind (H+) and ionospheric (O+) ions. The lateral flow component is directed opposite to the Venus orbital motion. A test of the energy and momentum balance between solar wind H+ and ionospheric O+ indicates that the energy and momentum delivered to O+ is proportional to the loss of energy and momentum by solar wind H+. The combined antisunward and lateral H+ and O+ flow wraps over the planetary atmosphere, from the terminator into the nightside. The net lateral flow near Venus is in the direction of the Venus atmospheric superrotation. Further down in the Venus plasma tail the flow display a circular motion around the central tail axis. The general agreement in direction between the nightside ion flow over the Northern hemisphere, and the retrograde motion of the Venus atmosphere, implies a cause-effect relation between the ionospheric O+ flow and the atmospheric neutral flow. This underlying connection is further strengthened by the fact the the O+ flow velocity in the 200-300 km altitude range follows the same power law curve as that fitted to the atmospheric zonal wind velocity profile [1]. The combined ion + neutral wind profile therefore implies momentum balance between the ionospheric and atmospheric retrograde flow. The fact that the O+ flow is driven by solar wind forcing leaves us with the question: Is the superrotating upper atmosphere at Venus a consequence of solar wind forcing? Is the ion flow capable of accelerating, and maintaining, a superrotating upper atmosphere at Venus? Combining ion data [2] with a fluid dynamic model of the energy and momentum transfer of ions to neutrals we find that this is certainly possible. The ionospheric O+ energy and momentum observed is sufficient to accelerate, and maintain superrotating velocites, after a few million years - minute compared to evolutionary time scales of a planet. [1] Schubert G., C. Covey, A. Del Genio, L.S. Elson et al., J. Geophys. Res., 85, 8007-8025, 1980 [2] Lundin, R.; Barabash, S.; Futaana, Y.; Sauvaud, J.-A.; Fedorov, A.; Perez-de-Tejada, H., Ion flow and momentum transfer in the Venus plasma environment, Icarus, 215, 751-758, 2011

Lundin, R.; Barabash, S.; Futaana, S.; Holmstrom, M.; Perez-de-Tejada, H.; Sauvaud, J.-A.

2012-04-01

57

Venus: A total mass estimate  

International Nuclear Information System (INIS)

Reductions of four independent blocks of Pioneer Venus Orbiter Doppler radio tracking data have produced very consistent determinations of the GM of Venus (the product of the universal gravitational constant and total mass of Venus). These estimates have uncertainties that are significantly smaller than any values published to data. The value of GM is also consistent with previously published results in that it falls within their one-sigma uncertainties. The value of 324858.60 ± 0.05 km3/sec2 is the best estimate.

1990-01-01

58

Progress report on VENUS  

International Nuclear Information System (INIS)

[en] The construction of VENUS, a next generation superconducting Electron Cyclotron Resonance ion source designed to operate at 28 GHz, is complete. The cryostat including the superconducting magnet assembly was delivered in September 2001. During acceptance tests, the superconducting magnets produced an axial magnetic field strength of 4T at injection, 3T at extraction, and a radial field strength of 2T at the plasma chamber wall without any quenches. These fields are sufficient for optimum operation at 28 GHz. The cryogenic system for VENUS has been designed to operate at 4.2 K with two cryocoolers each providing up to 45 W of cooling at 50 K and 1.5 W at 4 K in a closed loop mode without further helium transfers. However, during the acceptance tests an excessive heat leak of about 3W was measured. In addition, the liquid helium heat exchanger did not work properly and had to be redesigned. The cryogenic system modifications will be described. In addition, an update on the installation of the ion source and its beam line components will be given

2002-01-01

59

Progress report on VENUS  

Energy Technology Data Exchange (ETDEWEB)

The construction of VENUS, a next generation superconducting Electron Cyclotron Resonance ion source designed to operate at 28 GHz, is complete. The cryostat including the superconducting magnet assembly was delivered in September 2001. During acceptance tests, the superconducting magnets produced an axial magnetic field strength of 4T at injection, 3T at extraction, and a radial field strength of 2T at the plasma chamber wall without any quenches. These fields are sufficient for optimum operation at 28 GHz. The cryogenic system for VENUS has been designed to operate at 4.2 K with two cryocoolers each providing up to 45 W of cooling at 50 K and 1.5 W at 4 K in a closed loop mode without further helium transfers. However, during the acceptance tests an excessive heat leak of about 3W was measured. In addition, the liquid helium heat exchanger did not work properly and had to be redesigned. The cryogenic system modifications will be described. In addition, an update on the installation of the ion source and its beam line components will be given.

Leitner, Matthaeus A.; Leitner, Daniela; Abbott, Steve R.; Taylor, Clyde E.; Lyneis, Claude

2002-09-03

60

Evidence for lightning on Venus  

International Nuclear Information System (INIS)

[en] Measurements obtained by the Pioneer Orbiter of the electric field, magnetic field and the electron density of the Venus atmospheres are presented and the tentative conclusion that the events recorded are due to Venusian lightning is discussed. (UK)

1979-06-14

 
 
 
 
61

Short large-amplitude magnetic structures (SLAMS) at Venus  

Science.gov (United States)

We present the first observation of magnetic fluctuations consistent with short large-amplitude magnetic structures (SLAMS) in the foreshock of the planet Venus. Three monolithic magnetic field spikes were observed by the Venus Express on 11 April 2009. The structures were ˜1.5-11 s in duration, had magnetic compression ratios between ˜3 and 6, and exhibited elliptical polarization. These characteristics are consistent with the SLAMS observed at Earth, Jupiter, and Comet Giacobini-Zinner, and thus we hypothesize that it is possible SLAMS may be found at any celestial body with a foreshock.

Collinson, G. A.; Wilson, L. B., III; Sibeck, D. G.; Shane, N.; Zhang, T. L.; Moore, T. E.; Coates, A. J.; Barabash, S.

2012-10-01

62

Global cloud properties on Venus from orbital infrared spectroscopy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis describes the derivation of Venusian global cloud properties from infrared remote sensing data obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the European Space Agency Venus Express satellite. A computationally-efficient retrieval method is designed to e...

Barstow, Joanna Katy; Taylor, Fredric W.

63

Crustal deformation: Earth vs Venus  

International Nuclear Information System (INIS)

It is timely to consider the possible tectonic regimes on Venus both in terms of what is known about Venus and in terms of deformation mechanisms operative on the earth. Plate tectonic phenomena dominate tectonics on the earth. Horizontal displacements are associated with the creation of new crust at ridges and destruction of crust at trenches. The presence of plate tectonics on Venus is debated, but there is certainly no evidence for the trenches associated with subduction on the earth. An essential question is what kind of tectonics can be expected if there is no plate tectonics on Venus. Mars and the Moon are reference examples. Volcanic constructs appear to play a dominant role on Mars but their role on Venus is not clear. On single plate planets and satellites, tectonic structures are often associated with thermal stresses. Cooling of a planet leads to thermal contraction and surface compressive features. Delamination has been propsed for Venus by several authors. Delamination is associated with the subduction of the mantle lithosphere and possibly the lower crust but not the upper crust. The surface manifestations of delamination are unclear. There is some evidence that delamination is occurring beneath the Transverse Ranges in California. Delamination will certainly lead to lithospheric thinning and is likely to lead to uplift and crustal thinning.

1989-01-01

64

Identification of Postclassic Maya Constellations from the Venus Pages of the Dresden Codex  

Directory of Open Access Journals (Sweden)

Full Text Available Ancient Mayan civilization, flourished from 1200 B.C. to 1500 A.D., has left numerous hieroglyphic texts on astronomical observations and calendar. In particular, the Dresden Codex contains the most details of such ancient Mayan heritage. Page 24 and those from 46 to 50 of the Dresden Codex describe the Mayan Venus calendar along with the augural descriptions. We note that the calendar in Dresden Codex is Venus-solar calendar. Our work focuses on the possibility that the calendar was made to work in conjunction with the periodic appearance of constellations on the sky. By analyzing the descriptions in the Venus pages, we propose that the columns in each page describe the motion of Venus with respect to major constellations at dates corresponding to special events while the calendar dates increase horizontally in the synodic period of Venus. We present twenty Mayan constellations identified from the Venus pages assuming that the first date of page 46 is February 6, 1228. We also report our understanding of verb expressions about the relative movement of constellations and Venus.La civilización maya, que floreció del 1200 a.C. a 1500 d.C., dejó numerosos textos jeroglíficos sobre el calendario y observaciones astronómicos. El Códice de Dresde, en particular, contiene el más detallado de dichos antiguos legados mayas. Las páginas 24 y 46 a 50 de dicho códice describen el calendario de Venus con los augurios correspondientes. Nosotros hemos notado que éste es un calendario Venus-Solar, y nuestro trabajo se enfoca sobre la posibilidad de que estuviera hecho para trabajar en conjunción con la aparición de determinadas constelaciones en el cielo. Es a través del análisis y descripción de las páginas de Venus que proponemos que las columnas en cada página describen el movimiento de Venus respecto de constelaciones mayores, en fechas que corresponden a eventos especiales, mientras que las fechas calendáricas se incrementan horizontalmente dentro del periodo sinódico de Venus. Aquí presentamos veinte constelaciones mayas identificadas desde las páginas de Venus asumiendo que la primera fecha, en la página 46, fue febrero 6 de 1228. También reportamos, como entendemos, las expresiones verbales sobre el movimiento de Venus y las constelaciones.

Changbom Park; Heajoo Chung

2010-01-01

65

Identification of Postclassic Maya Constellations from the Venus Pages of the Dresden Codex  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish La civilización maya, que floreció del 1200 a.C. a 1500 d.C., dejó numerosos textos jeroglíficos sobre el calendario y observaciones astronómicos. El Códice de Dresde, en particular, contiene el más detallado de dichos antiguos legados mayas. Las páginas 24 y 46 a 50 de dicho códice describen el calendario de Venus con los augurios correspondientes. Nosotros hemos notado que éste es un calendario Venus-Solar, y nuestro trabajo se enfoca sobre la posibilidad de q (more) ue estuviera hecho para trabajar en conjunción con la aparición de determinadas constelaciones en el cielo. Es a través del análisis y descripción de las páginas de Venus que proponemos que las columnas en cada página describen el movimiento de Venus respecto de constelaciones mayores, en fechas que corresponden a eventos especiales, mientras que las fechas calendáricas se incrementan horizontalmente dentro del periodo sinódico de Venus. Aquí presentamos veinte constelaciones mayas identificadas desde las páginas de Venus asumiendo que la primera fecha, en la página 46, fue febrero 6 de 1228. También reportamos, como entendemos, las expresiones verbales sobre el movimiento de Venus y las constelaciones. Abstract in english Ancient Mayan civilization, flourished from 1200 B.C. to 1500 A.D., has left numerous hieroglyphic texts on astronomical observations and calendar. In particular, the Dresden Codex contains the most details of such ancient Mayan heritage. Page 24 and those from 46 to 50 of the Dresden Codex describe the Mayan Venus calendar along with the augural descriptions. We note that the calendar in Dresden Codex is Venus-solar calendar. Our work focuses on the possibility that the (more) calendar was made to work in conjunction with the periodic appearance of constellations on the sky. By analyzing the descriptions in the Venus pages, we propose that the columns in each page describe the motion of Venus with respect to major constellations at dates corresponding to special events while the calendar dates increase horizontally in the synodic period of Venus. We present twenty Mayan constellations identified from the Venus pages assuming that the first date of page 46 is February 6, 1228. We also report our understanding of verb expressions about the relative movement of constellations and Venus.

Park, Changbom; Chung, Heajoo

2010-01-01

66

Why Venus has No Moon  

Science.gov (United States)

Venus does not have a moon. We argue that this is at least as surprising as the presence of Earth's moon and more surprising than the absence of a substantial moon for Mercury or Mars. We do not know if Venus ever had a moon. The accepted explanation for Earth's moon is a giant impact with an impactor on the order of one Mars mass. Given current theories of solar system formation, it is unlikely that Venus would have avoided such a large collision. Simulations suggest that most large collisions create a disk from which a moon forms. Moreover, the natural outcome is one where the sense of orbital motion and planetary spin are the same, leading to outward tidal evolution. Despite the smaller sphere of influence of Venus relative to Earth, and the larger solar tidal influence, only very large moons or very dissipative tides allow such a moon to escape. The alternative of inward evolution and coalescence cannot be explained without a second large impact that provides an angular momentum impulse of the opposite sense. A two large collision hypothesis is presented, and argued for. Since tidal evolution is primarily symmetric with respect to relative mean motion, the moon created by the first giant impact returns to Venus on roughly the same timescale as the time between giant impacts, 10^7 years. This hypothesis also allows Venus to eventually evolve to the current slow retrograde rotation state, an outcome that is otherwise difficult to explain quantitatively, notwithstanding the accepted current balance between solar thermal and solid body tides. The two giant impact hypothesis may have isotopic and possibly compositional consequences for Venus but the coalescence is unlikely to have left a clear geophysical or geological trace. We have not identified a clear observational test of this model.

Alemi, Alex; Stevenson, D.

2006-09-01

67

Implications of 36A excess on Venus  

International Nuclear Information System (INIS)

[en] The finding of 36A excess on Venus by the mass-spectroscopic measurement of the Venus Pioneer appears to endorse the more rapid accretion theory of Venus than the Earth and the secondary origin of the terrestrial atmosphere. (Auth.)

1979-01-01

68

Commissioning of the superconducting ECR ion source VENUS  

International Nuclear Information System (INIS)

[en] VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end. The magnetic confinement configuration consists of three superconducting axial coils and six superconducting radial coils in a sextupole configuration. The nominal design fields of the axial magnets are 4T at injection and 3T at extraction; the nominal radial design field strength at the plasma chamber wall is 2T, making VENUS the world most powerful ECR plasma confinement structure. The magnetic field strength has been designed for optimum operation at 28 GHz. The four-year VENUS project has recently achieved two major milestones: The first plasma was ignited in June, the first mass-analyzed high charge state ion beam was extracted in September of 2002. The pa per describes the ongoing commissioning. Initial results including first emittance measurements are presented

2003-01-01

69

Commissioning of the superconducting ECR ion source VENUS  

Energy Technology Data Exchange (ETDEWEB)

VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end. The magnetic confinement configuration consists of three superconducting axial coils and six superconducting radial coils in a sextupole configuration. The nominal design fields of the axial magnets are 4T at injection and 3T at extraction; the nominal radial design field strength at the plasma chamber wall is 2T, making VENUS the world most powerful ECR plasma confinement structure. The magnetic field strength has been designed for optimum operation at 28 GHz. The four-year VENUS project has recently achieved two major milestones: The first plasma was ignited in June, the first mass-analyzed high charge state ion beam was extracted in September of 2002. The pa per describes the ongoing commissioning. Initial results including first emittance measurements are presented.

Leitner, Daniela; Abbott, Steve R.; Dwinell, Roger D.; Leitner, Matthaeus; Taylor, Clyde; Lyneis, Claude M.

2003-05-15

70

Promoting Creative Thinking and Expression of Science Concepts among Elementary Teacher Candidates through Science Content Movie Creation and Showcasing  

Science.gov (United States)

This article reports the phases of design and use of video editing technology as a medium for creatively expressing science content knowledge in an elementary science methods course. Teacher candidates communicated their understanding of standards-based core science concepts through the creation of original digital movies. The movies were assigned…

Hechter, Richard P.; Guy, Mark

2010-01-01

71

Electrical memory in Venus flytrap.  

UK PubMed Central (United Kingdom)

Electrical signaling, memory and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since the XIX century. The electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf in 0.3 s without mechanical stimulation of trigger hairs. Here we developed a new method for direct measurements of the exact electrical charge utilized by the D. muscipula Ellis to facilitate the trap closing and investigated electrical short memory in the Venus flytrap. As soon as the 8 microC charge for a small trap or a 9 microC charge for a large trap is transmitted between a lobe and midrib from the external capacitor, the trap starts to close at room temperature. At temperatures 28-36 degrees C a smaller electrical charge of 4.1 microC is required to close the trap of the D. muscipula. The cumulative character of electrical stimuli points to the existence of short-term electrical memory in the Venus flytrap. We also found sensory memory in the Venus flytrap. When one sustained mechanical stimulus was applied to only one trigger hair, the trap closed in a few seconds.

Volkov AG; Carrell H; Baldwin A; Markin VS

2009-06-01

72

Electrical memory in Venus flytrap.  

Science.gov (United States)

Electrical signaling, memory and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since the XIX century. The electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf in 0.3 s without mechanical stimulation of trigger hairs. Here we developed a new method for direct measurements of the exact electrical charge utilized by the D. muscipula Ellis to facilitate the trap closing and investigated electrical short memory in the Venus flytrap. As soon as the 8 microC charge for a small trap or a 9 microC charge for a large trap is transmitted between a lobe and midrib from the external capacitor, the trap starts to close at room temperature. At temperatures 28-36 degrees C a smaller electrical charge of 4.1 microC is required to close the trap of the D. muscipula. The cumulative character of electrical stimuli points to the existence of short-term electrical memory in the Venus flytrap. We also found sensory memory in the Venus flytrap. When one sustained mechanical stimulus was applied to only one trigger hair, the trap closed in a few seconds. PMID:19356999

Volkov, Alexander G; Carrell, Holly; Baldwin, Andrew; Markin, Vladislav S

2009-03-20

73

Biologically closed electrical circuits in venus flytrap.  

Science.gov (United States)

The Venus flytrap (Dionaea muscipula Ellis) is a marvel of plant electrical, mechanical, and biochemical engineering. The rapid closure of the Venus flytrap upper leaf in about 0.1 s is one of the fastest movements in the plant kingdom. We found earlier that the electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf without mechanical stimulation of trigger hairs. The Venus flytrap can accumulate small subthreshold charges and, when the threshold value is reached, the trap closes. Here, we investigated the electrical properties of the upper leaf of the Venus flytrap and proposed the equivalent electrical circuit in agreement with the experimental data. PMID:19211696

Volkov, Alexander G; Carrell, Holly; Markin, Vladislav S

2009-02-11

74

Spaceborne radar studies of Venus  

Energy Technology Data Exchange (ETDEWEB)

Data obtained from the Pioneer Venus radar mapper experiment are discussed. The mission was primarily developed to study the atmosphere of Venus. A highly eccentric orbit (eccentricity of 0.84, period of 24 h) was selected. The instrumentation has two operating modes: altimetry and imaging. Three parameters were measured for every radar spot size: altitude, surface roughness and radar reflectivity at a normal incidence. The measurements have been extended to a topographic map. The results suggest that the Beta region consists of two large shields and that the equatorial region is dominated by Aphrodite Terra. It also appears that the surface of Venus is very smooth and that it lacks great basins and the global plate tectonics present on earth.

Nozette, S.

1980-01-01

75

Rate of volcanism on Venus  

Energy Technology Data Exchange (ETDEWEB)

The maintenance of the global H/sub 2/SO/sub 4/ clouds on Venus requires volcanism to replenish the atmospheric SO/sub 2/ which is continually being removed from the atmosphere by reaction with calcium minerals on the surface of Venus. The first laboratory measurements of the rate of one such reaction, between SO/sub 2/ and calcite (CaCO/sub 3/) to form anhydrite (CaSO/sub 4/), are reported. If the rate of this reaction is representative of the SO/sub 2/ reaction rate at the Venus surface, then we estimate that all SO/sub 2/ in the Venus atmosphere (and thus the H/sub 2/SO/sub 4/ clouds) will be removed in 1.9 million years unless the lost SO/sub 2/ is replenished by volcanism. The required rate of volcanism ranges from about 0.4 to about 11 cu km of magma erupted per year, depending on the assumed sulfur content of the erupted material. If this material has the same composition as the Venus surface at the Venera 13, 14 and Vega 2 landing sites, then the required rate of volcanism is about 1 cu km per year. This independent geochemically estimated rate can be used to determine if either (or neither) of the two discordant (2 cu km/year vs. 200 to 300 cu km/year) geophysically estimated rates is correct. The geochemically estimated rate also suggests that Venus is less volcanically active than the Earth.

Fegley, B. Jr.; Prinn, R.G.

1988-07-01

76

Transmission spectrum of Venus as a transiting exoplanet  

CERN Document Server

On 5-6 June 2012, Venus will be transiting the Sun for the last time before 2117. This event is an unique opportunity to assess the feasibility of the atmospheric characterisation of Earth-size exoplanets near the habitable zone with the transmission spectroscopy technique and provide an invaluable proxy for the atmosphere of such a planet. In this letter, we provide a theoretical transmission spectrum of the atmosphere of Venus that could be tested with spectroscopic observations during the 2012 transit. This is done using radiative transfer across Venus' atmosphere, with inputs from in-situ missions such as Venus Express and theoretical models. The transmission spectrum covers a range of 0.1-5 {\\mu}m and probes the limb between 70 and 150 km in altitude. It is dominated in UV by carbon dioxide absorption producing a broad transit signal of ~20 ppm as seen from Earth, and from 0.2 to 2.7 {\\mu}m by Mie extinction (~5 ppm at 0.8 {\\mu}m) caused by droplets of sulfuric acid composing an upper haze layer above th...

Ehrenreich, David; Widemann, Thomas; Gronoff, Guillaume; Tanga, Paolo; Barthélemy, Mathieu; Lilensten, Jean; Etangs, Alain Lecavelier des; Arnold, Luc

2011-01-01

77

Next generation ECR ion sources: First results of the superconducting 28 GHz ECRIS - VENUS  

International Nuclear Information System (INIS)

[en] VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (rare isotope accelerator) front end. The goal of the VENUS ECR ion source project as the RIA R and D injector is the production of 200 e?A of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5 e?A of U48+, a low current, very high charge state beam. To achieve those ambitious goals, the VENUS ECR ion source has been designed for optimum operation at 28 GHz. The nominal design fields of the axial magnets are 4 T at injection and 3 T at extraction; the nominal radial design field strength at the plasma chamber wall is 2 T, making VENUS currently the world's most powerful ECR plasma confinement structure. Recently, the six year project has made significant progress. In June 2002, the first plasma was ignited at 18 GHz. During 2003, the VENUS ECR ion source was commissioned at 18 GHz, while preparations for 28 GHz operation were being conducted. In May 2004 28 GHz microwave power has been coupled into the VENUS ECR ion source for the first time. Preliminary performance-tests with oxygen, xenon and bismuth at 18 GHz and 28 GHz have shown promising results. Intensities close to or exceeding the RIA requirements have been produced for those few test beams. The paper will briefly describe the design of the VENUS source and its beam analyzing system. Results at 18 GHz and 28 GHz including first emittance measurements will be described

2005-01-01

78

Models of the internal structure of Venus  

Energy Technology Data Exchange (ETDEWEB)

A survey is made of the physics of the interiors of Venus. The introduction explains the main concepts used in the construction of models of Venus and the history of the question; observational data are gathered and analyzed. The method of constructing the models of the planet is explained and earth-like models of Venus and parametrically simple PVM models are discussed. Within the compass of a physical model of Venus, the thermodynamics of the mantle and core is constructed and questions are discussed concerning the heat conduction, temperature distribution in the lithosphere and the thermal flux from the interior of Venus, the electrical conduction and mechanical quality, and large-scale steady stresses in the mantle of Venus. A rheological model of the crust and mantle is constructed. In conclusion, the question as to the distribution of radioactivity and convection in the interior of the planet is discussed.

Zharkov, V.N. (AN SSSR, Moscow. Inst. Fiziki Zemli)

1983-10-01

79

Abstracts for the venus geoscience tutorial and venus geologic mapping workshop  

Energy Technology Data Exchange (ETDEWEB)

Abstracts and tutorial are presented from the workshop. Representative titles are: Geology of Southern Guinevere Planitia, Venus, Based on Analyses of Goldstone Radar Data; Tessera Terrain: Characteristics and Models of Origin; Venus Volcanism; Rate Estimates from Laboratory Studies of Sulfur Gas-Solid Reactions; and A Morphologic Study of Venus Ridge Belts.

1989-01-01

80

The magnetosheath and magnetotail of Venus  

Energy Technology Data Exchange (ETDEWEB)

The subjects to be discussed in this review, the Venus magnetosheath and magnetotail, make up a major portion, but by no means the entirety, of the interaction of the solar wind with Venus. The authors describe the observational history and assess the current understanding of the magnetosheath and magnetotail of Venus, stressing recent developments. They make recommendations for research that can be done using existing observations, as well as desirable trajectory and instrumentation characteristics for future spacecraft missions.

Phillips, J.L.; McComas, D.J. (Los Alamos National Lab., NM (United States))

1991-01-01

 
 
 
 
81

Magellan at Venus - First results  

International Nuclear Information System (INIS)

First results of mapping the Venusian surface on the basis of data from the Magellan spacecraft are presented, together with the description of the Magellan measurement instruments. These consist of a SAR, which bounces short pulses of radio energy off the planet's surface for 37 min of each orbit, when it is closest to Venus, and a radar altimeter, which repeatedly determines the height of the landscape directly below it. The paper describes key features of several impact craters mapped by Magellan, including the Crater Golubkina, the crater farm and the Gumby feature near the Lavinia Planitia region, a 9 x 12-km kidney-shaped crater, and a radar-bright feature considered to be an evidence of explosive volcanism on Venus

1990-01-01

82

How the Venus flytrap snaps.  

UK PubMed Central (United Kingdom)

The rapid closure of the Venus flytrap (Dionaea muscipula) leaf in about 100 ms is one of the fastest movements in the plant kingdom. This led Darwin to describe the plant as "one of the most wonderful in the world". The trap closure is initiated by the mechanical stimulation of trigger hairs. Previous studies have focused on the biochemical response of the trigger hairs to stimuli and quantified the propagation of action potentials in the leaves. Here we complement these studies by considering the post-stimulation mechanical aspects of Venus flytrap closure. Using high-speed video imaging, non-invasive microscopy techniques and a simple theoretical model, we show that the fast closure of the trap results from a snap-buckling instability, the onset of which is controlled actively by the plant. Our study identifies an ingenious solution to scaling up movements in non-muscular engines and provides a general framework for understanding nastic motion in plants.

Forterre Y; Skotheim JM; Dumais J; Mahadevan L

2005-01-01

83

How the Venus flytrap snaps  

Science.gov (United States)

The rapid closure of the Venus flytrap (Dionaea muscipula) leaf in about 100ms is one of the fastest movements in the plant kingdom. This led Darwin to describe the plant as ``one of the most wonderful in the world''. The trap closure is initiated by the mechanical stimulation of trigger hairs. Previous studies have focused on the biochemical response of the trigger hairs to stimuli and quantified the propagation of action potentials in the leaves. Here we complement these studies by considering the post-stimulation mechanical aspects of Venus flytrap closure. Using high-speed video imaging, non-invasive microscopy techniques and a simple theoretical model, we show that the fast closure of the trap results from a snap-buckling instability, the onset of which is controlled actively by the plant. Our study identifies an ingenious solution to scaling up movements in non-muscular engines and provides a general framework for understanding nastic motion in plants.

Forterre, Yoël; Skotheim, Jan M.; Dumais, Jacques; Mahadevan, L.

2005-01-01

84

An overview of venus geology.  

UK PubMed Central (United Kingdom)

The Magellan spacecraft is producing comprehensive image and altimetry data for the planet Venus. Initial geologic mapping of the planet reveals a surface dominated by volcanic plains and characterized by extensive volcanism and tectonic deformation. Geologic and geomorphologic units include plains terrains, tectonic terrains, and surficial material units. Understanding the origin of these units and the relation between them is an ongoing task of the Magellan team.

Saunders RS; Arvidson RE; Head JW 3rd; Schaber GG; Stofan ER; Solomon SC

1991-04-01

85

Recent progress on the superconducting ion source VENUS.  

UK PubMed Central (United Kingdom)

The 28 GHz Ion Source VENUS (versatile ECR for nuclear science) is back in operation after the superconducting sextupole leads were repaired and a fourth cryocooler was added. VENUS serves as an R&D device to explore the limits of electron cyclotron resonance source performance at 28 GHz with its 10 kW gryotron and optimum magnetic fields and as an ion source to increase the capabilities of the 88-Inch Cyclotron both for nuclear physics research and applications. The development and testing of ovens and sputtering techniques cover a wide range of applications. Recent experiments on bismuth demonstrated stable operation at 300 e?A of Bi(31+), which is in the intensity range of interest for high performance heavy-ion drivers such as FRIB (Facility for Rare Isotope Beams). In addition, the space radiation effects testing program at the cyclotron relies on the production of a cocktail beam with many species produced simultaneously in the ion source and this can be done with a combination of gases, sputter probes, and an oven. These capabilities are being developed with VENUS by adding a low temperature oven, sputter probes, as well as studying the RF coupling into the source.

Benitez JY; Franzen KY; Hodgkinson A; Loew T; Lyneis CM; Phair L; Saba J; Strohmeier M; Tarvainen O

2012-02-01

86

Recent progress on the superconducting ion source VENUS  

Science.gov (United States)

The 28 GHz Ion Source VENUS (versatile ECR for nuclear science) is back in operation after the superconducting sextupole leads were repaired and a fourth cryocooler was added. VENUS serves as an R&D device to explore the limits of electron cyclotron resonance source performance at 28 GHz with its 10 kW gryotron and optimum magnetic fields and as an ion source to increase the capabilities of the 88-Inch Cyclotron both for nuclear physics research and applications. The development and testing of ovens and sputtering techniques cover a wide range of applications. Recent experiments on bismuth demonstrated stable operation at 300 e?A of Bi31+, which is in the intensity range of interest for high performance heavy-ion drivers such as FRIB (Facility for Rare Isotope Beams). In addition, the space radiation effects testing program at the cyclotron relies on the production of a cocktail beam with many species produced simultaneously in the ion source and this can be done with a combination of gases, sputter probes, and an oven. These capabilities are being developed with VENUS by adding a low temperature oven, sputter probes, as well as studying the RF coupling into the source.

Benitez, J. Y.; Franzen, K. Y.; Hodgkinson, A.; Loew, T.; Lyneis, C. M.; Phair, L.; Saba, J.; Strohmeier, M.; Tarvainen, O.

2012-02-01

87

Recent progress on the superconducting ion source VENUS  

Energy Technology Data Exchange (ETDEWEB)

The 28 GHz Ion Source VENUS (versatile ECR for nuclear science) is back in operation after the superconducting sextupole leads were repaired and a fourth cryocooler was added. VENUS serves as an R and D device to explore the limits of electron cyclotron resonance source performance at 28 GHz with its 10 kW gryotron and optimum magnetic fields and as an ion source to increase the capabilities of the 88-Inch Cyclotron both for nuclear physics research and applications. The development and testing of ovens and sputtering techniques cover a wide range of applications. Recent experiments on bismuth demonstrated stable operation at 300 e{mu}A of Bi{sup 31+}, which is in the intensity range of interest for high performance heavy-ion drivers such as FRIB (Facility for Rare Isotope Beams). In addition, the space radiation effects testing program at the cyclotron relies on the production of a cocktail beam with many species produced simultaneously in the ion source and this can be done with a combination of gases, sputter probes, and an oven. These capabilities are being developed with VENUS by adding a low temperature oven, sputter probes, as well as studying the RF coupling into the source.

Benitez, J. Y.; Franzen, K. Y.; Hodgkinson, A.; Loew, T.; Lyneis, C. M.; Phair, L.; Saba, J.; Strohmeier, M. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Tarvainen, O. [Accelerator Laboratory, Department of Physics, University of Jyvaeskylae, FIN-40014 (Finland)

2012-02-15

88

Oxygen Escape from Venus During High Dynamic Pressure ICMEs  

Science.gov (United States)

Previous studies using data from Pioneer Venus suggested that oxygen ion escape flux may be enhanced by orders of magnitude during Interplanetary Coronal Mass Ejections. However, this large enhancement has been ambiguous in Venus Express ion data - with some analyses showing no flux enhancement or a small enhancement (within 2 times undisturbed cases). One possible explanation is that high escape flux may be due to high dynamic pressure in the solar wind, and the dynamic pressure has been lower during the VEX time period. So, we focus on ICMEs with the largest dynamic pressure and with VEX sampling of the escaping ions during the sheath of the ICMEs (during which the highest dynamic pressures in the solar wind occur). We will show the characteristics of these large events measured by VEX, and compare them to the largest ICMEs measured by PVO. We will then discuss estimates of the oxygen ion escape flux during these events.

McEnulty, Tess; Luhmann, J. G.; Brain, D. A.; Fedorov, A.; Jian, L. K.; Russell, C. T.; Zhang, T.; Möstl, C.; Futaana, Y.; de Pater, I.

2013-10-01

89

Substorm activity in Venus's magnetotail  

Directory of Open Access Journals (Sweden)

Full Text Available The magnetotail of the induced magnetosphere of Venus is investigated through the magnetic field and plasma data of Venus Express. A comparison is made between two neutral sheet crossings. One crossing shows the magnetic field is rather quiet and the plasma instrument indicates a change from energetic (few 100 eV) to low energy (few 10 eV) ions. The other crossing shows more dynamics in the magnetic field, including signatures that are interpreted as characteristic of a reconnection site, and the plasma instrument indicates ions that are energized to 1500 to 2000 eV, in the same magnetospheric region where in the first crossing only low energy ions showed up.

M. Volwerk; M. Delva; Y. Futaana; A. Retinò; Z. Vörös; T. L. Zhang; W. Baumjohann; S. Barabash

2009-01-01

90

Change over a service learning experience in science undergraduates' beliefs expressed about elementary school students' ability to learn science  

Science.gov (United States)

This longitudinal investigation explores the change in four (3 female, 1 male) science undergraduates' beliefs expressed about low-income elementary school students' ability to learn science. The study sought to identify how the undergraduates in year-long public school science-teaching partnerships perceived the social, cultural, and economic factors affecting student learning. Previous service-learning research infrequently focused on science undergraduates relative to science and society or detailed expressions of their beliefs and field practices over the experience. Qualitative methodology was used to guide the implementation and analysis of this study. A sample of an additional 20 science undergraduates likewise involved in intensive reflection in the service learning in science teaching (SLST) course called Elementary Science Education Partners (ESEP) was used to examine the typicality of the case participants. The findings show two major changes in science undergraduates' belief expressions: (1) a reduction in statements of beliefs from a deficit thinking perspective about the elementary school students' ability to learn science, and (2) a shift in the attribution of students, underlying problems in science learning from individual-oriented to systemic-oriented influences. Additional findings reveal that the science undergraduates perceived they had personally and profoundly changed as a result of the SLST experience. Changes include: (1) the gain of a new understanding of others' situations different from their own; (2) the realization of and appreciation for their relative positions of privilege due to their educational background and family support; (3) the gain in ability to communicate, teach, and work with others; (4) the idea that they were more socially and culturally connected to their community outside the university and their college classrooms; and (5) a broadening of the way they understood or thought about science. Women participants stated that the experience validated their science and science-related career choices. Results imply that these changes have the potential to strengthen the undergraduate pursuit of science-related careers and will contribute positive influences to our education system and society at large.

Goebel, Camille A.

91

Plasma waves near venus: initial observations.  

UK PubMed Central (United Kingdom)

The Pioneer Venus electric field detector observes significant effects of the interaction of the solar wind with the ionosphere of Venus all along the orbiter trajectory. Information is obtained on plasma oscillations emitted by suprathermal electrons beyond the bows shock, on sharp and diffuse shock structures, and on waveparticle interaction phenomena that are important near the boundary of the dayside ionosphere.

Scarf FL; Taylor WW; Green IM

1979-02-01

92

Volcanism on Venus: a connecting link  

Energy Technology Data Exchange (ETDEWEB)

On the basis of data obtained during recent investigations of Venus the suggestion is made that the presence of electrical discharges in the atmosphere close to the surface, the variable density of the submicron haze and the peculiarity of cloud microphysics can be jointly explained in the frame of the hypothesis about volcanic erruptions on the surface of Venus.

Ksanfomaliti, L.V.

1984-01-01

93

First Results of the Superconducting ECR Ion Source Venus with 28 GHz  

International Nuclear Information System (INIS)

VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end. The magnetic confinement configuration consists of three superconducting axial coils and six superconducting radial coils in a sextupole configuration. The nominal design fields of the axial magnets are 4T at injection and 3T at extraction; the nominal radial design field strength at the plasma chamber wall is 2T, making VENUS the world most powerful ECR plasma confinement structure. From the beginning, VENUS has been designed for optimum operation at 28 GHz with high power (10 kW).In 2003 the VENUS ECR ion source was commissioned at 18 GHz, while preparations for 28 GHz operation were being conducted. During this commissioning phase with 18 GHz, tests with various gases and metals have been performed with up to 2000 W RF power. At the initial commissioning tests at 18 GHz, 1100 e?A of O6+, 160 e?A of Xe20+, 160 e?A of Bi25+ and 100 e?A of Bi30+ and 11 e?A of Bi41+ were produced.In May 2004 the 28 GHz microwave power has been coupled into the VENUS ECR ion source. At initial operation more than 320 e?A of Xe20+ (twice the amount extracted at 18 GHz), 240 e?A of Bi24+ and Bi25+, and 245 e?A of Bi29+ were extracted. The paper briefly describes the design of the VENUS source, the 28 GHz microwave system and its beam analyzing system. First results at 28 GHz including emittance measurements are presented.

2005-03-15

94

First Results of the Superconducting ECR Ion Source Venus with 28 GHz  

Science.gov (United States)

VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end. The magnetic confinement configuration consists of three superconducting axial coils and six superconducting radial coils in a sextupole configuration. The nominal design fields of the axial magnets are 4T at injection and 3T at extraction; the nominal radial design field strength at the plasma chamber wall is 2T, making VENUS the world most powerful ECR plasma confinement structure. From the beginning, VENUS has been designed for optimum operation at 28 GHz with high power (10 kW). In 2003 the VENUS ECR ion source was commissioned at 18 GHz, while preparations for 28 GHz operation were being conducted. During this commissioning phase with 18 GHz, tests with various gases and metals have been performed with up to 2000 W RF power. At the initial commissioning tests at 18 GHz, 1100 e?A of O6+, 160 e?A of Xe20+, 160 e?A of Bi25+ and 100 e?A of Bi30+ and 11 e?A of Bi41+ were produced. In May 2004 the 28 GHz microwave power has been coupled into the VENUS ECR ion source. At initial operation more than 320 e?A of Xe20+ (twice the amount extracted at 18 GHz), 240 e?A of Bi24+ and Bi25+, and 245 e?A of Bi29+ were extracted. The paper briefly describes the design of the VENUS source, the 28 GHz microwave system and its beam analyzing system. First results at 28 GHz including emittance measurements are presented.

Leitner, D.; Lyneis, C. M.; Abbott, S. R.; Dwinell, R. D.; Collins, D.; Leitner, M.

2005-03-01

95

Comparative aspects of Venus and terrestrial meteorology  

Energy Technology Data Exchange (ETDEWEB)

The observations and measurements made by Pioneer Venus orbiters are presented in terms of comparison of Venus and terrestrial meteorology. Although the temperature-pressure profiles of the two planets differ at lower altitudes, the temperatures are similar over their common range of pressures except for a much cooler mesosphere on Venus. The additional similarities between the earth and Venus relate to the warm polar stratospheres and the zonally-averaged energy budgets of the two planets. A difference in the mean radiation budgets for Venus is the relative smallness of the upward and downward thermal flux components. It is noted that the observed similarities reflect common mechanisms despite the difference in the dynamical regimes of the two planets.

Taylor, F.W. (Oxford University, Oxford, England); Elson, L.S. (California Institute of Technology, Jet Propulsion Laboratory, Pasadena, Calif.)

1980-01-01

96

The final status of Japanese Venus Climate Orbiter (PLANET-C) in the integration test  

Science.gov (United States)

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 4 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 rotates westward. The systematic, continuous imaging observations will provide us with an unprecedented large dataset of the Venusian atmospheric dynamics. Planet-C will be launched in 2010 and will reach Venus in 5 months. Nominal operation period is 2 earth years. It is now under the final integration test at ISAS/JAXA in Sagamihara, which started in June 2009. We will report the final status of the spacecraft before the launch.

Nakamura, M.; Imamura, T.; Ishii, N.; Satoh, T.; Ueno, M.; Abe, T.; Suzuki, M.; Yamazaki, A.; Iwagami, N.; Taguchi, M.; Watanabe, S.; Takahashi, Y.

2009-12-01

97

Commissioning of the superconducting ECR ion source VENUS at 18 GHz  

International Nuclear Information System (INIS)

[en] During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation are now underway. During the commissioning phase with 18 GHz, tests with various gases and metals have been performed with up to 2000 W RF power. The ion source performance is very promising [1,2]. VENUS (Versatile ECR ion source for Nuclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end. The goal of the VENUS ECR ion source project as the RIA R and D injector is the production of 240e(micro)A of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5e(micro)A of U48+, a low current, very high charge state beam. To meet these ambitious goals, VENUS has been designed for optimum operation at 28 GHz. This frequency choice has several design consequences. To achieve the required magnetic confinement, superconducting magnets have to be used. The size of the superconducting magnet structure implies a relatively large plasma volume. Consequently, high power microwave coupling becomes necessary to achieve sufficient plasma heating power densities. The 28 GHz power supply has been delivered in April 2004

2004-01-01

98

Commissioning of the superconducting ECR ion source VENUS at 18 GHz  

Energy Technology Data Exchange (ETDEWEB)

During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation are now underway. During the commissioning phase with 18 GHz, tests with various gases and metals have been performed with up to 2000 W RF power. The ion source performance is very promising [1,2]. VENUS (Versatile ECR ion source for Nuclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end. The goal of the VENUS ECR ion source project as the RIA R&D injector is the production of 240e{micro}A of U{sup 30+}, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5e{micro}A of U{sup 48+}, a low current, very high charge state beam. To meet these ambitious goals, VENUS has been designed for optimum operation at 28 GHz. This frequency choice has several design consequences. To achieve the required magnetic confinement, superconducting magnets have to be used. The size of the superconducting magnet structure implies a relatively large plasma volume. Consequently, high power microwave coupling becomes necessary to achieve sufficient plasma heating power densities. The 28 GHz power supply has been delivered in April 2004.

Leitner, Daniela; Abbott, Steven R.; Dwinell, Roger D.; Leitner, Matthaeus; Taylor, Clyde E.; Lyneis, Claude M.

2004-06-01

99

Venus Atmospheric Circulation from Digital Tracking of VMC Images  

Science.gov (United States)

The Venus Monitoring Camera on Venus Express has been returning images of Venus in four filters since April 2006 on almost every orbit. These images portray the southern hemisphere of Venus at spatial resolutions ranging from ~ 50 km per pixel to better than ~ 10 km per pixel depending on when the planet was imaged from orbit. Images covering a substantial portion of the planet and separated by ~ 45 min to one hour have been mapped into rectilinear projection to enable use of digital tracking technique for the measurement of cloud motions on an orbit by orbit basis. The aggregate results are in good agreement with visual tracking results as well as from the previous missions [1] and show evidence of temporal variations, large scale waves and solar thermal tides in low and mid latitudes. The digital tracking results for the meridional component confirm the poleward flow increasing from low latitudes to mid-latitudes and then showing a tendency to weaken. However, the confidence in high latitude measurements is lower due to the peculiar nature of the cloud morphology that is generally streaky and quite different from the low latitudes. The meridional profile of the average zonal wind at higher latitudes is of considerable interest. At high and polar latitudes, a vortex organization is evident in the data consistently, with the core region centered over the pole. The images show variability in structure of the ultraviolet signature of the "S" shaped feature seen in the VIRTIS data on the capture orbit [2]. However, the cloud morphologies seen poleward of ~ 50 degrees latitude also makes digital tracking less reliable due to absence of discrete features at the spatial resolution of the VMC images acquired in the apoapsis portion of the Venus Express orbit. It is expected that images obtained closer to the planet will enable a determination of the zonal wind profile with better confidence which will be useful in elucidating the nature of the transient features seen in the core region of the Venus vortex. References [1] Limaye, S. S. Venus atmospheric circulation: Known and unknown, J. Geophys. Res., 112, E04S09, doi:10.1029/2006JE002814 (2007). [2] Piccioni, G, Drossart, P., Sanchez-Lavega, A., Hueso, R., Taylor, F., Wilson, C., Grassi, D., Zasova, L., Moriconi, M., Adriani, A., Lebonnois, S., Coradini, A., Bézard, B., Angrilli, F., Arnold, G., Baines, K. H., Bellucci, G., Benkhoff, J., Bibring, J. P., Blanco, A., Blecka, M. I., Carlson, R. W., Di Lellis, A., Encrenaz, T., Erard, S., Fonti1, S., Formisano, V., Fouchet, T., Garcia1, R., Haus, R., J. Helbert, J., Ignatiev, N. I., Irwin, P., Langevin,Y.,Lopez-Valverde, M. A., Luz, D., Marinangeli, L., Orofino, V., Rodin, A. V., Roos-Serote, M. C., Saggin, B., ,Stam, D. M., Titov, D., Visconti, G., and Zambelli M. South-polar features on Venus similar to those near the north, Nature, 450, 637-640, doi:10.1038/nature06209 (2007).

Limaye, S.; Moissl, R.; Markiewicz, W.; Titov, D.

2008-09-01

100

Proton cyclotron wave generation mechanisms upstream of Venus  

International Nuclear Information System (INIS)

Complete text of publication follows. Recent long term observations of proton cyclotron waves in the upstream region of Venus raise the question, under which general solar wind conditions these waves are generated and maintained. Magnetometer data of the Venus Express spacecraft for two Venusian years of observations are analyzed before, during and after the occurrence of the waves. The classical mechanism for nearly perpendicular configurations of the interplanetary magnetic field (BIMF) and the solar wind velocity (VSW) with ion pick-up into a ring-distribution in velocity space is investigated for its efficiency, as well as wave generation under quasi-parallel conditions for the VSW and BIMF , when the solar wind motional electric field is weak. It is found that stable magnetic field conditions for up to 20-30 minutes are required to enable sufficient ion pick-up and growth of the left-hand polarized wave component to obtain observable waves in the magnetometer data. Only few cases with persistent waves under quasi-perpendicular conditions of BIMF and VSW are detected. This indicates that instabilities driven by field-aligned planetary ion beams act as main generation mechanism for the proton cyclotron waves observed upstream of the Venus bow shock.

2009-01-01

 
 
 
 
101

Venus nitric oxide nightglow mapping from SPICAV nadir observations  

Science.gov (United States)

Nitric oxide ? (190-240 nm) and ? (255-270 nm) bands have been observed on the Venus nightside with Venus Express SPICAV instrument operated in the nadir mode. These ultraviolet emissions arise from the de-excitation of NO molecules created by radiative recombination of O(3P) and N(4S) atoms. These atoms are produced on the dayside of the planet through photodissociation of CO2 and N2 molecules and are transported to the nightside by the global subsolar to antisolar circulation. We analyze a wide dataset of nadir observations obtained since 2006 to determine the statistical distribution of the NO nightglow and its variability. Individual observations show a great deal of variability and may exhibit multiple maxima along latitudinal cuts. We construct and compare a global NO map with the results obtained during the Pioneer-Venus mission and with the recently observed O2(a1?g) nightglow distribution. The NO airglow distribution shows a statistical bright region extending from 01:00 to 03:30 local time and 25°S to 10°N, very similar to the Pioneer results obtained 35 years earlier during maximum solar activity conditions. The shift from the antisolar point and the difference with the O2 airglow indicate that superrotating zonal winds are statistically weak near 97 km, but play an important role near 115 km. We compare these results with other evidence for superrotation in the thermosphere and point out possible sources of momentum transfer.

Stiepen, A.; Gérard, J.-C.; Dumont, M.; Cox, C.; Bertaux, J.-L.

2013-09-01

102

Mars is close to venus--female reproductive proteins are expressed in the fat body and reproductive tract of honey bee (Apis mellifera L.) drones.  

UK PubMed Central (United Kingdom)

Vitellogenin (Vg) and lipophorin (Lp) are lipoproteins which play important roles in female reproductive physiology of insects. Both are actively taken up by growing oocytes and especially Vg and its receptor are considered as female-specifically expressed. The finding that the fat body of in honey bee (Apis mellifera) drones synthesizes Vg and is present in hemolymph has long been viewed as a curiosity. The recent paradigm change concerning the role played by Vg in honey bee life history, especially social division of labor, has now led us to investigate whether a physiological constellation similar to that seen in female reproduction may also be represented in the male sex. By means of Western blot analysis we could show that both Vg and Lp are present in the reproductive tract of adult drones, including the accessory (mucus) glands, but apparently are not secreted. Furthermore, we analyzed the transcript levels of the genes encoding these proteins (vg and lp), as well as their putative receptors (Amvgr and Amlpr) in fat body and accessory glands. Whereas lp, vg and Amlpr transcript levels decreased with age in both tissues, Amvgr mRNA levels increased with age in fat body. To our knowledge this is the first report that vitellogenin and its receptor are co-expressed in the reproductive system of a male insect. We interpret these findings as a cross-sexual transfer of a social physiological trait, associated with the rewiring of the juvenile hormone/vitellogenin circuitry that occurred in the female sex of honey bees.

Colonello-Frattini NA; Guidugli-Lazzarini KR; Simões ZL; Hartfelder K

2010-11-01

103

Mars is close to venus--female reproductive proteins are expressed in the fat body and reproductive tract of honey bee (Apis mellifera L.) drones.  

Science.gov (United States)

Vitellogenin (Vg) and lipophorin (Lp) are lipoproteins which play important roles in female reproductive physiology of insects. Both are actively taken up by growing oocytes and especially Vg and its receptor are considered as female-specifically expressed. The finding that the fat body of in honey bee (Apis mellifera) drones synthesizes Vg and is present in hemolymph has long been viewed as a curiosity. The recent paradigm change concerning the role played by Vg in honey bee life history, especially social division of labor, has now led us to investigate whether a physiological constellation similar to that seen in female reproduction may also be represented in the male sex. By means of Western blot analysis we could show that both Vg and Lp are present in the reproductive tract of adult drones, including the accessory (mucus) glands, but apparently are not secreted. Furthermore, we analyzed the transcript levels of the genes encoding these proteins (vg and lp), as well as their putative receptors (Amvgr and Amlpr) in fat body and accessory glands. Whereas lp, vg and Amlpr transcript levels decreased with age in both tissues, Amvgr mRNA levels increased with age in fat body. To our knowledge this is the first report that vitellogenin and its receptor are co-expressed in the reproductive system of a male insect. We interpret these findings as a cross-sexual transfer of a social physiological trait, associated with the rewiring of the juvenile hormone/vitellogenin circuitry that occurred in the female sex of honey bees. PMID:20600084

Colonello-Frattini, Nínive Aguiar; Guidugli-Lazzarini, Karina Rosa; Simões, Zilá Luz Paulino; Hartfelder, Klaus

2010-07-02

104

Comet Halley: The view from Pioneer Venus  

Energy Technology Data Exchange (ETDEWEB)

The plans to scan Halley's Comet at close range using the Pioneer Venus Orbiter are discussed. The composition of comets, their paths through space, and the history of comet encounters are examined. An ultraviolet spectrometer aboard the spacecraft will determine the composition of the gaseous coma and will measure the total gas production during its passage. The Pioneer Venus Orbiter will observe the comet for five weeks before solar interference with communications occurs as Venus passes on the far side of the Sun from Earth. Diagrams of the solar system and the relationship of the comet to the planets and the Sun are provided.

1989-01-01

105

Signs of possible volcanism on Venus  

Energy Technology Data Exchange (ETDEWEB)

In this paper the author discusses some independent facts established by exploration of Venus, and endeavors to clarify the origin of such phenomena as the electrical activity of the atmosphere, the bimodal particle distribution in the clouds on Venus, and the variable properties of the upper cloud deck, all discovered by polarimetric and radiometric techniques. Analysis of recent spacecraft data suggests that the frequent electrical discharges in the surface layers of the Venus atmosphere, the variable density of the submicron haze above the clouds and certain properties of the cloud microphysics can jointly be explained if the planetary surface is undergoing volcanic eruptions.

Ksanfomaliti, L.V.

1985-04-01

106

Meteoric ion layers in the ionospheres of venus and mars: Early observations and consideration of the role of meteor showers  

Science.gov (United States)

Layers of metal ions produced by meteoroid ablation have been known in Earth's ionosphere for decades, but have only recently been discovered at Venus and Mars. Here we report the results of a search for meteoric layers in earlier datasets from Venus and Mars. We find 13 candidates at Venus in Mariner 10, Venera 9/10, and Pioneer Venus Orbiter data that augment the 18 previously identified in Venus Express data. We find 8 candidates at Mars in Mariner 7 and Mariner 9 data that augment the 71 and 10 previously identified in Mars Global Surveyor and Mars Express data, respectively. These new findings extend the ranges of conditions under which meteoric layers have been observed, support studies of the temporal variability of meteoric layers, and (for Venus) independently confirm the existence of meteoric layers. One of the proposed causes of temporal variations in the occurrence rate of meteoric layers is meteor showers. This possibility is controversial, since meteor showers have minimal observed effect on meteoric layers in Earth's ionosphere. In order to aid progress towards a resolution of this issue, we present a series of tests for this hypothesis.

Withers, Paul; Christou, A. A.; Vaubaillon, J.

2013-10-01

107

Compilation System for Venus Radar Mission (Magellan).  

Science.gov (United States)

A synthetic aperture radar (SAR) compilation system was developed for extraction of topographic information of Venus from stereoradar imagery to be obtained from the Magellan mission. The system was developed for an AS-11AM analytical stereoplotter. Exten...

S. S. C. Wu F. J. Schafer A. Howington

1987-01-01

108

Laying bare Venus' dark secrets  

Energy Technology Data Exchange (ETDEWEB)

Ground-based IR observations of the dark side of Venus obtained in 1983 and 1985 with the Anglo-Australian Telescope are studied. An IR spectrum of Venus' dark side is analyzed. It is observed that the Venus atmosphere is composed of CO and radiation escapes only at 1.74 microns and 2.2 to 2.4 microns. The possible origin of the radiation, either due to absorbed sunlight or escaping thermal radiation, was investigated. These two hypotheses were eliminated, and it is proposed that the clouds of Venus are transparent and the radiation originates from the same stratum as the brighter portions but is weakened by the passage through the upper layer. The significance of the observed dark side markings is discussed.

Allen, D.A.

1987-10-01

109

The high-latitude ionospheres of the Earth and Venus  

Science.gov (United States)

The presence of a planetary magnetic field at Earth and the absence of such a field at Venus results in substantial differences in the dynamics and morphology of the high-latitude ionospheres. In both cases photoionisation is the primary mechanism by which the dayside ionosphere is created while particle precipitation and transport processes act to maintain the plasma densities at night. However the mechanisms driving plasma transport at Earth and Venus are fundamentally different and so the planetary ionospheres respond differently to solar activity. The transport of plasma has implications for aeronomy and atmospheric chemistry in the night sector. In the terrestrial case plasma is frozen in to the magnetic field. Transport in the polar regions is largely due to the high-latitude convection pattern which results from interaction of the terrestrial magnetic field with the interplanetary magnetic field (IMF) carried by the solar wind [1]. The convection varies with the orientation of the IMF and, under appropriate conditions, dayside plasma can be transported antisunward [2]. At Venus plasma transport is primarily driven by the day-to-night pressure gradient [3]. Lowering of the dayside ionopause under conditions of low solar flux inhibits this process [4] but it has been observed to have a significant effect in the pre-dawn sector at low-latitudes under conditions of moderate solar activity [5]. Aberystwyth University's ionospheric radiotomography experiment routinely observes the plasma distribution in the high-latitude terrestrial ionosphere in a latitude versus altitude plane. The polar orbit of Venus Express is ideal for investigating the Venusian high-latitude ionosphere close to the solar terminator with periapsis located close to 86o N. The ASPERA-4 instrument records the first extended in situ data set of the plasma environment under conditions of low solar activity. These two experiments provide a database covering all solar wind conditions and local time sectors. When Earth and Venus are aligned along the Parker spiral the two planets experience similar solar wind conditions. Observations conducted under these conditions close to solar minimum are presented at both planets and comparisons are drawn. The role of plasma transport is of particular interest and is discussed with reference to the driving processes. References: [1] Dungey, J. W. (1961) Phys. Rev. Let., 6, 47-49. [2] Foster, J. C. (1984) JGR, 89, 855-865. [3] Knudsen et al. (1981) GRL, 8, 241-244. [4] Knudsen et al. (1987) JGR, 92, 13391-13398. [5] Brannon et al. (1993) GRL, 20, 2739-2742.

Middleton, Helen; Wood, Alan; Pryse, Eleri; Grande, Manuel; Fallows, Richard

2010-05-01

110

[Transfection of HL-60 cells by Venus lentiviral vector].  

UK PubMed Central (United Kingdom)

In order to study the potential of Venus, lentiviral vector, applied to acute myeloid leukemia, the recombinant vector Venus-C3aR was transfected into 293T packing cells by DNA-calucium phosphate coprecipitation. All virus stocks were collected and transfected into HL-60, the GFP expression in HL-60 cells was measured by flow cytometry. The expression level of C3aR1 in transfected HL-60 cells was identified by RT-PCR and flow cytometry. The lentiviral toxicity on HL-60 was measured by using CCK-8 method and the ability of cell differentiation was observed. The results indicated that the transfection efficacy of letivial vector on HL-60 cells was more than 95%, which meets the needs for further study. C3aR1 expression on HL-60 cells increased after being transfected with recombinant lentiviral vector. Before and after transfection, the proliferation and differentiation of cells were not changed much. It is concluded that the lentiviral vector showed a high efficacy to transfect AML cells and can be integrated in genome of HL-60 cells to realize the stable expression of interest gene. Meanwhile, lentiviral vector can not affect HL-60 cell ability to proliferate and differentiate.

Li Z; Hu SY; Cen JN; Chen ZX

2013-06-01

111

Results of the first statistical study of pioneer Venus orbiter plasma observations in the distant Venus tail: Evidence for a hemispheric asymmetry in the pickup of ionospheric ions  

International Nuclear Information System (INIS)

Pioneer Venus Orbiter plasma and magnetometer observations from the first nine tail seasons of crossings of the Venus wake are used to study ion pickup in the far wake of an unmagnetized object embedded in the solar wind. This first statistical study treats all of the plasma spectra containing pickup ions in the vicinity of the Venus tail. The author finds a hemispheric asymmetry in the pickup of ionospheric ions, with approximately four times more O+ events observed in the northern magnetic hemisphere (where Z double-prime > O), i.e., the induced electric field points outward, (away from the ionopause boundary) than in the southern (Z double-prime + events, 125, or 75%, occurred in the northern hemisphere when position is calculated in terms of Venus radii and 129 or 77% occurred in the northern hemisphere when position is expressed in gyroradii. This hemisphere asymmetry in ion pickup is consistent with the prediction of the Cloutier et al. (1974) mass loading model for Venusian ions above the ionopause boundary.

1989-01-01

112

Results of the first statistical study of pioneer Venus orbiter plasma observations in the distant Venus tail: Evidence for a hemispheric asymmetry in the pickup of ionospheric ions  

Energy Technology Data Exchange (ETDEWEB)

Pioneer Venus Orbiter plasma and magnetometer observations from the first nine tail seasons of crossings of the Venus wake are used to study ion pickup in the far wake of an unmagnetized object embedded in the solar wind. This first statistical study treats all of the plasma spectra containing pickup ions in the vicinity of the Venus tail. The author finds a hemispheric asymmetry in the pickup of ionospheric ions, with approximately four times more O{sup +} events observed in the northern magnetic hemisphere (where Z{double prime} > O), i.e., the induced electric field points outward, (away from the ionopause boundary) than in the southern (Z{double prime} < O) magnetic hemisphere. Out of a total of 167 large O{sup +} events, 125, or 75%, occurred in the northern hemisphere when position is calculated in terms of Venus radii and 129 or 77% occurred in the northern hemisphere when position is expressed in gyroradii. This hemisphere asymmetry in ion pickup is consistent with the prediction of the Cloutier et al. (1974) mass loading model for Venusian ions above the ionopause boundary.

Intriligator, D.S. (Carmel Research Center, Santa Monica, CA (USA))

1989-02-01

113

Venus Transit 2004: A Virtual Education Approach to Measuring the Cosmos  

Science.gov (United States)

On June 8th 2004, a celestial event of immense historical scientific importance will once again occur as the silhouette of the planet Venus crosses the disk of the Sun. There have been only six occurrences of the transit of Venus since the invention of the telescope, the last five having been observed; the last one occurring in 1882. No one alive today has seen this event. Predicted by Kepler and Horrocks among others, Venus Transit provided a crucial test bed for the calculation of the Astronomical Unit and therefore was critical to our first real glimpses at the size and scale of the universe. The NASA OSS Education Support Network and its partner organizations in space science education have undertaken to capitalize on this event to provide educational programs, products, and remote observations of the transit to students, teachers, amateur astronomers, and the public. Online transit images from remote observatories spaced in latitude will allow both formal and informal education audiences to recreate the historic calculation of the AU and thus, the size of the solar system. Information and activities on related topics including planetary comparisons, stellar parallax, and the search for extra solar planets coupled with math, geography, and history components will be developed along with a web cast from Europe, museum programs, and other special events. This paper will describe the Venus Transit education program in its entirety and show how scientists can participate.

Mayo, L. A.

2003-05-01

114

Haze above the clouds on the night side of Venus from VIRTIS-M VEX observations  

Science.gov (United States)

VIRTIS-M -mapping spectrometer on Venus Express, worked on orbit around Venus from 2006 to 2009 years. There were obtained a lot of spectacular results on the night side of Venus in two geometries of measurements: nadir and limb modes. Nadir data don't allow obtaining vertical profile of aerosol, but make possible to map the upper boundary of the clouds. Limb data has an advantage in the air mass, which exceeds by a factor of 50 comparing to nadir data, giving possibility to observe even very thin hazes and obtain vertical profile. Polar orbit of Venus Express with pericenter at 75 N latitude allows to carry out limb measurements in the northern hemisphere. From the distance of 15 000 km to the planet the vertical haze profile is obtained with vertical resolution of 2.5 km. The observed haze in the spectral windows from 1 to 2.3 µm scatters the thermal radiation of the lower atmosphere. In the 4-5 µm range we observe the thermal emission of the haze parallel with scattered thermal emission of the upper clouds. Preliminary overview of the data shows different character of the haze at low and high latitudes: at high latitudes a haze typically is observed as a layer centered at altitudes 75-85 km. Vertical opacity profiles and estimation of haze properties are obtained. This work is in progress. Russian authors thank Russian Foundation of Basic Research for financial support, grant RFFI 12-02-12018a

Zasova, Ludmila; Ignatiev, Nikolay; Gorinov, Dmitry; Scherbina, Marina; Piccioni, Giuseppe; Drossart, Pierre

2013-04-01

115

Venus project : experimentation at ENEA`s pilot site  

Energy Technology Data Exchange (ETDEWEB)

The document describes the ENEA`s (Italian Agency for New Technologies, Energy and the Environment) experience in the Venus Project (Esprit III ). Venus is an advanced visual interface based on icon representation that permits to end-user to inquiry databases. VENUS interfaces to ENEA`s databases: cometa materials Module, Cometa Laboratories Module and European Programs. This report contents the results of the experimentation and of the validation carried out in ENEA`s related to the Venus generations. Moreover, the description of the architecture, the user requirements syntesis and the validation methodology of the VENUS systems have been included.

Bargellini, M.L.; Fontana, F. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dip. Innovazione; Bucci, C.; Ferrara, F.; Sottile, P.A. [GESI s.r.l., Rome (Italy); Niccolai, L.; Scavino, G. [Rome Univ. Sacro Cuore (Italy); Mancini, R.; Levialdi, S. [Rome Univ. La Sapienza (Italy). Dip. di Scienze dell`Informazione

1996-12-01

116

Planetary probe: origin of atmosphere of venus.  

UK PubMed Central (United Kingdom)

The high temperatures and chemical composition, as determined by space probe and terrestrial observation, suggest that the present atmosphere of Venus has formed by chemical interaction with the lithosphere. Although the precise reactions have not been identified, good theoretical approximations to the molecular abundance may be obtained from reactions applicable to terrestial rocks. The high temperatures and chemical reactivity create conditions on Venus which are fundamentally different from those on the cooler terrestrial planets where the attainment of equilibrium is prevented by kinetic barriers.

Mueller RF

1969-03-01

117

Morphometry of meteorite craters of Venus  

International Nuclear Information System (INIS)

The results of morphometric analysis of meteorite craters on Venus identified on Venera 15/16 space probes images are given. Estimations of depth of the craters, heights of central peaks over the crater floor and angle of inner slope of the craters have been made. The obtained estimations are compared with the appropriate data on the terrestrial and lunar meteorite craters. A conclusion has been made that in relation to depth/diameter ratio the craters of Venus are closer to terrestrial meteorite craters

1989-01-01

118

Radiative energy balance of the Venus mesosphere  

Energy Technology Data Exchange (ETDEWEB)

An accurate radiative transfer model for line-by-line gaseous absorption, as well as for cloud absorption and multiple scattering, is used in the present calculation of solar heating and thermal cooling rates for standard temperature profiles and temperatures yielded by the Venera 15 Fourier Spectrometer Experiment. A strong dependency is noted for heating and cooling rates on cloud-structure variations. The Venus mesosphere is characterized by main cloud-cover heating and overlying-haze cooling. These results are applicable to Venus atmosphere dynamical models. 24 refs.

Haus, R.; Goering, H. (Heinrich-Hertz-Institut fuer Atmosphaerenforschung und Geomagnetismus, Berlin (German Democratic Republic))

1990-03-01

119

Pioneer Venus observations of the Venus dayglow spectrum 1250--1430 A  

Energy Technology Data Exchange (ETDEWEB)

The spectrum of the dayglow of Venus between 1250 and 1430 A has been measured by the Pioneer Venus Orbiter Ultraviolet Spectrometer. Four bands of the (14,v'') progression in the fourth positive system of carbon monoxide are identified and their excitation mechanism is shown to be fluorescent scattering of the solar Lyamn alpha line. The (14,3) and (14,4) bands at 1317 and 1354 A are blended with the atomic oxygen 1304 and 1356 A lines. The (14,5) band at 1392 A is a prominent unblended spectral feature in the Venus dayglow. This identification provides an additional remote sensing technique to determine the density distribution of carbon monoxide in the upper atmosphere of Venus.

Durrance, S.T.; Barth, C.A.; Ian, A.; Stewart, F.

1980-03-01

120

ANALYSIS OF X-RAY SPECTRA EMITTED FROM THE VENUS ECR ION SOURCE  

Energy Technology Data Exchange (ETDEWEB)

The Versatile Electron Cyclotron resonance ion source for Nuclear Science (VENUS), located at Lawrence Berkeley National Lab’s 88-inch cyclotron, extracts ion beams from a plasma created by ionizing a gas with energetic electrons. Liquid-helium cooled superconducting coils produce magnetic fi elds that confi ne the plasma and high microwave frequencies heat the electrons enough to allow for successive ionizations of the neutral gas atoms. The combination of strong plasma confi nement and high microwave frequencies results in VENUS’ production of record breaking ion beam currents and high charge state distributions. While in operation, VENUS produces signifi cant quantities of bremsstrahlung, in the form of x-rays, primarily through two processes: 1) electron-ion collisions within the plasma, and 2) electrons are lost from the plasma, collide with the plasma chamber wall, and radiate bremsstrahlung due to their sudden deceleration. The bremsstrahlung deposited into the plasma chamber wall is absorbed by the cold mass used to maintain superconductivity in the magnets and poses an additional heat load on the cryostat. In order for VENUS to reach its maximum operating potential of 10 kW of 28 GHz microwave heating frequency, the heat load posed by the emitted bremsstrahlung must be understood. In addition, studying the bremsstrahlung under various conditions will help further our understanding of the dynamics within the plasma. A code has been written, using the Python programming language, to analyze the recorded bremsstrahlung spectra emitted from the extraction end of VENUS. The code outputs a spectral temperature, which is relatively indicative of the temperature of the hot electrons, and total integrated count number corresponding to each spectra. Bremsstrahlung spectra are analyzed and compared by varying two parameters: 1) the heating frequency, 18 GHz and 28 GHz, and 2) the ratio between the minimum magnetic fi eld and the resonant magnetic fi eld, .44 and .70, at the electron resonant zone.

Benitez, J.; Leitner, D.

2008-01-01

 
 
 
 
121

Remote Raman - laser induced breakdown spectroscopy (LIBS) geochemical investigation under Venus atmospheric conditions  

Energy Technology Data Exchange (ETDEWEB)

The extreme Venus surface temperatures ({approx}740 K) and atmospheric pressures ({approx}93 atm) create a challenging environment for surface missions. Scientific investigations capable of Venus geochemical observations must be completed within hours of landing before the lander will be overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing the geochemical science goals without the risks associated with collecting samples and bringing them into the lander. Wiens et al. and Sharma et al. demonstrated that both analytical techniques can be integrated into a single instrument capable of planetary missions. The focus of this paper is to explore the capability to probe geologic samples with Raman - LIBS and demonstrate quantitative analysis under Venus surface conditions. Raman and LIBS are highly complementary analytical techniques capable of detecting both the mineralogical and geochemical composition of Venus surface materials. These techniques have the potential to profoundly increase our knowledge of the Venus surface composition, which is currently limited to geochemical data from Soviet Venera and VEGA landers that collectively suggest a surface composition that is primarily tholeiitic basaltic with some potentially more evolved compositions and, in some locations, K-rich trachyandesite. These landers were not equipped to probe the surface mineralogy as can be accomplished with Raman spectroscopy. Based on the observed compositional differences and recognizing the imprecise nature of the existing data, 15 samples were chosen to constitute a Venus-analog suite for this study, including five basalts, two each of andesites, dacites, and sulfates, and single samples of a foidite, trachyandesite, rhyolite, and basaltic trachyandesite under Venus conditions. LIBS data reduction involved generating a partial least squares (PLS) model with a subset of the rock powder standards to quantitatively determine the major elemental abundance of the remaining samples. PLS analysis suggests that the major element compositions can be determined with root mean square errors ca. 5% (absolute) for SiO{sub 2}, Al{sub 2}O{sub 3}, Fe{sub 2}O{sub 3}(total), MgO, and CaO, and ca. 2% or less for TiO{sub 2}, Cr{sub 2}O{sub 3}, MnO, K{sub 2}O, and Na{sub 2}O. Finally, the Raman experiments have been conducted under supercritical CO{sub 2} involving single-mineral and mixed-mineral samples containing talc, olivine, pyroxenes, feldspars, anhydrite, barite, and siderite. The Raman data have shown that the individual minerals can easily be identified individually or in mixtures.

Clegg, Sanuel M [Los Alamos National Laboratory; Barefield, James E [Los Alamos National Laboratory; Humphries, Seth D [Los Alamos National Laboratory; Wiens, Roger C [Los Alamos National Laboratory; Vaniman, D. T. [Los Alamos National Laboratory; Sharma, S. K. [UNIV OF HAWAII; Misra, A. K. [UNIV OF HAWAII; Dyar, M. D. [MT. HOLYOKE COLLEGE; Smrekar, S. E. [JET PROPULSION LAB.

2010-12-13

122

Oxygen ion escape from Venus in a global hybrid simulation: role of the ionospheric O+ ions  

Directory of Open Access Journals (Sweden)

Full Text Available We study the solar wind induced oxygen ion escape from Venus' upper atmosphere and the Venus Express observations of the Venus-solar wind interaction by the HYB-Venus hybrid simulation code. We compare the simulation to the magnetic field and ion observations during an orbit of nominal upstream conditions. Further, we study the response of the induced magnetosphere to the emission of planetary ions. The hybrid simulation is found to be able to reproduce the main observed regions of the Venusian plasma environment: the bow shock (both perpendicular and parallel regions), the magnetic barrier, the central tail current sheet, the magnetic tail lobes, the magnetosheath and the planetary wake. The simulation is found to best fit the observations when the planetary oxy~escape rate is in the range from 3×1024 s?1 to 1.5×1025 s?1. This range was also found to be a limit for a test particle-like behaviour of the planetary ions: the higher escape rates manifest themselves in a different global configuration of the Venusian induced magnetosphere.

R. Jarvinen; E. Kallio; P. Janhunen; S. Barabash; T. L. Zhang; V. Pohjola; I. Sillanpää

2009-01-01

123

Mesospheric vertical thermal structure and winds on Venus from HHSMT CO spectral-line observations  

CERN Multimedia

We report vertical thermal structure and wind velocities in the Venusian mesosphere retrieved from carbon monoxide (12CO J=2-1 and 13CO J=2-1) spectral line observations obtained with the Heinrich Hertz Submillimeter Telescope (HHSMT). We observed the mesosphere of Venus from two days after the second Messenger flyby of Venus (on June 5 2007 at 23:10 UTC) during five days. Day-to-day and day-to-night temperature variations and short-term fluctuations of the mesospheric zonal flow were evident in our data. The extensive layer of warm air detected recently by SPICAV at 90 - to 100 km altitude is also detected in the temperature profiles reported here. These data were part of a coordinated ground-based Venus observational campaign in support of the ESA Venus Express mission. Furthermore, this study attempts to cross-calibrate space- and ground-based observations, to constrain radiative transfer and retrieval algorithms for planetary atmospheres, and to contribute to a more thorough understanding of the global pa...

Rengel, M; Jarchow, C

2008-01-01

124

Analyses of EW processes in VENUS  

Energy Technology Data Exchange (ETDEWEB)

Present status of analyses for electro-weak processes by the VENUS collaboration is presented. Topics covered are; (1) leptonic processes that include Bhabha, {mu}- and {gamma}-pair productions, (2) hadronic processes including total cross-section (R{sub had}) and charm and bottom quark productions, and (3) single photon events. All results are very preliminary. (author).

Sumiyoshi, T. [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

1993-04-01

125

Venus surface power and cooling systems  

Science.gov (United States)

A mission to the surface of Venus would have high scientific value, but most electronic devices and sensors cannot operate at the 450 °C ambient surface temperature of Venus. Power and cooling systems were analyzed for Venus surface operation. A radioisotope power and cooling system was designed to provide electrical power for a probe operating on the surface of Venus. For a mission duration of substantial length, the use of thermal mass to maintain an operable temperature range is likely impractical, and active refrigeration may be required to keep components at a temperature below ambient. Due to the high thermal convection of the high-density atmosphere, the heat rejection temperature was assumed to be at a 500 °C radiator temperature, 50 °C above ambient. The radioisotope Stirling power converter designed produces a thermodynamic power output capacity of 478.1 W, with a cooling power of 100 W. The overall efficiency is calculated to be 23.36%. The mass of the power converter is estimated at approximately 21.6 kg.

Landis, Geoffrey A.; Mellott, Kenneth C.

2007-12-01

126

Radar determination of the radius of venus.  

UK PubMed Central (United Kingdom)

The radius of Venus has been determined from radar-range data taken at the Jet Propulsion Laboratory's Goldstone facility. A simultaneous intergration of the equations of motion of the solar-system fit to this time-delay data gave a value of 6053.7 +/- 2.2 kilometers. A discussion of other Venusian radius determinations is made.

Melbourne WG; Muhleman DO; O'handley DA

1968-05-01

127

Solar activity and conjunctions of Venus  

Energy Technology Data Exchange (ETDEWEB)

Between 1856 and 1954, i.e. during 9 solar cycles, the Wolf numbers were significantly higher at superior conjunctions of Venus than an inferior conjunctions. The role of small isolated spots could be of some importance, but no theoretical explanation for the observed differences has been proposed.

Link, F.; Link, J. (Institut d' Astrophysique, 79 - Paris (France))

1983-06-20

128

Laboratory corroboration of the pioneer venus gas chromatograph analyses.  

UK PubMed Central (United Kingdom)

Laboratory simulation and tests of the inlet sampling system and columns of the Pioneer Venus gas chromatograph show that the sensitivity to argon is not diminished after the column regeneration step, argon isotopes are not separated, oxygen and sulfur dioxide are not produced in the inlet sampling system from sulfur trioxide, and sulfur trioxide is not formed from sulfur dioxide and oxygen. Comparisons of the volatile inventory of Venus and Earth imply similar efficiencies of early outgassing but a lower efficiency for later outgassing in the case of Venus. The high oxidation state of the Venus atmosphere in the region of cloud formation may prohibit the generation of elemental sulfur particles.

Oyama VI; Carle GC; Woeller F; Pollack JB

1979-07-01

129

Cometary water on Venus - implications of stochastic impacts  

Energy Technology Data Exchange (ETDEWEB)

Attention is given to a Venus water abundance model, incorporating a stochastic cometary source and nonthermal hydrogen escape, that reproduces both the near-steady-state balance between escape loss and infall replenishment implied by Venus' short water lifetime, and the consistency of the observed deuterium-to-hydrogen ratio with a steady state. It is shown that the stochastic variability of each of these quantities is large. Water's quasi-steady state on Venus is judged to be mediated by comet impacts, leading to an obscuration of the early water history of Venus by the history of random impacts. 40 references.

Grinspoon, D.H.; Lewis, J.S.

1988-04-01

130

The radar scattering characteristics of Venus landforms  

International Nuclear Information System (INIS)

Nine geologic units are identified in a recently published Arecibo image of the Venus equatorial region. A detailed examination of the radar scattering properties of these units using data from the imaging mode of the Pioneer Venus Radar Mapper (PVM) shows them to fall into three distinct classes: (1) dark plains, (2) tessera, narrow-spaced parallel lineaments, and bright and dark banded terrain, and (3) bright plains, mottled plains, ovoids, lineament belts, and edifices. Additional units interpreted to be analogous to those mapped from the Arecibo data are identified in the region imaged exclusively by PVM, and are found to have similar scattering properties. An examination of the scattering properties of units mapped as tessera--Tellus Regio and eastern Beta Regio, as compared with the northern flanks of Thetis Regio--leads to the conclusion that part of Thetis possesses characteristics similar to Tellus.

1990-01-01

131

Venus transit, aureole and solar diameter  

CERN Document Server

The possibility to measure the solar diameter using the transits of Mercury has been exploited to investigate the past three centuries of its evolution and to calibrate these measurements made with satellites. This measurement basically consists to compare the ephemerides of the internal contact timings with the observed timings. The transits of Venus of 2004 and 2012 gave the possibility to apply this method, involving a planet with atmosphere, with the refraction of solar light through it creating a luminous arc all around the disk of the planet. The observations of the 2012 transit made to measure the solar diameter participate to the project Venus Twilight Experiment to study the aureole appearing around it near the ingress/egress phases.

Xie, Wenbin; Wang, Xiaofan; Tanga, Paolo

2012-01-01

132

Venus y el fin del mundo  

Directory of Open Access Journals (Sweden)

Full Text Available Este artículo busca demostrar que los argumentos generales acerca de la exploración científica valen también para las ciencias espaciales. El trabajo se basa en el ejemplo de la exploración de Venus y lo que esta nos dice acerca de nuestro propio planeta. Argumenta que el concepto de la probabilidad de Leslie es incorrecto, como también lo son las dudas sobre la evidencia Venusiana. Así mismo, concluye que no se puede rechazar la importancia que tienen los descubrimientos inesperados que han resultado de la exploración de Venus para ayudarnos a comprender nuestro propio planeta. Y que si van a ser rechazados estos descubrimientos debe ser por razones científicas, no por intuiciones acerca de la probabilidad.

Gonzalo Munévar

2006-01-01

133

Plasma channels in the Venus upper ionosphere  

Directory of Open Access Journals (Sweden)

Full Text Available The structure of the Venus nightside ionosphere is modeled in terms of a flow configuration derived from the position of the intermediate transition along the flanks of the ionosheath downstream from the magnetic polar regions. It is suggested that the shocked solar wind erodes more strongly the polar ionosphere producing plasma channels that extend downstream from the magnetic polar regions. Such features represent the main source of mass loss along the plasma tail and imply a small overall solar wind-induced depletion of the planetary ionosphere. The plasma channels can account for the observation of ionospheric holes in PVO passes through the Venus wake. The expected flow distribution within the wake is consistent with the entry of plasma fluxes from the magnetic polar regions that was suggested earlier to account for geometry of the nightside ionopause (Pérez de Tejada, 1980).

H. Pérez de Tejada

2001-01-01

134

La Hieroglyphica y el Nacimiento de Venus  

Directory of Open Access Journals (Sweden)

Full Text Available Sin duda a Botticelli se le debe el honor de ser el primero en pintar cuadros mitológicos monumentales que en tamaño competían con el arte religioso de la época. Entre sus argumentos, los más afamados vienen a ser las dos pinturas (hacia 1478) hoy custodiadas en los Uffizi y que conocemos como La Primavera y el Nacimiento de Venus, fábulas que proceden muy probablemente de la Villa di Castello de la que era propietario Lorenzo de Pierfrancesco, primo de Lorenzo de Médici y mecenas del maestro pintor. Las dos pinturas, como analizan importantes historiadores como Gombrich y Panofsky parecen responder a un concreto programa argumentai de claro sentido platónico y que explican la idea del Amor a través de la Venus Humanitas y la Celestis, es decir, el sentimiento humano y el contemplativo, comportamientos generados por Dios y por lo tanto, buenos en sí mismos…

González de Zarate, Jesús maría

2003-01-01

135

Nature of the ultraviolet absorber in the venus clouds: inferences based on pioneer venus data.  

Science.gov (United States)

Several photometric measurements of Venus made from the Pioneer Venus orbiter and probes indicate that solar near-ultraviolet radiation is being absorbed throughout much of the main cloud region, but little above the clouds or within the first one or two optical depths. Radiative transfer calculations were carried out to simulate both Pioneer Venus and ground-based data for a number of proposed cloud compositions. This comparison rules out models invoking nitrogen dioxide, meteoritic material, and volatile metals as the source of the ultraviolet absorption. Models involving either small ( approximately 1 micrometer) or large ( approximately 10 micrometers) sulfur particles have some serious difficulties, while ones invoking sulfur dioxide gas appear to be promising. PMID:17778908

Pollack, J B; Ragent, B; Boese, R; Tomasko, M G; Blamont, J; Knollenberg, R G; Esposito, L W; Stewart, A I; Travis, L

1979-07-01

136

Venus clouds: a dirty hydrochloric Acid model.  

UK PubMed Central (United Kingdom)

The spectral and polarization data for Venus are consistent with micrometer-sized aerosol cloud particles of hydrochloric acid with soluble and insoluble iron compounds, whose source could be volcanic or crustal dust. The yellow color of the clouds could be due to absorption bands in the near ultraviolet involving ferric iron and chlorine complexes. The ultraviolet features could arise from variations in the concentrations of iron and hydrochloric acid in the cloud particles.

Hapke B

1972-02-01

137

Pioneer Venus orbiter magnetic field and plasma observations in the Venus magnetotail  

Energy Technology Data Exchange (ETDEWEB)

This study uses Pioneer Venus orbiter (PVO) magnetometer and plasma analyzer measurements to investigate the draped-field tail of Venus with an emphasis on determining the magnetic field and plasma conditions within the various tail regions and their dependence upon interplanetary magnetic field (IMF) orientation. For this purpose PVO orbits during which the spacecrafts high inclination trajectory took it through the central magnetotail were identified. Analysis of the observations taken during those orbits indicates that the distribution of plasma within the magnetotail is highly asymmetric and controlled by the orientation of the IMF. In the plasma sheet and adjacent lobe regions downstream of the Venus hemisphere over which the solar wind motional electric field, is directed away from the planet, PVO observed increasing fluxes of H{sup +} and O{sup +} as the spacecraft moves away from the tail axis toward the outer boundary of the tail. No O{sup +} ions were observed outside of the magnetotail based upon the magnetic field data and the definitions adopted in this study. Downstream of the Venus hemisphere over which the solar wind motional electric field is directed in toward the planet, PVO does not usually observe significant fluxes of E/Q = 0-8 kV ions, except sometimes directly adjacent to the outer boundary of the tail. These results are interpreted as being due to the more efficient pick-up of newly ionized atmospheric neutrals over the Venus hemisphere where the initial gyromotion takes the newly created ions away from the dense, lower atmosphere where they might be lost due to scattering (Cloutier et al., 1974). The implications of these findings for the formation and maintenance of the Venus magnetotail are discussed.

Slavin, J.A. (NASA Goddard Space Flight Center, Greenbelt, MD (USA)); Intriligator, D.S. (Carmel Research Center, Santa Monica, CA (USA)); Smith, E.J. (California Institute of Technology, Pasadena (USA))

1989-03-01

138

Average configuration of the induced venus magnetotail  

International Nuclear Information System (INIS)

[en] In this paper we discuss the interaction of the solar wind flow with Venus and describe the morphology of magnetic field line draping in the Venus magnetotail. In particular, we describe the importance of the interplanetary magnetic field (IMF) X-component in controlling the configuration of field draping in this induced magnetotail, and using the results of a recently developed technique, we examine the average magnetic configuration of this magnetotail. The derived J x B forces must balance the average, steady state acceleration of, and pressure gradients in, the tail plasma. From this relation the average tail plasma velocity, lobe and current sheet densities, and average ion temperature have been derived. In this study we extend these results by making a connection between the derived consistent plasma flow speed and density, and the observational energy/charge range and sensitivity of the Pioneer Venus Orbiter (PVO) plasma analyzer, and demonstrate that if the tail is principally composed of O+, the bulk of the plasma should not be observable much of the time that the PVO is within the tail. Finally, we examine the importance of solar wind slowing upstream of the obstacle and its implications for the temperature of pick-up planetary ions, compare the derived ion temperatures with their theoretical maximum values, and discuss the implications of this process for comets and AMPTE-type releases

1985-01-01

139

Solar diameter with 2012 Venus transit  

CERN Multimedia

The role of Venus and Mercury transits is crucial to know the past history of the solar diameter. Through the W parameter, the logarithmic derivative of the radius with respect to the luminosity, the past values of the solar luminosity can be recovered. The black drop phenomenon affects the evaluation of the instants of internal and external contacts between the planetary disk and the solar limb. With these observed instants compared with the ephemerides the value of the solar diameter is recovered. The black drop and seeing effects are overcome with two fitting circles, to Venus and to the Sun, drawn in the undistorted part of the image. The corrections of ephemerides due to the atmospheric refraction will also be taken into account. The forthcoming transit of Venus will allow an accuracy on the diameter of the Sun better than 0.01 arcsec, with good images of the ingress and of the egress taken each second. Chinese solar observatories are in the optimal conditions to obtain valuable data for the measurement ...

Sigismondi, Costantino

2012-01-01

140

Venus tectonics: initial analysis from magellan.  

UK PubMed Central (United Kingdom)

Radar imaging and altimetry data from the Magellan mission have revealed a diversity of deformational features at a variety of spatial scales on the Venus surface. The plains record a superposition of different episodes of deformation and volcanism; strain is both areally distributed and concentrated into zones of extension and shortening. The common coherence of strain patterns over hundreds of kilometers implies that many features in the plains reflect a crustal response to mantle dynamic processes. Ridge belts and mountain belts represent successive degrees of lithospheric shortening and crustal thickening; the mountain belts also show widespread evidence for extension and collapse both during and following crustal compression. Venus displays two geometrical patterns of concentrated lithospheric extension: quasi-circular coronae and broad rises with linear rift zones; both are sites of significant volcanism. No long, large-offset strike-slip faults have been observed, although limited local horizontal shear is accommodated across many zones of crustal shortening. In general, tectonic features on Venus are unlike those in Earth's oceanic regions in that strain typically is distributed across broad zones that are one to a few hundred kilometers wide, and separated by stronger and less deformed blocks hundreds of kilometers in width, as in actively deforming continental regions on Earth.

Solomon SC; Head JW; Kaula WM; McKenzie D; Parsons B; Phillips RJ; Schubert G; Talwani M

1991-04-01

 
 
 
 
141

Average configuration of the induced venus magnetotail  

Energy Technology Data Exchange (ETDEWEB)

In this paper we discuss the interaction of the solar wind flow with Venus and describe the morphology of magnetic field line draping in the Venus magnetotail. In particular, we describe the importance of the interplanetary magnetic field (IMF) X-component in controlling the configuration of field draping in this induced magnetotail, and using the results of a recently developed technique, we examine the average magnetic configuration of this magnetotail. The derived J x B forces must balance the average, steady state acceleration of, and pressure gradients in, the tail plasma. From this relation the average tail plasma velocity, lobe and current sheet densities, and average ion temperature have been derived. In this study we extend these results by making a connection between the derived consistent plasma flow speed and density, and the observational energy/charge range and sensitivity of the Pioneer Venus Orbiter (PVO) plasma analyzer, and demonstrate that if the tail is principally composed of O/sup +/, the bulk of the plasma should not be observable much of the time that the PVO is within the tail. Finally, we examine the importance of solar wind slowing upstream of the obstacle and its implications for the temperature of pick-up planetary ions, compare the derived ion temperatures with their theoretical maximum values, and discuss the implications of this process for comets and AMPTE-type releases.

McComas, D.J.; Spence, H.E.; Russell, C.T.

1985-01-01

142

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

UK PubMed Central (United Kingdom)

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.

Schulze-Makuch D; Dohm JM; Fairén AG; Baker VR; Fink W; Strom RG

2005-12-01

143

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

Science.gov (United States)

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. PMID:16379531

Schulze-Makuch, Dirk; Dohm, James M; Fairén, Alberto G; Baker, Victor R; Fink, Wolfgang; Strom, Robert G

2005-12-01

144

Schumann Resonances Seen in the Venus Ionosphere: Possible Probes of Venus Interior  

Science.gov (United States)

Schumann resonances are wave paths that circle the globe bouncing between the conducting surface or interior of a planet and its ionosphere. On Earth, these resonances start at about 7 Hz. We see apparent resonance bands in the Venus ionosphere but at these frequencies are not clearly at the Schumann resonant frequencies. This could be due to the different reflection depth of the Venus interior, but we do not yet have sufficient events to determine if this is the cause of the frequency shift. We will continue to search for new events.

Russell, C. T.; Hart, R.; Strangeway, R. J.; Zhang, T. L.

2012-09-01

145

Electromagnetic Waves Observed on a Flight over a Venus Electrical Storm  

Science.gov (United States)

The observations of electromagnetic signals from 0 to 64 Hz using the two fluxgate magnetometers on Venus Express have been enabled by new, improved cleaning algorithms. These data reveal two types of signals that are associated with electrical activity in Venus' atmosphere. The first signals occur below about 20 Hz, where signals can propagate perpendicular to the magnetic field. These signals consist of waves arriving from different directions across the field just as expected from discharges occurring in different places within the clouds beneath the spacecraft. The other type of signal occurs both at high (>20 Hz) and low (<20 Hz) frequencies and represent connection along the magnetic field to a more distant storm. The signals are right-hand circularly polarized and propagate parallel to the magnetic field. The former event was on the dayside and the latter event on the night side. These events appear to require magnetic fields that dip into the atmosphere away from their usual horizontal orientation. We continue to survey the Venus Express data for more search intervals.

Russell, C. T.; Leinweber, H.; Zhang, T. L.; Daniels, J. T. M.; Strangeway, R. J.; Wei, H. Y.

2012-09-01

146

Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars  

Directory of Open Access Journals (Sweden)

Full Text Available Foreshock ions are compared between Venus and Mars at energies of 0.6~20 keV using the same ion instrument, the Ion Mass Analyser, on board both Venus Express and Mars Express. Venus Express often observes accelerated protons (2~6 times the solar wind energy) that travel away from the Venus bow shock when the spacecraft location is magnetically connected to the bow shock. The observed ions have a large field-aligned velocity compared to the perpendicular velocity in the solar wind frame, and are similar to the field-aligned beams and intermediate gyrating component of the foreshock ions in the terrestrial upstream region. Mars Express does not observe similar foreshock ions as does Venus Express, indicating that the Martian foreshock does not possess the intermediate gyrating component in the upstream region on the dayside of the planet. Instead, two types of gyrating protons in the solar wind frame are observed very close to the Martian quasi-perpendicular bow shock within a proton gyroradius distance. The first type is observed only within the region which is about 400 km from the bow shock and flows tailward nearly along the bow shock with a similar velocity as the solar wind. The second type is observed up to about 700 km from the bow shock and has a bundled structure in the energy domain. A traversal on 12 July 2005, in which the energy-bunching came from bundling in the magnetic field direction, is further examined. The observed velocities of the latter population are consistent with multiple specular reflections of the solar wind at the bow shock, and the ions after the second reflection have a field-aligned velocity larger than that of the de Hoffman-Teller velocity frame, i.e., their guiding center has moved toward interplanetary space out from the bow shock. To account for the observed peculiarity of the Martian upstream region, finite gyroradius effects of the solar wind protons compared to the radius of the bow shock curvature and effects of cold ion abundance in the bow shock are discussed.

M. Yamauchi; Y. Futaana; A. Fedorov; R. A. Frahm; J. D. Winningham; E. Dubinin; R. Lundin; S. Barabash; M. Holmström; C. Mazelle; J.-A. Sauvaud; T. L. Zhang; W. Baumjohann; A. J. Coates; M. Fraenz

2011-01-01

147

The venus kinase receptor (VKR) family: structure and evolution.  

UK PubMed Central (United Kingdom)

BACKGROUND: Receptor tyrosine kinases (RTK) form a family of transmembrane proteins widely conserved in Metazoa, with key functions in cell-to-cell communication and control of multiple cellular processes. A new family of RTK named Venus Kinase Receptor (VKR) has been described in invertebrates. The VKR receptor possesses a Venus Fly Trap (VFT) extracellular module, a bilobate structure that binds small ligands to induce receptor kinase activity. VKR was shown to be highly expressed in the larval stages and gonads of several invertebrates, suggesting that it could have functions in development and/or reproduction. RESULTS: Analysis of recent genomic data has allowed us to extend the presence of VKR to five bilaterian phyla (Platyhelminthes, Arthropoda, Annelida, Mollusca, Echinodermata) as well as to the Cnidaria phylum. The presence of NveVKR in the early-branching metazoan Nematostella vectensis suggested that VKR arose before the bilaterian radiation. Phylogenetic and gene structure analyses showed that the 40 receptors identified in 36 animal species grouped monophyletically, and likely evolved from a common ancestor. Multiple alignments of tyrosine kinase (TK) and VFT domains indicated their important level of conservation in all VKRs identified up to date. We showed that VKRs had inducible activity upon binding of extracellular amino-acids and molecular modeling of the VFT domain confirmed the structure of the conserved amino-acid binding site. CONCLUSIONS: This study highlights the presence of VKR in a large number of invertebrates, including primitive metazoans like cnidarians, but also its absence from nematodes and chordates. This little-known RTK family deserves to be further explored in order to determine its evolutionary origin, its possible interest for the emergence and specialization of Metazoa, and to understand its function in invertebrate development and/or reproductive biology.

Vanderstraete M; Gouignard N; Ahier A; Morel M; Vicogne J; Dissous C

2013-01-01

148

Automatic calibration system for VENUS lead glass counters  

International Nuclear Information System (INIS)

Automatic calibration system for VENUS lead glass counters has been constructed. It consists of a moving table, position sensors, control electronics and a master minicomputer, (micro-11 of DEC). The system has been well operated for six months and one third of VENUS lead glass counters have been calibrated. (author)

1985-01-01

149

Critical experiments: Recent and future international programmes in VENUS  

International Nuclear Information System (INIS)

This paper outlines the outstanding measurement capabilities of the VENUS critical facility, by giving examples of validation calculations against the two experimental databases VIPEX and VIPO. Then, the two future programmes, called REBUS-BWR and VIPOX, are investigated by calculation. The paper ends by prospecting other possible projects with VENUS. (author)

2003-01-01

150

Helium on Venus: implications for uranium and thorium  

Energy Technology Data Exchange (ETDEWEB)

Helium is removed at an average rate of 10/sup 6/ atoms per square centimeter per second from Venus's atmoshere by the solar wind following ionization above the plasmapause. The surface source of helium-4 on Venus is similar to that on Earth, suggesting comparable abundance of crustal uranium and thorium.

Prather, M.J.; McElroy, M.B.

1983-04-22

151

Venus transit 2004: Illustrating the capability of exoplanet transmission spectroscopy  

CERN Multimedia

The transit of Venus in 2004 offered the rare possibility to remotely sense a well-known planetary atmosphere using ground-based observations for absorption spectroscopy. Transmission spectra of Venus' atmosphere were obtained in the near infrared using the Vacuum Tower Telescope (VTT) in Tenerife. Since the instrument was designed to measure the very bright photosphere of the Sun, extracting Venus' atmosphere was challenging. CO_2 absorption lines could be identified in the upper Venus atmosphere. Moreover, the relative abundance of the three most abundant CO_2 isotopologues could be determined. The observations resolved Venus' limb, showing Doppler-shifted absorption lines that are probably caused by high-altitude winds. This paper illustrates the ability of ground-based measurements to examine atmospheric constituents of a terrestrial planet atmosphere which might be applied in future to terrestrial extrasolar planets.

Hedelt, P; Brown, T; Vera, M Collados; Rauer, H; Schleicher, H; Schmidt, W; Schreier, F; Titz, R

2011-01-01

152

Initial observations of the nightside ionosphere of venus from pioneer venus orbiter radio occultations.  

UK PubMed Central (United Kingdom)

Pioneer Venus orbiter dual-frequency radio occultation measurements have produced many electron density profiles of the nightside ionosphere of Venus. Thirty-six of these profiles, measured at solar zenith angles (chi) from 90.60 degrees to 163.5 degrees , are discussed here. In the "deep" nightside ionosphere (chi > 110 degrees ), the structure and magnitude of the ionization peak are highly variable; the mean peak electron density is 16,700 +/- 7,200 (standard deviation) per cubic centimeter. In contrast, the altitude of the peak remains fairly constant with a mean of 142.2 +/- 4.1 kilometers, virtually identical to the altitude of the main peak of the dayside terminator ionosphere. The variations in the peak ionization are not directly related to contemporal variations in the solar wind speed. It is shown that electron density distributions similar to those observed in both magnitude and structure can be produced by the precipitation on the nightside of Venus of electron fluxes of about 108 per square centimeter per second with energies less than 100 electron volts. This mechanism could very likely be responsible for the maintenance of the persistent nightside ionosphere of Venus, although transport processes may also be important.

Kliore AJ; Patel IR; Nagy AF; Cravens TE; Gombosi TI

1979-07-01

153

Topographic comparisons of uplift features on Venus and Earth: Implications for Venus tectonics  

Science.gov (United States)

Venus and Earth display different hypsography. We use topographic profiles to search for well-understood terrestrial analogs to venusian features. Specifically, by using cross-correlation, we correlate average profiles for terrestrial rifts (slow and fast, "ultra-slow," incipient and inactive) and also hotspots (oceanic and continental) with those for venusian chasmata and regiones, to draw inferences as to the processes responsible for shaping Venus' surface. Correlations tend to improve with faster spreading rates; Venus' correlations rank considerably lower than terrestrial ones, suggesting that if chasmata are analogous to terrestrial spreading centers, then spreading on Venus barely attains ultra-slow rates. Individual features' normalized average profiles are correlated with profiles of other such features to establish the degree of similarity, which in turn allows for the construction of a covariance matrix. Principal component analysis of this covariance matrix shows that Yellowstone more strongly resembles Atla, Beta and W. Eistla regiones than it does the terrestrial oceanic hotspots, and that venusian chasmata, especially Ganis, most closely resemble the ultra-slow spreading Arctic ridge.

Stoddard, Paul R.; Jurdy, Donna M.

2012-02-01

154

The Venus nitric oxide night airglow: Model calculations based on the Venus thermospheric general circulation model  

Energy Technology Data Exchange (ETDEWEB)

Pioneer Venus (PV) orbiter ultraviolet spectrometer (OUVS) images of the nightside airglow in the (0, 1) {delta} band of nitric oxide showed a maximum whose average location was at 0200 local solar time just south of the equator. The average airglow brightness calculated over a portion of the nightside for 35 early orbits during the Pioneer Venus mission was a factor of 4 lower than this maximum. Recent recalibration of the PV OUVS instrument and reanalysis of the data yield new values for this statistical maximum (1.9 {plus minus} 0.6 kR) and the nightside average (400-460 {plus minus} 120 R) nightglow. This emission is produced by radiative recombination of N and O atoms transported from their source on the dayside to the nightside by the Venus thermospheric circulation. The Venus Thermospheric General Circulation Model (VTGCM) has been extended to incorporate odd nitrogen chemistry in order to examine the dynamical and chemical processes required to give rise to this emission. Its predictions of dayside N atom densities are also compared with empirical models based on Pioneer Venus measurements. Calculations are presented corresponding to OUVS data taken during solar maximum. The average production of nitrogen atoms on the dayside is about 9.0 {times} 10{sup 9} atoms cm{sup {minus}2} s{sup {minus}1}. Approximately 30% of this dayside source is required for transport to the nightside to yield the observed dark-disk nightglow features. The statistical location and intensity of the bright spot are well reproduced, as well as the altitude of the airglow layer. The importance of the large-scale transport and eddy diffusion on the global N({sup 4}S) distribution is also evaluated.

Bougher, S.W. (Univ. of Arizona, Tucson (United States)); Gerard, J.C. (Univ. de Liege, Ougree-Liege (Belgium)); Stewart, A.I.F.; Fesen, C.G. (Univ. of Colorado, Boulder (United States))

1990-05-01

155

Isostatic compensation of Ishtar Terra, Venus  

Science.gov (United States)

We have used spherical harmonic representations of the Venus topography and geopotential, obtained from Magellan data, to evaluate isostatic support in several areas within the Ishtar Terra highlands, including the Lakshmi plateau, its surrounding mountain belts, namely Akna and Freyja, and Maxwell Montes, and the Fortuna Tessera province. We find that topography in Ishtar is largely isostatically compensated (>80%). Regional geoidtopography variations in the subregions can be explained by a combination of Airy (crustal thickening) and thermal (lithospheric thinning) mechanisms, provided Venus has a thick reference thermal lithosphere (~300-400 km). With the exception of eastern Fortuna, low elevation areas (h4 km above MPR) with small GTRs are almost certainly Airy compensated via thickened crust. Relatively large (>60 km) total Airy crustal thicknesses obtained in the western Ishtar mountain belts, together with a probable basalt-eclogite phase change, suggest a possible silicic composition for these structures, provided they are older than ~25-50 Ma. Lakshmi Planum seems essentially thermally supported, with the thermal lithosphere thinned to ~100 km. We suggest, as one possibility, that the lithospheric thinning process under Lakshmi is delamination of a dense eclogite lower lithosphere layer into the mantle. The decrease in GTR observed in Ishtar between Lakshmi to the west (GTR ~20 m/km), Maxwell and west Fortuna (GTR~8 m/km), and eastern Fortuna (GTR~4 m/km) may correspond to a decay in thermal compensation attributed to lithospheric delamination, which would be fairly recent (~100 Ma) in Lakshmi, partially decayed in west Fortuna, and absent in east Fortuna, where a mostly Airy-supported topography is essentially relaxed with no thermal uplift. Alternatively, if surficial concentrations in radiogenic elements were prevalent throughout the crust, partial melting of a thickened crust could account for the thermal uplift in Lakshmi and west Fortuna. The zero-elevation basaltic crustal thickness H ~24 km obtained for the east Fortuna Tessera region may be representative of the ambient crustal thickness in the Venus lowlands. Our findings support multicomponent models for tectonic and volcanic activity in Ishtar. The thick ambient crust and thermal lithosphere implied by this study agree with observational constraints such as support of extreme elevations, large topographic slopes, unrelaxed craters, and the thick elastic lithosphere suggested by flexure studies. If the ambient thermal lithosphere on Venus were to be relatively thin (~100-200 km), with a cold mantle and radiogenic elements concentrated in the crust, then thermal evolution on Venus may be in quasi-steady state, with the geodynamic evolution in monotonic decline. However, if the ambient thermal lithosphere is very thick (~300-400 km), as suggested by our thermal model fits, then it is consistent with the predictions of strongly unsteady state thermal evolution models and an interior which is currently heating up. This would support the view that catastrophic resurfacing on Venus might be episodic.

Kucinskas, Algis B.; Turcotte, Donald L.; Arkani-Hamed, Jafar

156

Structural evolution of western Fortuna Tessera, Venus  

Science.gov (United States)

Western Fortuna Tessera, Ishtar Terra, records polyphase deformation. Structures include: ribbons forming long, narrow, steep-sided troughs that reflect surface layer extension; N-trending folds related to Maxwell Montes deformation; short, wide, NW-trending graben that reflect late local extension; and, within the southwestern map area, gentle, E-trending warps, which postdate ribbon structures. Flood lava flows postdate deformation. Ribbon structures change orientation radially from NNE to WNW. These observations caution against the correlation of Fortuna Tessera with tessera elsewhere on Venus and against the proposal that tessera forms a global stratigraphic layer.

Pritchard, M. E.; Hansen, V. L.; Willis, J. J.

1997-09-01

157

ATMOSPHERIC CHEMISTRY OF VENUS-LIKE EXOPLANETS  

International Nuclear Information System (INIS)

We use thermodynamic calculations to model atmospheric chemistry on terrestrial exoplanets that are hot enough for chemical equilibria between the atmosphere and lithosphere, as on Venus. The results of our calculations place constraints on abundances of spectroscopically observable gases, the surface temperature and pressure, and the mineralogy of the planetary surface. These results will be useful in planning future observations of the atmospheres of terrestrial-sized exoplanets by current and proposed space observatories such as the Hubble Space Telescope, Spitzer, the James Webb Space Telescope, and Darwin.

2011-03-01

158

Characterizing the Venus atmospheric dynamics from ground-based Doppler velocimetry  

Science.gov (United States)

We present an analysis of observations of Venus made with the UVES instrument (Ultraviolet and Visual Echelle Spectrograph) at ESO's Very Large Telescope (VLT). The observations were carried out in May and June 2007 with the aim of characterizing the zonal wind flow in the atmosphere of Venus during the nominal mission phase of Venus Express. Doppler velocimetry measurements are based on solar Fraunhofer lines in the visible, probing the cloud tops velocity close to 65 km altitude. The narrow slit width of the UVES instrument, combined with the large apparent angular size of the planet, allows to simultaneously achieve high spectral resolving power and high spatial resolution. The observations were made at a central wavelength of 580 nm with the UVES red arm and at 437 and 860 nm in dichroic mode, using both the blue and red arms. In one observation block the field has been derotated in order to align the 0.3-arcsec aperture perpendicularly to Venus's rotation axis, while in other observations it was aligned parallel to it. In each case, spatial information, respectively in the East-West and in the North-South direction, is preserved in the spectra in the direction perpendicular to dispersion, allowing to spatially resolve relative variations in atmospheric rotation. We estimate both the relative variations of the atmospheric rotation with latitude and the hemispheric asymmetry of the zonal wind between 35S and 35N. The absolute magnitude of the zonal winds at latitudes of 23S, 13S and 2S has also been determined. [P. Machado acknowledges support from Fundação para a Ciência e a Tecnologia, grant SFRH-BD-66473-2009.

Machado, Pedro; Luz, David; Widemann, Thomas; Lellouch, Emmanuel; Witasse, Olivier; Bertaux, Jean-Loup

2010-05-01

159

Venus - Concentrations of radar-reflective minerals by wind  

International Nuclear Information System (INIS)

The effectiveness of wind in concentrating minerals with high radar reflectiveness on the surface of Venus is investigated experimentally in the Venus Wind Tunnel (Greeley et al., 1984) under CO2 densities typical of Venusian conditions. Density sorting of sand particles during the formation of microdunes is demonstrated, and calculations show that wind-blown deposits of dense conductive material such as ilmenite need to be only a few cm thick to account for the local enhancements of radar reflectivity observed by Pioneer Venus at wavelength 17 cm. 28 refs.

1991-01-01

160

Croconic acid - An absorber in the Venus clouds  

Energy Technology Data Exchange (ETDEWEB)

The absorbing species responsible for the UV cloud features and pale yellow hue of the Venus clouds is presently suggested to be the carbon monoxide-polymer croconic acid, which strongly absorbs in the blue and near-UV. Laboratory absorption-coefficient measurements of a dilute solution of croconic acid in sulfuric acid are used as the bases of cloud-scattering models; the Venus planetary albedo's observed behavior in the blue and near-UV are noted to be qualitatively reproduced. Attention is given to a plausible croconic acid-production mechanism for the Venus cloudtop region. 34 references.

Hartley, K.K.; Wolff, A.R.; Travis, L.D.

1989-02-01

 
 
 
 
161

Venus geology and geophysics: a review of some recent studies  

Energy Technology Data Exchange (ETDEWEB)

The nature of the surface of Venus is being revealed by a series of investigations using spacecraft observations and measurements from the Soviet and US space probes and Earth-based radar telescope observations. This paper reviews a series of recent studies on the global properties of Venus, the characteristics of the Venera and Vega landing sites, and the geological and geophysical processes operating to form and modify the surface of Venus. Emphasis is placed on studies reported at the series of Brown University-Vernadsky Institute microsymposia.

Head, J.W.; Crumpler, L.C.; Bindschadler, D.L.; Stofan, E.R.; Vorder Bruegge, R.W.; Campbell, D.B.

1987-10-01

162

Comparative plasma tails of Venus and comets  

International Nuclear Information System (INIS)

A review of current models of solar wind flow in the plasma tails of weakly magnetized bodies is presented. Measurements conducted by the Mariner 5 spacecraft, the Veneras 9 and 10, and the PVO orbiters, in the Venus tail, and with the ICE spacecraft in the tail of Comet Giacobini-Zinner, reveal common plasma properties which suggest that similar physical processes are operative. Most notable is the observation of decreased flow velocities and enhanced plasma temperatures in the vicinity of their plasma tails. In Venus, the measured velocity and temperature fields are consistent with the effects of frictional forces between the mass-loaded ionosheath flow and the ionosphere along the (magnetic) polar regions of the ionopause. It is argued that similar conditions exist at a cometary ionopause and that the distribution of magnetic fluxes in a cometary tail is controlled by the entry of plasma fluxes from the (magnetic) polar regions of the comet's ionospheric obstacle. This question is further addressed in connection with the two-step shape of the magnetic profile measured across the tail of the comet. It is suggested that the low intensity outer increases of the magnetic lobes are associated with the draping of the interplanetary magnetic field lines around the comet's ionospheric obstacle, and that the higher intensity increases seen in the inner regions of the magnetic lobes are due to an additional compression of magnetic fluxes produced by the entry of plasma particles into the tail

1987-01-01

163

The Cold Storage of Venus Nectarin Cultivars  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study was to determine storage and shelf life of Venus nectarine cultivar grown inMersin (Tarsus/Yenice). Fruits were kept at 0°C and %85-90ºC relative humidity for 8 weeks. In addition,three replicates of fruits removed from storage room at a week interval were kept at 20°C and %65-70ºCrelative humidity for 6 days. Percent weight loss, skin color (L*, a*, b*), fruit flesh firmness (kg force), totalsoluble solids (%), pH, titretable acidity (g malic acid / 100 ml), physiological and fungal disorders weredetermined in the fruit samples taken during cold storage at a week interval and those kept at 20°C at a twodayinterval. Weight loss increased during storage and reached to about 5% at the end of storage. Fruit fleshfirmness decreased, but still remained above 4 kg-force at the end of 8-week storage. Total soluble solid (%)increased while titretable acidity (%) decreased. As the storage period was extended the shelf life wasshortened. Venus nectarine cultivars could be kept at 0°C and 85-90% relative humidity for 7 weeks andcould have 4-day shelf life after cold storage.

A. E. Ozdemir; E. Erturk; M. Celik; R. Dilbaz

2006-01-01

164

Position and shape of the Venus bow shock: Pioneer Venus Orbiter observations  

International Nuclear Information System (INIS)

[en] In this study magnetometer data from the Poineer Venus Orbiter is used to examine the position and shape of this planet's bow shock. Utilizing crossings identified on 86 occasions during the first 65 orbits a mean shock surface is defined for sun-Venus-satellite angles of 60--110 0. Both the shock shape and variance in location are found to be very similar to the terrestrial case for the range in SVS angle considered. However, while the spread in shock positions at the earth is due predominantly to the magnetopause location varying in response to solar wind dynamic pressure, ionopause altitude variations can have little effect on total obstacle radius. Thus, the Cytherean shock is sometimes observed much closer to or farther from the planet than previously predicted by gasdynamic theory applied to the deflection of flow about a blunt body which acts neither as source nor sink for any portion of the flow

1979-01-01

165

Thermal Structure and Major Ion Composition of the Venus Ionosphere: First RPA Results from Venus Orbiter.  

UK PubMed Central (United Kingdom)

Thermal plasma quantities measured by, the retarding potential analyzer (RPA) are, together with companion Pioneer Venus measurements, the first in situ measurements of the Venus ionosphere. High ionospheric ion and electron temperatures imply significant solar wind heating of the ionosphere. Comparison of the measured altitude profiles of the dominant ions with an initial modlel indicates that the ionosphere is close to diffusive equilibrium. The ionopause height was observed to vary from 400 to 1000 kilometers in early orbits. The ionospheric particle pressure at the ionopause is apparently balanced at a solar zenith angle of about 70 degrees by the magnetic field pressure with little contribution from energetic solar wind particles. The measured ratio of ionospheric scale height to ionopause radius is consistent with that inferred from previously measured bow shock positions.

Knudsen WC; Spenner K; Whitten RC; Spreiter JR; Miller KL; Novak V

1979-02-01

166

Experimental Reconstruction of Lomonosov's Discovery of Venus's Atmosphere with Antique Refractors During the 2012 Transit of Venus  

CERN Multimedia

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 if proper experimental techniques as described by Lomonosov in his 1761 report are employed.

Koukarine, Alexandre; Petrunin, Yuri; Shiltsev, Vladimir

2012-01-01

167

Line parameters for the 01111-00001 band of 12C16O18O from SOIR measurements of the Venus atmosphere  

International Nuclear Information System (INIS)

[en] CO2 is the major constituent of the atmosphere of Venus. Absorption lines due to its 12C16O18O isotopologue have been observed for the first time in Venus spectra in the 2930-3015 cm-1 spectral region, where the HITRAN database does not contain any line from this isotopologue. The measurements were performed by the SOIR instrument, which is part of the SPICAV/SOIR instrument on board the Venus Express mission of ESA. SOIR measured the atmospheric transmission of the upper atmosphere of Venus (z>70 km) by performing a solar occultation experiment using the atmosphere as a gigantic absorption cell. The identification of this newly observed band was first made recently from Mars atmosphere observations by US colleagues. We have made independent theoretical calculations of the positions of the lines of this new 01111-00001 absorption band, which coincide perfectly with the positions of the observed lines. Assuming an oxygen isotopic ratio similar to the one measured previously in the lower atmosphere of Venus, the line strengths of each observed line are deduced and listed

2008-01-01

168

Quantitative Analysis of Venus Radar Backscatter Data in Arcgis.  

Science.gov (United States)

Ongoing mapping of the Ganiki Planitia (V14) quadrangle of Venus and definition of material units has involved an integrated but qualitative analysis of Magellan radar backscatter images and topography using standard geomorphological mapping techniques. H...

S. M. Long E. B. Grosfils

2005-01-01

169

VENUS-F: A fast lead critical core for benchmarking  

Energy Technology Data Exchange (ETDEWEB)

The zero-power thermal neutron water-moderated facility VENUS at SCK-CEN has been extensively used for benchmarking in the past. In accordance with GEN-IV design tasks (fast reactor systems and accelerator driven systems), the VENUS facility was modified in 2007-2010 into the fast neutron facility VENUS-F with solid core components. This paper introduces the projects GUINEVERE and FREYA, which are being conducted at the VENUS-F facility, and it presents the measurement results obtained at the first critical core. Throughout the projects other fast lead benchmarks also will be investigated. The measurement results of the different configurations can all be used as fast neutron benchmarks. (authors)

Kochetkov, A.; Wagemans, J.; Vittiglio, G. [SCK.CEN, Boeretang 200, 2400 Mol (Belgium)

2011-07-01

170

A note on comparison of scientific impact expressed by number of citations in different fields of science  

CERN Multimedia

Citation distributions for 1992, 1994, 1996, 1997, 1999, and 2001, which were published in the 2004 report of the National Science Foundation, USA, are analyzed. It is shown that the ratio of the total number of citations of any two broad fields of science remains close to constant over the analyzed years. Basing on this observation, normalization of total numbers of citations with respect to the number of citations in mathematics is suggested as a tool for comparing scientific impact expressed by the number of citations in different fields of science.

Podlubny, I

2004-01-01

171

Nature of the magnetic flux ropes in the Venus ionosphere  

Energy Technology Data Exchange (ETDEWEB)

The onset of gutter instability at the moving, accelerating ionopause on Venus may allow magnetic flux tubes of solar wind to penetrate the interior of the ionosphere. As the ionospheric ions cross the lateral tube walls, an axial current of solar-wind electrons will enter, twisting the field lines into a rope. Such a mechanism would explain data recorded on the Pioneer Venus mission.

Dubinin, E.M.; Izrailevich, P.L.; Podgornyi, I.M.; Shkol' nikova, S.I.

1980-03-01

172

Viscous flow circulation of the solar wind behind Venus  

Energy Technology Data Exchange (ETDEWEB)

A latitudinal circulation model of solar wind flow in the near wake of Venus is presented. It is shown that solar wind fluxes entering through the polar terminator can be viscously forced to lower latitutdes. The resulting motion produces a downstream elongation of the nightside polar ionosphere out to the downstream extension of the middle- and low-latitude ionopause. The geometry suggested by this flow circulation model provides a simple explanation of the ionospheric bulge inferred from the Pioneer Venus observations.

Perez-de-Tejada, H.

1980-02-29

173

The multistring model VENUS for ultrarelativistic heavy ion collisions  

Energy Technology Data Exchange (ETDEWEB)

The event generator VENUS is based on a multistring model for heavy ion collisions at ultrarelativistic energies. The model is a straightforward extension of a successful model for soft proton-proton scattering, the latter one being consistent with e/sup )plus/)e/sup )minus/) annihilation and deep inelastic lepton scattering. Comparisons of VENUS results with pA and recent AA data alow some statements about intranuclear cascading. 18 refs., 7 figs

Werner, K.

1988-02-01

174

Closing of venus flytrap by electrical stimulation of motor cells.  

Science.gov (United States)

Electrical signaling and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since XIX century, but the exact mechanism of Venus flytrap closure is still unknown. We found that the electrical stimulus between a midrib and a lobe closes the Venus flytrap leaf by activating motor cells without mechanical stimulation of trigger hairs. The closing time of Venus flytrap by electrical stimulation of motor cells is 0.3 s, the same as mechanically induced closing. The mean electrical charge required for the closure of the Venus flytrap leaf is 13.6 microC. Ion channel blockers such as Ba(2+), TEACl as well as uncouplers such as FCCP, 2,4-dinitrophenol and pentachlorophenol dramatically decrease the speed of the trap closing. Using an ultra-fast data acquisition system with measurements in real time, we found that the action potential in the Venus flytrap has a duration time of about 1.5 ms. Our results demonstrate that electrical stimulation can be used to study mechanisms of fast activity in motor cells of the plant kingdom. PMID:19516982

Volkov, Alexander G; Adesina, Tejumade; Jovanov, Emil

2007-05-01

175

Closing of venus flytrap by electrical stimulation of motor cells.  

UK PubMed Central (United Kingdom)

Electrical signaling and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since XIX century, but the exact mechanism of Venus flytrap closure is still unknown. We found that the electrical stimulus between a midrib and a lobe closes the Venus flytrap leaf by activating motor cells without mechanical stimulation of trigger hairs. The closing time of Venus flytrap by electrical stimulation of motor cells is 0.3 s, the same as mechanically induced closing. The mean electrical charge required for the closure of the Venus flytrap leaf is 13.6 microC. Ion channel blockers such as Ba(2+), TEACl as well as uncouplers such as FCCP, 2,4-dinitrophenol and pentachlorophenol dramatically decrease the speed of the trap closing. Using an ultra-fast data acquisition system with measurements in real time, we found that the action potential in the Venus flytrap has a duration time of about 1.5 ms. Our results demonstrate that electrical stimulation can be used to study mechanisms of fast activity in motor cells of the plant kingdom.

Volkov AG; Adesina T; Jovanov E

2007-05-01

176

Dynamic model of Venus's gravity field  

Energy Technology Data Exchange (ETDEWEB)

Unlike Earth, long wavelength gravity anomalies and topography correlate well on Venus. Venus's admittance curve from spherical harmonic degree 2 to 18 is inconsistent with either Airy or Pratt isostasy, but is consistent with dynamic support from mantle convection. A model using whole mantle flow and a high viscosity near surface layer overlying a constant viscosity mantle reproduces this admittance curve. On Earth, the effective viscosity deduced from geoid modeling increases by a factor of 300 from the asthenosphere to the lower mantle. These viscosity estimates may be biased by the neglect of lateral variations in mantle viscosity associated with hot plumes and cold subducted slabs. The different effective viscosity profiles for Earth and Venus may reflect their convective styles, with tectonism and mantle heat transport dominated by hot plumes on Venus and by subducted slabs on Earth. Convection at degree 2 appears much stronger on Earth than on Venus. A degree 2 convective structure may be unstable on Venus, but may have been stabilized on Earth by the insulating effects of the Pangean supercontinental assemblage.

Kiefer, W.S.; Richards, M.A.; Hager, B.H.; Bills, B.G.

1984-08-01

177

Surface age of venus: use of the terrestrial cratering record  

Energy Technology Data Exchange (ETDEWEB)

The average crater age of Venus' northern hemisphere may be less than 250 m.y. assuming equivalence between the recent terrestrial cratering rate and that on Venus for craters greater than or equal to 20 km in diameter. For craters larger than this threshold size, below which crater production is significantly affected by the Venusian atmosphere, there are fairly strong observational grounds for concluding that such an equivalence in cratering rates on Venus and Earth may exist. However, given the uncertainties in the role of both active and inactive comet nuclei in the cratering history of Earth, we conclude that the age of the observed surface in the northern hemisphere of Venus could be as great as the 450-m.y. mean age of the Earth's crust. The observed surface of Venus might be even older, but no evidence from the crater observations supports an age as great as 1 b.y. If the age of the observed Venusian surface were 1 b.y., it probably should bear the impact scars of a half dozen or more large comet nuclei that penetrated the atmosphere and formed craters well over 100 km in diameter. Venera 15/16 mapped only about 25% of Venus; the remaining 75% may tell us a completely different story.

Schaber, G.G.; Shoemaker, E.M.; Kozak, R.C.

1987-10-01

178

Mars, Venus and Gray: Gender Communication  

Directory of Open Access Journals (Sweden)

Full Text Available This research tests the propositions relating to gender communication by Gray (1992) in his book titled “Men are from Mars, Women are from Venus” This book has been the source of gender-related controversy since its publication. The sample consisted of 182 executives and non-executives (73 males and 109 females). T-test results show that out of 23 statements made by Gray (1992), only 8 were supported, 10 were not supported and 5 were actually true for the opposite gender. This research is indeed timely in that it addresses the long disservice to women. So the way forward into the future would be to train people on how to communicate better by making them aware that different people have different preferences and styles of communication, rather than essentializing and gender-stereotyping.

Kamarul Zaman Ahmad; Kalaiselvee Rethinam

2010-01-01

179

An Encounter between the Sun and Venus  

CERN Multimedia

The astronomical event of the year will take place on Tuesday, 8 June, when Venus transits across the disk of the sun. In the framework of CERN's 50th anniversary celebrations, the CERN Astronomy Club and the Orion Club invite you to attend their observation of the event on the car park of the Val-Thoiry shopping centre (France) between 7.15 a.m. and 1.30 p.m. Various instruments will be set up in a special tent so that the event can be observed without any risk of damage to the eyes. As the observation of this astronomical event will depend on the weather forecast, confirmation of the above arrangements will be given on the 50th anniversary website the day before.

2004-01-01

180

CO measurements and climatology from SOIR measurements in the upper atmosphere of Venus  

Science.gov (United States)

Previous measurements of the Venus atmosphere were performed essentially in the mesosphere below 100 km and below the clouds. Information about minor atmospheric constituents, their concentration, reactions, sources and sinks is incomplete, as for example only scarce measurements have been performed above 100 km altitude. SOIR is designed to measure the atmospheric transmission in the IR (2.2-4.3 µm) at high resolution (0.12 cm-1) using solar occultations. This technique allows for the derivation of unique information about the vertical structure and composition of the Venus mesosphere [1,2]. The primary source of CO in the atmosphere of Venus is the photodissociation of CO2 by solar UV at altitudes higher than 120 km. It was shown that CO exhibits a significant diurnal variation and strong year to year variations [3,4], but also latitudinal variations. CO concentration and vmr between 70 and 125 km have been recently retrieved from SOIR data for both terminators. The solar occultations with a high vertical resolution are mainly located at latitudes comprised between 60° and 90° N, but the latitudinal coverage of CO measurements is more complete if we also consider occultations for which the vertical resolution is coarser. We will present an overview of the CO measurements obtained by the SOIR instrument over the last 3 years in order to complete the climatology of CO above the clouds in the atmosphere of Venus. We will also discuss a puzzling strong minimum of the CO vmr in the 80-90 km region found by SOIR, which had escaped detection up to now. 1. A. Mahieux, S. Berkenbosch, R. Clairquin, D. Fussen, N. Mateshvili, E. Neefs, D. Nevejans, B. Ristic, A. C. Vandaele, V. Wilquet, D. Belyaev, A. Fedorova, O. Korablev, E. Villard, F. Montmessin and J.-L. Bertaux, "In-Flight performance and calibration of SPICAV SOIR on board Venus Express", Applied Optics 47 (13), 2252-65 (2008). 2. D. Nevejans, E. Neefs, E. Van Ransbeeck, S. Berkenbosch, R. Clairquin, L. De Vos, W. Moelans, S. Glorieux, A. Baeke, O. Korablev, I. Vinogradov, Y. Kalinnikov, B. Bach, J.-P. Dubois and E. Villard, "Compact high-resolution space-borne echelle grating spectrometer with AOTF based on order sorting for the infrared domain from 2.2 to 4.3 micrometer", Applied Optics 45 (21), 5191-5206 (2006). 3. R. T. Clancy, B. Sandor and G. H. Moriarty-Schieven, "Observational definition of the Venus mesopause: vertical structure, diurnal variation, and temporal instability", Icarus 161 (1), 1-16 (2003). 4. M. Gurwell, D. O. Muhleman, K. Shah, G. Berge, D. J. Rudy and A. W. Grossman, "Observations of the CO bulge on Venus and implications for mesospheric winds", Icarus 115 (1), 141-158 (1995).

Mahieux, A.; Drummond, R.; Wilquet, V.; Vandaele, A. C.; Fedorova, A.; Villard, E.; Montmessin, F.; Bertaux, J.-L.

2009-04-01

 
 
 
 
181

The 28 GHZ, 10 KW, CW Gyrotron Generator for the VENUS ECR Ion Source at LBNL  

International Nuclear Information System (INIS)

The VIA-301 HeatwaveTM gyrotron generator was specifically designed to meet the requirements of the Venus ECR Ion Source at the Lawrence Berkeley National Laboratory (LBNL). VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end].This VIA-301 HeatwaveTM gyrotron system provides 100 watts to 10 kW continuous wave (CW) RF output at 28 GHz. The RF output level is smoothly controllable throughout this entire range. The power can be set and maintained to within 10 watts at the higher power end of the power range and to within 30 watts at the lower power end of the power range. A dual directional coupler, analog conditioning circuitry, and a 12-bit analog input to the embedded controller are used to provide a power measurement accurate to within 2%. The embedded controller completes a feedback loop using an external command set point for desired power output. Typical control-loop-time is on the order of 500 mS. Hard-wired interlocks are provided for personnel safety and for protection of the generator system. In addition, there are software controlled interlocks for protection of the generator from high ambient temperature, high water temperature, and other conditions that would affect the performance of the generator or reduce the lifetime of the gyrotron. Cooling of the gyrotron and power supply is achieved using both water and forced circulation of ambient air. Water-cooling provides about 80% of the cooling requirement. Input power to the generator from the prime power line is less than 60 kW at full power. The HeatwaveTM may be operated locally via its front panel or remotely via either RS-232 and/or Ethernet connections. Through the RS-232 the forward power, the reflected power, the interlock status and crucial operating parameters are transmitted and tied into the VENUS PLC control system.The paper describes the gyrotron system, control software, the user interface, the main system parameter, and performance in respect to output power stability.

2005-03-15

182

Schistosoma mansoni: structural and biochemical characterization of two distinct Venus Kinase Receptors.  

UK PubMed Central (United Kingdom)

Venus Kinase Receptors (VKRs) are atypical transmembrane proteins composed of an extracellular Venus FlyTrap module linked through a single helix to a tyrosine kinase domain similar to that of insulin receptors. This structure was first described in Schistosoma mansoni, then in a selected range of invertebrates, including many insects. The preferential expression of VKRs in larvae and gonads suggested their role in development and reproduction. While a single vkr gene was consistently found in all genomes, we identified two distinct vkr genes in S. mansoni. Our data indicated that Smvkr1 and Smvkr2 are very similar in structure and likely originated from gene duplication. Both genes are expressed in all the parasite stages and encode homologous proteins with a conserved VKR structure. Recombinant SmVKR1 and SmVKR2 exhibit tyrosine kinase activities dependent on the binding of distinct small ligand molecules. SmVKR1 and SmVKR2 could represent paralogs with different functions in the parasite.

Gouignard N; Vanderstraete M; Cailliau K; Lescuyer A; Browaeys E; Dissous C

2012-09-01

183

Schistosoma mansoni: structural and biochemical characterization of two distinct Venus Kinase Receptors.  

Science.gov (United States)

Venus Kinase Receptors (VKRs) are atypical transmembrane proteins composed of an extracellular Venus FlyTrap module linked through a single helix to a tyrosine kinase domain similar to that of insulin receptors. This structure was first described in Schistosoma mansoni, then in a selected range of invertebrates, including many insects. The preferential expression of VKRs in larvae and gonads suggested their role in development and reproduction. While a single vkr gene was consistently found in all genomes, we identified two distinct vkr genes in S. mansoni. Our data indicated that Smvkr1 and Smvkr2 are very similar in structure and likely originated from gene duplication. Both genes are expressed in all the parasite stages and encode homologous proteins with a conserved VKR structure. Recombinant SmVKR1 and SmVKR2 exhibit tyrosine kinase activities dependent on the binding of distinct small ligand molecules. SmVKR1 and SmVKR2 could represent paralogs with different functions in the parasite. PMID:21616067

Gouignard, Nadege; Vanderstraete, Mathieu; Cailliau, Katia; Lescuyer, Arlette; Browaeys, Edith; Dissous, Colette

2011-05-15

184

Influence of Asteroid and Comet Impacts on Atmospheric Abundances at Venus, Earth, and Mars  

Science.gov (United States)

Asteroid and comet impacts have undoubtedly altered the atmospheres of the terrestrial planets over billions of years. Impacts are capable of either delivering or removing atmospheric particles from a planet depending upon the characteristics of the impact. With many thousands of impacts large enough to alter the atmospheres of each terrestrial planet, all with varying compositions, velocities, impact angles, and sizes, it is not entirely clear how impacts have contributed to changes in atmospheric abundance over time. Some theoretical and numerical work has been undertaken in the past for generic individual impacts, and several studies have considered the net effect of impacts on the atmospheres of Mars and Earth over time. However, the full parameter space of atmospheric impact calculations remains unexplored, particularly in regards to Venus and the effect of oblique impacts on atmospheres. This work uses Monte Carlo simulations to model atmospheric erosion and delivery from impacts at Venus, Earth, and Mars. Flexibility in the code allows us to examine the effects of changing impactor populations (i.e. size and composition), velocity distributions, and angles of impact on the resultant atmospheric pressure, as well as the different sensitivities to these factors between the planets. The work we present relies on published analytic expressions for the effects of individual impacts. However, the results of detailed simulations of individual impacts (e.g. using the RAGE hydrocode) can be incorporated into our future modeling efforts to help validate these expressions.

Heath, Caitlin; Brain, D. A.

2013-10-01

185

Venus volcanism: initial analysis from magellan data.  

UK PubMed Central (United Kingdom)

Magellan images confirm that volcanism is widespread and has been fimdamentally important in the formation and evolution of the crust of Venus. High-resolution imaging data reveal evidence for intrusion (dike formation and cryptodomes) and extrusion (a wide range of lava flows). Also observed are thousands of small shield volcanoes, larger edifices up to several hundred kilometers in diameter, massive outpourings of lavas, and local pyroclastic deposits. Although most features are consistent with basaltic compositions, a number of large pancake-like domes are morphologically similar to rhyolite-dacite domes on Earth. Flows and sinuous channels with lengths of many hundreds of kilometers suggest that extremely high effusion rates or very fluid magmas (perhaps komatiites) may be present. Volcanism is evident in various tectonic settings (coronae, linear extensional and compressional zones, mountain belts, upland rises, highland plateaus, and tesserae). Volcanic resurfacing rates appear to be low (less than 2 Km(3)/yr) but the significance of dike formation and intrusions, and the mode of crustal formation and loss remain to be established.

Head JW; Campbell DB; Elachi C; Guest JE; McKenzie DP; Saunders RS; Schaber GG; Schubert G

1991-04-01

186

Solar wind origin of Ar-36 on Venus  

Energy Technology Data Exchange (ETDEWEB)

An examination is conducted concerning the circumstances under which the difference between earth and Venus (and Mars) fits naturally into theories in which the terrestrial planets formed by the gradual sweeping up of planetesimals in an essentially gas-free protoplanetary swarm. The primary purpose of the reported investigation is to use observational data to define restrictions on planetary formation theories that would be imposed if most of Venus' inert gases come from the solar wind. The observational data support the suggestion that the abundances of Ar, Kr, and Xe on Venus have been augmented by a component of solar composition. Solar wind implantation at an early stage of accumulation provides a natural way of producing the observed extreme heliocentric distribution of this component, provided that accumulation occurred after dissipation of solar gas from the solar nebula

Wetherill, G.W.

1981-04-01

187

Propagation of the trip behavior in the VENUS vertex chamber  

Energy Technology Data Exchange (ETDEWEB)

The high voltage system of the VENUS vertex chamber occasionally trips by a discharge somewhere among cathode electrodes during data taking. This trip behavior induces often additional trips at other electrodes such as the skin and the grid electrodes in the vertex chamber. This propagation mechanism of trips is so complicated in this system related with multi-electrodes. Although the vertex chamber is already installed inside the VENUS detector and consequently the discharge is not able to observe directly, a trial to estimate the propagation has been done using only the information which appears around the trip circuits and the power supply of the vertex chamber. (author).

Ohama, Taro; Yamada, Yoshikazu

1995-03-01

188

Magnetic field overshoots in the Venus blow shock  

Energy Technology Data Exchange (ETDEWEB)

An examination of Pioneer Venus Orbiter fluxgate magnetometer data has shown that magnetic field overshoots occur not only behind quasi-perpendicular bow shocks but also behind quasi-parallel shocks. Overshoots are assocciated only with supercritical shocks. Their amplitudes increase with increasing fast Mach number. Solar wind beta has a lesser effect. The thickness of the overshoot increases with decreasing Theta-BN. The thickness of apparent overshoots detected behind 4 strong fast interplanetary shocks (M greater than M/crit) is about 3 orders of magnitude larger. Multiple crossings of the Venus bow shock were observed mainly at turbulent shocks. Their occurence is not influenced by Theta-BN. 15 references.

Tatrallyay, M.; Luhmann, J.G.; Russell, C.T.

1984-01-01

189

Electrical Properties of the Venus Surface from Bistatic Radar Observations  

UK PubMed Central (United Kingdom)

A bistatic radar experiment in 1994, involving reception on Earth of a specularly reflected, linearly polarized 13-centimeter-wavelength signal transmitted from the Magellan spacecraft in orbit around Venus, has established that the surface materials viewed at low and intermediate altitudes on Venus have a relative dielectric permittivity of 4.0 ± 0.5. However, bistatic results for the Maxwell Montes highlands imply an electrically lossy surface with an imaginary dielectric permittivity of -i 100 ± 50, probably associated with a specific conductivity of about 13 mhos per meter. Candidates for highlands surface composition include ferroelectrics, a thin frost of elemental tellurium, or a plating of magnetite or pyrites.

Pettengill GH; Ford PG; Simpson RA

1996-06-01

190

Observe how radar was used to map Venus  

Science.gov (United States)

This series of five animations summarizes how the Magellan Radar Mapping Mission created a map of Venus. High school students can see that dense cloud cover obscured the planet's surface and how radar was used to penetrate the clouds and measure the topography. The animations also demonstrate how the images were captured in long strips and sent back to Earth. Sample image strips are shown, as well as the final product: a rotating map of Venus. Movie controls allow students to repeat, pause, or step through the animation, which can give students more time to analyze the images. Copyright 2005 Eisenhower National Clearinghouse

Education, Terc. C.; Littell, Mcdougal

2003-01-01

191

Wind streaks on venus: clues to atmospheric circulation.  

UK PubMed Central (United Kingdom)

Magellan images reveal surface features on Venus attributed to wind processes. Sand dunes, wind-sculpted hills, and more than 5830 wind streaks have been identified. The streaks serve as local "wind vanes," representing wind direction at the time of streak formation and allowing the first global mapping of near-surface wind patterns on Venus. Wind streaks are oriented both toward the equator and toward the west. When streaks associated with local transient events, such as impact cratering, are deleted, the westward component is mostly lost but the equatorward component remains. This pattern is consistent with a Hadley circulation of the lower atmosphere.

Greeley R; Schubert G; Limonadi D; Bender KC; Newman WI; Thomas PE; Weitz CM; Wall SD

1994-01-01

192

Fundamental issues in the geology and geophysics of venus.  

UK PubMed Central (United Kingdom)

A number of important and currently unresolved issues in the global geology and geophysics of Venus will be addressable with the radar imaging, altimetry, and gravity measurements now forthcoming from the Magellan mission. Among these are the global volcanic flux and the rate of formation of new crust; the global heat flux and its regional variations; the relative importance of localized hot spots and linear centers of crustal spreading to crustal formation and tectonics; and the planform of mantle convection on Venus and the nature of the interactions among interior convective flow, near-surface deformation and magmatism.

Solomon SC; Head JW

1991-04-01

193

Plasma vortices and lateral forcing of the Venus upper atmosphere  

Science.gov (United States)

A statistical analysis of the ion flow near Venus reveals a significant curvature of the flow over the North Pole region. The curved flow of solar wind (H+) and ionospheric (O+) ions, results from a combination of an antisunward and lateral solar wind flow, the lateral flow component directed opposite to the Venus orbital motion [1]. The combined antisunward and lateral H+ and O+ flow wraps over the planetary atmosphere, from the terminator into the nightside. The lateral flow dominates close to the planet on the nightside. We note that the net lateral flow in the flank/nightside of Venus is in the direction of the Venus atmospheric superrotation. Further down in the Venus plasma tail, the flow inside the induced magnetosphere boundary (IMB) forms a vortex curving tailward. On the other hand, the flow outside IMB in the dense magnetosheath plasma (H+) is essentially tailward, indicating that the plasma vortex inside IMB comprise planetary ions, their curved motion set up by dayside lateral solar wind forcing of ionospheric ions. A test of the energy and momentum balance between solar wind H+ and ionospheric O+ in the altitude interval 1200 - 600 km, demonstrates a close connection between the energy and momentum gain by O+ and the energy and momentum delivered by solar wind H+. The general agreement in direction between the nightside ion flow over the Northern hemisphere, and the retrograde motion of the Venus atmosphere, suggests a connection between the ionospheric O+ flow and the atmospheric neutral flow. That connection is further strengthened by the fact the O+ flow velocity in the 200-300 km altitude range aligns with the power law curve describing the atmospheric zonal wind velocity profile versus altitude. The joint ion/neutral wind power-law profile therefore suggests momentum coupling between the ionospheric and atmospheric flow velocity. The fact that the O+ flow is driven by solar wind forcing leaves us with the question: Is the characteristic zonal wind profile of the Venus atmospheric superrotation a consequence of solar wind forcing? Is the measured ionospheric O+ mass flow capable of accelerating, and maintaining, a superrotating upper atmosphere at Venus?

Lundin, R.; Barabash, S.; Futaana, S.; Holmstrom, M.; Perez-de-Tejada, H.; Sauvaud, J.-A.

2012-09-01

194

The Venus ultraviolet aurora: A soft electron source  

Energy Technology Data Exchange (ETDEWEB)

The Pioneer Venus Orbiter Ultraviolet Spectrometer has recorded continuous but variable emissions of atomic oxygen at 1,304 and 1,356 {angstrom} in images of the nightside of Venus. The authors show that the observed intensities are consistent with the presence of precipitation of soft electrons into the nightside thermosphere. Model calculations are presented in which upper and lower limits to the magnitude of the electron flux necessary to produce the observed intensities are derived. Constraints are imposed on the energy spectrum of the electrons by the measured ion densities and by the predicted intensities of other emissions that have not been detected.

Fox, J.L. (State Univ. of New York, Stony Brook (USA)); Stewart, A.I.F. (Univ. of Colorado, Boulder (USA))

1991-06-01

195

Suprathermal ions observed upstream of the Venus bow shock  

Energy Technology Data Exchange (ETDEWEB)

Suprathermal ions with arrival directions quite distinct from those of the solar wind have been detected upstream of the Venus bow shock. We examine the possibility that these events could be caused by instrumental of spacecraft effects of that they could be either solar wind disturbances, planetary pickup ions, or suprathermal ions upstream of the Venus bow shock and conclude that they are consistent with upstream suprathermal ions associated with the bow shock that are observed downstream from the points of intersection of their extrapolated trajectories with the shock. copyright American Geophysical Union 1989

Moore, K.R.; McComas, D.J.; Russell, C.T.; Mihalov, J.D.

1989-04-01

196

Vénus version Express  

Science.gov (United States)

En avril 2006, Vénus a "capturé" un objet d'un genre particulier: une sonde robotique européenne, baptisée Venus Express et destinée à scruter cette planète sous tous les angles. Bilan de cette mission 5 ans après le lancement de la sonde, dont 4 d'observations vénusiennes.

Nazé, Yaël

2010-04-01

197

Science objectives and observing strategy for the OMEGA imaging spectrometer on Mars-Express  

Science.gov (United States)

The science objectives of OMEGA, which were first defined at the time of instruments selection for Mars-Express, were recently updated to integrate new results from MGS and Odyssey concerning three main fields: Martian surface and atmosphere, and polar processes. Thematic categories of observations are derived from the scientific objectives whenever spectral observations from OMEGA are expected to provide insights to Mars present situation and evolution. Targets within these categories are selected on the basis of their expected usefulness, which is related to their intrinsic properties and to the instrument capabilities. The whole surface will be mapped at low resolution (~5 km/pixel) in the course of the nominal mission, and possibly routinely at very coarse resolution to monitor time-varying processes from apocenter. However, only 5% of the surface can be observed at high resolution (up to 350 m/pixel) owing to constraints on telemetry rate. HR targets are therefore selected on the basis of telemetry constraints, orbital parameters, observing opportunities (visibility under given conditions), and spacecraft functionalities (e.g., depointing capacity), then prioritized within each category according to the probability to perform significant observations with OMEGA (in many situations, according to the estimated dust coverage). Target selection is performed interactively between OMEGA co-Is, in close contact with teams from other MEx experiments (mostly HRSC, PFS and Spicam) and other missions (e.g., MER and MRO). Most HR surface targets are selected on the basis of deep examination of Viking, THEMIS, and MOC HR images. Other surface targets include areas presenting unusual spectral properties in previous observations, or suspected to exhibit signatures of hydrothermal activity. Proposed landing sites and suggested source areas for the SNC meteorites are also included. Atmospheric/polar objectives more often translate as particular observing modes, sometimes at HR (e.g., limb observations, EPF sequences). The constraints are related to local time and seasonal occurrence of particular processes, and to spacecraft pointing. About 1000 HR targets are currently identified in the Southern hemisphere (first six month in orbit). The targets are described in a database with geographic coordinates in IAU-2000 system, context and detailed images, optimum observing conditions, science rationale and references. This database is currently being interfaced with ESA's MAPSS planning software.

Erard, S.; Bibring, J.-P.; Drossart, P.; Forget, F.; Schmitt, B.; OMEGA Team

2003-04-01

198

High intensity production of high and medium charge state uraniumand other heavy ion beams with VENUS  

Energy Technology Data Exchange (ETDEWEB)

The next generation, superconducting ECR ion source VENUS(Versatile ECR ion source for NUclear Science) started operation with 28GHzmicrowave heating in 2004. Since then it has produced world recordion beam intensities. For example, 2850 e mu A of O6+, 200 e mu A of U33+or U34+, and in respect to high charge state ions, 1 e mu A of Ar18+, 270e mu A of Ar16+, 28 e mu A of Xe35+ and 4.9 e mu A of U47+ have beenproduced. A brief overview of the latest developments leading to theserecord intensities is given and the production of high intensity uraniumbeams is discussed in more detail.

Leitner, Daniela; Galloway, Michelle L.; Loew, Timothy J.; Lyneis, Claude M.; Rodriguez, Ingrid Castro; Todd, Damon S.

2007-11-15

199

Observations of D/H ratios in H2O, HCl, and HF on Venus and new DCl and DF line strengths  

Science.gov (United States)

Intensities of the spectral lines in the fundamental bands of D35Cl and DF were calculated using the semi-empirical dipole moment functions derived from the most accurate and precise measurements of intensities of the ro-vibrational lines of H35Cl and HF. Values obtained in this way for the deuterated species are superior to any available measured or calculated data to date. Our study of the D/H ratios in H2O, HCl, and HF on Venus is based on spatially-resolved high-resolution spectroscopy using the CSHELL spectrograph at NASA IRTF. Search for DF on Venus using its R5 (1-0) line at 3024.054 cm-1 results in a DF mixing ratio of 0.23 ± 0.11 ppb that corresponds to (D/H)HF = 420 ± 200 times that in the Standard Mean Ocean Water (SMOW). H2O abundances on Venus were retrieved using lines at 3022.366 and 3025.761 cm-1 that were observed at an exceptionally low overhead telluric water abundance of 0.3 pr. mm. The measured H2O mixing ratios at 74 km vary insignificantly between 55°S and 55°N with a mean value of 3.2 ppm. When compared with simultaneous observations of HDO near 2722 cm-1, this results in (D/H)H2O = 95 ± 15 times SMOW. Reanalysis of the observation of the D35Cl R4 (1-0) line at 2141.540 cm-1 (Krasnopolsky, V.A. [2012b]. Icarus 219, 244-249) using the improved line strength and more thorough averaging of the spectra gives (D/H)HCl = 190 ± 50 times SMOW. The similarity of the measured (D/H)H2O = 95 ± 15 at 74 km with 120 ± 40 observed by De Bergh et al. (De Bergh, C., Bezard, B., Owen, T., Crisp, D., Maillard, J.P., Lutz, B.L. [1991]. Science 251, 547-549) below the clouds favors the constant (D/H)H2O from the surface to the mesosphere, in accord with the prediction by theory. D/H ? 100 removes a difference of a factor of 2 between H2O abundances in the observations by Krasnopolsky (Krasnopolsky, V.A. [2010b]. Icarus 209, 314-322) and the Venus Express nadir observations (Cottini, V., Ignatiev, N.I., Piccioni, G., Drossart, P., Grassi, D., Markiewicz, W.J. [2012]. Icarus 217, 561-569). Equivalent widths of the HDO and H2O lines are similar in our observations; therefore some errors cancel out in their ratios. Photochemistry of HCl in the mesosphere tends to enrich D in HCl and deplete it in H2O. This may be an explanation of the twofold difference between the observed D/H in HCl and H2O. An alternative explanation is based on (D/H)H2O ? 200 observed in the mesosphere by Bjoraker et al. (Bjoraker, G.L., Larson, H.P., Mumma, M.J., Timmermann, R., Montani, J.L. [1992]. Bull. Am. Astron. Soc. 24, 995) and Fedorova et al. (Fedorova, A. et al. J. Geophys. Res. 113, E00B22). This means an effective exchange of D between H2O and HCl and almost equal D/H in both species. However, this requires a twofold increase in D/H from the lower atmosphere to the mesosphere. This increase is not supported by theory; furthermore, condensation processes usually deplete D/H above the clouds. Photochemistry of HF has not been studied; it proceeds mostly in the lower thermosphere, and D/H in HF may be very different from that in H2O. Overall, the observational data on D/H in all hydrogen-bearing species on Venus are helpful to solve the problem of deuterium fractionation on Venus.

Krasnopolsky, V. A.; Belyaev, D. A.; Gordon, I. E.; Li, G.; Rothman, L. S.

2013-05-01

200

Waves in Venus's middle and upper atmosphere: Implications of Pioneer Venus probe data above the clouds  

Energy Technology Data Exchange (ETDEWEB)

Probe data showing the presence of waves in Venus's middle and upper atmosphere are critically reevaluated and extended to 138 km, near the level of in-situ data taken by the Pioneer Venus orbiter. Uncertainties in temperature are determined. They are typically about 0.1 times amplitude, thus supporting the reality of large amplitude oscillations approaching 40 K at 120 km. Growth rates above 100 km follow approximately the inverse square root of density until saturation occurs (in the sense that lapse rates become adiabatic in the expanding segment of the wave). The waves then break at the 120 km level, providing a source for the friction required in models to match the observed day-night temperature contrast in Venus's lower thermosphere. The data correlate to an unexpected degree with temperatures from the Pioneer Venus orbiter atmospheric drag (OAD) experiment taken at altitudes of 140 to 165 km, which, especially for the night probe, extend not only the mean temperature structure, but also the oscillation structure of the probe data at the same local Venus time. OAD temperatures depend on local Venus time and altitude, but, in the limited number of observations, appear independent of observing date over periods of up to 11 days, and correlate as described with probe data taken 65 to 137 days earlier. These observations lead to the suggestion that the thermospheric waves are solar-fixed, induced either by the major subsidence across the terminators or as continuations upward of waves in the middle atmosphere. The wave structure in the large probe sounding below 100 km is similar to, but does not quantitatively support the solar-tidal model of Pechmann and Ingersoll, which gives much larger amplitudes and different wave phases.

Seiff, A. (San Jose State Univ. Foundation, Moffett Field, CA (USA)); Kirk, D.B. (Univ. of Oregon, Eugene (USA))

1991-07-01

 
 
 
 
201

In vivo imaging of intersynaptic vesicle exchange using VGLUT1 Venus knock-in mice.  

UK PubMed Central (United Kingdom)

The vesicular glutamate transporter VGLUT1 loads synaptic vesicles with the neurotransmitter glutamate and thereby determines glutamate release at many synapses in the mammalian brain. Due to its function and selective localization, VGLUT1 is one of the most specific markers for glutamatergic synaptic vesicles. It has been used widely to identify glutamatergic synapses, and its expression levels are tightly correlated with changes in quantal size, modulations of synaptic plasticity, and corresponding behaviors. We generated a fluorescent VGLUT1(Venus) knock-in mouse for the analysis of VGLUT1 and glutamatergic synaptic vesicle trafficking. The mutation does not affect glutamatergic synapse function, and thus the new mouse model represents a universal tool for the analysis of glutamatergic transmitter systems in the forebrain. Previous studies demonstrated synaptic vesicle exchange between terminals in vitro. Using the VGLUT1(Venus) knock-in, we show that synaptic vesicles are dynamically shared among boutons in the cortex of mice in vivo. We provide a detailed analysis of synaptic vesicle sharing in vitro, and show that network homeostasis leads to dynamic scaling of synaptic VGLUT1 levels.

Herzog E; Nadrigny F; Silm K; Biesemann C; Helling I; Bersot T; Steffens H; Schwartzmann R; Nägerl UV; El Mestikawy S; Rhee J; Kirchhoff F; Brose N

2011-10-01

202

Comparisons of venus surface compositions with terrestrial ocean floor rocks  

Energy Technology Data Exchange (ETDEWEB)

Statistical comparison of Venera and Vega lander x-ray fluorescence spectrometer measurements of the composition of the Venus surface with an extensive database of compositional data for terrestrial ocean floor rocks indicates that the Venera 14 data matches certain tholeiitic basalts from the Kane Fracture Zone (KFZ) in the Mid-Atlantic Ridge (22-25/sup 0/N) at high confidence levels. The tholeiites most similar to the Venera measurements are very primitive, low-calcium, high-alumina pillow basalts depleted in clinopyroxene, and are relatively unique to certain fracture zones in oceanic regions. If the Venera 14 analogy is valid, the implication is that certain Venus basaltic magmas have lost clinopyroxene at relatively high pressures by fractionation, perhaps within a deep source region. Comparisons of Venera 13 and Vega 2 data with oceanic rocks yield poorer matches. Venera 13 matches Loihi seamount alkali basalts, as well as potassic mafic rocks from oceanic island such as Tristan de Cunha. The best analogy to Vega 2 may be altered gabbros or basic lavas from terrestrial basic intrusions such as the Troodos ophiolite. The close similarity of a representative sample of Venera 14 material with distinctive ocean floor tholeiitic basalts suggests that deep magma storage regions exist on Venus, and that derivation of both tholeiitic and alkalic magmas from a single primitive parent may be an important process on Venus.

Garvin, J.B.; Bryan, W.B.

1987-10-01

203

Distribution of tessera terrain on Venus: Prediction for Magellan  

International Nuclear Information System (INIS)

Tessera terrain is the dominant tectonic unit in the northern hemisphere of Venus and is characterized by complex sets of intersecting structural trends and distinctive radar properties due to a high degree of meter and sub-meter scale (5 cm to 10 m) roughness. Based on these distinctive radar properties, a prediction of the global distribution of tessera can be made using Pioneer Venus (PV) reflectivity and roughness data. Where available, Venera 15/16 and Arecibo images and PV diffuse scattering data were used to evaluate the prediction. From this assessment, the authors conclude that most of the regions with prediction values greater than 0.6 (out of 1) are likely to be tessera, and are almost certain to be tectonically deformed. Lada Terra and Phoebe Regio are very likely to contain tessera terrain, while much of Aphrodite Terra is most likely to be either tessera or a landform which has not yet been recognized on Venus. This prediction map will assist in targeting Magellan investigations of Venus tectonics

1990-01-01

204

Magellan: Preliminary description of Venus surface geologic units  

International Nuclear Information System (INIS)

Observations from approximately one-half of the Magellan nominal eight-month mission to map Venus are summarized. Preliminary compilation of initial geologic observations of the planet reveals a surface dominated by plains that are characterized by extensive and intensive volcanism and tectonic deformation. Four broad categories of units have been identified: plains units, linear belts, surficial units, and terrain units

1991-01-01

205

Possible Signs of Life on the Planet Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is possible, the question on the existence of extraterrestrial life will be answered not as a result of its search for in other worlds removed by distances of dozens of parsecs but on the surface of Venus, i.e., of the nearest planet of the Solar sy...

Leonid V. Ksanfomality

206

Distribution of tessera terrain on Venus: Prediction for Magellan  

Energy Technology Data Exchange (ETDEWEB)

Tessera terrain is the dominant tectonic unit in the northern hemisphere of Venus and is characterized by complex sets of intersecting structural trends and distinctive radar properties due to a high degree of meter and sub-meter scale (5 cm to 10 m) roughness. Based on these distinctive radar properties, a prediction of the global distribution of tessera can be made using Pioneer Venus (PV) reflectivity and roughness data. Where available, Venera 15/16 and Arecibo images and PV diffuse scattering data were used to evaluate the prediction. From this assessment, the authors conclude that most of the regions with prediction values greater than 0.6 (out of 1) are likely to be tessera, and are almost certain to be tectonically deformed. Lada Terra and Phoebe Regio are very likely to contain tessera terrain, while much of Aphrodite Terra is most likely to be either tessera or a landform which has not yet been recognized on Venus. This prediction map will assist in targeting Magellan investigations of Venus tectonics.

Bindschadler, D.L.; Head, J.W. (Brown Univ. (USA)); Kreslavsky, M.A.; Shkuratov, Yu.G. (Kharkov State Univ. (USSR)); Ivanov, M.A.; Basilevsky, A.T. (Vernadsky Institute, Moscow (USSR))

1990-02-01

207

Electrotonic and action potentials in the Venus flytrap.  

UK PubMed Central (United Kingdom)

The electrical phenomena and morphing structures in the Venus flytrap have attracted researchers since the nineteenth century. We have observed that mechanical stimulation of trigger hairs on the lobes of the Venus flytrap induces electrotonic potentials in the lower leaf. Electrostimulation of electrical circuits in the Venus flytrap can induce electrotonic potentials propagating along the upper and lower leaves. The instantaneous increase or decrease in voltage of stimulating potential generates a nonlinear electrical response in plant tissues. Any electrostimulation that is not instantaneous, such as sinusoidal or triangular functions, results in linear responses in the form of small electrotonic potentials. The amplitude and sign of electrotonic potentials depend on the polarity and the amplitude of the applied voltage. Electrical stimulation of the lower leaf induces electrical signals, which resemble action potentials, in the trap between the lobes and the midrib. The trap closes if the stimulating voltage is above the threshold level of 4.4V. Electrical responses in the Venus flytrap were analyzed and reproduced in the discrete electrical circuit. The information gained from this study can be used to elucidate the coupling of intracellular and intercellular communications in the form of electrical signals within plants.

Volkov AG; Vilfranc CL; Murphy VA; Mitchell CM; Volkova MI; O'Neal L; Markin VS

2013-06-01

208

Results of Recent Studies of MARS and Venus.  

Science.gov (United States)

Due to the launching of a series of robot space stations major advances have been made in research on earth's nearest neighbors, the planet Venus and Mars. Flights of spaceships, together with the perfection of the technology of observations made on earth...

N. L. Lukashevich

1976-01-01

209

Astronomers, Transits of Venus, and the Birth of Experimental Psychology  

Science.gov (United States)

The eighteenth century transits of Venus were regarded as the most important astronomical events of their era. Halley's expectation was that by observing the contact points between the limbs of Venus and the Sun, this distance could be determined to an accuracy of one part in 500. But in the event, it proved otherwise. But, as the British historian Agnes Clerke wrote in 1902: "A transit of Venus seems, at first sight, full of promise for solving the problem of the sun's distance. For nothing would appear easier than to determine exactly either the duration of the passage of a small, dark orb across a large brilliant disc, or the instant of its entry upon or exit from it". But in that word `exactly' what snares and pitfalls lie hid!” In the post-mortem analysis of the disappointing results, astronomers devoted a great deal of effort to understand the sources of errors. They rehearsed their observational techniques by observing, under strictly controlled conditions, transits of artificial planets across artificial Suns, and studied such parameters as attention and reflex reaction. In the process, the transits of Venus provided an important impetus to the early development of experimental psychology.

Sheehan, William; Thurber, S.

2012-01-01

210

New Results with the superconducting ECR ion source VENUS  

International Nuclear Information System (INIS)

[en] During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR ion source project as the RIA R and D injector is the production of 240emA of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5emA of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W RF power and the performance is very promising. For example, 1100 e mu A of O6+,180 e mu A of Ar12+, 150 emA of Xe20+ and 100 emA of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner. In FY04 a 10 kW, 28 GHz gyrotron system will be added, which will enable VENUS to reach full performance. The performance of the VENUS ion source, low energy beam transport (LEBT) and its closed loop cryogenic system are described in the paper. Recently, a new high temperature axial oven has been installed in the source and the first results on metal beams such as bismuth are given. The design of the 28 GHz, 10 kW gyrotron system is also be described. During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5 emA of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W RF power and the performance is very promising. For example, 1100 e mu A of O6+, 180 e muA of Ar12+, 150 emA of Xe20+ and 100 emA of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner. In FY04 a 10kW, 28 GHz gyrotron system will be added, which will enable VENUS to reach full performance. The performance of the VENUS ion source, low energy beam transport (LEBT) and its closed loop cryogenic system are described in the paper. Recently, a new high temperature axial oven has been installed in the source and the first results on metal beams such as bismuth are given. The design of the 28 GHz, 10 kW gyrotron system is also be described

2004-01-01

211

New Results with the superconducting ECR ion source VENUS  

Energy Technology Data Exchange (ETDEWEB)

During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR ion source project as the RIA R&D injector is the production of 240emA of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5emA of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W RF power and the performance is very promising. For example, 1100 e mu A of O6+,180 e mu A of Ar12+, 150 emA of Xe20+ and 100 emA of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner. In FY04 a 10 kW, 28 GHz gyrotron system will be added, which will enable VENUS to reach full performance. The performance of the VENUS ion source, low energy beam transport (LEBT) and its closed loop cryogenic system are described in the paper. Recently, a new high temperature axial oven has been installed in the source and the first results on metal beams such as bismuth are given. The design of the 28 GHz, 10 kW gyrotron system is also be described. During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5 emA of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W RF power and the performance is very promising. For example, 1100 e mu A of O6+, 180 e muA of Ar12+, 150 emA of Xe20+ and 100 emA of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner. In FY04 a 10kW, 28 GHz gyrotron system will be added, which will enable VENUS to reach full performance. The performance of the VENUS ion source, low energy beam transport (LEBT) and its closed loop cryogenic system are described in the paper. Recently, a new high temperature axial oven has been installed in the source and the first results on metal beams such as bismuth are given. The design of the 28 GHz, 10 kW gyrotron system is also be described.

Lyneis, C.M.; Leitner, D.; Abbott, S.R.; Dwinell, R.D.; Leitner,M.; Silver, C.S.; Taylor, C.

2004-05-13

212

Heliospheric current sheet inclinations at Venus and Earth  

Directory of Open Access Journals (Sweden)

Full Text Available We investigate the inclinations of heliospheric current sheet at two sites in interplanetary space, which are generated from the same solar source. From the data of solar wind magnetic fields observed at Venus (0.72 AU) and Earth (1 AU) during December 1978-May 1982 including the solar maximum of 1981, 54 pairs of candidate sector boundary crossings are picked out, of which 16 pairs are identified as sector boundaries. Of the remainder, 12 pairs are transient structures both at Venus and Earth, and 14 pairs are sector boundaries at one site and have transient structures at the other site. It implies that transient structures were often ejected from the coronal streamer belt around the solar maximum. For the 16 pairs of selected sector boundaries, we determine their normals by using minimum variance analysis. It is found that most of the normal azimuthal angles are distributed between the radial direction and the direction perpendicular to the spiral direction both at Venus and Earth. The normal elevations tend to be smaller than ~ 45° with respect to the solar equatorial plane, indicating high inclinations of the heliospheric current sheet, in particular at Earth. The larger scatter in the azimuth and elevation of normals at Venus than at Earth suggests stronger effects of the small-scale structures on the current sheet at 0.72 AU than at 1 AU. When the longitude difference between Venus and Earth is small (<40° longitudinally), similar or the same inclinations are generally observed, especially for the sector boundaries without small-scale structures. This implies that the heliospheric current sheet inclination tends to be maintained during propagation of the solar wind from 0.72 AU to 1 AU. Detailed case studies reveal that the dynamic nature of helmet streamers causes variations of the sector boundary structure.Key words. Interplanetary physics (interplanetary magnetic fields; sources of solar wind)

G. Ma; K. Marubashi; T. Maruyama

0000-01-01

213

Sequencing Medicago truncatula expressed sequenced tags using 454 Life Sciences technology  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background In this study, we addressed whether a single 454 Life Science GS20 sequencing run provides new gene discovery from a normalized cDNA library, and whether the short reads produced via this technology are of value in gene structure annotation. Results A single 454 GS20 sequencing run on adapter-ligated cDNA, from a normalized cDNA library, generated 292,465 reads that were reduced to 252,384 reads with an average read length of 92 nucleotides after cleaning. After clustering and assembly, a total of 184,599 unique sequences were generated containing over 400 SSRs. The 454 sequences generated hits to more genes than a comparable amount of sequence from MtGI. Although short, the 454 reads are of sufficient length to map to a unique genome location as effectively as longer ESTs produced by conventional sequencing. Functional interpretation of the sequences was carried out by Gene Ontology assignments from matches to Arabidopsis and was shown to cover a broad range of GO categories. 53,796 assemblies and singletons (29%) had no match in the existing MtGI. Within the previously unobserved Medicago transcripts, thousands had matches in a comprehensive protein database and one or more of the TIGR Plant Gene Indices. Approximately 20% of these novel sequences could be found in the Medicago genome sequence. A total of 70,026 reads generated by the 454 technology were mapped to 785 Medicago finished BACs using PASA and over 1,000 gene models required modification. In parallel to 454 sequencing, 4,445 5'-prime reads were generated by conventional sequencing using the same library and from the assembled sequences it was shown to contain about 52% full length cDNAs encoding proteins from 50 to over 500 amino acids in length. Conclusion Due to the large number of reads afforded by the 454 DNA sequencing technology, it is effective in revealing the expression of transcripts from a broad range of GO categories and contains many rare transcripts in normalized cDNA libraries, although only a limited portion of their sequence is uncovered. As with longer ESTs, 454 reads can be mapped uniquely onto genomic sequence to provide support for, and modifications of, gene predictions.

Cheung Foo; Haas Brian J; Goldberg Susanne MD; May Gregory D; Xiao Yongli; Town Christopher D

2006-01-01

214

Dynamics of the Venus ionosphere. Final technical report, 1 January 1985-31 May 1988  

Energy Technology Data Exchange (ETDEWEB)

Data from the Pioneer-Venus orbiter has demonstrated the importance of understanding ion dynamics in the Venus ionosphere. The analysis of the data has shown that during solar maximum the topside Venus ionosphere in the dark hemisphere is generated almost entirely on the dayside of the planet during solar maximum, and flows with supersonic velocities across the terminator into the nightside. The flow field in the ionosphere is mainly axially-symmetric about the sun-Venus axis, as are most measured ionospheric quantities. The primary data base used consisted of the ion velocity measurements made by the RPA during three years that periapsis of the orbiter was maintained in the Venus ionosphere. Examples of ion velocities were published and modeled. This research examined the planetary flow patterns measured in the Venus ionosphere, and the physical implications of departures from the mean flow.

Miller, K.L.

1988-01-01

215

Orientation of planetary O/sup +/ fluxes and magnetic field lines in the Venus wake  

Energy Technology Data Exchange (ETDEWEB)

The conditions in which planetary ions are picked up by the solar wind are examined using the plasma and magnetic field observations made with the Pioneer Venus Orbiter at Venus. It is shown that in the outer regions of the venusian far wake the displacement of planetary O/sup +/ particles, characteristic of the Venus upper ionosphere, does not occur necessarily along the magnetic field lines but approximately in the direction of the shocked solar wind.

Perez-de-Tejada, H. (Universidad Nacional Autonoma de Mexico. Inst. de Geofysica); Intriligator, D.S. (Carmel Research Center, Santa Monica, CA (USA)); Russell, C.T. (California Univ., Los Angeles (USA). Inst. of Geophysics and Planetary Physics)

1982-09-23

216

Charge-exchange in the magnetosheaths of Venus and Mars: a comparison  

Energy Technology Data Exchange (ETDEWEB)

The amount of solar wind absorption due to charge-exchange in the Martian magnetosheath is evaluated and found to be about an order of magnitude less than that in the Venus magnetosheath. This difference might explain the observed difference in the scaled position and shape between the shocks at Venus and Mars. The lower solar wind absorption for Mars is attributable to the less dense hot oxygen corona of Mars compared to Venus.

Russell, C.; Gombosi, T.I.; Horanyi, M.; Cravens, T.E.; Nagy, A.F.

1983-02-01

217

The 1986 eastern (evening) apparition of the planet Venus - Visual and photographic observations  

Energy Technology Data Exchange (ETDEWEB)

This report summarizes visual and photographic observations of the planet Venus for the 1986 eastern (evening) apparition, based on an extensive analysis of data submitted by ALPO Venus Section observers in the U.S. and three other countries. Sources of data and the instruments used in acquiring information about Venus are emphasized, with a statistical analysis of the categories of features seen or suspected in the atmosphere of Venus at visual wavelengths, both in integrated light and with color filters. A similar treatment is given to the cusps, cusp-caps, and cusp-bands, together with a discussion of dark-hemisphere phenomena, including the ashen light. 5 refs.

Benton, J.L. Jr. (Association of Lunar and Planetary Observers, San Francisco, CA (USA))

1990-07-01

218

Western Eisila Regio, Venus: Radar properties of volcanic deposits  

International Nuclear Information System (INIS)

1988 Arecibo Observatory dual-polarization radar images are presented for Western Eisila Regio, Venus. The polarization information and Pioneer-Venus Orbiter reflectivity and altimetry data are analyzed for volcanic deposits on two 400-500 km radius constructs, Sif and Gula Montes. Many of the large effusive deposits studied appear to require superposed flows or multiple vents to explain the observed progression of roughness along their length. High Fresnel reflectivity material may be present along the summit region of Gula Mons and in an embayed tessera-like region to the N. Radar-dark units on the flanks of Sif Mons are inferred to be pyroclastic deposits, but radar-dark features near the summits of both edifices are more consistent with very smooth lava flows. Higher spatial resolution Magellan data will be useful in testing these predictions.

1990-01-01

219

Photophysical Properties of Cerulean and Venus Fluorescent Proteins  

Science.gov (United States)

Cerulean and Venus are recently developed fluorescent proteins, often used as a donor-acceptor pair by researchers in FRET based co-localization studies. We characterized the fluorescent properties of these two proteins in a broad spectral range (form Ultra-Violet to Visible region). Excitation spectra, lifetimes and polarization spectra show significant energy transfer from aromatic amino acids to the fluorescent protein chromophore. High steady-state anisotropy values and the lack of a fast component in anisotropy decays show that the fluorescent protein chromophore is rigidly fixed within the protein structure. Furthermore, we show that the chromophores are not accessible to external quenchers such as acrylamide or potassium iodide (KI), allowing the removal of ‘unwanted’ background in the environment with external quencher, while leaving the Cerulean/Venus fluorescence unchanged.

Sarkar, Pabak; Koushik, Srinagesh V.; Vogel, Steven S.; Gryczynski, Ignacy; Gryczynski, Zygmunt

2009-01-01

220

The thermal balance of the atmosphere of Venus  

International Nuclear Information System (INIS)

[en] Current knowledge of the temperature structure of the atmosphere of Venus is briefly summarized. The principal features to be explained are the high surface temperature, the small horizontal temperature contrasts near the cloud tops in the presence of strong apparent motions, and the low value of the exospheric temperature. In order to understand the role of radiative and dynamical processes in maintaining the thermal balance of the atmosphere, a great deal of additional data on the global temperature structure, solar and thermal radiation fields, structure and optical properties of the clouds, and circulation of the atmosphere are needed. The ability of the Pioneer Venus Orbiter and Multiprobe Missions to provide these data is indicated. (Auth.)

1977-01-01

 
 
 
 
221

Galileo ultraviolet spectrometer experiment: initial venus and interplanetary cruise results.  

UK PubMed Central (United Kingdom)

The Galileo Extreme Ultraviolet Spectrometer obtained a spectrum of Venus atmospheric emissions in the 55.0- to 125.0-nanometer (nm) wavelength region. Emissions of helium (58.4 nm), ionized atomic oxygen (83.4 nm), and atomic hydrogen (121.6 nm), as well as a blended spectral feature of atomic hydrogen (Lyman-beta) and atomic oxygen (102.5 nm), were observed at 3.5-nm resolution. During the Galileo spacecraft cruise from Venus to Earth, Lyman-alpha emission from solar system atomic hydrogen (121.6 nm) was measured. The dominant source of the Lyman-alpha emission is atomic hydrogen from the interstellar medium. A model of Galileo observations at solar maximum indicates a decrease in the solar Lyman-alpha flux near the solar poles. A strong day-to-day variation also occurs with the 27-day periodicity of the rotation of the sun.

Hord CW; Barth CA; Esposito LW; McClintock WE; Pryor WR; Simmons KE; Stewart AI; Thomas GE; Ajello JM; Lane AL; West RW; Sandel BR; Broadfoot AL; Hunten DM; Shemansky DE

1991-09-01

222

Dynamics, winds, circulation and turbulence in the atmosphere of Venus  

International Nuclear Information System (INIS)

With the possible exception of the lowest one or two scale heights, the dominant mode of circulation of Venus' atmosphere is a rapid, zonal, retrograde motion. Global albedo variations in the ultraviolet may reflect planetary scale waves propagating relative to the zonal winds. Other special phenomena such as cellular convection in the subsolar region and internal gravity waves generated in the interaction of the zonal circulation with the subsolar disturbance may also be revealed in ultraviolet imagery of the atmosphere. The contributions of experiments on the Orbiter and Entry Probes of Pioneer Venus toward unravelling the mystery of the planet's global circulation and the role played by waves, instabilities and convection therein are discussed. (Auth.).

1977-01-01

223

Magellan - Early results from the Venus mapping mission  

Energy Technology Data Exchange (ETDEWEB)

Some results obtained with the Magellan Venus Radar Mapper are presented. Mapping was initiated on October 26, 1990 and has completed over 714 orbits of image data, covering 40 percent of the surface of Venus. Mapping began at 330 deg east longitude, mapping from the north pole to about 78 deg south latitude. Included are the regions of Ishtar Terra, Sedna, Guinevere and Lavinia Planitiae, and Lada Terra. Features discernable from the mapping include high and lowland plains, evidence of volcanic activity, and impact craters from 6 km to over 50 km across. Some Magellan scientific discoveries are listed, including evidence of a predominant role of ballistic volcanism, extensive and intensive tectonics, a moderate rate of volcanic and tectonic resurfacing, and a low rate of weathering and wind erosion. Other discoveries concerning techntonics, volcanism, impact cratering, and exogenous resurfacing are also listed. Magellan image coverage is discussed, and a chronology of the development of VOIR and Magellan is provided.

Saunders, R.S.

1991-01-01

224

Lucrecio: textos breves sobre Venus, el amor y la muerte  

Directory of Open Access Journals (Sweden)

Full Text Available Se presentan tres textos originales del poeta-filósofo Lucrecio, con sus correspondientes traducciones al castellano y comentarios. Los textos seleccionados del "De rerum natura" son representativos de los principales tópicos del autor. El primero es la invocación a Venus con que comienza la obra. El segundo versa sobre la pasión del amor. El último texto aborda el tema epicúreo del temor a la muerte. (In this article three original texts by poet-philosopher Lucrecius are presented, with their corresponding Spanish translations and commentaries. The texts, taken from "De rerum natura", are representative of the author’s main themes. The first is an invocation to Venus, the second is about the passion of love, and the last one deals with the epicurean topic of the fear of death.)

Eduardo Molina Cantó

1998-01-01

225

Temporal Variability and Latitudinal Jets in Venus's Zonal Wind Profiles  

Science.gov (United States)

We have observed Venus's night hemisphere from NASA's IRTF (Infrared Telescope Facility) during each inferior conjunction since 2001 to quantify the motion of features in Venus's lower and middle cloud decks. We now present latitudinal profiles from 11 nights, obtained in May and July 2004, February 2006 and September 2007. In about 7 of the 11 nights there are zonal jets near 45N and/or -50S, with speed differentials of 5 to 15 m/s relative to the adjacent equatorward latitude bands. These jets may be evidence of episodic Hadley cell-type circulation. About half of the nights show relatively constant velocity profiles between the latitudes of 50N to 50S, suggesting that considerable mixing is taking place between latitudes. Our most remarkable result is the temporal variability in the median zonal speeds from day to day. For example, the median velocity near the equator increases from 53 to 65 m/s over the period from July 11 - 13, 2004, and increases from 65 to 82 m/s over the period from Sept. 9 - 11, 2007. These velocity changes are too great to be due to the tracking of clouds that are in the middle vs. lower cloud deck, nor can they be caused by clouds that occupy different altitudes; a velocity variation of 25% corresponds to an altitude difference of 15 km, based on vertical profiles of zonal windspeeds from tracking of Pioneer Venus and Venera descent probes. Fifteen km is greater than the expected variation in either cloud base. VIRTIS observations of Venus's southern hemisphere were also obtained in September 2007 and should be able to corroborate or contradict the observed variations. This work was supported by NASA's Planetary Astronomy and Atmospheres programs.

Young, Eliot F.; Bullock, M. A.; Tavenner, T.; Coyote, S.; Murphy, J. R.

2008-09-01

226

Blob tectonics: A prediction for Western Aphrodite Terra, Venus  

Energy Technology Data Exchange (ETDEWEB)

It is proposed that the Western Aphrodite Terra region of Venus was formed by four diapirs of heated mantle material, or blobs, rising to the surface in a region of convective upwelling. The four blobs are in different stages of evolution, producing different topography, gravity anomalies, and morphology. The authors show that this model is consistent with available data and make specific predictions that can be tested with Magellan radar data.

Herrick, R.R.; Phillips, R.J. (Southern Methodist Univ., Dallas, TX (USA))

1990-11-01

227

Geologic Map of the Mylitta Fluctus Quadrangle (V-61), Venus  

Science.gov (United States)

INTRODUCTION The Magellan Mission The Magellan spacecraft orbited Venus from August 10, 1990, until it plunged into the Venusian atmosphere on October 12, 1994. Magellan Mission objectives included: (1) improving knowledge of the geological processes, surface properties, and geologic history of Venus by analysis of surface radar characteristics, topography, and morphology, and (2) improving the knowledge of the geophysics of Venus by analysis of Venusian gravity. The Magellan spacecraft carried a 12.6-cm radar system to map the surface of Venus. The transmitter and receiver systems were used to collect three data sets: (1) synthetic aperture radar (SAR) images of the surface, (2) passive microwave thermal emission observations, and (3) measurements of the backscattered power at small angles of incidence, which were processed to yield altimetric data. Radar imaging, altimetric, and radiometric mapping of the Venusian surface was done in mission cycles 1, 2, and 3 from September 1990 until September 1992. Ninety-eight percent of the surface was mapped with radar resolution on the order of 120 meters. The SAR observations were projected to a 75-m nominal horizontal resolution, and these full-resolution data compose the image base used in geologic mapping. The primary polarization mode was horizontal-transmit, horizontal-receive (HH), but additional data for selected areas were collected for the vertical polarization sense. Incidence angles varied between about 20? and 45?. High resolution Doppler tracking of the spacecraft took place from September 1992 through October 1994 (mission cycles 4, 5, 6). Approximately 950 orbits of high-resolution gravity observations were obtained between September 1992 and May 1993 while Magellan was in an elliptical orbit with a periapsis near 175 km and an apoapsis near 8,000 km. An additional 1,500 orbits were obtained following orbit-circularization in mid-1993. These data exist as a 75? by 75? harmonic field.

Ivanov, Mikhail A.; Head, James W., III

2006-01-01

228

The expression and interpretation of uncertain forensic science evidence: verbal equivalence, evidence strength, and the weak evidence effect.  

UK PubMed Central (United Kingdom)

Standards published by the Association of Forensic Science Providers (2009, Standards for the formulation of evaluative forensic science expert opinion, Science & Justice, Vol. 49, pp. 161-164) encourage forensic scientists to express their conclusions in the form of a likelihood ratio (LR), in which the value of the evidence is conveyed verbally or numerically. In this article, we report two experiments (using undergraduates and Mechanical Turk recruits) designed to investigate how much decision makers change their beliefs when presented with evidence in the form of verbal or numeric LRs. In Experiment 1 (N = 494), participants read a summary of a larceny trial containing inculpatory expert testimony in which evidence strength (low, moderate, high) and presentation method (verbal, numerical) varied. In Experiment 2 (N = 411), participants read the same larceny trial, this time including either exculpatory or inculpatory expert evidence that varied in strength (low, high) and presentation method (verbal, numerical). Both studies found a reasonable degree of correspondence in observed belief change resulting from verbal and numeric formats. However, belief change was considerably smaller than Bayesian calculations would predict. In addition, participants presented with evidence weakly supporting guilt tended to "invert" the evidence, thereby counterintuitively reducing their belief in the guilt of the accused. This "weak evidence effect" was most apparent in the verbal presentation conditions of both experiments, but only when the evidence was inculpatory. These findings raise questions about the interpretability of LRs by jurors and appear to support an expectancy-based account of the weak evidence effect.

Martire KA; Kemp RI; Watkins I; Sayle MA; Newell BR

2013-06-01

229

Magellan radar to reveal secrets of enshrouded Venus  

International Nuclear Information System (INIS)

Imaging Venus with a synthetic aperture radar (SAR) with 70 percent global coverage at 1-km optical line-pair resolution to provide a detailed global characterization of the volcanic land-forms on Venus by an integration of image data with altimetry is discussed. The Magellan radar system uses navigation predictions to preset the radar data collection parameters. The data are collected in such a way as to preserve the Doppler signature of surface elements and later they are transmitted to the earth for processing into high-resolution radar images. To maintain high accuracy, a complex on-board filter algorithm allows the altitude control logic to respond only to a narrow range of expected photon intensity levels and only to signals that occur within a small predicted interval of time. Each mapping pass images a swath of the planet that varies in width from 20 to 25 km. Since the orbital plane of the spacecraft remains fixed in the inertial space, the slow rotation of Venus continually brings new areas into view of the spacecraft.

1990-01-01

230

Variations in effective compensation depth across Aphrodite Terra, Venus  

Energy Technology Data Exchange (ETDEWEB)

Aphrodite Terra is the largest elevated terrain on Venus and it serves as a focal point in current discussions of global tectonic style. Using the topography and gravity data acquired by the Pioneer Venus Orbiter (PVO) the authors have estimated an effective depth of Airy compensation for each of 75 orbital arcs that provide fairly uniform areal coverage of the entire province. The most pronounced pattern that emerges is a general increase in compensation depth to the east. The most rapid change occurs near 135{degree}; the average west of there is 70 km, while the average to the east is 230 km. Superimposed on this larger trend are five distinctive regional patterns, four well defined peaks and one interval of widely scattered and poorly constrained depths. The maxima in compensation depth are well correlated with regional topographic highs. While these observations are easily reconciled with the general notion that Aphrodite is a region of crustal divergence, the great depth of compensation is difficult to accord with the more specific suggestion that Aphrodite is a terrestrial type divergent plate margin. The alternative suggestion that Aphrodite, and the other equatorial highlands on Venus, are surface manifestations of hot upwelling mantle plumes is consistent both with the great depths of compensation and with the pattern of regional peaks and intervening troughs. The broader scale increase in effective depth of compensation from west to east is more enigmatic, but it might reflect an age progression of the plumes.

Herrick, R.R.; Hall, S.A. (Univ. of Houston, TX (USA)); Bills, B.G.

1989-06-01

231

Solar diameter with 2012 Venus transit: history and opportunities  

CERN Multimedia

The role of Venus and Mercury transits is crucial to know the past history of the solar diameter. Through the W parameter, the logarithmic derivative of the radius with respect to the luminosity, the past values of the solar luminosity can be recovered. The black drop phenomenon affects the evaluation of the instants of internal and external contacts between the planetary disk and the solar limb. With these observed instants compared with the ephemerides the value of the solar diameter is recovered. The black drop and seeing effects are overcome with two fitting circles, to Venus and to the Sun, drawn in the undistorted part of the image. The corrections of ephemerides due to the atmospheric refraction will also be taken into account. The forthcoming transit of Venus will allow an accuracy on the diameter of the Sun better than 0.01 arcsec, with good images of the ingress and of the egress taken each second. Chinese solar observatories are in the optimal conditions to obtain valuable data for the measurement ...

Sigismondi, Costantino

2012-01-01

232

Tessera terrain, Venus: Characterization and models for origin and evolution  

Energy Technology Data Exchange (ETDEWEB)

Tessera terrain is the dominant tectonic landform in the northern high latitudes of Venus mapped by the Venera 15 and 16 orbiters and is concentrated in the region between the mountain ranges of western Ishtar Terra and Aphrodite Terra. Tesserae are characterized by regionally high topography, a high degree of small scale surface roughness, and sets of intersecting tectonic features. Available Pioneer Venus line of sight gravity data suggest that tessera terrain is compensated at shallow depths relative to many topographic highs on Venus and may be supported by crustal thickness variations. Three types of tessera terrain can be defined on the basis of structural patterns: subparallel ridged terrains (T{sub sr}), trough and ridge terrain (T{sub tr}), and disrupted terrain (T{sub ds}). Observed characteristics of tessera terrain are compared to predictions of models in order to begin to address the question of its origin and evolution. Formational models, in which high topography is created along with surface deformation, include (1) horizontal convergence, (2) mantle upwelling, (3) crustal underplating, and (4) a seafloor spreading analogy. Modification models, in which deformation occurs as a response to the presence of elevated regions, consist of (1) gravity sliding and (2) gravitational relaxation. The authors find that horizontal convergence and late stage gravitational relaxation are the most consistent with basic observations for subparallel ridged terrain and disrupted terrain. Understanding of the basic structural characteristics of trough and ridge terrain is more tentative, and models involving a spreading process or convergence and relaxation merit further study.

Bindschadler, D.L.; Head, J.W. (Brown Univ., Providence, RI (USA))

1991-04-10

233

Venus Ionospheric Hole Behavior in the Context of Channel Crossings  

Science.gov (United States)

There is clearly a need to better understand the topology and physical mechanisms of the nightside ionospheric holes on Venus and the disturbed, so called “disappearing” nightside ionosphere seen under the active part of the solar cycle. . One mechanism in particular, by de-Tejada, [2004, 2006], is the channel mechanism, in which the solar wind erodes the upper ionosphere in a channel that extends to low altitudes Some features of the PVO crossings of nightside ionosphere density depressions are consistent with crossings of the Pioneer Venus Orbiter through the channels that extend downstream from the magnetic polar regions. The hole width and depth in his interpretation become broader with increasing Psw. The de-Tejada mechanism will be extended further by examining in statistical detail nightside plasma measurements of Pioneer Venus Orbiter of the structure downstream from the magnetic polar region. Data from all nightside passes will be used to construct statistical altitude profiles of the depression structures (holes or channels) as a function of magnetic latitude, local time, solar wind pressure, and IMF. The depression structures will then be compared for consistency with the expectancies of the channel mechanism.

Hoegy, W. R.; Grebowsky, J. M.

2010-12-01

234

Magellan radar to reveal secrets of enshrouded Venus  

Energy Technology Data Exchange (ETDEWEB)

Imaging Venus with a synthetic aperture radar (SAR) with 70 percent global coverage at 1-km optical line-pair resolution to provide a detailed global characterization of the volcanic land-forms on Venus by an integration of image data with altimetry is discussed. The Magellan radar system uses navigation predictions to preset the radar data collection parameters. The data are collected in such a way as to preserve the Doppler signature of surface elements and later they are transmitted to the earth for processing into high-resolution radar images. To maintain high accuracy, a complex on-board filter algorithm allows the altitude control logic to respond only to a narrow range of expected photon intensity levels and only to signals that occur within a small predicted interval of time. Each mapping pass images a swath of the planet that varies in width from 20 to 25 km. Since the orbital plane of the spacecraft remains fixed in the inertial space, the slow rotation of Venus continually brings new areas into view of the spacecraft.

Saunders, R.S. (JPL, Pasadena, CA (USA))

1990-09-01

235

First Measurements of ClO in the Venus Mesosphere  

Science.gov (United States)

The first measurements of ClO in the Venus mesosphere are presented, based upon submm (352.88 GHz) spectroscopic observations in Oct-Dec 2010 (made with JCMT - the James Clerk Maxwell Telescope, Mauna Kea, Hawaii). CO2 is photolyzed to CO+O in the Venus thermosphere. If 3-body recombination were the only mechanism for regenerating CO2, models show the equilibrium Venus atmosphere would have large (10s of percent) abundances of CO and molecular oxygen. Three catalytic recombination mechanisms for stabilizing the atmosphere as CO2 have been proposed (Yung and Demore, 1982). The three suggested mechanisms involve hydrogen chemistry, nitrogen chemistry, and chlorine chemistry, respectively. Our ClO measurement confirms for the first time that chlorine catalysis indeed does play a large role in stabilizing the bulk atmosphere as CO2. This result neither requires nor rules out the possibility that hydrogen and/or nitrogen catalysis may also contribute to CO2 recombination. Altitude distribution, retrieved based upon shape of the pressure- broadened ClO absorption line, indicates there is more ClO in the upper mesosphere (above ~85 km) than at lower altitudes. The possibility that ClO abundance may be time variable will be discussed. [We acknowledge NASA for their funding of this project.

Sandor, Brad J.; Clancy, R.

2013-10-01

236

Nonlinear dynamics of the movement of the venus flytrap.  

Science.gov (United States)

The Venus flytrap has long been regarded as one of the most amazing examples of movement in the plant kingdom. The trapping ability of the flytrap consists of three unique features. First, trap closure represents one of the fastest movements in the plant kingdom. Second, a decision-making stage allows the plant to "decide" whether to completely close or open the trap, based on stimuli provided from the trapped object. Finally, the Venus flytrap contains a "memory function" that requires two mechanical stimuli within about 30 seconds to initiate trap closure. The movement involved in trap closure consists of nonlinear dynamics that have not been well understood. By understanding the movement, through nonlinear dynamics analysis, it will be possible to better understand this biological process. A mathematical model describing the movement of the Venus flytrap was first proposed by the authors in Yang et al., Plant Signal. Behav. 5(8), 968-978 (2010). In the current work, the earlier research has been advanced and an in-depth nonlinear and control analysis of the dynamic process has been provided. PMID:22843018

Li, Yongfeng; Lenaghan, Scott C; Zhang, Mingjun

2012-07-28

237

Nonlinear dynamics of the movement of the venus flytrap.  

UK PubMed Central (United Kingdom)

The Venus flytrap has long been regarded as one of the most amazing examples of movement in the plant kingdom. The trapping ability of the flytrap consists of three unique features. First, trap closure represents one of the fastest movements in the plant kingdom. Second, a decision-making stage allows the plant to "decide" whether to completely close or open the trap, based on stimuli provided from the trapped object. Finally, the Venus flytrap contains a "memory function" that requires two mechanical stimuli within about 30 seconds to initiate trap closure. The movement involved in trap closure consists of nonlinear dynamics that have not been well understood. By understanding the movement, through nonlinear dynamics analysis, it will be possible to better understand this biological process. A mathematical model describing the movement of the Venus flytrap was first proposed by the authors in Yang et al., Plant Signal. Behav. 5(8), 968-978 (2010). In the current work, the earlier research has been advanced and an in-depth nonlinear and control analysis of the dynamic process has been provided.

Li Y; Lenaghan SC; Zhang M

2012-10-01

238

Magnetization of the ionospheres of Venus and Mars: Results from radio occultation measurements  

Energy Technology Data Exchange (ETDEWEB)

In situ measurements by the Pioneer Venus orbiting spacecraft, conducted during solar maximum only, have shown that magnetization (permeation of large-scale magnetic fields) of the ionosphere of Venus occurs under high solar wind dynamic pressure and that this takes place most frequently near the subsolar region. In this paper, the authors use remote sensing radio occultation measurements to study magnetization of the ionospheres of Venus and Mars based on these characteristics. For Venus they take advantage of the unique data set consisting of 148 electron density profiles deduced from Pioneer Venus radio occultation measurements. They demonstrate that radio occultation measurements yield results on frequency of occurrence of magnetization during solar maximum that are similar to those obtained from the Pioneer Venus in situ magnetic field measurements. During solar minimum, for which direct ionospheric measurements have never been made, they find that magnetization of the Venus ionosphere is more pervasive than at solar maximum. Magnetization extends to higher solar zenith angles (SZA) and appears stronger than at solar maximum. These results confirm that during solar minimum, the high solar wind dynamic pressure state is more prevalent at Venus because the ionospheric plasma pressure is weaker than at solar maximum. Comparison of a large number of electron density profiles of Mars (deduced from radio occultation measurements by the Viking 1 and 2 and Mariner 9 spacecraft for SZA > 46{degrees}) with those of Venus shows an absence of the ledge and disturbed topside plasma observed in the Venus profiles. These results, however, do not constitute evidence against magnetization of the ionosphere of Mars, as Shinagawa and Cravens (1989) have shown on their one-dimensional MHD models that, even when the ionosphere of Mars is highly magnetized, the magnetic structure differs from that at Venus, and a ledge does not form in its electron density profiles.

Woo, R.; Kliore, A.J. (California Inst. of Tech., Pasadena (USA))

1991-07-01

239

Longwave Infrared Camera onboard the Venus Climate Orbiter  

Science.gov (United States)

The Longwave Infrared Camera (LIR) onboard the first Japanese Venus mission, PLANET-C, or the Venus Climate Orbiter, operates in the middle infrared region with a single bandpass filter of 8 12 ?m, measuring thermal radiation emitted from the cloud tops of the Venusian atmosphere. A horizontal wind vector field at the cloud-top height will be retrieved by means of a cloud tracking method. In addition, absolute temperature will be determined with an accuracy of 3 K. Since solar irradiation scattered by the atmosphere is much weaker than the atmospheric thermal radiation, LIR can continuously monitor a hemispheric wind field independent of the local time of the apocenter throughout the mission life. Wind and temperature fields obtained by LIR will provide key parameters to solve climatological issues related to the Venusian atmosphere. The use of an uncooled micro-bolometer array (UMBA), which requires no cryogenic apparatus, as an image sensor contributes to the reduction of power consumption and the weight of the LIR imager. An instrumental field-of-view of 12° is equal to the angle subtended by Venus when observed from a height of 9.5 Rv. The pixel field-of-view corresponds to a spatial resolution of 70 km viewed from the apocenter. A mechanical shutter functions not only as an optical shutter but also as a reference blackbody. The temperature stability of the sensor is especially important, because fluctuation of thermal radiation from the internal environment of the sensor itself causes background noise. Therefore, the temperature of the UMBA package is stabilized at 313 ± 0.1 K with a feedback controlled Peltier cooler/heater, and a NETD of 0.3 K, which is required for this infrared imager, will be achieved. Flat field images are taken with the shutter closed several seconds before and after 1 s exposure for a Venus thermal image. After a Venus image is taken, the LIR imager takes a cold calibration image of deep space. This measurement sequence is repeated every two hours when the spacecraft is orbiting at apocenter. Image data are transmitted down to the Earth after onboard calibration and data compression by common digital electronics.

Taguchi, M.; Fukuhara, T.; Imamura, T.; Nakamura, M.; Iwagami, N.; Ueno, M.; Suzuki, M.; Hashimoto, G. L.; Mitsuyama, K.

240

Venus-Earth-Mars: Comparative Climatology and the Search for Life in the Solar System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Both Venus and Mars have captured the human imagination during the twentieth century as possible abodes of life. Venus had long enchanted humans—all the more so after astronomers realized it was shrouded in a mysterious cloak of clouds permanently hiding the surface from view. It was also the closes...

Roger D. Launius

 
 
 
 
241

Effect of Interplanetary Matter on the Spin Evolutions of Venus and Mercury  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Differs from other planets in the Solar System, the Venus has a retrograde and long-period rotation. To ex-plain the special spin of the Venus, mechanisms such as core mantle friction inside planet[1], atmospheric tide[2-7], or twain effects together[8-11], and impact with a giant object[12,13] have...

Qingxiang Nie; Chuan Li; Fengshou Liu

242

New possibilities of the MEG and VENUS projects in the high energy physics  

International Nuclear Information System (INIS)

The data on the MEG (PSI, EC) and VENUS (LBNL, USA) projects state are given. A new detector (MEG project), permitting to investigate breaking the flavor of leptons, was developed and is constructed. The VENUS project is connected with developing and creation of the source of heavy multicharged ions, including uranium ions. The superconducting magnetic system for this source is developed and completely fabricated

2005-01-01

243

To what extent is mass loading responsible for the Venus bowshock precursor  

Energy Technology Data Exchange (ETDEWEB)

Significant ion and electron flux enhancements immediately upstream of the Venus bow shock were observed by the Electron Temperature Probe on the Pioneer Venus Orbiter. It is shown that mass loading of the solar wind by oxygen ions accounts for only about 10 percent of the observed effect.

Fontheim, E.G.; Brace, L.H.

1988-03-01

244

Relief and geology of the northern polar region of the planet Venus  

Energy Technology Data Exchange (ETDEWEB)

A description is given of the topographic features of the relief of the northern polar region of the planet Venus. The main morphological types of terrains and also their geological relations are characterized. The relative age sequence of the geological subdivisions in the northern polar region of Venus is discussed.

Kuz' min, R.O.; Burba, G.A.; Shashkina, V.P.; Bogomolov, A.F.; Zherikhin, N.V.; Skrypnik, G.I.; Kudrin, L.V.; Berman, M.Yu.; Rzhiga, O.N.; Sidorenko, A.I.; Aleksandrov, Yu.N.

1987-01-01

245

Investigation of plasma density bulge in front of Venus bow shock. Final technical report  

Energy Technology Data Exchange (ETDEWEB)

Significant ion and electron flux enhancements immediately upstream of the Venus bow shock were observed by the Electron Temperature Probe on the Pioneer Venus Orbiter. Mass loading of the solar wind by oxygen ions accounts for only about 10 percent of the observed effect.

1990-01-01

246

Project ExPreSS: Social studies and science remediation program for the Georgia High School Graduation Test  

Science.gov (United States)

Over half of the states now require students to pass a high stakes exit exam before being allowed to graduate from high school. No Child Left Behind requires that standardized testing be included to determine whether or not a school makes Adequate Yearly Progress (AYP). The purpose of this study is to examine the results of the Georgia High School Graduation Test (GHSGT) of students who participated in the remedial program Project ExPreSS with those students who did not participate. Using a quantitative research design, the question that will be answered is whether Project ExPreSS makes a difference in passing the GHSGT in science and social studies among three groups: all Georgia students, African American students in one Georgia school system, and all students in one Georgia school system. A chi-square test was conducted and a determination was made that there is a statistically significant relationship between project participation and pass-fail status in all but one area. The majority of students in this study were 17--18 years of age and were taking the science or social studies section of the GHSGT for the second time. The findings of this study will be important not only for Georgia and the school system examined, but also for other states and systems that give High Stakes Exit Exams (HSEEs). The results indicate that highly focused remedial programs like Project ExPreSS make a difference for students who may not be successful on their first attempt at passing a HSEE.

Shearouse, Randy

247

Hemispheric distributions of HCl above and below the Venus’ clouds by ground-based 1.7 ?m spectroscopy  

Science.gov (United States)

The abundance of hydrogen chloride (HCl) in the Venus atmosphere was measured by ground-based IR spectroscopy. The dayside measurements were performed in May 2007 with a resolution of 40,000, and the nightside measurements in October 1999 with a resolution of 1000. The hemispheric distributions of the HCl mixing ratio measured above the Venus’ clouds show no significant structure with a disc-averaged value of 0.74±0.06 ppm which is in the similar range as the previous report of 0.6±0.2 ppm. The representative height for the dayside measurements is estimated to be 60 66 km. Recent results by Venus Express/SPICAV/SOIR show much smaller values of 0.1 0.2 ppm at 64 94 km; however the direct comparison is difficult due to the different spatial conditions. The hemispheric distributions of the 35Cl/37Cl isotope ratio are also found to show no significant structure with a disc-averaged value of 3.1±0.4 which coincides with the terrestrial value of 3.1. The HCl mixing ratios below the clouds are also found to show no significant structure with a disc-averaged value of 0.40±0.05 ppm, which is similar to the previous reports of 0.4 0.5 ppm. The larger HCl mixing ratio above the clouds than below suggests the production of HCl in the cloud region or above. Also, a uniform hemispherical distribution of H2O is found below the clouds with a disc-averaged mixing ratio of 25±5 ppm; this is in the same range as the previous measurements. Those uniform distributions of HCl and H2O support the fact that their chemical lifetimes are much longer than that of mixing as has been discussed so far.

Iwagami, N.; Ohtsuki, S.; Tokuda, K.; Ohira, N.; Kasaba, Y.; Imamura, T.; Sagawa, H.; Hashimoto, G. L.; Takeuchi, S.; Ueno, M.; Okumura, S.

2008-08-01

248

Mantle dynamics in Mars and Venus: Influence of an immobile lithosphere on three-dimensional mantle convection  

International Nuclear Information System (INIS)

Numerical calculations of fully three-dimensional convection in constant viscosity, compressible spherical shells are interpreted in terms of possible convective motions in the mantles of Venus and Mars. The shells are heated both internally and from below to account for radiogenic heating, secular cooling, and heat flow from the core. The lower boundary of each of the shells is isothermal and shear stress free, as appropriate to the interface between a mantle and a liquid outer core. The upper boundary of each of the shells is rigid and isothermal, as appropriate to the base of a thick immobile lithosphere. Calculations with shear stress-free upper boundaries are also carried out to assess the role of the rigid surface condition. The ratio of the inner radius of each shell to its outer radius is in accordance with possible core sizes in both Venus and Mars. A calculation is also carried out for a Mars model with a small core to simulate mantle convection during early core formation. Different relative proportions of internal and bottom heating are investigated, ranging from nearly complete heating from within to almost all heating from below. The Rayleigh numbers of all the cases are approximately 100 times the critical Rayleigh numbers for the onset of convection. Cylindrical plumes are the prominent form of upwelling in the models independent of the surface boundary condition so long as sufficient heat derives from the core. Thus major volcanic centers on Mars, such as Tharsis and Elysium, and the coronae and some equatorial highlands on Venus may be the surface expressions of cylindrical mantle plumes.

1990-01-01

249

The June 2012 transit of Venus. Framework for interpretation of observations  

CERN Document Server

Ground based observers have on 5/6th June 2012 the last opportunity of the century to watch the passage of Venus across the solar disk from Earth. Venus transits have traditionally provided unique insight into the Venus atmosphere through the refraction halo that appears at the planet outer terminator near ingress/egress. Much more recently, Venus transits have attracted renewed interest because the technique of transits is being successfully applied to the characterization of extrasolar planet atmospheres. The current work investigates theoretically the interaction of sunlight and the Venus atmosphere through the full range of transit phases, as observed from Earth and from a remote distance. Our model predictions quantify the relevant atmospheric phenomena, thereby assisting the observers of the event in the interpretation of measurements and the extrapolation to the exoplanet case. Our approach relies on the numerical integration of the radiative transfer equation, and includes refraction, multiple scatter...

Muñoz, A García

2012-01-01

250

El pedido de armas de Venus a Vulcano (En. 8. 370-406): algunos intertextos Venus' request of armours from Vulcan (Aen. 8. 370-406): some intertexts  

Directory of Open Access Journals (Sweden)

Full Text Available El objetivo de este artículo es estudiar el episodio de Eneida 8 en el cual Venus le solicita a Vulcano la elaboración de armas para Eneas. En particular, nos interesa indagar las relaciones de intertextualidad que establece con cuatro pasajes de la tradición épica: Ilíada 18, Ilíada 14, Odisea 8 y el proemio de De rerum natura de Lucrecio. El análisis de la imitatio virgiliana contribuye al estudio de la complejidad del personaje de Venus.The aim of this paper is to study the episode of Aeneid 8 in which Venus asks Vulcan to make an armour for Aeneas. In particular, we are interested in investigating the intertextual relationships which it bears to four passages of the epic tradition: Iliad 18, Iliad 14, Odyssey 8 and Lucretius' proem to De rerum natura. The analysis of Virgilian imitatio contributes to the study of the complexity of Venus' character.

María Emilia Cairo

2010-01-01

251

El pedido de armas de Venus a Vulcano (En. 8. 370-406): algunos intertextos/ Venus' request of armours from Vulcan (Aen. 8. 370-406): some intertexts  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish El objetivo de este artículo es estudiar el episodio de Eneida 8 en el cual Venus le solicita a Vulcano la elaboración de armas para Eneas. En particular, nos interesa indagar las relaciones de intertextualidad que establece con cuatro pasajes de la tradición épica: Ilíada 18, Ilíada 14, Odisea 8 y el proemio de De rerum natura de Lucrecio. El análisis de la imitatio virgiliana contribuye al estudio de la complejidad del personaje de Venus. Abstract in english The aim of this paper is to study the episode of Aeneid 8 in which Venus asks Vulcan to make an armour for Aeneas. In particular, we are interested in investigating the intertextual relationships which it bears to four passages of the epic tradition: Iliad 18, Iliad 14, Odyssey 8 and Lucretius' proem to De rerum natura. The analysis of Virgilian imitatio contributes to the study of the complexity of Venus' character.

Cairo, María Emilia

2010-06-01

252

Need for a mission to understand the Earth-Venus-Mars difference in Nitrogen  

Science.gov (United States)

This presentation is based on a satellite mission proposal that was submitted to ESA's call for a Small Mission in June 2012. Although the mission was not selected, its science was recommended by the Solar System Exploration Working Group. Nitrogen is a key element for life as an inevitable part of the amino acid and protein. While nitrogen is abundant on the Earth (the amount in the soil, crust, and ocean are small compared to the atmospheric amount) and on Venus (only 3% but pressure is 90 times of the Earth, resulting in three times as the Earth), Martian atmosphere has very little nitrogen, about only 0.01% of the Earth or Venus (with 10% of planetary mass). This contrasts the oxygen abundance, which is found in all three planets (Martian case, it is now believed to exist in the crust as oxidized rocks because the observed escape rate is equivalent only 10 m deep water). Considering the fact that nitrogen is much more difficult to be ionized than oxygen due to triple chemical binding and that dependence of the ion outflow from the ionosphere on the geomagnetic activity is more drastic for cold nitrogen ion than cold oxygen ions, absence of the nitrogen only on the Mars is a mystery, while this absence might explain the absence of life on Mars at the present knowledge. From these viewpoints, it is important to understand the dynamic of N+ and N2+ at different solar conditions, e.g., its difference from oxygen dynamics for whatever the planet. One reason for lack of such measurement except cold ions is the difficulty in separating hot N+ from O+ in the modern time-of-flight instruments, but it is now most likely possible to separate O+ and N+ using magnetic mass analyzer if we mask H+ and if we limit the angular coverage to minimize contamination. The nitrogen study in space requires a dedicated space mission that covers both the polar region and inner magnetosphere. Instrumentation for such a mission also benefits study of inner magnetospheric study, substorm studies, and basic plasma physics such as ion energization. We present the science and instrumentation of the proposed NITRO mission.

Yamauchi, Masatoshi; Dandouras, Iannis; Rathsman, Peter

2013-04-01

253

Critical roles of a dendritic cell subset expressing a chemokine receptor, XCR1.  

UK PubMed Central (United Kingdom)

Dendritic cells (DCs) consist of various subsets that play crucial roles in linking innate and adaptive immunity. In the murine spleen, CD8?(+) DCs exhibit a propensity to ingest dying/dead cells, produce proinflammatory cytokines, and cross-present Ags to generate CD8(+) T cell responses. To track and ablate CD8?(+) DCs in vivo, we generated XCR1-venus and XCR1-DTRvenus mice, in which genes for a fluorescent protein, venus, and a fusion protein consisting of diphtheria toxin receptor and venus were knocked into the gene locus of a chemokine receptor, XCR1, which is highly expressed in CD8?(+) DCs. In both mice, venus(+) cells were detected in the majority of CD8?(+) DCs, but they were not detected in any other cells, including splenic macrophages. Venus(+)CD8?(+) DCs were superior to venus(-)CD8?(+) DCs with regard to their cytokine-producing ability in response to TLR stimuli. In other tissues, venus(+) cells were found primarily in lymph node (LN)-resident CD8?(+), LN migratory and peripheral CD103(+) DCs, which are closely related to splenic CD8?(+) DCs, although some thymic CD8?(-)CD11b(-) and LN CD103(-)CD11b(-) DCs were also venus(+). In response to dsRNAs, diphtheria toxin-treated XCR1-DTR mice showed impaired CD8(+) T cell responses, with retained cytokine and augmented CD4(+) T cell responses. Furthermore, Listeria monocytogenes infection and anti-L. monocytogenes CD8(+) T cell responses were defective in diphtheria toxin-treated XCR1-DTRvenus mice. Thus, XCR1-expressing DCs were required for dsRNA- or bacteria-induced CD8(+) T cell responses. XCR1-venus and XCR1-DTRvenus mice should be useful for elucidating the functions and behavior of XCR1-expressing DCs, including CD8?(+) and CD103(+) DCs, in lymphoid and peripheral tissues.

Yamazaki C; Sugiyama M; Ohta T; Hemmi H; Hamada E; Sasaki I; Fukuda Y; Yano T; Nobuoka M; Hirashima T; Iizuka A; Sato K; Tanaka T; Hoshino K; Kaisho T

2013-06-01

254

Nighttime photochemical model and night airglow on Venus  

Science.gov (United States)

The photochemical model for the Venus nighttime atmosphere and night airglow (Krasnopolsky, 2010, Icarus 207, 17–27) has been revised to account for the SPICAV detection of the nighttime ozone layer and more detailed spectroscopy and morphology of the OH nightglow. Nighttime chemistry on Venus is induced by fluxes of O, N, H, and Cl with mean hemispheric values of 3×1012, 1.2×109, 1010, and 1010 cm?2 s?1, respectively. These fluxes are proportional to column abundances of these species in the daytime atmosphere above 90 km, and this favors their validity. The model includes 86 reactions of 29 species. The calculated abundances of Cl2, ClO, and ClNO3 exceed a ppb level at 80–90 km, and perspectives of their detection are briefly discussed. Properties of the ozone layer in the model agree with those observed by SPICAV. An alternative model without the flux of Cl agrees with the observed O3 peak altitude and density but predicts an increase of ozone to 4×108 cm?3 at 80 km. Reactions H+O3 and O+HO2 that may excite the OH nightglow have equal column rates. However, the latter is shifted to 92–94 km, and the models agree better with the nightglow observations if O+HO2 does not contribute to the OH excitation. Schemes for quenching of the OH vibrational quanta by CO2 are chosen to fit the observed band distribution in the ?v=1 sequence at 2.9 ?m. The models agree with all observational constraints for the mean nighttime atmosphere. Analytic relationships between the nightglow intensities, the ozone layer, and the input fluxes of atomic species are given. The model results are compared with those of three-dimensional models for the Venus thermosphere.

Krasnopolsky, Vladimir A.

2013-09-01

255

Absorption of whistler mode waves in the ionosphere of venus.  

UK PubMed Central (United Kingdom)

It is shown that whistler mode waves from the ionosheath of Venus are absorbed by Landau damping at the dayside ionosphere boundary. This process heats the ionospheric electrons and it may provide an important energy input into the dayside ionosphere. Cyclotron damping of the waves does not occur in the same region. However, Landau damping of ionosheath waves is apparently not an important energy source in the nightside ionosphere. Impulsive events in the nightside ionosphere seem to fall into two classes: (i) lightning signals (near periapsis) and (ii) noise, which may be caused by gradient or current instabilities.

Taylor WW; Scarf FL; Russell CT; Brace LH

1979-07-01

256

L'intégration des mots venus d'ailleurs  

Directory of Open Access Journals (Sweden)

Full Text Available Cet article fait partie des textes venant du colloque Ranaclès 2004, organisé Lille 3 par Annick Rivens Mompean et Martine Eisenbeis. Date de réception de l'article : janvier 2005 1. Introduction Rien n'est plus dépaysant que de se plonger dans l'origine des mots d'une langue car, à côté du lexique transmis en ligne directe, il y a aussi des mots venus d'ailleurs, au gré de l'histoire des populations, provoquant ainsi des métissages, parfois rejetés mais le plus souvent réussis. Pour ces mots...

Henriette Walter

2005-01-01

257

Large-scale volcanism associated with coronae on Venus  

Science.gov (United States)

The formation and evolution of coronae on Venus are thought to be the result of mantle upwellings against the crust and lithosphere and subsequent gravitational relaxation. A variety of other features on Venus have been linked to processes associated with mantle upwelling, including shield volcanoes on large regional rises such as Beta, Atla and Western Eistla Regiones and extensive flow fields such as Mylitta and Kaiwan Fluctus near the Lada Terra/Lavinia Planitia boundary. Of these features, coronae appear to possess the smallest amounts of associated volcanism, although volcanism associated with coronae has only been qualitatively examined. An initial survey of coronae based on recent Magellan data indicated that only 9 percent of all coronae are associated with substantial amounts of volcanism, including interior calderas or edifices greater than 50 km in diameter and extensive, exterior radial flow fields. Sixty-eight percent of all coronae were found to have lesser amounts of volcanism, including interior flooding and associated volcanic domes and small shields; the remaining coronae were considered deficient in associated volcanism. It is possible that coronae are related to mantle plumes or diapirs that are lower in volume or in partial melt than those associated with the large shields or flow fields. Regional tectonics or variations in local crustal and thermal structure may also be significant in determining the amount of volcanism produced from an upwelling. It is also possible that flow fields associated with some coronae are sheet-like in nature and may not be readily identified. If coronae are associated with volcanic flow fields, then they may be a significant contributor to plains formation on Venus, as they number over 300 and are widely distributed across the planet. As a continuation of our analysis of large-scale volcanism on Venus, we have reexamined the known population of coronae and assessed quantitatively the scale of volcanism associated with them. In particular, we have examined the percentage of coronae associated with volcanic flow fields (i.e., a collection of digitate or sheet-like lava flows extending from the corona interior or annulus); the range in scale of these flow fields; the variations in diameter, structure and stratigraphy of coronae with flow fields; and the global distribution of coronae associated with flow fields.

Roberts, K. Magee; Head, James W.

1993-03-01

258

Venus' Clouds as Inferred from the Phase Curves Acquired by IR1 and IR2 on board Akatsuki  

Science.gov (United States)

We present phase curves for Venus in the 1-2 ?m wavelength region, acquired with IR1 and IR2 on board Akatsuki (February - March 2011). A large discrepancy with the previously-published curves was found in the small phase angle range (0o-30o). Through analysis by radiative-transfer computation, it was found that the visibility of larger (~1 ?m or larger) cloud particles was significantly higher than in the standard cloud model. Although the cause is unknown, this may be related to the recently reported increase in the abundance of SO2 in the upper atmosphere. It was also found that the cloud top is located at ~75 km and that 1-?m particles exist above the cloud, both of these results being consistent with recent studies based on the Venus Express observations in 2006-2008. Further monitoring, including photometry for phase curves, polarimetry for aerosol properties, spectroscopy for SO2 abundance, and cloud opacity measurements in the near-infrared windows, is required in order to understand the mechanism of this large-scale change.

Satoh, T.; Ohtsuki, S.; Iwagami, N.; Ueno, M.; Uemizu, K.; Suzuki, M.; Hashimoto, G. L.; Sakanoi, T.; Kasaba, Y.; Nakamura, R.; Imamura, T.; Nakamura, M.; Fukuhara, T.; Yamazaki, A.; Yamada, M.

2012-04-01

259

Venus-Earth-Mars: Comparative Climatology and the Search for Life in the Solar System  

Directory of Open Access Journals (Sweden)

Full Text Available Both Venus and Mars have captured the human imagination during the twentieth century as possible abodes of life. Venus had long enchanted humans—all the more so after astronomers realized it was shrouded in a mysterious cloak of clouds permanently hiding the surface from view. It was also the closest planet to Earth, with nearly the same size and surface gravity. These attributes brought myriad speculations about the nature of Venus, its climate, and the possibility of life existing there in some form. Mars also harbored interest as a place where life had or might still exist. Seasonal changes on Mars were interpreted as due to the possible spread and retreat of ice caps and lichen-like vegetation. A core element of this belief rested with the climatology of these two planets, as observed by astronomers, but these ideas were significantly altered, if not dashed during the space age. Missions to Venus and Mars revealed strikingly different worlds. The high temperatures and pressures found on Venus supported a “runaway greenhouse theory,” and Mars harbored an apparently lifeless landscape similar to the surface of the Moon. While hopes for Venus as an abode of life ended, the search for evidence of past life on Mars, possibly microbial, remains a central theme in space exploration. This survey explores the evolution of thinking about the climates of Venus and Mars as life-support systems, in comparison to Earth.

Roger D. Launius

2012-01-01

260

Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the first S-band (2.3 GHz) radio scintillations observed in the ionosphere of Venus and discovered when the Pioneer Venus Orbiter spacecraft traversed the ionosphere of Venus. In situ plasma measurements as well as propagation calculations confirm that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. While these topside plasma irregularities have not been studied before, simultaneous magnetic field measurements presented here reveal that they are associated with the penetration of large-scale magnetic fields in the ionosphere. Previous studies based on extensive magnetic field measurements have shown that the presence of large-scale magnetic fields occurs in the subsolar region when the solar wind dynamic pressure exceeds the ionospheric plasma pressure. As with the large-scale magnetic fields, the disturbed plasma and resulting scintillations are therefore a manifestation of high-dynamic solar wind interaction with the ionosphere. Since the scintillations only occur in the subsolar region of Venus, the global morphology of ionospheric scintillations at Venus is different from that of the terrestrial ionosphere, where scintillations are observed in both polar and equatorial regions, with peaks occurring during nighttime. This difference apparently stems from the fact that Venus is not a magnetic planet. The authors also demonstrate that the disturbed plasma produced by the high-dynamic solar wind interaction can be remotely sensed by scintillations during radio occultation measurements, that is, when the spacecraft is outside the ionosphere.

Woo, R.; Sjogren, W.L.; Kliore, A.J. (California Institute of Technology, Pasadena (USA)); Luhmann, J.G. (Univ. of California, Los Angeles (USA)); Brace, L.H. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1989-02-01

 
 
 
 
261

Temperature structure in the lower atmosphere of Venus - new results derived from Pioneer Venus entry probe measurements  

Energy Technology Data Exchange (ETDEWEB)

The Pioneer Venus Small-Probe Net Flux Radiometer temperature sensor and its calibration, the thermal model of the sensor head, the procedure for deriving atmospheric temperature from the sensor temperatures, and the new temperature results for each entry probe are reported. The new results are compared with those of the Small-Probe Atmospheric Structure experiment and with simple models of diurnal and latitudinal temperature contrasts. A dynamical inconsistency between these results and low-latitude measurements by the Sounder probe is described, and possible ways to resolve it are considered. 34 references.

Sromovsky, L.A.; Revercomb, H.E.; Suomi, V.E.

1985-06-01

262

Ionization efficiency studies for xenon ions with thesuperconducting ECR ion source VENUS  

Energy Technology Data Exchange (ETDEWEB)

Ionization efficiency studies for high charge state xenon ions using a calibrated gas leak are presented. A 75% enriched {sup 129}Xe gas leak with a gas flow equivalent to 5.11p{mu}A was used in all the measurements. The experiments were performed at the VENUS (Versatile ECR ion source for Nuclear Science) ion source for 18 GHz, 28 GHz and double frequency operation. Overall, total ionization efficiencies close to 100% and ionization efficiencies into a single charge state up to 22% were measured. The influence of the biased disk on the ionization efficiency was studied and the results were somewhat surprising. When the biased disk was removed from the plasma chamber, the ionization efficiency was dramatically reduced for single frequency operation. However, using double frequency heating the ionization efficiencies achieved without the biased disk almost matched the ionization efficiencies achieved with the biased probe. In addition, we have studied the influence of the support gas on the charge state distribution of the xenon ions. Either pure oxygen or a mixture of oxygen and helium were used as support gases. The addition of a small amount of helium can increase the ionization efficiency into a single charge state by narrowing the charge state distribution. Furthermore by varying the helium flow the most efficient charge state can be shifted over a wide range without compromising the ionization efficiency. This is not possible using only oxygen as support gas. Results from these studies are presented and discussed.

Leitner, Daniela; Lyneis, Claude M.; Todd, DamonS.; Tarvainen,Olli

2007-06-05

263

Sun Earth Day 2012, The Transit of Venus: From Mauna Kea to the World  

Science.gov (United States)

For 2012, NASA’s Sun Earth Day program ( http://sunearthday.nasa.gov/ and http://venustransit.nasa.gov/ ), now in its 13th year, featured the transit of Venus as well as other close celestial encounters. A NASA sponsored team of scientists, social media experts, telescope technicians, students, and the NASA EDGE webcasting team journeyed to the 14,000 foot summit of Mauna Kea in Hawaii to view and share with the world this wondrous last in a lifetime show. Fifteen NASA missions participated providing educational resources and science content. And when it was all over, it was the biggest education event NASA ever held, bigger than the Super Bowl, the last shuttle flight, or Prince William’s wedding. Over 600 million web hits, 7.7 million web streams, and an estimated 500 million to 1 billion people reached. This presentation will highlight this phenomenal education program, discuss best practices, and show how we are replicating the Sun Earth Day approach and methods for other event based education programs.

Mayo, Louis

2012-10-01

264

Selective incarceration of caesium ions by Venus flytrap action of a flexible framework sulfide  

International Nuclear Information System (INIS)

The selective capture of Cs+ from solution is relevant to the remediation of nuclear waste and remains a significant challenge. Here we describe a new framework composed of ((CH3)2NH2)+ and (Ga2Sb2S7)2- layers, which are perforated with holes. Shape selectivity couples with framework flexibility, allowing the compound to respond to the ion-exchange process. The size, shape and flexibility of the holes allow Cs+ ions in an aqueous solution to selectively pass through and enter the material via an ion-exchange process. Following capture, the structure dynamically closes its holes in a manner reminiscent of a Venus flytrap, which prevents the Cs+ ions from leaching out. This process has useful implications in the separation science of Cs as it relates to the clean-up of nuclear waste. The dynamic response we describe here provides important insights for designing new materials for the selective removal of difficult-to-capture ions.

2010-03-01

265

Selective incarceration of caesium ions by Venus flytrap action of a flexible framework sulfide.  

Energy Technology Data Exchange (ETDEWEB)

The selective capture of Cs{sup +} from solution is relevant to the remediation of nuclear waste and remains a significant challenge. Here we describe a new framework composed of [(CH{sub 3}){sub 2}NH{sub 2}]{sup +} and [Ga{sub 2}Sb{sub 2}S{sub 7}]{sup 2-} layers, which are perforated with holes. Shape selectivity couples with framework flexibility, allowing the compound to respond to the ion-exchange process. The size, shape and flexibility of the holes allow Cs{sup +} ions in an aqueous solution to selectively pass through and enter the material via an ion-exchange process. Following capture, the structure dynamically closes its holes in a manner reminiscent of a Venus flytrap, which prevents the Cs{sup +} ions from leaching out. This process has useful implications in the separation science of Cs as it relates to the clean-up of nuclear waste. The dynamic response we describe here provides important insights for designing new materials for the selective removal of difficult-to-capture ions.

Ding, N.; Kanatzidis, M. G. (Materials Science Division); (Northwestern Univ.)

2009-12-01

266

Selective incarceration of caesium ions by Venus flytrap action of a flexible framework sulfide  

Science.gov (United States)

The selective capture of Cs+ from solution is relevant to the remediation of nuclear waste and remains a significant challenge. Here we describe a new framework composed of [(CH3)2NH2]+ and [Ga2Sb2S7]2- layers, which are perforated with holes. Shape selectivity couples with framework flexibility, allowing the compound to respond to the ion-exchange process. The size, shape and flexibility of the holes allow Cs+ ions in an aqueous solution to selectively pass through and enter the material via an ion-exchange process. Following capture, the structure dynamically closes its holes in a manner reminiscent of a Venus flytrap, which prevents the Cs+ ions from leaching out. This process has useful implications in the separation science of Cs as it relates to the clean-up of nuclear waste. The dynamic response we describe here provides important insights for designing new materials for the selective removal of difficult-to-capture ions.

Ding, Nan; Kanatzidis, Mercouri G.

2010-03-01

267

In-core and ex-core calculations of the VENUS simulated PWR benchmark experiment  

International Nuclear Information System (INIS)

[en] The VENUS PWR engineering mockup experiment was established to simulate a beginning-of-life, generic PWR configuration at the zero-power VENUS critical facility located at CEN/SCK, Mol, Belgium. The experimental measurement program consists of (1) gamma scans to determine the core power distribution, (2) in-core and ex-core foil activations, (3) neutron spectrometer measurements, and (4) gamma heating measurements with TLD's. Analysis of the VENUS benchmark has been performed with two-dimensional discrete ordinates transport theory, using the DOT-IV code

1985-01-01

268

Characterization of Venera 15/16 geologic units from Pioneer Venus reflectivity and roughness data  

Energy Technology Data Exchange (ETDEWEB)

The characterization of geologic units defined for the Venus surface on the basis of Venera 15/16 image data is presently conducted in light of Pioneer Venus reflectivity and rms slope data. Four geologic-unit groups are distinguished: smooth rocky units, rough ones, rough high-dielectric units, and diffusely-scattering ones. Models have been tested for the surface-property origins of several units, and it is determined that plains and tectonic units may be contrasted in terms not only of surface roughness but of surface-roughening tectonic deformation that appears to dominate the erosional regime of Venus. 41 references.

Bindschadler, D.L.; Head, J.W.

1989-01-01

269

Distant bow shock and magnetotail of Venus: magnetic field and plasma wave observations  

Energy Technology Data Exchange (ETDEWEB)

An examination of the magnetic field and plasma wave data obtained by the Pioneer Venus orbiter in the wake region behind Venus discloses a well developed bow shock whose location is similar to that observed on previous missions in contrast to the dayside bow shock. Venus also has a well developed magnetotail in which the field strength is enhanced over magetosheath values and in which the magnetic field is aligned approximately with the solar wind direction. The boundary between magnetosheath and magnetotail is also marked by a change in the plasma wave spectrum.

Russell, C.T.; Luhmann, J.G.; Elphic, R.C.; Scarf, F.L.

1981-07-01

270

In-core and ex-core calculations of the VENUS simulated PWR benchmark experiment  

Energy Technology Data Exchange (ETDEWEB)

The VENUS PWR engineering mockup experiment was established to simulate a beginning-of-life, generic PWR configuration at the zero-power VENUS critical facility located at CEN/SCK, Mol, Belgium. The experimental measurement program consists of (1) gamma scans to determine the core power distribution, (2) in-core and ex-core foil activations, (3) neutron spectrometer measurements, and (4) gamma heating measurements with TLD's. Analysis of the VENUS benchmark has been performed with two-dimensional discrete ordinates transport theory, using the DOT-IV code.

Williams, M.L.; Chowdhury, P.; Landesman, M.; Kam, F.B.K.

1985-01-01

271

Global hybrid simulation of unmagnetized planets: Comparison of Venus and Mars  

Energy Technology Data Exchange (ETDEWEB)

Results from three-dimensional hybrid particle simulations of the solar wind interaction with the planets Mars and Venus are presented. The simulations produce shocks and magnetic barriers which are asymmetric. These results are qualitatively in agreement with data. In the absence of an ionosphere the subsolar shock standoff distance was found to agree with the observations if the Hall current is limited. It was also found that the solar wind interaction with Mars and Venus was substantially different. The interaction with Venus can be generally viewed as a magnetized interaction. The Mars interaction is very kinetic in nature and appears not to have a shock in the classic sense.

Brecht, S.H.; Ferrante, J.R. (Berkeley Research Associates, CA (USA))

1991-07-01

272

Venus mesosphere and thermosphere. III. Three-dimensional general circulation with coupled dynamics and composition  

Energy Technology Data Exchange (ETDEWEB)

The three-dimensional structure and circulation of Venus' upper mesosphere and thermosphere is examined by means of a modification of NCAR's earth thermosphere general circulation model, using the parameterizations from an earlier two-dimensional Venus model that included eddy diffusion and wave drag. Many of the observed Venus thermosphere features are found to be reproduced by the model, which thereby serves as a benchmark on which to incorporate additional minor constituents and test new self-consistent parameterizations for wave drag and superrotation. 36 references.

Bougher, S.W.; Roble, R.G.E.; Dickinson, R.E.; Ridley, E.C.

1988-03-01

273

Initial pioneer venus magnetic field results: dayside observations.  

UK PubMed Central (United Kingdom)

Initial observations by the Pioneer Venus mangnetometer in the sunlit ionosphere reveal a dynamic ionosphere, very responsive to external solar-wind conditions. The localtions of the bow shock and ionosphere are variable. The strength of the magnetic field just olutside the ionopause is in approximate pressure balance with the thermal plasma of the ionosphere and changes markedly from day, to day in response to changes in solar wind pressure. The field strength in the ionosphere is also variable from day to day. The field is often weak, at most a few gammas, but reaching many tens of gammas for periods of the order of seconds. These field enchantments are interpreted as due to the passage of spacecraft through flux ropes consisting of bundles of twisted field lines surrounded by the ionospheric plasma. The helicity of the flux varies through the flux tube, with lows pitch angles on the inside and very lage angles in the low-field outer edges of the ropes. These ropes may have external or internal sources. Consistent with previous results, the average position of the bow shock is much closer to the planet than would be expected if the solar wnd were completely deflected by the planet. In total, these observations indicate that the solar wind plays a significant role in the physics of the Venus ionosphere.

Russell CT; Elphic RC; Slavin JA

1979-02-01

274

The discovery of X-rays from Venus with Chandra  

CERN Multimedia

On January 10 and 13, 2001, Venus was observed for the first time with an X-ray astronomy satellite. The observation, performed with the ACIS-I and LETG/ACIS-S instruments on Chandra, yielded data of high spatial, spectral, and temporal resolution. Venus is clearly detected as a half-lit crescent, with considerable brightening on the sunward limb. The morphology agrees well with that expected from fluorescent scattering of solar X-rays in the planetary atmosphere. The radiation is observed at discrete energies, mainly at the O-K_alpha energy of 0.53 keV. Fluorescence radiation is also detected from C-K_alpha at 0.28 keV and, marginally, from N-K_alpha at 0.40 keV. An additional emission line is indicated at 0.29 keV, which might be the signature of the C 1s --> pi* transition in CO2 and CO. Evidence for temporal variability of the X-ray flux was found at the 2.6 sigma level, with fluctuations by factors of a few times indicated on time scales of minutes. All these findings are fully consistent with fluorescen...

Dennerl, K; Englhauser, J; Lisse, C M; Wolk, S

2002-01-01

275

Spectra of simulated lightning on Venus, Jupiter, and Titan.  

UK PubMed Central (United Kingdom)

Laser-induced plasmas in various gas mixtures were used to simulate lightning in other planetary atmospheres. This method of simulation has the advantage of producing short-duration, high-temperature plasmas free from electrode contamination. The laser-induced plasma discharges in air are shown to accurately simulate terrestrial lightning and can be expected to simulate lightning spectra in other planetary atmospheres. Spectra from 240 to 880 nm are presented for simulated lightning in the atmospheres of Venus, Earth, Jupiter, and Titan. The spectra of lightning on the other giant planets are expected to be similar to that of Jupiter because the atmospheres of these planets are composed mainly of hydrogen and helium. The spectra of Venus and Titan show substantial amounts of radiation due to the presence of carbon atoms and ions and show CN Violet radiation. Although small amounts of CH4 and NH3 are present in the Jovian atmosphere, only emission from hydrogen and helium is observed. Most differences in the spectra can be understood in terms of the elemental ratios of the gas mixtures. Consequently, observations of the spectra of lightning on other planets should provide in situ estimates of the atmospheric and aerosol composition in the cloud layers in which lightning is occurring. In particular, the detection of inert gases such as helium should be possible and the relative abundance of these gases compared to major constituents might be determined.

Borucki WJ; McKenzie RL; McKay CP; Duong ND; Boac DS

1985-01-01

276

A Potential Super-Venus in the Kepler-69 System  

CERN Multimedia

Transiting planets have greatly expanded and diversified the exoplanet field. These planets provide greater access to characterization of exoplanet atmospheres and structure. The Kepler mission has been particularly successful in expanding the exoplanet inventory, even to planets smaller than the Earth. The orbital period sensitivity of the Kepler data is now extending into the Habitable Zones of their host stars, and several planets larger than the Earth have been found to lie therein. Here we examine one such proposed planet, Kepler-69c. We provide new orbital parameters for this planet and an in-depth analysis of the Habitable Zone. We find that, even under optimistic conditions, this 1.7 R$_\\oplus$ planet is unlikely to be within the Habitable Zone of Kepler-69. Furthermore, the planet receives an incident flux of 1.91 times the solar constant, which is similar to that received by Venus. We thus suggest that this planet is likely a super-Venus rather than a super-Earth in terms of atmospheric properties a...

Kane, Stephen R; Gelino, Dawn M

2013-01-01

277

A POTENTIAL SUPER-VENUS IN THE KEPLER-69 SYSTEM  

Energy Technology Data Exchange (ETDEWEB)

Transiting planets have greatly expanded and diversified the exoplanet field. These planets provide greater access to characterization of exoplanet atmospheres and structure. The Kepler mission has been particularly successful in expanding the exoplanet inventory, even to planets smaller than the Earth. The orbital period sensitivity of the Kepler data is now extending into the habitable zones of their host stars, and several planets larger than the Earth have been found to lie therein. Here we examine one such proposed planet, Kepler-69c. We provide new orbital parameters for this planet and an in-depth analysis of the habitable zone. We find that, even under optimistic conditions, this 1.7 R{sub Circled-Plus} planet is unlikely to be within the habitable zone of Kepler-69. Furthermore, the planet receives an incident flux of 1.91 times the solar constant, which is similar to that received by Venus. We thus suggest that this planet is likely a super-Venus rather than a super-Earth in terms of atmospheric properties and habitability, and we propose follow-up observations to disentangle the ambiguity.

Kane, Stephen R.; Gelino, Dawn M. [NASA Exoplanet Science Institute, Caltech, MS 100-22, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Barclay, Thomas, E-mail: skane@ipac.caltech.edu [NASA Ames Research Center, M/S 244-30, Moffett Field, CA 94035 (United States)

2013-06-20

278

LIR: Longwave Infrared Camera onboard the Venus orbiter Akatsuki  

Science.gov (United States)

The Longwave Infrared Camera (LIR) is one of a suite of cameras onboard the Venus orbiter Akatsuki. It will take images of thermal radiation in the wavelength range of 8-12 ?m emitted by the Venus cloud tops. The use of an uncooled micro-bolometer array as an infrared image sensor makes LIR a lightweight, small and low-power consumption instrument with a required noise equivalent temperature difference of 0.3 K. Temperature and horizontal wind fields at the cloud-top will be retrieved for both dayside and nightside with equal quality. This will provide key observations to understand the mechanism of super rotation and the thermal budget of the planet. LIR will also monitor variations of the polar dipole and collar which are characteristic thermal features in the Venusian atmosphere. Mechanisms of the upper-cloud formation will be investigated using sequences of close-up images. The morphology of the nightside upper cloud will be studied in detail for the first time.

Fukuhara, T.; Taguchi, M.; Imamura, T.; Nakamura, M.; Ueno, M.; Suzuki, M.; Iwagami, N.; Sato, M.; Mitsuyama, K.; Hashimoto, G. L.; Ohshima, R.; Kouyama, T.; Ando, H.; Futaguchi, M.

2011-09-01

279

Impact craters on venus: initial analysis from magellan.  

UK PubMed Central (United Kingdom)

Magellan radar images of 15 percent of the planet show 135 craters of probable impact origin. Craters more than 15 km across tend to contain central peaks, multiple central peaks, and peak rings. Many craters smaller than 15 km exhibit multiple floors or appear in clusters; these phenomena are attributed to atmospheric breakup of incoming meteoroids. Additionally, the atmosphere appears to have prevented the formation of primary impact craters smaller than about 3 km and produced a deficiency in the number of craters smaller than about 25 km across. Ejecta is found at greater distances than that predicted by simple ballistic emplacement, and the distal ends of some ejecta deposits are lobate. These characteristics may represent surface flows of material initially entrained in the atmosphere. Many craters are surrounded by zones of low radar albedo whose origin may have been deformation of the surface by the shock or pressure wave associated with the incoming meteoroid. Craters are absent from several large areas such as a 5 million square kilometer region around Sappho Patera, where the most likely explanation for the dearth of craters is volcanic resurfacing. There is apparently a spectrum of surface ages on Venus ranging approximately from 0 to 800 million years, and therefore Venus must be a geologically active planet.

Phillips RJ; Arvidson RE; Boyce JM; Campbell DB; Guest JE; Schaber GG; Soderblom LA

1991-04-01

280

Small domes on Venus: Probable analogs of Icelandic lava shields  

International Nuclear Information System (INIS)

On the basis of observed shapes and volumetric estimates, the authors interpret small, dome-like features on radar images of Venus to be analogs of Icelandic lava-shield volcanoes. Using morphometric data for venusian domes in Aubele and Slyuta, as well as their own measurements of representative dome volumes and areas from Tethus Regio, they demonstrate that the characteristic aspect ratios and flank slopes of these features are consistent with a subclass of low Icelandic lava-shield volcanoes (LILS). LILS are slightly convex in cross-section with typical flank slopes of ?3 degree. Plausible lava-shield-production rates for the venusian plains suggest formation of ?53 million shields over the past 0.25 Ga. The cumulative global volume of lava that would be associated with this predicted number of lava shields is only a factor of 3-4 times that of a single oceanic composite shield volcano such as Mauna Loa. The global volume of all venusian lava shields in the 0.5-20-km size range would only contribute a meter of resurfacing over geologically significant time scales. Thus, venusian analogs to LILS may represent the most abundant landform on the globally dominant plains of Venus, but would be insignificant with regard to the global volume of lava extruded. As in Iceland, associated lavas from fissure eruptions probably dominate plains volcanism and should be evident on the higher resolution Magellan radar images.

1990-01-01

 
 
 
 
281

Possible Signs of Life on the Planet Venus  

Directory of Open Access Journals (Sweden)

Full Text Available It is possible, the question on the existence of extraterrestrial life will be answered not as a result of its search for in other worlds removed by distances of dozens of parsecs but on the surface of Venus, i.e., of the nearest planet of the Solar system. The search for “habitable zones” in extrasolar planetary systems is based on the postulate on “normal” physical conditions, i.e., the pressure, temperature, and maybe atmospheric composition similar to those on Earth. But could not such an approach be a kind of “terrestrial chauvinism”? Considering the conditions on Venus as a possible analogue of physical conditions on low-orbiting exoplanets of the “super-Earths” type, a new analysis of Venusian surface panoramas’ details has been made. These images were produced by the VENERA landers in 1975 and 1982. A few relatively large objects were found with size ranging from a decimeter to half meter and with unusual morphology. The objects were observed in some images, but were absent in the other or altered their shape. The article presents the obtained results and analyzes the evidence of reality of these objects.

Leonid V. Ksanfomality

2013-01-01

282

Venus exospheric structure: the role of solar radiation pressure  

International Nuclear Information System (INIS)

The existence of a ''hot'' population of hydrogen atoms in the Venus exosphere is well known. In the outer coronal region where it is dominant (r>? 2.0Rv), hydrogen atoms are also subject to a relatively strong radiation pressure exerted by resonant scattering of solar Lyman-? photons. Collisionless models illustrating the consequent structure are discussed, with the nonthermal population mimicked by a dual Maxwellian exobase kinetic distribution. In these models, a considerable fraction of the ''hot'' atoms outside 2.0Rv belongs to the quasi-satellite component, this fraction exceeding 1/2 for 4.0Rvv. Quasi-satellites also raise the kinetic temperature near 2.0Rv by ? 150 K. Solar ionization of bound atoms occurs mainly outside the ionopause, yielding a partial escape flux >?2 x 106 cm-2s-1 over the dayside exobase for assumed solar conditions. The inclusion of a cold exobase prescribed by Pioneer Venus observations has little influence on the outer region (in particular, the quasi-satellite component is unaltered) except that the transition to ''hot'' kinetic character occurs closer to the exobase on the nightside due to the colder main exobase temperatures there. Lastly, a ''tail'' of bound atoms is formed as in the terrestrial situation. (author).

1989-01-01

283

ESA's Planetary Science Archive: Status and Plans  

Science.gov (United States)

Scientific and engineering data from ESA's planetary missions are made accessible to the world-wide scientific community via the Planetary Science Archive (PSA). The PSA consists of online services incorporating search, preview, download, notification and delivery basket functionality. The PSA currently holds data from Mars Express, Venus Express, SMART-1, Huygens, Rosetta and Giotto, as well as several ground-based cometary observations. It will be used for archiving on ExoMars, BepiColombo and for the European contributions to Chandrayaan-1. The focus of the PSA activities is on the long-term preservation of data and knowledge from ESA's planetary missions. Scientific users can access the data online using several interfaces: - The Advanced Search Interface allows complex parameter based queries, providing the end user with a facility to complete very specific searches on meta-data and geometrical parameters. - The Map-based Interface is currently operational only for Mars Express HRSC and OMEGA data. This interface allows an end-user to specify a region-of-interest by dragging a box onto a base map of Mars. From this interface, it is possible to directly visualize query results. The Map-based and Advanced interfaces are linked and cross-compatible. If a user defines a region-of-interest in the Map-based interface, the results can be refined by entering more detailed search parameters in the Advanced interface. - The FTP Browser Interface is designed for more experienced users, and allows for direct browsing and access of the data set content through ftp-tree search. Each dataset contains documentation and calibration information in addition to the scientific or engineering data. All PSA data are prepared by the corresponding instrument teams, and are made to comply with the internationally recognized PDS standards. PSA supports the instrument teams in the full archiving process, from the definition of the data products, meta-data and product labels through to validation and ingestion of the products into the archive. To ensure a common archiving approach for all of ESA's planetary missions as well as to provide a similar data quality and standard for end users, a tool has been developed supporting the instrument teams in syntactically validating their datasets before delivering to the PSA. This tool, and the overall archiving process is being streamlined in line with the re-development of the science ground segment for Rosetta. This will be very important for the efficient handling and release of data during Rosetta's encounter with the comet Churyamov-Gerasimenko. A major focus for the PSA in 2013 will be to establish a PSA User Group (PSA-UG) and host a first working meeting. The PSA-UG is comprised of 6-8 members chosen to ensure an appropriate range of expertise in disciplines important for the PSA. They shall be a major driver for the future development of the PSA and its data content, and will be a focus for the interests of the scientific community. PSA personnel are the ESA representatives on the committee of the International Planetary Data Alliance (IPDA), an international collaboration of space agencies with a mission of providing access to scientific data returned from Solar System missions archived at international data centers. Venus Express data are already made available internationally via the 'PDAP' protocol thanks to this collaboration. A key IPDA project for 2013 is the implementation of the emerging PDS4 data standards. The new Standards aim to provide a framework for capturing planetary science data results in international archives based on a homogeneous set of standards that can be extended as needed for international usage. PSA are co-leading this project, using the upcoming BepiColombo mission to develop our first PDS4 data models.

Heather, David; Barthelemy, Maud; Manaud, Nicolas; Martinez, Santa; Szumlas, Marek; Vazquez, Jose Luis; Arviset, Christophe; Osuna, Pedro; PSA Development Team

2013-04-01

284

DNA methylation, an epigenetic mode of gene expression regulation in reproductive science.  

UK PubMed Central (United Kingdom)

DNA methylation is an important part of the epigenetic code governing gene expression. In human reproductive diseases, recent studies have shown the existence ofdeviations from the normal methylation profile at various genome loci. In this review, this type of epigenetic alterations is explored inpathological spermatogenesis, ovarian diseases, placental syndromes, such as preeclampsia and Intra-Uterine Growth Restriction, uterine diseases such as endometriosis, and putative pathophysiological effects of Assisted Reproductive Technologies. We review the notion of epigenetics, the technical methods available to analyze methylation, and the known associations between reproductive diseases and DNA methylation, focusing on human pathologies and on animal models when available. We show that imprinted genes control regions (ICRs) are a prominent and frequent target of methylation anomalies in reproductive disorders, but such alterations also affect non-imprinted genes. The mechanistic aspects of gene regulation in response to methylation anomalies are also discussed in this review when they have been investigated.

Calicchio R; Doridot L; Miralles F; Méhats C; Vaiman D

2013-07-01

285

Sprite discharges on Venus and Jupiter-like planets: a laboratory investigation  

CERN Multimedia

Large sprite discharges at high atmospheric altitudes have been found to be physically similar to small streamer discharges in air at sea level density. Based on this understanding, we investigate possible sprite discharges on Venus or Jupiter-like planets through laboratory experiments on streamers in appropriate CO2-N2 and H2-He mixtures. First, the scaling laws are experimentally confirmed by varying the density of the planetary gasses. Then streamer diameters, velocities and overall morphology are investigated for sprites on Venus and Jupiter; they are quite similar to those on earth, but light emissions in the visible range are fainter by two orders of magnitude. The discharge spectra are measured; they are dominated by the minority species N2 on Venus, while signatures of both species are found on Jupiter-like planets. The spectrum of a fully developed spark on Venus is measured. We show that this spectrum is significantly different from the expected sprite spectrum.

Dubrovin, Daria; van Veldhuizen, Eddie; Ebert, Ute; Yair, Yoav; Price, Colin; 10.1029/2009JA014851

2010-01-01

286

VULCAN: A Concept Study for a New Frontiers-Class Venus Lander  

Science.gov (United States)

VULCAN is a concept study for a New Frontiers mission to Venus to analyze atmospheric and surface composition. The mission would provide ~1 hr of atmospheric descent data and ~2 hrs of surface measurements, including detailed imaging and chemistry.

Stickle, A. M.; Banks, M. E.; Benecchi, S. D.; Bradley, B. K.; Budney, C. J.; Clark, G. B.; Corbin, B. A.; James, P. B.; Kumar, K.; O'Brien, R. C.; Rivera-Valentin, E. G.; Saltman, A.; Schmerr, N.; Seubert, C. R.; Siles, J. V.; Stockton, A. M.; Taylor, C.; Zanetti, M.

2012-03-01

287

Long-wave tangential stresses in the lithosphere and mantle of Venus  

Energy Technology Data Exchange (ETDEWEB)

The loading coefficients are calculated for real models of Venus taking into account the asthenosphere for anomalous density waves positioned at different characteristic levels. An associated analysis of the topography and the non-equilibrium part of the gravitational field allows one to determine long-wave primary tangential stresses in the lithosphere and mantle for zonal harmonics with n = 2-8. The stresses in the lithosphere of Venus are approximately equal to 30 bar, while those in the lower mantle can be up to 45 bar, but they are only on the order of a few bars in the weakened upper mantle. The low level of tangential stresses in the core and mantle of Venus is an important indication that the interior of the planet is intensely heated. A conclusion is drawn on aseismic nature of Venus.

Zharkov, V.N.; Marchenkov, K.I.; Lyubimov, V.M.

1987-01-01

288

Titan is to Earth's Hydrological Cycle what Venus is to its Greenhouse Effect  

Science.gov (United States)

Titan serves as an extreme extrapolation of Earth's possible present trend toward more violent rainstorms interspersed by long droughts, much as Venus has acted as a bogeyman to illustrate the perils of enhanced greenhouse warming.

Lorenz, R. D.

2012-06-01

289

Snap Trap of the Venus's Flytrap, Dionaea muscipula Ellis ex L. (Droseraceae)  

Science.gov (United States)

A snap trap of the Venus's flytrap, Dionaea muscipula Ellis ex L. (Droseraceae), native in North America forms a sister group with widely distributed aquatic snap trap species Aldrovanda vesiculosa L.

Mitsuyasu Hasebe (The Graduate University for Advanced Studies;School of Life Science - Department of Molecular B ADR;POSTAL)

2004-03-09

290

Venusians: the Planet Venus in the 18th-Century Extraterrestrial Life Debate  

Science.gov (United States)

In the seventeenth and eighteenth centuries it became possible to believe in the existence of life on other planets on scientific grounds. Once the Earth was no longer the center of the universe according to Copernicus, once Galileo had aimed his telescope at the Moon and found it a rough globe with mountains and seas, the assumption of life on other planets became much less far-fetched. In general there were no actual differences between Earth and Venus, since both planets orbited the Sun, were of similar size, and possessed mountains and an atmosphere. If there is life on Earth, one may ponder why it could not also exist on Venus. In the extraterrestrial life debate of the seventeenth and eighteenth centuries, the Moon, our closest celestial body, was the prime candidate for life on other worlds, although a number of scientists and scholars also speculated about life on Venus and on other planets, both within our solar system and beyond its frontiers. This chapter discusses the arguments for life on Venus and those scientific findings that were used to support them, which were based in particular on assumptions and claims that both mountains and an atmosphere had been found on Venus. The transits of Venus in the 1760s became especially important for the notion that life could thrive on Venus. Here, I detect two significant cognitive processes that were at work in the search for life on Venus, i.e., analogical reasoning and epistemic perception, while analogies and interpretations of sensory impressions based on prior knowledge played an important role in astrobiological theories.

Duner, David

2013-05-01

291

Venus Twilight Experiment : Observation and analysis of the aureole during the 2012 transit  

Science.gov (United States)

On 5-6 June 2012, Venus will be transiting the Sun for the last time in this century. This unique opportunity, besides offering the opportunity of investigating the mesosphere of the planet, also provides a significant nearby analog of exoplanet transits. Several studies using the transmission spectroscopy technique have provided significant insights into the atmospheric composition, structure, and dynamics of hot giant exoplanets. In this context, Venus is our closest model for a telluric exoplanet.

Widemann, T.; Tanga, P.; Sicardy, B.; Machado, P.; Braga-Ribas, F.; Veillet, C.; Pasachoff, J.; Colas, F.; Vachier, F.; Bouley, S.; Maquet, L.; Berthier, J.; Fukuhara, T.; Luz, D.

2012-09-01

292

A comparative study of Venus and Mars: upper atmospheres, ionospheres and solar wind interactions  

International Nuclear Information System (INIS)

Both Venus and Mars have extended atmospheres with CO2 dominating in the lower thermosphere and O at higher altitudes. Although O is depleted at Mars in the lower thermosphere, the low gravity can make O to be larger at Mars than at Venus for altitudes above about 250 Km. Hot neutrals exist both at Venus and Mars, but the densities are large enough at Venus alone to play a significant role in the solar wind interaction. The venus atmosphere is found to be very insensitive to solar EUV variability, with the exospheric temperature changing only by about 60 K over a solar cycle. In contrast, the exospheric temperatures at Mars, deduced mainly from plasma scale heights, indicate a variation from 150 K to 400 K over a solar cycle. However, no direct measurements of the neutral atmosphere over a solar cycle exist to make a definitive statement. On Venus the major ion is O+ in the upper ionosphere, while O2+ dominates in most part of the Mars ionosphere. During solar minimum, when the ionosphere is weak, the solar wind compresses the Venus ionosphere to its limiting altitude in the photodynamical regime, forming a thick ionopause. This thick ionopause is also seen at times of high Psw during solar maximum. Mars ionosphere is weak and its ionopause is also observed to be thick, similar to the one observed at Venus. This provides evidence for direct interaction of solar wind with the ionosphere of Mars suggesting that Mars does not have an intrinsic magnetic field of any consequence. However, ionospheric outflows from Mars, similar to those on Earth have been observed on Phobos-2 which have been interpreted as an evidence for Mars intrinsic magnetic field. (author). 186 refs., 17 figs

1990-01-01

293

A comparison of induced magnetotails of planetary bodies: Venus, Mars, and Titan  

Energy Technology Data Exchange (ETDEWEB)

The Pioneer Venus orbiter (PVO), PHOBOS 2, and Voyager 1 spacecraft have together provided observations of three planetary bodies with induced magnetotails: Venus, Mars, and Titan. During the extended mission of PVO, the tail of Venus was probed at an altitude of {approximately} 1.3 planetary radii, which provided a more appropriate basis for comparison with the Mars data (at {approximately} 2.7 planetary radii), and Titan data ({approximately} 2.5 planetary radii downstream), then the previously analyzed Venus tail data obtained near PVO apoapsis ({approximately} 12 planetary radii). A parallel examination of the magnetic properties of these tails at downstream distances within 3 planetary radii reveals the following similarities and differences. In the cases of Venus and Mars, which are always embedded in the supermagnetosonic solar wind flow, the tail lobe fields are smoothly joined to the draped magnetosheath fields at their outer boundaries, but separated in the center by a distinct, and sometimes narrow, current sheet. The tail of Mars has a cross section that is wider, when scaled by the planet radius, than that at Venus (as found by earlier MARS spacecraft experiments), a lobe field strength that is about the same as that at Venus by {approximately}1.5 times. The tail of Titan appears similar to the others except that there is no bow shock and little or no draped magnetosheath field signature since the surrounding magnetospheric plasma flow is submagnetosonic (although super-Alfvenic). The lobe field strengths are about half those at Venus and Mars, while the cross-tail field is almost negligible. The near-Titan tail diameter is close to the body diameter.

Luhmann, J.G.; Russell, C.T. (Univ. of California, Los Angeles (USA)); Schwingenschuh, K. (Space Research Inst., Graz (Austria)); Yeroshenko, Ye. (USSR Space Research Inst., Moscow (USSR))

1991-07-01

294

Poética y variantes del mito: Venus en Julián del Casal, Rubén Darío y José Lezama Lima  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Este trabajo indaga las resemantizaciones del mito de Venus en tres poetas latinoamericanos: Julián del Casal, Rubén Darío y José Lezama Lima teniendo en cuenta la intertextualidad y las poéticas correspondientes. Abstract in english This paper analyses the Venus myth appropiation into the poetry of Julián del Casal, Rubén Darío and José Lezama Lima considering their poetry and intertextuality.

Chazarreta, Daniela Evangelina

2011-12-01

295

Geology of coronae and domal structures on Venus and models of their origin  

Energy Technology Data Exchange (ETDEWEB)

Coronae (160 to 670 km across) and domal structures (greater than 1000 km across) are complex topographic highs on Venus that were affected by volcanic and topographic processes. The geology of coronae and a major domal structure, Beta Regio, are documented using Pioneer Venus, Arecibo, and Venera 15/16 data. The evolution and possible models of origin of these features are also investigated. Beta Regio is a 2000 x 2300 km topographic high located in the equatorial region of Venus that rises over 5 km above the surrounding region. Within Beta Regio lie two large volcanic shields, Theia and Rhea Mons. Coronae are circular to elongate structures on Venus, characterized by an annulus of concentric compressional ridges and relatively raised topography surrounded by a peripheral trough. Volcanic domes, flows and edifices, as well as tectonic lineaments characterize the interiors of coronae. Thirty one coronae were detected on Venus. Two analytical models were developed that are consistent with the general characteristics and evolution of coronae: hotspot or rising mantle diapir model and sinking mantle diapir model. Coronae appear to be part of a continuum of thermally produced features on Venus, along with volcanic complexes and domal structures such as Beta Regio.

Stofan, E.R.

1989-01-01

296

Tectonics of Lakshmi Planum, Venus: Tests for Magellan  

International Nuclear Information System (INIS)

The origin of Lakshmi Planum and its surrounding mountain belts remains an important unresolved element in the global tectonic framework of Venus. From the perspective of gravity signature and potential driving forces, the mantle upwelling model is the simplest and its principal failure, that it cannot produce radial shortening on the uplift periphery, may be resolved if the lithosphere is laterally heterogeneous. The preferred model consists of a hot mantle plume rising beneath a pre-existing block of tessera. The lithosphere is weakened at this hotter and presumably thicker crust, and the outward near-surface flow is attenuated at the peripheral discontinuity in lithospheric strength. Crustal thickening and mountain belt formation occur there. The authors propose several criteria to test this tessera-plume model together with its competitors at the higher resolution in both imaging and gravity afforded by the Magellan mission

1990-01-01

297

Magellan: electrical and physical properties of venus' surface.  

UK PubMed Central (United Kingdom)

Magellan probes Venus' surface by 12.6-cm-wavelength vertical and oblique radar scattering and measures microwave thermal emission. Emissivity and root-meansquare slope maps between 330 degrees and 30 degrees E and 90 degrees N and 80 degrees S are dissimilar, although some local features are exceptions. Inferred surface emissivities typically are approximately 0.85, but vary from approximately 0.35 at Maxwell to approximately 0.95 northeast of Gula Mons and other locations. Lowest emissivities appear in topographically high areas; this relation suggests that a phase change or differences in chemical weathering occur at about 6055-kilometer radius. Initial results indicate that there are significant variations in the surface scattering function.

Tyler GL; Ford PG; Campbell DB; Elachi C; Pettengill GH; Simpson RA

1991-04-01

298

System of tectonic features common to Earth, Mars, and Venus  

Energy Technology Data Exchange (ETDEWEB)

Investigations of landforms on the terrestrial planets have revealed a system of tectonic features consisting of long, narrow, regularly spaced folds and/or thrust faults, referred to as wrinkle ridges, and conjugate sets of cross-trending strike-slip faults. These are observed in the Yakima fold belt of the Columbia Plateau, Earth, the ridged plains of the Tharsis province, Mars, and the lowland plains of Lavinia Planitia, Venus. The wrinkle ridges and strike-slip faults reflect a relatively small amount of crustal shortening in these regions of distributed deformation. The observed geometric relations between the structures are consistent with those predicted by the Coulomb-Anderson model. Although the tectonic settings of the provinces studied on the three planets are very different, the crustal materials appear to have deformed in a similar manner.

Watters, T.R. (Smithsonian Institution, Washington, DC (United States))

1992-07-01

299

Blonde Venus y el género cinematográfico de la mujer caída  

Directory of Open Access Journals (Sweden)

Full Text Available Este artículo analiza algunos problemas relacionados con la representación de la mujer caída en la película Blonde Venus, ya que su tratamiento poco convencional provocó muchos contratiempos con la censura, conflicto que permite observar de cerca los mecanismos de representación del cine clásico de Hollywood. Aunque la película retoma la dicotomía presente en la representación occidental entre la imagen de la madre y de la prostituta (entre María y Eva), el personaje de Marlene Dietrich encarna ambos papeles al mismo tiempo, generando ambigüedades y contradicciones que desestabilizan los discursos moralistas tanto de la mujer caída como del ama de casa. Dichos discursos cobraron auge a fines del siglo XIX y posteriormente fueron retomados por el cine.

María Paula Noval Morgan

2011-01-01

300

Venus atmosphere profile from a maximum entropy principle  

Directory of Open Access Journals (Sweden)

Full Text Available The variational method with constraints recently developed by Verkley and Gerkema to describe maximum-entropy atmospheric profiles is generalized to ideal gases but with temperature-dependent specific heats. In so doing, an extended and non standard potential temperature is introduced that is well suited for tackling the problem under consideration. This new formalism is successfully applied to the atmosphere of Venus. Three well defined regions emerge in this atmosphere up to a height of 100 km from the surface: the lowest one up to about 35 km is adiabatic, a transition layer located at the height of the cloud deck and finally a third region which is practically isothermal.

L. N. Epele; H. Fanchiotti; C. A. García Canal; A. F. Pacheco; J. Sañudo

2007-01-01

 
 
 
 
301

Leaf Closure in the Venus Flytrap: An Acid Growth Response  

Science.gov (United States)

The rapid closure of leaves in the Venus flytrap (Dionaea muscipula) involves irreversible cell enlargement, which can be initiated by acidifying the cell walls to pH 4.50 and below. Leaves infiltrated with neutral buffers that keep the pH above 4.50 to 4.75 will not close in response to stimulation of their trigger hairs even though the action potentials that ordinarily cause closure are produced. During the 1 to 3 seconds required for closure about 29 percent of the cellular adenosine triphosphate is lost. It is likely that this adenosine triphosphate is used in very rapid transport of hydrogen ions from the motor cells and that the movement is due to a mechanism of ``acid growth.''

Williams, Stephen E.; Bennett, Alan B.

1982-12-01

302

Leaf closure in the venus flytrap: an Acid growth response.  

UK PubMed Central (United Kingdom)

The rapid closure of leaves in the Venus flytrap (Dionaea muscipula) involves irreversible cell enlargement, which can be initiated by acidifying the cell walls to pH 4.50 and below. Leaves infiltrated with neutral buffers that keep the pH above 4.50 to 4.75 will not close in response to stimulation of their trigger hairs even though the action potentials that ordinarily cause closure are produced. During the 1 to 3 seconds required for closure about 29 percent of the cellular adenosine triphosphate is lost. It is likely that this adenosine triphosphate is used in very rapid transport of hydrogen ions from the motor cells and that the movement is due to a mechanism of "acid growth."

Williams SE; Bennett AB

1982-12-01

303

Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating  

CERN Multimedia

Traditionally stellar radiation has been the only heat source considered capable of determining global climate on long timescales. Here we show that terrestrial exoplanets orbiting low-mass stars may be tidally heated at high enough levels to induce a runaway greenhouse for a long enough duration for all the hydrogen to escape. Without hydrogen, the planet no longer has water and cannot support life. We call these planets "Tidal Venuses," and the phenomenon a "tidal greenhouse." Tidal effects also circularize the orbit, which decreases tidal heating. Hence, some planets may form with large eccentricity, with its accompanying large tidal heating, and lose their water, but eventually settle into nearly circular orbits in the habitable zone (HZ). However, these planets are not habitable as past tidal heating desiccated them, and hence should not be ranked highly for detailed follow-up observations aimed at detecting biosignatures. We simulate the evolution of hypothetical planetary systems in a quasi-continuous ...

Barnes, Rory; Goldblatt, Colin; Meadows, Victoria S; Kasting, James F; Heller, Rene

2012-01-01

304

Cloning, purification, crystallization and preliminary X-ray analysis of a bacterial GABA receptor with a Venus flytrap fold.  

Science.gov (United States)

In response to infection by the pathogen Agrobacterium tumefaciens, plants synthesize several stress amino acids, including gamma-aminobutyric acid (GABA), which modulates the expression of bacterial virulence factors. GABA penetrates into the bacterial cytoplasm via an ABC transporter that is associated with the periplasmic receptor Atu2422. Mature receptor Atu2422 (without its signal peptide) was overexpressed in Escherichia coli, purified and crystallized. A complete data set was collected to 1.35 A resolution at 100 K. The crystals belonged to the monoclinic space group C2 and contained one molecule in the asymmetric unit. Molecular replacement was performed and the initial electron-density maps revealed a closed form of this Venus flytrap (VFT) receptor, suggesting the presence of an endogenous E. coli ligand. PMID:19052373

Moréra, Solange; Gueguen-Chaignon, Virginie; Raffoux, Aurélie; Faure, Denis

2008-11-28

305

Cloning, purification, crystallization and preliminary X-ray analysis of a bacterial GABA receptor with a Venus flytrap fold.  

UK PubMed Central (United Kingdom)

In response to infection by the pathogen Agrobacterium tumefaciens, plants synthesize several stress amino acids, including gamma-aminobutyric acid (GABA), which modulates the expression of bacterial virulence factors. GABA penetrates into the bacterial cytoplasm via an ABC transporter that is associated with the periplasmic receptor Atu2422. Mature receptor Atu2422 (without its signal peptide) was overexpressed in Escherichia coli, purified and crystallized. A complete data set was collected to 1.35 A resolution at 100 K. The crystals belonged to the monoclinic space group C2 and contained one molecule in the asymmetric unit. Molecular replacement was performed and the initial electron-density maps revealed a closed form of this Venus flytrap (VFT) receptor, suggesting the presence of an endogenous E. coli ligand.

Moréra S; Gueguen-Chaignon V; Raffoux A; Faure D

2008-12-01

306

The Solar and Thermal Radiation Field Below the Venus Clouds  

Science.gov (United States)

Even though the H2SO4 clouds that shroud Venus reflect ~80% of the incident sunlight and absorb more than half of the rest, entry probes show that the atmosphere is well illuminated between the cloud base ( ~47.5 km) and the surface. For example, the Pioneer Venus Large Probe entered near the dawn terminator (7:38 AM) and measured downward solar fluxes decreasing from ~200 W/m2 to ~20 W/m2 between the cloud base and surface (Tomasko et al., JGR, 85, 1980). The Venera spectrophotometers showed that the sunlight is most intense at 0.5 1 ? m, except in the near-IR spectral windows at 1.0, 1.1, 1.18, 1.27, 1.31, 1.74, and 2.3 ? m. The sub-cloud region is also illuminated by thermal emission from hot surface and lower atmosphere. This emission is most intense in these spectral windows, where it contributes 0.1 to 1 W/m2/sr/ ? m. A spectrum resolving multiple scattering model was used to study the spectral and angular distribution of this radiation to assess the feasibility of descent imaging from entry probes. The radiation field is azimuthally uniform everywhere below the clouds, even when the sun is on the horizon. At ? 10 km) images of the surface at visible wavelengths. Fortunately, Rayleigh scattering decreases as 1/? 4, such that ? R<1 at 1.0? m. This spectral region is also relatively free of absorption by gases. It therefore may provide the best opportunity to image the surface from a falling probe. This work is supported by the NASA Planetary Atmospheres Program.

Crisp, D.

2000-10-01

307

Venus, Earth's structural sister: Investigations using radar imagery  

Science.gov (United States)

Students construct a geologic map of a region of Venus' surface using NASA Magellan synthetic aperture radar(SAR) data (provided) and/or synthetic stereo data (provided, and constructed using Magellan SAR and altimetry data)- 3D anaglyph viewed through red-blue glasses. Mapping can be done digitally using Adobe Illustrator (or a similar graphic program) or using hard copy images and overhead transparencies for mapping. Students construct a complete geologic map, determine a geologic history for the area, and propose hypotheses for the evolution of a large quasi-circular geomorphic/geologic feature that occurs within the map area. Students also propose tests of their hypotheses (whether such tests can be accomplished through further mapping, future missions, experiments, theoretical arguments, calculations, etc.). Students must clearly identify assumptions they make in their hypotheses/models. Individual, or small group, write-ups and completed geologic maps summarize student analysis. This activity connects structural geology to other fields, and provides the students with an opportunity to experience geologic investigation in which there is no single right answer, but there are "wrong" or unlikely hypotheses. This exercise helps students think outside the box with little fear given that they are dealing with - literally - an extraterrestrial world in which very little is known - and yet, we assume that chemistry and physics, as we know them, likely operated on Earth's sister planet. Students are given a short introductory presentation about the environmental conditions of Venus (which could have been different in the past), and an introduction to radar data before they begin.

Hansen, Vicki

308

Venus flytrap biomechanics: forces in the Dionaea muscipula trap.  

UK PubMed Central (United Kingdom)

Biomechanics of morphing structures in the Venus flytrap has attracted the attention of scientists during the last 140 years. The trap closes in a tenth of a second if a prey touches a trigger hair twice. The driving force of the closing process is most likely due to the elastic curvature energy stored and locked in the leaves, which is caused by a pressure differential between the upper and lower layers of the leaf. The trap strikes, holds and compresses the prey. We have developed new methods for measuring all these forces involved in the hunting cycle. We made precise calibration of the piezoelectric sensor and performed direct measurements of the average impact force of the trap closing using a high speed video camera for the determination of time constants. The new equation for the average impact force was derived. The impact average force between rims of two lobes in the Venus flytrap was found equal to 149 mN and the corresponding pressure between the rims was about 41 kPa. Direct measurements of the constriction force in the trap of Dionaea muscipula was performed during gelatin digestion. This force increases in the process of digestion from zero to 450 mN with maximal constriction pressure created by the lobes reaching to 9 kPa. The insects and different small prey have little chance to escape after the snap of the trap. The prey would need to overpower the "escaping" force which is very strong and can reach up to 4N.

Volkov AG; Harris SL 2nd; Vilfranc CL; Murphy VA; Wooten JD; Paulicin H; Volkova MI; Markin VS

2013-01-01

309

Ecotoxicological evaluation of tributyltin toxicity to the equilateral venus clam, Gomphina veneriformis (Bivalvia: Veneridae).  

UK PubMed Central (United Kingdom)

Tributyltin (TBT) is the most common pesticide in marine and freshwater environments. To evaluate the potential ecological risk posed by TBT, we measured biological responses such as growth rate, gonad index, sex ratio, the percentage of intersex gonads, filtration rate, and gill abnormalities in the equilateral venus clam (Gomphina veneriformis). Additionally, the biochemical and molecular responses were evaluated in G. veneriformis exposed to various concentrations of TBT. The growth of G. veneriformis was significantly delayed in a dose-dependent manner after exposure to all tested TBT concentrations. After TBT was administered to G. veneriformis, the gonad index decreased and the sex balance was altered. The percentage of intersex gonads also increased significantly in treated females, whereas no intersex gonads were detected in the solvent control group. Additionally, intersex gonads were detected in male G. veneriformis specimens exposed to relatively high TBT concentrations (20 ?g L?¹). The filtration rate was also reduced in a dose-dependent manner in TBT-exposed G. veneriformis. We also noted abnormal gill morphology in TBT-exposed G. veneriformis. Furthermore, increases in antioxidant enzyme activities were observed in TBT-exposed G. veneriformis clams, regardless of dosage. Vitellogenin gene expression also increased significantly in a dose-dependent manner in G. veneriformis exposed to TBT. These results provide valuable information regarding our understanding of the toxicology of TBT in G. veneriformis. Moreover, the responses of biological and molecular factors could be utilized as information for risk assessments and marine monitoring of TBT toxicity.

Park K; Kim R; Park JJ; Shin HC; Lee JS; Cho HS; Lee YG; Kim J; Kwak IS

2012-03-01

310

Transit Observations as Means to Re-establish the Reputation of the Russian Academy of Sciences  

Science.gov (United States)

This paper explores how Catherine II used the worldwide attention given to observations of the transit of Venus to bring back the Russian Academy of Sciences into international recognition. Starting from the planned observations of the transit of Venus at various locations of the Russian Empire, the expeditions became more complex because naturalists were added to the astronomical expeditions. As the naturalists got separate instructions, their expeditions became more and more independent of the astronomers and eventually became known as the famous Academic Expeditions with a tremendous output of publications. This was the second huge effort made by Russia during the eighteenth century to explore scientifically remote parts of its empire. As far as individual Venus transit expeditions are concerned, this paper focuses on those that visited places in the southern parts of the Ural Mountains and the northern shores of the Caspian Sea.

Bucher, Gudrun

2013-05-01

311

Signatures and Characteristics of Internal Gravity Waves in the Venus' and Mars' Atmospheres as Revealed by the Radio Occultation Temperature Data Analysis  

Science.gov (United States)

It is well known that internal gravity waves (IGWs) affect the structure and mean circulation of the Earth' middle and upper atmosphere by transporting energy and horizontal momentum upward from the lower atmosphere. The IGWs modulate the background atmospheric structure, producing a periodic pattern of spatial and temporal variations in the wind velocity, temperature and density. Similar effects are anticipated for the Venus and Mars since IGWs are a characteristic of stably stratified atmosphere. For instance, Yakovlev et al. (1991) and Gubenko et al. (2008a) used the radio occultation (RO) data from Venera 15 and 16 missions to investigate the thermal structure and layering of the Venus' middle atmosphere. They noted that a wavelike periodic structure commonly appears in retrieved vertical profiles at altitudes above 60 km in the atmosphere where the static stability is large. Through comparisons between Magellan RO observations in the Venus' atmosphere, Hinson and Jenkins (1995) have demonstrated that small scale variations in retrieved temperature profiles at altitudes from 60 to 90 km are caused by a spectrum of vertical propagating IGWs. Temperature profiles from the Mars Global Surveyor (MGS) measurements reveal vertical wavelike structures assumed to be atmospheric IGWs in the Mars' lower atmosphere (Creasey et al., 2006). The very large IGW amplitudes inferred from MGS RO data imply a very significant role for IGWs in the atmospheric dynamics of Mars as well. There is one general problem inherent to all measurements of IGWs. Observed wavelike variations may alternatively be caused by the IGWs, turbulence or persistent layers in the atmosphere, and it is necessary to have an IGW identification criterion for the correct interpretation of obtained results. In this context, we have developed an original method for the determination of internal gravity wave parameters from a single vertical temperature profile measurement in a planetary atmosphere (Gubenko et al., 2008b, 2011). This method does not require any additional information not contained in the profile and may be used for the analysis of profiles measured by various techniques. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied, the analyzed temperature fluctuations can be considered as wave-induced. The method is based on the analysis of relative amplitude thresholds of the wave temperature field and on the linear IGW saturation theory in which amplitude thresholds are restricted by dynamical (shear) instability processes in the atmosphere. When the amplitude of an internal wave reaches the shear instability limit, energy is assumed to be dissipated in such a way that the amplitude is maintained at the instability limit as the wave propagates upwards. An application of the developed method to the RO temperature data has given the possibility to identify the IGWs in the Venus' and Mars' atmospheres and to determine the magnitudes of key wave parameters such as the intrinsic frequency, amplitudes of vertical and horizontal perturbations of the wind velocity, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase (and group) speeds, kinetic and potential energy, vertical fluxes of the wave energy and horizontal momentum. The obtained results of internal wave studies in the Venus' and Mars' atmospheres deduced from the Magellan and MGS RO temperature profiles are presented and discussed. This work was partially supported by the RFBR Grant (No. 10-02-01015-a) and program OFN-15 of the Russian Academy of Sciences. References Creasey, J. E., Forbes, J. M., and Hinson, D. P.: Global and seasonal distribution of gravity wave activity in Mars' lower atmosphere derived from MGS radio occultation data, Geophys. Res. Lett., 33, L01803, doi: 10.1029/2005GL024037, 2006. Gubenko, V.N., Andreev, V.E., and Pavelyev, A.G.: Detection of layering in the upper cloud layer of Venus northern polar atmosphere observed from radio occultation data, J. Geophys. Res., 113, E03001, doi:10.1029/2007

Gubenko, Vladimir; Pavelyev, Alexander; Andreev, Vitali; Salimzyanov, Rishat; Pavelyev, Alexey

2012-07-01

312

MHD and Kinetic Modeling of the Ionospheres of Venus and Mars  

International Nuclear Information System (INIS)

It is widely recognized that both Venus and Mars possess no significant global intrinsic magnetic fields, and that the solar wind interacts directly with the upper atmospheres and ionospheres of Venus and Mars. In addition, local crustal magnetic fields are also present in various regions at Mars, suggesting that some regions of the Martian ionosphere are influenced not only by the solar wind but also by the crustal magnetic field. Previous studies have suggested that the basic structures of the ionospheres of the planets can be described by fluid and MHD(magnetohydrodynamic) processes. Various models of the ionospheres of Venus and Mars based on the MHD formulation have been constructed during the last two decades. Although the MHD approach has been successful in reproducing the ionospheres of the planets, some studies have indicated that MHD modeling is not necessarily appropriate in the regions of the topside ionosphere, the ionopause, and the magnetosheath, where the ion kinetic processes are likely to play an important role. The kinetic processes in the topside ionosphere might have significant influences even in the lower ionosphere. Thanks to a great progress made for computer power as well as the efficiency of calculations of the hybrid model, high-resolution kinetic models of the solar wind interaction with Venus and Mars, which self-consistently include the ionosphere, have been developed. In this paper, status of MHD and kinetic modeling of the ionospheres of Venus and Mars is briefly reviewed.

2009-06-16

313

International Ultraviolet Explorer observations of Venus SO sub 2 and SO  

Energy Technology Data Exchange (ETDEWEB)

Results of recent International Ultraviolet Explorer (IUE) observations of Venus made on January 20, 1987, and April 2 and 3, 1988, along with a reanalysis of the 1979 observations (Conway et al., 1979) are presented. The observations indicate that the amount of sulfur dioxide at the cloud tops of Venus declined by a factor of 8 {plus minus} 4 from 3809 {plus minus} 70 ppb in 1987 and 1988. These values are consistent with the Pioneer Venus results (L.W. Esposito, A recalibration of the solar flux for Pioneer Venus results and a comparison of existing SO{sub 2} measurements on Venus, unpublished manuscript, 1989). The authors identify absorption features of sulfur monoxide for the first time, and estimate the SO mixing ratio above the cloud level is 20 {plus minus} 10 ppb for 1979. This is consistent with photochemical models by Winick and Stewart (1980) and Yung and DeMore (1982) and with the upper limit from Wilson et al. (1981).

Na, Chan Y.; Esposito, L.W.; Skinner, T.E. (Univ. of Colorado, Boulder (United States))

1990-05-20

314

Learning from the Venus Flytrap: A Biomimetic Responsive Interface  

Science.gov (United States)

The ability to have controllable and fast property changes to a material surface over large length scales is desirable for a variety of functions including chemical sensors, antimicrobial devices, ``smart'' adhesives, and drug delivery coatings. Recently, many strategies, including shape memory and environment selectivity, have been developed for synthesizing responsive surfaces, but the response times are often too slow or non-sensitive. Here, we present a new strategy for responsive surfaces or interfaces that builds upon the response mechanism of the Venus flytrap, which exhibits one of the most rapid movements in the plant kingdom. This rapid, controllable movement is largely attributed to the geometry of the leaflets, which can undergo a snap-through elastic instability upon development of a critical pressure. Learning from nature, we have made a responsive interface with controlled, elastic instabilities capable of large geometric changes across very short timescales. We present the fabrication of a responsive surface of microlenses with a controlled, predictable geometry that undergoes a rapid snap-through transition when triggered by various stimuli.

Holmes, Douglas P.; Crosby, Alfred J.

2007-03-01

315

National Academy of Sciences and Academy of Sciences of the USSR workshop on structure of the eucaryotic genome and regulation of its expression  

Energy Technology Data Exchange (ETDEWEB)

This report provides a brief overview of the Workshop on Structure of the Eukaryotic Genome and Regulation of its Expression held in Tbilisi, Georgia, USSR. The report describes the presentations made at the meeting but also goes on to describe the state of molecular biology and genetics research in the Soviet Union and makes recommendations on how to improve future such meetings.

1990-01-01

316

National Academy of Sciences and Academy of Sciences of the USSR workshop on structure of the eucaryotic genome and regulation of its expression. Final report  

Energy Technology Data Exchange (ETDEWEB)

This report provides a brief overview of the Workshop on Structure of the Eukaryotic Genome and Regulation of its Expression held in Tbilisi, Georgia, USSR. The report describes the presentations made at the meeting but also goes on to describe the state of molecular biology and genetics research in the Soviet Union and makes recommendations on how to improve future such meetings.

1990-12-31

317

Effects of large-scale magnetic fields in the Venus ionosphere  

Energy Technology Data Exchange (ETDEWEB)

Theoretical models of the ionosphere of Venus have been constructed in the past without due consideration of the fact that the ionosphere is sometimes magnetized. This paper examines some differences between the magnetized and unmagnetized dayside Venus ionosphere using the Pioneer Venus Orbiter Langmuir probe and magnetometer data. Particular attention is given to the evaluation of the altitude profiles of the thermal electron heating and comparison of the magnitude of the magnetic force with other forces in the ionosphere. Several examples illustrate how heating profiles are different in the magnetized ionosphere with effective heating below 200 km altitude reduced by orders of magnitude compared to the field-free ionosphere. The force associated with the magnetic field is comparable to other forces in the magnetized ionosphere. The measured plasma density, electron temperature and magnetic field thus suggest that large-scale magnetic fields should be included in future ionosphere models. 18 references.

Luhmann, J.G. (Univ. of California, Los Angeles); Elphic, R.C.

1982-01-01

318

The effect of recent Venus transit on Earth?s atmosphere  

Directory of Open Access Journals (Sweden)

Full Text Available Some experiments on June 8, 2004, the day of transit of Venus across the Sun, were undertaken at Kolkata (latitude: 22°34lN) to observe the effect, if any, of transit of Venus on FWF, ELF and VLF amplitudes. The result shows a good correlation between their temporal variations during the transit. The observation was unbelievable as the Venus subtends only 1/32th of the cone subtended by Sun on Earth. This anomaly may be explained on the assumption that the height of Venusian atmosphere with high content of CO2, and nitrogen which absorbs electromagnetic and corpuscular radiations from Sun, depleting the solar radiation reaching the Earth to a considerable extent. As a result, relevant parameters of Earth?s atmosphere are modulated and here we show how these changes are reflected in identical behaviour of fair weather field and ELF and VLF spectra.

S. S. De; B. K. De; S. K. Adhikari; B. K. Sarkar; S. K. Sarkar; A. Guha; P. K. Mandal; S. K. Mandal; H. P. Sardar; M. Ray

2006-01-01

319

Analysis of data from the Pioneer Venus Sounder Probe mass spectrometer  

Energy Technology Data Exchange (ETDEWEB)

The composition of the lower atmosphere of the planet Venus from 62 km to the surface was measured by a neutral gas mass spectrometer onboard of the Pioneer Venus Sounder Probe. Fifty-one mass spectra were obtained with an average altitude resolution of approximately 1 km. The instrument measured the composition of the gases relative to CO2, the dominant gas, that is sampled from the Venus atmosphere through a special leak. The mass range extended from 1 to 208 amu with a sensitivity of the order of 1 ppm relative to CO2, but for the noble gases it was nearly 100 times better. A description of the instrument and the initial results are reported.

Hoffman, J.H.

1981-05-01

320

The Effect of Recent Venus Transit on Earth?s Atmosphere  

Directory of Open Access Journals (Sweden)

Full Text Available Some experiments on June 8, 2004, the day of transit of Venus across the Sun, were undertaken at Kolkata (latitude: 23034? N) to observe effect, if any, of transit of Venus on FWF, ELF and VLF amplitudes. The result shows good correlation between their temporal variations during the transit. The observation was unbelievable as the Venus subtends only 1/32th of the cone subtended by Sun on Earth. This anomaly may be explained on the assumption that the height of Venusian atmosphere with high content of CO2, and nitrogen which absorbs electromagnetic and corpuscular radiations from Sun, depleting the solar radiation reaching the Earth to a considerable extent. As a result, relevant parameters of Earth?s atmosphere are modulated and here we show how these changes are reflected in identical behaviour of fair weather field and ELF and VLF spectra.

S. S. De; B. K. De; S. K. Adhikari; B. K. Sarkar; S. K. Sarkar; A. Guha; P. K. Mandal; S. K. Mandal; H. P. Sardar; M. Ray

2006-01-01

 
 
 
 
321

Generation of adeno-associated virus vector enabling functional expression of oxytocin receptor and fluorescence marker genes using the human eIF4G internal ribosome entry site element.  

Science.gov (United States)

We developed the AAV-Oxtr-IRES-Venus vector to rescue the oxytocin receptor (Oxtr) gene functionally at restricted regions in the brains of Oxtr knockout mice. First we chose human eIF4G gene-derived IRES to co-express Venus, a fluorescent marker gene, with Oxtr. With selected human eIF4G IRES, we constructed the AAV-Oxtr-IRES-Venus vector, and it caused expression of the Venus gene in the brain when 1 microl of viral solution (9.4x10(7) vg) was injected into the medial amygdaloid nucleus. In primary neuronal cells transduced with this viral vector and followed by oxytocin administration, functional expression of OXTR was detected by Ca(2+) imaging assay. PMID:19734647

Sato, Keisuke; Date, Shiori; Aoyagi, Yumi; Kasahara, Yoshiyuki; Nawa, Akihiko; Mizukami, Hiroaki; Hidema, Shizu; Ozawa, Keiya; Nishimori, Katsuhiko

2009-09-07

322

An observational study of the nightside ionospheres of Mars and Venus with radio occultation methods  

Energy Technology Data Exchange (ETDEWEB)

An analysis of Mars and Venus nightside electron density profiles obtained with radio occultation methods shows how the nightside ionospheres of both planets vary with solar zenith angle. From previous studies it is known that the dayside peak electron densities at Mars and Venus show a basic similarity in that they both exhibit Chapman layer-like behavior. In contrast, the peak altitudes at mars behave like an ideal Chapman layer on the dayside, whereas the altitude of the peak at Venus is fairly constant up to the terminator. The effect of major dust storms can also be seen in the peak altitudes at Mars. All Venus nightside electron density profiles show a distinct main peak for both solar minimum and maximum, whereas many profiles from the nightside of Mars do not show any peak at all. This suggests that the electron density in the Mars nightside ionosphere is frequently too low to be detected by radio occultation. On the Pioneer Venus orbiter, disappearing ionospheres were observed near solar maximum in the in-situ data when the solar wind dynamic pressure was exceptionally high. This condition occurs because the high solar wind dynamic pressure decreases the altitude of the ionopause near the terminator below {approximately}250 km, thus reducing the normal nightward transport of dayside ionospheric plasma. On the basis of the Venus observations, one might predict that if a positive correlation of nightside peak density with dynamic pressure was found, it could mean that transport from the dayside is the only significant source for the nightside ionosphere of Mars. The lack of a correlation would imply that the precipitation source at Mars is quite variable.

Zhang, M.H.G. (Austrian Academy of Sciences, Graz (Austria)); Luhmann, J.G. (Univ. of California, Los Angeles (United States)); Kliore, A.J. (Jet Propulsion Lab., Pasadena, CA (United States))

1990-10-01

323

Magnetotails at unmagnetized bodies: Comparison of comet Giacobini-Zinner and Venus  

Energy Technology Data Exchange (ETDEWEB)

Both Comet Giacobini-Zinner (G-Z) and Venus have magnetotails consisting of draped interplanetary magnetic field lines. This field line draping is caused by a velocity shear between regions of greater flow speeds away from the bodies and lesser flow speeds near to the bodies. Data observed within the Venus magnetotail by the Pioneer Venus Orbiter and within the G-Z tail by the International Cometary Explorer traversal of G-Z have previously been combined with stress balance considerations to infer many of the physical characteristics of these two magnetotails. In the present paper the authors compare and contrast these physical characteristics and thereby examine those aspects of the interactions with the solar wind and draped magnetotail forming processes which are common at the two bodies, and those which are different. They find that the near ionopause environs play a crucial role in the tail formation process at both Venus and G-Z and that draping at the two very different sized bodies occurs on ionopause scale sizes. On the other hand, ion densities, downtail mass fluxes, tailward J {times} B forces, and lobe betas are factors of {approximately}10{sup 4}, 50, 100, and 20 times greater in the G-Z tail than in Venus', while bulk flow speeds and ion temperatures are factors of {approximately}15 and 240 times lower. These large quantitative differences in the properties within the two magnetotails are attributable to the significantly greater upstream mass loading of the solar wind by the extended neutral atmosphere at G-Z (comets in general) compared to the gravitationally bound atmosphere of Venus.

McComas, D.J.; Gosling, J.T. (Los Alamos National Lab., NM (United States)); Russell, C.T. (Univ. of California, Los Angeles (United States)); Slavin, J.A. (Jet Propulsion Lab., Pasadena, CA (United States))

1987-09-01

324

Magma generation on Mars: amounts, rates, and comparisons with Earth, moon, and venus.  

UK PubMed Central (United Kingdom)

Total extrusive and intrusive magma generated on Mars over the last approximately 3.8 billion years is estimated at 654 x 10(6) cubic kilometers, or 0.17 cubic kilometers per year (km(3)/yr), substantially less than rates for Earth (26 to 34 km(3)/yr) and Venus (less than 20 km(3)/yr) but much more than for the Moon (0.025 km(3)/yr). When scaled to Earth's mass the martian rate is much smaller than that for Earth or Venus and slightly smaller than for the Moon.

Greeley R; Schneid BD

1991-11-01

325

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

International Nuclear Information System (INIS)

An account is given of the methodology as well as the results of coordinated Venus emission observations conducted at four wavelengths between 1.35 and 3.6 cm; the results are compared with other observations and with calculated mission spectra, with a view to suggestions that the microwave spectrum of Venus could be sensitive to the subcloud abundance of such constituents as SO2 and gaseous H2SO4. The observed emission spectrum is consistent with an average subcloud abundance of gaseous H2SO4 in equatorial and midlatitude regions of about 5 ppm. An upper limit is established for the subcloud SO2 abundance. 19 refs.

1990-01-01

326

Observations of the microwave emission of Venus from 1. 3 to 3. 6 cm  

Energy Technology Data Exchange (ETDEWEB)

An account is given of the methodology as well as the results of coordinated Venus emission observations conducted at four wavelengths between 1.35 and 3.6 cm; the results are compared with other observations and with calculated mission spectra, with a view to suggestions that the microwave spectrum of Venus could be sensitive to the subcloud abundance of such constituents as SO2 and gaseous H2SO4. The observed emission spectrum is consistent with an average subcloud abundance of gaseous H2SO4 in equatorial and midlatitude regions of about 5 ppm. An upper limit is established for the subcloud SO2 abundance. 19 refs.

Steffes, P.G.; Jenkins, J.M.; Klein, M.J. (Georgia Institute of Technology, Atlanta (USA) JPL, Pasadena, CA (USA))

1990-03-01

327

Heat input into the VENUS vertex chamber due to TRISTAN beams  

Energy Technology Data Exchange (ETDEWEB)

The VENUS vertex chamber is a drift chamber covering the interaction point of the VENUS detector to obtain precise vertex information at TRISTAN (e[sup +] e[sup -] collider). As a mixed gas of CO[sub 2] 92 % and C[sub 2]H[sub 6] 8 % is used for the chamber, the drift velocity of electron depends on the gas temperature in the chamber. In order to estimate the temperature of the chamber, a trial to obtain the pattern of heat input due to the beams to the vertex chamber has been done. (author).

Ohama, Taro.

1994-04-01

328

Implications of the gas compositional measurements of pioneer venus for the origin of planetary atmospheres.  

UK PubMed Central (United Kingdom)

Comparisons are made between the volatile inventories of the terrestrial planets, including Pioneer Venus data, and the predictions of three classes of theories for the origin of planetary atmospheres. Serious difficulties arise for the primary atmosphere and external source hypotheses. The grain accretion hypothesis can account for the trends in the volatile inventory from Venus to Earth to Mars, if volatiles were incorporated into planet-forming grains at nearly the same temperature for all of these planets, but at systematically lower pressures in the regions of planet formation farther from the center of the solar nebula.

Pollack JB; Black DC

1979-07-01

329

Magnetic fields in the ionospheric holes of venus: evidence for an intrinsic field  

Energy Technology Data Exchange (ETDEWEB)

The suggestion that the radial magnetic fields observed in the regions of depleted plasma density in the nightside Venus ionosphere arise from an intrinsic planetary field was recently made by Knudsen et al. (1982). In this report the polarities of these radial fields, as measured by the Pioneer Venus Orbiter magnetometer, are examined in detail in order to determine if there is a geographical organization of the field polarity or if the polarity of the radial field depends on the interplanetary field as previously proposed. The results of the data anlayisis indicate that a source in a planetary intrinsic field is unlikely.

Luhmann, J.G.; Russell, C.T.

1983-05-01

330

On the relationship between isostatic elevation and the wavelengths of tectonic surface features on Venus  

Energy Technology Data Exchange (ETDEWEB)

Venus lithospheric structure models are presently formulated in which regional isostatic elevation, d, and the spacing wavelength, lambda, of tectonic features formed due to horizontal extension and compression are functions of both surface thermal gradient and crustal thickness c. It is shown that, in areas of Venus where the upper mantle is stronger than the upper crust, the spacings of short-wavelength features should increase with increasing d, if that change in turn is due to increasing c, but should decrease with increasing d, if this change is in turn due to increasing surface thermal gradient. 48 refs.

Zuber, M.T.; Parmentier, E.M. (NASA, Goddard Space Flight Center, Greenbelt, MD (USA) Brown Univ., Providence, RI (USA))

1990-06-01

331

Solar cycle variations of the electron densities near the ionospheric peak of Venus  

Energy Technology Data Exchange (ETDEWEB)

Photochemical equilibrium calculations of electron and ion densities, appropriate for altitudes below about 180 km, were carried out for the Venus dayside ionosphere corresponding to solar cycle maximum and minimum conditions. The results were compared with data from radio occultation measurements. The agreement between the calculations and measurements was in general quite good. These comparisons indicate that the most commonly used neutral atmosphere model of Venus predicts densities which are somewhat low near the electron density peak for solar cycle maximum, but provides surprisingly good predictions for solar cycle minimum conditions.

Kim, J.; Nagy, A.F. (Univ. of Michigan, Ann Arbor (USA)); Cravens, T.E. (Univ. of Kansas, Lawrence (USA)); Kliore, A.J. (California Institute of Technology, Pasadena (USA))

1989-09-01

332

A numerical solution for thermal tides in the atmosphere of Venus  

Energy Technology Data Exchange (ETDEWEB)

The problems which emerge in choosing the basic equations and selecting the atmospheric heating function of the atmosphere during studies of Venus' atmospheric tides are presently approached via the numerical solution of the linear form of the basic equations. An analysis of the results thus obtained indicates that observations of the thermal parameters near the ground are important to the determination of the ground-heating mode of this planet's atmosphere. Pioneer Venus probe data are presently used to construct three heating models; the torque of the atmospheric tides is estimated to be 1.4 x 10 to the 16th J. 37 refs.

Shen, M.; Zhang, C.Z. (Nanjing Univ. (China))

1990-05-01

333

Asymmetries in the location of the Venus and Mars bow shock  

Energy Technology Data Exchange (ETDEWEB)

An examination of observations of the position of the terminator bow shock at Venus and Mars shows that the terminator bow shock varies with the angle between the local bow shock normal and the upstream magnetic field, {theta}{sub BN}. The part of the shock on the quasi-parallel side is closer to the planet than the part on the quasi-perpendicular side, a result which had been sggested by an earlier computer simulation by Thomas and Winske (1990). This bow shock asymmetry is observed to be larger at Mars than at Venus.

Zhang, T.L.; Schwingenschuh, K. (Space Research Institute, Graz (Austria)); Russell, C.T.; Luhmann, J.G.

1991-02-01

334

A mathematical model on the closing and opening mechanism for venus flytrap.  

UK PubMed Central (United Kingdom)

This paper investigates the opening and closing mechanism for the Venus Flytrap (Dionaea muscipula). A mathematical model has been proposed to explain how the flytrap transitions between open, semi-closed, and closed states. The model accounts for the charge accumulation of action potentials, which generated by mechanical stimulation of the sensitive trigger hairs on the lobes of the flytrap. Though many studies have been reported for the Venus flytrap opening and closing mechanism, this paper attempts to explain the mechanism from nonlinear dynamics and control perspective.

Yang R; Lenaghan SC; Zhang M; Xia L

2010-08-01

335

A mathematical model on the closing and opening mechanism for venus flytrap.  

Science.gov (United States)

This paper investigates the opening and closing mechanism for the Venus Flytrap (Dionaea muscipula). A mathematical model has been proposed to explain how the flytrap transitions between open, semi-closed, and closed states. The model accounts for the charge accumulation of action potentials, which generated by mechanical stimulation of the sensitive trigger hairs on the lobes of the flytrap. Though many studies have been reported for the Venus flytrap opening and closing mechanism, this paper attempts to explain the mechanism from nonlinear dynamics and control perspective. PMID:21460610

Yang, Ruoting; Lenaghan, Scott C; Zhang, Mingjun; Xia, Lijin

2010-08-01

336

Sequencing and characterization of striped venus transcriptome expand resources for clam fishery genetics.  

UK PubMed Central (United Kingdom)

BACKGROUND: The striped venus Chamelea gallina clam fishery is among the oldest and the largest in the Mediterranean Sea, particularly in the inshore waters of northern Adriatic Sea. The high fishing pressure has lead to a strong stock abundance decline, enhanced by several irregular mortality events. The nearly complete lack of molecular characterization limits the available genetic resources for C. gallina. We achieved the first transcriptome of this species with the aim of identifying an informative set of expressed genes, potential markers to assess genetic structure of natural populations and molecular resources for pathogenic contamination detection. METHODOLOGY/PRINCIPAL FINDINGS: The 454-pyrosequencing of a normalized cDNA library of a pool C. gallina adult individuals yielded 298,494 raw reads. Different steps of reads assembly and filtering produced 36,422 contigs of high quality, one half of which (18,196) were annotated by similarity. A total of 111 microsatellites and 20,377 putative SNPs were identified. A panel of 13 polymorphic transcript-linked microsatellites was developed and their variability assessed in 12 individuals. Remarkably, a scan to search for contamination sequences of infectious origin indicated the presence of several Vibrionales species reported to be among the most frequent clam pathogen's species. Results reported in this study were included in a dedicated database available at http://compgen.bio.unipd.it/chameleabase. CONCLUSIONS/SIGNIFICANCE: This study represents the first attempt to sequence and de novo annotate the transcriptome of the clam C. gallina. The availability of this transcriptome opens new perspectives in the study of biochemical and physiological role of gene products and their responses to large and small-scale environmental stress in C. gallina, with high throughput experiments such as custom microarray or targeted re-sequencing. Molecular markers, such as the already optimized EST-linked microsatellites and the discovered SNPs will be useful to estimate effects of demographic processes and to detect minute levels of population structuring.

Coppe A; Bortoluzzi S; Murari G; Marino IA; Zane L; Papetti C

2012-01-01

337

Sequencing and Characterization of Striped Venus Transcriptome Expand Resources for Clam Fishery Genetics  

Science.gov (United States)

Background The striped venus Chamelea gallina clam fishery is among the oldest and the largest in the Mediterranean Sea, particularly in the inshore waters of northern Adriatic Sea. The high fishing pressure has lead to a strong stock abundance decline, enhanced by several irregular mortality events. The nearly complete lack of molecular characterization limits the available genetic resources for C. gallina. We achieved the first transcriptome of this species with the aim of identifying an informative set of expressed genes, potential markers to assess genetic structure of natural populations and molecular resources for pathogenic contamination detection. Methodology/Principal Findings The 454-pyrosequencing of a normalized cDNA library of a pool C. gallina adult individuals yielded 298,494 raw reads. Different steps of reads assembly and filtering produced 36,422 contigs of high quality, one half of which (18,196) were annotated by similarity. A total of 111 microsatellites and 20,377 putative SNPs were identified. A panel of 13 polymorphic transcript-linked microsatellites was developed and their variability assessed in 12 individuals. Remarkably, a scan to search for contamination sequences of infectious origin indicated the presence of several Vibrionales species reported to be among the most frequent clam pathogen's species. Results reported in this study were included in a dedicated database available at http://compgen.bio.unipd.it/chameleabase. Conclusions/Significance This study represents the first attempt to sequence and de novo annotate the transcriptome of the clam C. gallina. The availability of this transcriptome opens new perspectives in the study of biochemical and physiological role of gene products and their responses to large and small-scale environmental stress in C. gallina, with high throughput experiments such as custom microarray or targeted re-sequencing. Molecular markers, such as the already optimized EST-linked microsatellites and the discovered SNPs will be useful to estimate effects of demographic processes and to detect minute levels of population structuring.

Coppe, Alessandro; Bortoluzzi, Stefania; Murari, Giulia; Marino, Ilaria Anna Maria; Zane, Lorenzo; Papetti, Chiara

2012-01-01

338

Genetic engineering: Baculoviruses as expression vectors. (Latest citations from the Life Sciences Collection data base). Published Search  

Energy Technology Data Exchange (ETDEWEB)

The bibliography contains citations concerning the use of baculoviruses in genetic engineering. Baculoviruses produce large quantities of a specific gene. Topics include genetic replication, expression of selected genes in host cells, and protein expression using baculoviruses. Baculovirus introduction into mammals causing antibody expression is considered, and implications on vaccine programs are briefly discussed. (Contains a minimum of 112 citations and includes a subject term index and title list.)

1992-05-01

339

Evidence for volcanism in NW Ishtar Terra, Venus  

International Nuclear Information System (INIS)

Venera 15/16 radar data for an area in NW Ishtar Terra, Venus, show an area with moderate radar return and a smooth textured surface which embays low lying areas of the surrounding mountainous terrain. Although this unit may be an extension of the lava plains of Lakshmi Planum to the southeast, detailed study suggests a separate volcanic center in NW Ishtar Terra. Lakshmi Planum, on the Ishtar Terra highland, exhibits major volcanic and tectonic features. On the Venera radar image radar brightness is influenced by slope and roughness; radar-facing slopes (east-facing) and rough surfaces (approx. 8 cm average relief) are bright, while west-facing slopes and smooth surfaces are dark. A series of semi-circular features, apparently topographic depressions, do not conform in orientation to major structural trends in this region of NW Ishtar Terra. The large depression in NW Ishtar Terra is similar to the calderas of Colette and Sacajawea Paterae, as all three structures are large irregular depressions. NW Ishtar Terra appears to be the site of a volcanic center with a complex caldera structure, possibly more than one eruptive vent, and associated lobed flows at lower elevations. The morphologic similarity between this volcanic center and those of Colette and Sacajawea suggests that centralized eruptions have been the dominant form of volcanism in Ishtar. The location of this volcanic center at the intersection of two major compressional mountain belts and the large size of the calders (with an inferred larg/deep magma source) support a crustal thickening/melting rather than a hot-spot origin for these magmas.

1989-01-01

340

Tidal Venuses: triggering a climate catastrophe via tidal heating.  

UK PubMed Central (United Kingdom)

Traditionally, stellar radiation has been the only heat source considered capable of determining global climate on long timescales. Here, we show that terrestrial exoplanets orbiting low-mass stars may be tidally heated at high-enough levels to induce a runaway greenhouse for a long-enough duration for all the hydrogen to escape. Without hydrogen, the planet no longer has water and cannot support life. We call these planets "Tidal Venuses" and the phenomenon a "tidal greenhouse." Tidal effects also circularize the orbit, which decreases tidal heating. Hence, some planets may form with large eccentricity, with its accompanying large tidal heating, and lose their water, but eventually settle into nearly circular orbits (i.e., with negligible tidal heating) in the habitable zone (HZ). However, these planets are not habitable, as past tidal heating desiccated them, and hence should not be ranked highly for detailed follow-up observations aimed at detecting biosignatures. We simulated the evolution of hypothetical planetary systems in a quasi-continuous parameter distribution and found that we could constrain the history of the system by statistical arguments. Planets orbiting stars with masses<0.3 MSun may be in danger of desiccation via tidal heating. We have applied these concepts to Gl 667C c, a ?4.5 MEarth planet orbiting a 0.3 MSun star at 0.12 AU. We found that it probably did not lose its water via tidal heating, as orbital stability is unlikely for the high eccentricities required for the tidal greenhouse. As the inner edge of the HZ is defined by the onset of a runaway or moist greenhouse powered by radiation, our results represent a fundamental revision to the HZ for noncircular orbits. In the appendices we review (a) the moist and runaway greenhouses, (b) hydrogen escape, (c) stellar mass-radius and mass-luminosity relations, (d) terrestrial planet mass-radius relations, and (e) linear tidal theories.

Barnes R; Mullins K; Goldblatt C; Meadows VS; Kasting JF; Heller R

2013-03-01

 
 
 
 
341

Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source.  

Science.gov (United States)

High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency. PMID:18377002

Leitner, D; Benitez, J Y; Lyneis, C M; Todd, D S; Ropponen, T; Ropponen, J; Koivisto, H; Gammino, S

2008-03-01

342

MEASUREMENT OF THE HIGH ENERGY COMPONENT OF THE X-RAY SPECTRA INTHE VENUS ECR ION SOURCE  

Energy Technology Data Exchange (ETDEWEB)

High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for Nuclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental set-up to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular the collimation and background shielding can be problematic. In this paper we will discuss the experimental set-up for such a measurement, the energy calibration and background reduction, the correction for detector efficiency, the shielding of the detector and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power and heating frequency.

Leitner, Daniela; Benitez, Janilee Y.; Lyneis, Claude M.; Todd,Damon S.; Ropponen,Tommi; Ropponen,Janne; Koivisto, Hannu; Gammino, Santo

2007-11-15

343

The PSA: Planetary Science Archive  

Science.gov (United States)

Scientific and engineering data from ESA's planetary missions are made accessible to the world-wide scientific community via the Planetary Science Archive (PSA). The PSA consists of online services incorporating search, preview, download, notification and delivery basket functionality. Besides data from the GIOTTO spacecraft and several ground-based cometary observations, the PSA contains data from the Mars Express, Venus Express, Rosetta, SMART-1 and Huygens missions. The focus of the PSA activities is on the long-term preservation of data and knowledge from ESA's planetary missions. Scientific users can access the data online using several interfaces: - The Advanced Search Interface allows complex parameter based queries, providing the end user with a facility to complete very specific searches on meta-data and geometrical parameters. By nature, this interface requires careful use and heavy interaction with the end-user to input and control the relevant search parameters. - The Map-based Interface is currently operational only for Mars Express HRCS and OMEGA data. This interface allows an end-user to specify a region-of-interest by dragging a box onto a base map of Mars. From this interface, it is possible to directly visualize query results. The Map-based and Advanced interfaces are linked and cross-compatible. If a user defines a region-of-interest in the Map-based interface, the results can be refined by entering more detailed search parameters in the Advanced interface. - The FTP Browser Interface is designed for more experienced users, and allows for direct browsing and access of the data set content through ftp-tree search. Each dataset contains documentation and calibration information in addition to the scientific or engineering data. All data are prepared by the corresponding instrument teams, mostly located in Europe. PSA supports the instrument teams in the full archiving process, from the definition of the data products, meta-data and product labels through to validation and ingestion of the products into the archive. All data in the PSA are compatible with the Planetary Data System (PDS) Standard of NASA, and the PSA staff work in close collaboration with the PDS staff. To ensure a common archiving approach for all of ESA's planetary missions as well as to provide a similar data quality and standard for end users, a tool has been developed supporting the instrument teams in syntactically validating their datasets before delivering to the PSA. This tool, and the overall archiving process is being streamlined in line with the re-development of the science ground segment for Rosetta. This will be very important for the efficient handling and release of data during Rosetta's encounter with the comet Churyamov-Gerasimenko. A PSA advisory body has been established in order to assess the continuing development of the PSA. The advisory panel aims to meet regularly, reviewing the progress on defined requirements and providing feedback on our activities. New areas of data exploitation include attempts to standardize the way in which planetary data sets are constructed internationally. This is driving towards 'interoperability' of the data systems maintained at all Agencies archiving planetary data, and it is hoped that in the long-run any data can be obtained from any of the co-operating archives using the same protocol. Representatives from most major archiving agencies are members of the International Planetary Data Alliance (IPDA), and regular meetings are now taking place as standards are discussed.

Barthelemy, M.; Martinez, S.; Heather, D.; Vazquez, J. L.; Arviset, C.; Osuna, P.; PSA development Team

2012-04-01

344

Electrical and electrothermal conductivities of the ionospheres of Planets. II. Earth, Mars, and Venus  

International Nuclear Information System (INIS)

[en] The coefficients of the electrical and electrothermal conductivity were calculated for the dayside ionospheres of Earth, Mars, and Venus in the first, second, and third approximations of the decomposition by the Sonin polynomials method of Chapman-Enskog. The influence of the magnitude of the magnetic field H on the size of these coefficients and on the speed of convergence of the decomposition by Sonin polynomials is examined for the ionospheres of Mars and Venus. In the same context the influence of H on the contribution of the coefficients of ionic conductivity to the coefficients of the total conductivity is examined. It is shown that in practical calculations in the Earth's ionosphere the generally accepted first approximation of Hall, Pederson, and Cowling to the coefficients of electrical conductivity should be used. In calculations of these coefficients in the ionospheres of Mars and Venus one should use the first approximation near H ? 100 ? and the second approximation near H ? 10 ?. In the ionospheres of Earth, Mars, and Venus one should take the second approximation for the coefficients of electrical conductivity along the magnetic field and the third approximation for the coefficients of electrothermal conductivity. In the ionosphere of Earth, one may neglect thermal currents in the Hall and Pederson directions

1986-01-01

345

A derivation of the Mayan-to-Julian calendar correlation from the Dresden Codex Venus chronology.  

Science.gov (United States)

Chronological data derived from the Venus auxiliary table of the Dresden Codex, taken together with astronomical data pertaining to the planet, are employed here to derive the correlation between the Mayan and the Julian calendars and the respective associated day counts.

Lounsbury, F. G.

346

A transition metal complex (Venus flytrap cluster) for radioimmunodetection and radioimmunotherapy.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A novel transition metal complex, Venus flytrap cluster (VFC), is described for the preparation of radio-labeled antibodies. VFC contained 57Co, which was held tightly between the faces of two covalently bridged carborane ligands by cluster bonding of the metal with appropriate ligand orbitals. Anti...

Paxton, R J; Beatty, B G; Hawthorne, M F; Varadarajan, A; Williams, L E; Curtis, F L; Knobler, C B; Beatty, J D; Shively, J E

347

Effect of Interplanetary Matter on the Spin Evolutions of Venus and Mercury  

Directory of Open Access Journals (Sweden)

Full Text Available Differs from other planets in the Solar System, the Venus has a retrograde and long-period rotation. To ex-plain the special spin of the Venus, mechanisms such as core mantle friction inside planet[1], atmospheric tide[2-7], or twain effects together[8-11], and impact with a giant object[12,13] have been suggested. These mecha-nisms, however, need specific initial conditions with a remote probability [3,5]. The slow spin of Mercury cannot be explained very well. One viewpoint is that the unusual spins of Venus and Mercury might be naturally evolved from similar initial states by interaction with interplanetary matter during long-time evolu-tion. Based on the theory of planet formation and the orderliness of planetary distance, we discuss the possi-bility that the radial density distribution of interplanetary matter is undulated, and the wave function satisfies the formal Schrödinger equation. We calculate the evolution of planet spins under the effect of interplanetary matter during planets revolution and rotation. The results show that planets can naturally evolve to the cur-rent state (particularly the negative spin of the Venus) given the similar initial quick and positive spins.

Qingxiang Nie; Chuan Li; Fengshou Liu

2011-01-01

348

Coordinate Transformations of Low Beta Regions in the Nightside Venus Ionosphere  

Science.gov (United States)

Pioneer Venus Orbiter discovered regions of localized low plasma pressure and high magnetic pressure, or low beta regions, in the nightside ionosphere of Venus during its 14-year mission. These regions contain a magnetic field oriented nearly parallel to the sun-Venus line, where the pressure due to the magnetic field buildup is equal to the outside plasma pressure. The low beta regions are the result of ionospheric currents induced by the solar wind electric field and interplanetary magnetic field (IMF) with a configuration consistent with field-like draping of the IMF. Previous results using a coordinate system based on the IMF direction showed that the polarities of the radial-like fields were consistent with the IMF direction. However, that study reversed the magnetic longitude according to the IMF Y coordinate, which was not consistent with the local time variation of the regions. We look at the distribution of these events using a magnetic latitude based on the IMF direction but maintain the local time coordinate which is assumed to order the direction of ionospheric flows from the day into the night. Further, the magnetic fields at the edges of these low beta region are analyzed through Maxwell’s equations to examine the source and direction of the electric current flows that create the magnetic fields, showing horizontal currents perpendicular to the sun-Venus line present outside the regions.

Williamson, Hayley; Grebowsky, J.

2013-10-01

349

Venus: further evidence of impact cratering and tectonic activity from radar observations.  

UK PubMed Central (United Kingdom)

Earth-based radar images at a resolution of 10 kilometers show a diverse surface terrain on Venus, probably produced by both impact events and tectonic activity. Only a small number of craters of apparent impact origin are seen. Large-scale features show lineaments and parallel ridges suggesting tectonic origins.

Campbell DB; Burns BA; Boriakoff V

1979-06-01

350

Venus: further evidence of impact cratering and tectonic activity from radar observations.  

Science.gov (United States)

Earth-based radar images at a resolution of 10 kilometers show a diverse surface terrain on Venus, probably produced by both impact events and tectonic activity. Only a small number of craters of apparent impact origin are seen. Large-scale features show lineaments and parallel ridges suggesting tectonic origins. PMID:17814203

Campbell, D B; Burns, B A; Boriakoff, V

1979-06-29

351

Consequences of a hydrous mantle for Venus tectonics: Predictions for Magellan  

International Nuclear Information System (INIS)

The authors will consider the consequences of a Venus mantle enriched in water relative to the Earth. If the Moon-forming impact hypothesis is correct, Earth may have lost substantial volatiles. Venus, however, experienced no such impact and is therefore likely to be relatively more water-rich. They demonstrate that a higher abundance of water in the Venus mantle has the effect of inhibiting the rise of crust-forming melts and volatiles to the surface, which results in a thin stable crust, a dry, stiff upper mantle, and restricted magmatism. Conduction through a shallow thermal lithosphere dominates the removal of heat from the interior, and flow in the mantle is strongly coupled to the surface deformation. Current observations of Venus are consistent with this model. A review of the consequences of this model allows us to make predictions for the Magellan radar images. These include: (1) No evidence for plate tectonic processes; (2) younger apparent surface ages and enhanced crater relaxation for highland areas; (3) limited quantity of hot-spot volcanism, and (4) occasional evidence of localized magmatism (diatremes) associated with a volatile-rich mantle source. The model has implications to the Earth as well: in the absence of the Moon-forming impact, crustal formation in the water-rich Earth mantle may have been arrested, and plate recycling would have ceased early in the planet's history

1990-01-01

352

Volcanism and resurfacing on Venus at the full resolution of Magellan SAR data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We examine the importance of localized volcanism in resurfacing on Venus by analyzing the results of geologic mapping of a 12 degrees x 12 degrees area at the full resolution of Magellan SAR data. Resurfacing due to corona-, ridge-, and small volcano-related volcanism accounts for 27%, 6%, and 10% r...

Grindrod, PM; Stofan, ER; Guest, JE

353

An Overview of the 13:8 Mean Motion Resonance between Venus and Earth  

CERN Document Server

It is known since the seminal study of Laskar (1989) that the inner planetary system is chaotic with respect to its orbits and even escapes are not impossible, although in time scales of billions of years. The aim of this investigation is to locate the orbits of Venus and Earth in phase space, respectively to see how close their orbits are to chaotic motion which would lead to unstable orbits for the inner planets on much shorter time scales. Therefore we did numerical experiments in different dynamical models with different initial conditions -- on one hand the couple Venus-Earth was set close to different mean motion resonances (MMR), and on the other hand Venus' orbital eccentricity (or inclination) was set to values as large as e = 0.36 (i = 40deg). The couple Venus-Earth is almost exactly in the 13:8 mean motion resonance. The stronger acting 8:5 MMR inside, and the 5:3 MMR outside the 13:8 resonance are within a small shift in the Earth's semimajor axis (only 1.5 percent). Especially Mercury is strongly...

Bazsó, Ákos; Dvorak, Rudolf; Pilat-Lohinger, Elke; Lhotka, Christoph

2009-01-01

354

Results with the superconducting electron cyclotron resonance ion source VENUS (invited)  

International Nuclear Information System (INIS)

[en] During the last year, the VENUS electron cyclotron resonance (ECR) ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR ion source project as the RIA research and development injector is the production of 240 e?A of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5 e?A of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W rf power and the performance is very promising. For example, 1100 e?A of O6+, 180 e?A of Ar12+, 150 e?A of Xe20+, and 100 e?A of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner. In FY04 a 10 kW, 28 GHz gyrotron system will be added, which will enable VENUS to reach full performance. The performance of the VENUS ion source, low energy beam transport and its closed loop cryogenic system are described in the article. Recently, a high temperature axial oven has been installed in the source and the first results on metal beams such as bismuth are given. The design of the 28 GHz, 10 kW gyrotron system will also be described

2004-01-01

355

Simulating the thermochemical magmatic and tectonic evolution of Venus's mantle and lithosphere: Two-dimensional models  

Science.gov (United States)

Numerical convection models of the thermochemical evolution of Venus are compared to present-day topography and geoid and recent resurfacing history. The models include melting, magmatism, decaying heat-producing elements, core cooling, realistic temperature-dependent viscosity and either stagnant lid or episodic lithospheric overturn. In stagnant lid convection the dominant mode of heat loss is magmatic heat pipe, which requires massive magmatism and produces very thick crust, inconsistent with observations. Partitioning of heat-producing elements into the crust helps but does not help enough. Episodic lid overturn interspersed by periods of quiescence effectively loses Venus's heat while giving lower rates of volcanism and a thinner crust. Calculations predict 5-8 overturn events over Venus's history, each lasting ˜150 Myr, initiating in one place and then spreading globally. During quiescent periods convection keeps the lithosphere thin. Magmatism keeps the mantle temperature ˜constant over Venus's history. Crustal recycling occurs by entrainment in stagnant lid convection, and by lid overturn in episodic mode. Venus-like amplitudes of topography and geoid can be produced in either stagnant or episodic modes, with a viscosity profile that is Earth-like but shifted to higher values. The basalt density inversion below the olivine-perovskite transition causes compositional stratification around 730 km breakdown of this layering increases episodicity but far less than episodic lid overturn. The classical stagnant lid mode with interior temperature ˜rheological temperature scale lower than TCMB is not reached because mantle temperature is controlled by magmatism while the core cools slowly from a superheated start. Core heat flow decreases with time, possibly shutting off the dynamo, particularly in episodic cases.

Armann, Marina; Tackley, Paul J.

2012-12-01

356

The solar cycle dependence of the location and shape of the Venus bow shock  

Energy Technology Data Exchange (ETDEWEB)

From initial Pioneer Venus observations during the maximum of solar cycle 21 it was evident that the position of the Venus bow shock varies with solar activity. The bow shock radius in the terminator plane changed from 2.4 R{sub v} to 2.1 R{sub v} as solar activity went from maximum to minimum and, as activity has increased in cycle 22, it has increased again. The recent studies of the subsolar region show that the altitude of the nose of the bow shock varies from 1,600 km at solar minimum to 2,200 km at intermediate solar activity in concert with the terminator altitude so that the shape remains constant and only the size varies during the solar cycle. Using a gas dynamic model and the observed bow shock location, the authors infer the variation in the size of the effective obstacle during the solar cycle. At solar maximum, the effective obstacle is larger than the ionopause as if a magnetic barrier exists in the inner magnetosheath. This magnetic barrier acts as the effective obstacle deflecting the magnetosheath plasma about 500 km above the surface of Venus. However, at solar minimum the effective obstacle is well below the subsolar ionopause, and some absorption of the solar wind plasma by the Venus neutral atmosphere is suggested by these observations. The dependence of the solar cycle variation of the shock position on the orientation of the interplanetary magnetic field reinforces the idea that planetary ion pickup is important in the interaction of the solar wind with Venus.

Zhang, T.L.; Luhmann, J.G.; Russell, C.T. (Univ. of California, Los Angeles (USA))

1990-09-01

357

Study of neutron spectra and dose rates distribution in the VENUS reactor building with the Monte Carlo code TRIPOLI-2  

International Nuclear Information System (INIS)

[en] The new additional shielding system, the new measurement campaign and calculations with TRIPOLI-2 Monte Carlo code in order to study neutron spectra and dose rate distribution in VENUS Reactor are presented. (K.A.)

1995-01-01

358

V-Gram. A Newsletter for Persons Interested in the Exploration of Venus, No. 8, 24 March 1986.  

Science.gov (United States)

The status of the Magellan (MGN) Project (formerly the Venus Radar Mapper Project) is outlined and the impact of the Challenger accident on the planned mission launch date and use of residual Galileo hardware is discussed. The responsibilities and planned...

W. W. James

1986-01-01

359

A post-pioneer Venus reassessment of the Martian dayside ionosphere as observed by radio occultation methods  

Energy Technology Data Exchange (ETDEWEB)

The dayside altitude profiles of the electron density obtained with the radio occultation experiments on Mariners 4, 6, 7, and 9 and the Viking 1 and 2 spacecraft are collectively reanalyzed to determine the global characteristics of the dayside ionosphere of Mars. These analyses concentrate on the comparison of the properties of both the electron density peaks and the topside profiles with the behavior expected for a Chapman layer and that observed at Venus with the Pioneer Venus orbiter radio occultation experiment. As at Venus, the peak densities at Mars behave much like Chapman layer peaks with only slight departure from a (cos{theta}){sup 1/2} dependence, where {theta} is the solar zenith angle. In contrast, the peak heights depart from ideal Chapman layer behavior at Venus but not at Mars because the dayside neutral atmosphere at Venus depends on solar zenith angle. The global dust storm during the Mariner 9 main mission appears to have elevated the Martian ionosphere as a whole by {approximately}20-30 km without otherwise notably altering its density profile. These results generally corroborate the findings of earlier studies. An examination of the solar zenith angle dependence of density levels on the topsides of profiles obtained both at Mars and at Venus near solar minimum provides a new perspective on the solar zenith angle variation of the scale heights of the two ionospheres.

Zhang, M.H.G. (Univ. of Graz (Austria)); Luhmann, J.G. (Univ. of California, Los Angeles (USA)); Kliore, A.J. (Jet Propulsion Laboratory, Pasadena, CA (USA)); Kim, J. (Univ. of Michigan, Ann Arbor (USA))

1990-08-30

360

Simulating the Thermochemical Magmatic and Tectonic Evolution of Venus's Mantle and Lithosphere: Intrusive vs. Extrusive Magmatism  

Science.gov (United States)

Here we extend the models of [1]. Numerical convection models of the thermochemical evolution of Venus are compared to present-day topography and geoid, recent resurfacing history and surface deformation. The models include melting, magmatism, decaying heat-producing elements, core cooling, realistic temperature-dependent viscosity and either stagnant lid or episodic lithospheric overturn. In [1] it was found that in stagnant lid convection the dominant mode of heat loss is magmatic heat pipe, which requires massive magmatism and produces very thick crust, inconsistent with observations. Partitioning of heat-producing elements into the crust helps but does not help enough. Episodic lid overturn interspersed by periods of quiescence effectively loses Venus's heat while giving lower rates of volcanism and a thinner crust. Calculations predict 5-8 overturn events over Venus's history, each lasting ~150 Myr, initiating in one place and then spreading globally. During quiescent periods convection keeps the lithosphere thin. Magmatism keeps the mantle temperature constant over Venus's history. Crustal recycling occurs by entrainment in stagnant lid convection, and by lid overturn in episodic mode. Venus-like amplitudes of topography and geoid can be produced in either stagnant or episodic modes, with a viscosity profile that is Earth-like but shifted to higher values. The basalt density inversion below the olivine-perovskite transition causes compositional stratification around 730 km; breakdown of this layering increases episodicity but far less than episodic lid overturn. The classical stagnant lid mode with interior temperature rheological temperature scale lower than TCMB is not reached because mantle temperature is controlled by magmatism while the core cools slowly from a superheated start. Core heat flow decreases with time, possibly shutting off the dynamo, particularly in episodic cases. Here we extend [1] by considering intrusive magmatism as an alternative to the purely extrusive magmatism assumed in [1]. Intrusive magmatism warms and weakens the crust, resulting in substantial surface deformation and a thinner crust. This is further enhanced by using a basaltic rheology for the crust instead of assuming the same rheological parameters as for the mantle. Here we quantitatively analyse the resulting surface deformation and other signatures, and compare to observations in order to constrain the likely ratio of intrusive to extrusive magmatism. [1] Armann, M., and P. J. Tackley (2012), Simulating the thermochemical magmatic and tectonic evolution of Venus's mantle and lithosphere: Two-dimensional models, J. Geophys. Res., 117, E12003, doi:10.1029/2012JE004231.

Tackley, Paul; Armann, Marina

2013-04-01

 
 
 
 
361

Preliminary study of laser-induced breakdown spectroscopy (LIBS) for a Venus mission  

Energy Technology Data Exchange (ETDEWEB)

Laser-Induced Breakdown Spectroscopy (LIBS) has been proposed as a candidate analysis system for missions to Mars, asteroids, and recently Venus. This technique has several distinct advantages over other techniques which have been used on past missions (X-Ray fluorescence on Viking 1 and 2, 1976; APXS on Pathfiider, 1997; MER, 2004). Two of the more important advantages LIBS has over other techniques for a mission to Venus is rapid elemental analysis of both high and low Z value elements and stand-off analysis at distances of many meters. Rapid elemental analysis and stand-off analysis are very important to missions to Venus due to the harsh environment at the planet surface. From the Venera missions it is known that on the Venusian surface the pressures are approximately 9.1 MPa (90 atm) and the temperature is near 735 K. For these reasons, the Soviet Venera surface probes had operational lifetimes of less than 2 hours. Currently Venus is the target of one of four missions specifically mentioned for consideration for NASA's New Frontier Program with a launch date of 2010 or earlier. In light of this, it is beneficial to evaluate different analysis methods such as LIBS, which offer to greatly increase the scientific return from such a mission. Currently we have begun to evaluate LIBS detection in an environment with pressures and compositions which are similar to those found on Venus. Although the temperature of Venus ({approx} 735 K) has not been taken into account in these experiments, due to the high temperature of the plasma ({approx}8000 K) signifcant perturbations of excitation characteristics sufficient to affect LIBS analytical capability would not be expected. Previous work, however, has shown that the pressure of the surrounding atmosphere can have a strong effect on the detection of elements in soil. These studies have mainly concentrated on pressures at or below earth ambient pressure, but one study has shown successful results at elevated pressures (3.0 MPa). Here we show results from a LIBS study at 9.1 MPa (90 atm) which demonstrates the feasibility of using this technique for elemental analysis at high pressure.

Arp, Z. A. (Zane A.); Cremers, D. A. (David A.); Wiens, R. C. (Roger C.)

2004-01-01

362

Ciência e Tecnologia: expressões sutis da discriminação de gênero? (Science and Technology: subtle expressions of gender discrimination?)  

Directory of Open Access Journals (Sweden)

Full Text Available Resumo: O presente artigo pretende analisar como se manifesta a discriminação de gênero no cenário contemporâneo da Política de Ciência e Tecnologia Nacional. Para tanto, observa a participação de mulheres e homens na produção em C&T financiada pela Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico – FUNCAP. As discussões realizadas constituíram-se por meio de uma abordagem descritiva e de caráter quantitativo, tendo sido imprescindíveis o recurso à pesquisa bibliográfica e documental.Abstract: The present article analyses how gender discrimination takes place in the contemporary scenario of the Brazilian Science & Technology policies. In order to do so, the author has assessed the participation of male and female individuals in a research funded by the Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico – FUNCAP. The discussion was based on a descriptive and qualitative approach, along with a research of the relevant literature and documents, which proved to be essential to the work.

Vívian Matias dos Santos

2010-01-01

363

Desarrollo de las ciencias farmacéuticas: su expresión dialéctica en Cuba Development of pharmaceutical sciences: its dialectic expression in Cuba  

Directory of Open Access Journals (Sweden)

Full Text Available Se analizan los distintos períodos de desarrollo de la ciencia y se enmarcan las ciencias farmacéuticas en particular. Se expone cómo la práctica farmacéutica en el siglo XIX abandona su utilidad social para convertirse en una actividad mercantil, que deriva en el siglo XX en la aparición de consorcios transnacionales, todo lo cual va incidiendo en los países menos desarrollados, y de hecho en sus instituciones universitarias. Las universidades se vuelven dependientes de las economías imperantes, y estas a su vez condicionan un nivel correspondiente a los intereses clasistas. Se aborda la aparición de la enseñanza universitaria en Cuba antes de 1959, donde no constituye una excepción del resto de Latinoamérica. Se preconizan serias transformaciones en la Universidad de La Habana, a partir de la introducción del nuevo proyecto social cubanoThe different periods of the development of science are analyzed, making emphasis on the pharmaceutical sciences in particular. It is exposed how the pharmaceutical practice in the XIX century left its social usefulness to become a trading activity that gave rise in XX century to the appearance of transnational consortia, which influenced on the least developed countries and in their university institutions. The universities began to depend on the dominating economies, which at the same time conditioned a level corresponding to the classist interests. The appearance of the university teaching in Cuba before 1959, which was not an exception to the rest of Latin America, was dealt with. Serious transformations in the University of Havana were praised, starting from the introduction of the new Cuban social project

Eduardo Fernández-Sánchez

2008-01-01

364

Periplasmic domain of the sensor-kinase BvgS reveals a new paradigm for the Venus flytrap mechanism.  

UK PubMed Central (United Kingdom)

Two-component sensory transduction systems control important bacterial programs. In Bordetella pertussis, expression of the virulence regulon is controlled by the unorthodox BvgAS two-component system. BvgS is the prototype of a family of sensor-kinases that harbor periplasmic domains homologous to bacterial solute-binding proteins. Although BvgAS is active under laboratory conditions, no activating signal has been identified, only negative modulators. Here we show that the second periplasmic domain of BvgS interacts with modulators and adopts a Venus flytrap (VFT) fold. X-ray crystallography reveals that the two lobes of VFT2 delimitate a ligand-binding cavity enclosing fortuitous ligands. Most substitutions of putative ligand-binding residues in the VFT2 cavity keep BvgS active, and alteration of the cavity's electrostatic potential affects responsiveness to modulation. The crystal structure of this VFT2 variant conferring constitutive kinase activity to BvgS shows a closed cavity with another nonspecific ligand. Thus, VFT2 is closed and active without a specific agonist ligand, in contrast to typical VFTs. Modulators are antagonists of VFT2 that interrupt signaling. BvgAS is active for most of the B. pertussis infectious cycle, consistent with the proposed mechanism.

Herrou J; Bompard C; Wintjens R; Dupré E; Willery E; Villeret V; Locht C; Antoine R; Jacob-Dubuisson F

2010-10-01

365

Periplasmic domain of the sensor-kinase BvgS reveals a new paradigm for the Venus flytrap mechanism.  

Science.gov (United States)

Two-component sensory transduction systems control important bacterial programs. In Bordetella pertussis, expression of the virulence regulon is controlled by the unorthodox BvgAS two-component system. BvgS is the prototype of a family of sensor-kinases that harbor periplasmic domains homologous to bacterial solute-binding proteins. Although BvgAS is active under laboratory conditions, no activating signal has been identified, only negative modulators. Here we show that the second periplasmic domain of BvgS interacts with modulators and adopts a Venus flytrap (VFT) fold. X-ray crystallography reveals that the two lobes of VFT2 delimitate a ligand-binding cavity enclosing fortuitous ligands. Most substitutions of putative ligand-binding residues in the VFT2 cavity keep BvgS active, and alteration of the cavity's electrostatic potential affects responsiveness to modulation. The crystal structure of this VFT2 variant conferring constitutive kinase activity to BvgS shows a closed cavity with another nonspecific ligand. Thus, VFT2 is closed and active without a specific agonist ligand, in contrast to typical VFTs. Modulators are antagonists of VFT2 that interrupt signaling. BvgAS is active for most of the B. pertussis infectious cycle, consistent with the proposed mechanism. PMID:20855615

Herrou, Julien; Bompard, Coralie; Wintjens, René; Dupré, Elian; Willery, Eve; Villeret, Vincent; Locht, Camille; Antoine, Rudy; Jacob-Dubuisson, Françoise

2010-09-20

366

The Dionaea muscipula Ammonium Channel DmAMT1 Provides NH4(+) Uptake Associated with Venus Flytrap's Prey Digestion.  

UK PubMed Central (United Kingdom)

BACKGROUND: Ammonium transporter (AMT/MEP/Rh) superfamily members mediate ammonium uptake and retrieval. This pivotal transport system is conserved among all living organisms. For plants, nitrogen represents a macronutrient available in the soil as ammonium, nitrate, and organic nitrogen compounds. Plants living on extremely nutrient-poor soils have developed a number of adaptation mechanisms, including a carnivorous lifestyle. This study addresses the molecular nature, function, and regulation of prey-derived ammonium uptake in the Venus flytrap, Dionaea muscipula, one of the fastest active carnivores. RESULTS: The Dionaea muscipula ammonium transporter DmAMT1 was localized in gland complexes where its expression was upregulated upon secretion. These clusters of cells decorating the inner trap surface are engaged in (1) secretion of an acidic digestive enzyme cocktail and (2) uptake of prey-derived nutrients. Voltage clamp of Xenopus oocytes expressing DmAMT1 and membrane potential recordings with DmAMT1-expressing Dionaea glands were used to monitor and compare electrophysiological properties of DmAMT1 in vitro and in planta. DmAMT1 exhibited the hallmark biophysical properties of a NH4(+)-selective channel. At depolarized membrane potentials (Vm = 0), the Km (3.2 ± 0.3 mM) indicated a low affinity of DmAMT1 for ammonium that increased systematically with negative going voltages. Upon hyperpolarization to, e.g., -200 mV, a Km of 0.14 ± 0.015 mM documents the voltage-dependent shift of DmAMT1 into a NH4(+) transport system of high affinity. CONCLUSIONS: We suggest that regulation of glandular DmAMT1 and membrane potential readjustments of the endocrine cells provide for effective adaptation to varying, prey-derived ammonium sources.

Scherzer S; Krol E; Kreuzer I; Kruse J; Karl F; von Rüden M; Escalante-Perez M; Müller T; Rennenberg H; Al-Rasheid KA; Neher E; Hedrich R

2013-09-01

367

Sunlight refraction in the mesosphere of Venus during the transit on June 8th, 2004  

CERN Multimedia

Many observers in the past gave detailed descriptions of the telescopic aspect of Venus during its extremely rare transits across the Solar disk. In particular, at the ingress and egress, the portion of the planet's disk outside the Solar photosphere has been repeatedly perceived as outlined by a thin, bright arc ("aureole"). Those historical visual observations allowed inferring the existence of Venus' atmosphere, the bright arc being correctly ascribed to the refraction of light by the outer layers of a dense atmosphere. On June 8th, 2004, fast photometry based on electronic imaging devices allowed the first quantitative analysis of the phenomenon. Several observers used a variety of acquisition systems to image the event -- ranging from amateur-sized to professional telescopes and cameras -- thus collecting for the first time a large amount of quantitative information on this atmospheric phenomenon. In this paper, after reviewing some elements brought by the historical records, we give a detailed report of...

Tanga, P; Sicardy, B; Pasachoff, J M; Arnaud, J; Comolli, L; Rondi, A; Rondi, S; Suetterlin, P

2011-01-01

368

Numerical models of caldera-scale volcanic eruptions on Earth, venus, and Mars.  

UK PubMed Central (United Kingdom)

Volcanic eruptions of gassy magmas on Earth, Venus, and Mars produce plumes with markedly different fluid dynamics regimes. In large part the differences are caused by the differing atmospheric pressures and ratios of volcanic vent pressure to atmospheric pressure. For each of these planets, numerical simulations of an eruption of magma containing 4 weight percent gas were run on a workstation. On Venus the simulated eruption of a pressure-balanced plume formed a dense fountain over the vent and continuous pyroclastic flows. On Earth and Mars, simulated pressure-balanced plumes produced ash columns, ash falls, and possible small pyroclastic flows. An overpressured plume, illustrated for Mars, exhibited a complex supersonic velocity structure and internal shocks.

Kieffer SW

1995-09-01

369

Benchmark analysis of the DeCART MOC code with the VENUS-2 critical experiment  

International Nuclear Information System (INIS)

[en] Computational benchmarks based on well-defined problems with a complete set of input and a unique solution are often used as a means of verifying the reliability of numerical solutions. VENUS is a widely used MOX benchmark problem for the validation of numerical methods and nuclear data set. In this paper, the results of benchmarking the DeCART (Deterministic Core Analysis based on Ray Tracing) integral transport code is reported using the OECD/NEA VENUS-2 MOX benchmark problem. Both 2-D and 3-D DeCART calculations were performed and comparisons are reported with measured data, as well as with the results of other benchmark participants. In general the DeCART results agree well with both the experimental data as well as those of other participants. (authors)

2004-01-01

370

Large-scale patterns of eolian sediment transport on Venus: Predictions for Magellan  

International Nuclear Information System (INIS)

The atmosphere of Venus is likely to exert a major influence on the surface. Arecibo and Venera 15/16 observations of the population of impact craters with bright halos give direct evidence of surface modification, on the scale of centimeters, to smooth the surface on time scales of 50-250 my. Both chemical and mechanical modifications probably occur. Diurnal winds int he planetary boundary layer can transport particles. Using boundary layer theory, including the effects of topography, surface stresses and resulting transports and deposition of sand-size particles are calculated. Regional slopes are sites of largest surface stresses. Sand will be generally transported downhill, although there is a preferential net transport from east to west, in the same direction as the atmospheric superrotation. It is predicted here that streaks may be seen in the Magellan radar images which will indicate directions of net eolian transport on the surface of Venus

1990-01-01

371

Calculation of the neutron source distribution in the VENUS PWR Mockup Experiment  

Energy Technology Data Exchange (ETDEWEB)

The VENUS PWR Mockup Experiment is an important component of the Nuclear Regulatory Commission's program goal of benchmarking reactor pressure vessel (RPV) fluence calculations in order to determine the accuracy to which RPV fluence can be computed. Of particular concern in this experiment is the accuracy of the source calculation near the core-baffle interface, which is the important region for contributing to RPV fluence. Results indicate that the calculated neutron source distribution within the VENUS core agrees with the experimental measured values with an average error of less than 3%, except at the baffle corner, where the error is about 6%. Better agreement with the measured fission distribution was obtained with a detailed space-dependent cross-section weighting procedure for thermal cross sections near the core-baffle interface region. The maximum error introduced into the predicted RPV fluence due to source errors should be on the order of 5%.

Williams, M.L.; Morakinyo, P.; Kam, F.B.K.; Leenders, L.; Minsart, G.; Fabry, A.

1984-01-01

372

Laboratory model of the induced magnetosphere and its comparison with the spacecraft measurements near Venus  

Energy Technology Data Exchange (ETDEWEB)

A three-dimensional model of the induced magnetosphere in planetary bodies was made on the basis of the simulative experiment results. The existence of this magnetosphere is associated with unipolar induction currents. The appearance of of electrodynamic forces associated with the formation of the induced magnetosphere leads to the acceleration of ionospheric plasma downwards and to the formation of the plasma tail together with the magnetic tail. The night ionosphere can be explained by plasma flowing to the night side under the effect of these forces. In the case of Venus it is shown that for the variation of the solar wind dynamic pressure the magnetic field tubes can penetrate in from the solar wind because of the instability of the Venus ionosphere boundary moving with the acceleration. The penetration of ionosphere ions through the tube lateral walls produces the axial current of electrons from the solar wind leading to twisting of field tubes into the rope.

Dubinin, E.M.; Israelvich, P.L.; Podgorny, I.M.; Shkolnikova, S.I.

1980-01-01

373

Design of the extraction system and beamline of the superconducting ECR ion source VENUS  

Energy Technology Data Exchange (ETDEWEB)

A new, very high magnetic field superconducting ECR ion source, VENUS, is under construction at the LBNL 88-Inch Cyclotron [1,2]. The paper describes the VENUS extraction system and discusses the ion beam formation in the strong axial magnetic field (3 T) of the ECR ion source. Emittance values as expected from theory, which assumes a uniform plasma density across the plasma outlet hole, are compared with actual measurements from the AECR-U ion source. Results indicate that highly charged heavier ions are concentrated on the source axis. They are extracted from an ''effective'' plasma outlet hole, whose smaller radius must be included in ion optics simulations.

Leitner, Matthaeus A.; Wutte, Daniela C.; Lyneis, Claude M.

2001-05-07

374

Electron cooling by carbon monoxide in the atmospheres of Mars and Venus  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Electron cooling, in which free electrons lose energy to vibrational excitation of gases, has been identified as a significant process in the atmospheres of Mars and Venus for electron impact on CO2. This process does not appear to have been evaluated for CO, although the density of CO exceeds that of CO2 in the upper atmospheres of these planets. In this paper electron cooling rates for CO are calculated and compared with existing rates for CO2. It is found that electron cooling by CO becomes more significant than by CO2 above altitudes of about 300 km on Mars and about 168 km on Venus. The sensitivity of the calculated cooling rates to different measurements of the integral cross sections for electron-impact vibrational excitation of CO is also investigated. PACS Codes: 34.80.Gs, 96.12.Jt

Campbell Laurence; Brunger Michael J

2008-01-01

375

Mechanics without Muscles: Fast Motion of the Venus flytrap and Bio-inspired Robotics  

Science.gov (United States)

The rapid motion of plants has intrigued scientists for centuries. Plants have neither nerves nor muscles, yet the Venus flytrap can move in a fraction of a second to capture insects. Darwin did a first systematic study on the trap closure mechanism, and called this plant ``one of the most wonderful in the world''. Several physical mechanisms have since been proposed, such as the rapid loss of turgor pressure, an irreversible acid-induced wall loosening mechanism, and tsnap-through instability, but no unanimous agreement is reached. We propose a coupled mechanical bistable mechanism that explains the rapid closure of the Venus flytrap, consistent with experimental observations. Such bistable behaviors are theoretically modeled and validated with experiments. Biomimetic flytrap robots are also fabricated according to the learnt principles. It is thus promising to design smart bio-mimetic materials and devices with snapping mechanisms as sensors, actuators, artificial muscles and biomedical devices.

Chen, Zi; Guo, Qiaohang; Zheng, Huang; Li, Wei; Ding, Yiting; Su, Guiping; Lin, Junjie; Liu, Yuxin; Chen, Wenzhe; Taber, Larry

2013-03-01

376

Reassessing the possibility of life on venus: proposal for an astrobiology mission.  

Science.gov (United States)

With their similar size, chemical composition, and distance from the Sun, Venus and Earth may have shared a similar early history. Though surface conditions on Venus are now too extreme for life as we know it, it likely had abundant water and favorable conditions for life when the Sun was fainter early in the Solar System. Given the persistence of life under stabilizing selection in static environments, it is possible that life could exist in restricted environmental niches, where it may have retreated after conditions on the surface became untenable. High-pressure subsurface habitats with water in the supercritical liquid state could be a potential refugium, as could be the zone of dense cloud cover where thermoacidophilic life might have retreated. Technology based on the Stardust Mission to collect comet particles could readily be adapted for a pass through the appropriate cloud layer for sample collection and return to Earth. PMID:12469368

Schulze-Makuch, Dirk; Irwin, Louis N

2002-01-01

377

Neutron and gamma ray flux calculations for the VENUS PWR engineering mockup  

International Nuclear Information System (INIS)

[en] This paper describes the analysis of neutron and gamma ray fluxes in the VENUS PWR engineering mockup. The analysis was performed using the methods and procedures used to analyze commercial PWR's. Specifically, two-dimensional discrete ordinates transport theory calculations were performed using the DOT IIIW code. Calculated results are presented for eight fast-neutron reactions and for gamma ray energy-deposition rates. The calculated effects of photo reactions on neutron dosimetry are also presented. (Auth.)

1984-01-01

378

Peculiarities of the Venus dayside ionosphere in years of low an high solar activity  

International Nuclear Information System (INIS)

A series of dual-frequency radio occultation experiments, conducted in 1983-1984 with the use of the ''Venera-15, -16'' satellites, enabled to find characteristics of the dayside Venus ionosphere for intermediate state of solar activity. Correlation of these data with similar results of the ''Venera -9, -10'' and ''Pioner-Venera'' satellites enabled to reveal some peculiarities of ionosphere behaviour, related to the phase of solar activity cycle.

1987-01-01

379

The Venus of Milo and the dawn of facial asymmetry research.  

UK PubMed Central (United Kingdom)

The dawn of facial asymmetry research dates back to the second half of the last century and started with a discussion about the asymmetry of the face of the Venus of Milo. These early observations revealed some of the lateralized patterns of the two facial halves of which we are now aware. Since these studies have up until now been completely neglected, the present review tries to provide the forgotten beginning of this avenue of lateralization research.

Güntürkün O

1991-07-01

380

Harry Potter and the Upcoming Venus-Jupiter Conjunction: A Unique Outreach Opportunity  

Science.gov (United States)

As we prepare for the International Year of Astronomy 2009 (IYA2009), we should be on the lookout for celestial events which we can use not only to popularise the IYA2009 and practise our outreach skills, but which also have natural connections to popular culture. The Venus-Jupiter conjunction this autumn is such an opportunity, given several direct connections to the use of astronomy in J. K. Rowling's famous Harry Potter universe.

Larsen, K.

2008-09-01

 
 
 
 
381

One-dimensional multi-species MHD model of the ionospheres of Venus and Mars  

International Nuclear Information System (INIS)

[en] The behavior of the ionospheric magnetic fields and ionospheric plasma of the dayside ionospheres of Venus and Mars was studied using a one-dimensional multi-species MHD model. The coupled continuity, momentum, and Maxwell's equations were solved simultaneously for the major ions and for the magnetic field. In the ionosphere of Venus, the calculated magnetic-filed profiles were in good agreement with observations obtained by the Pioneer Venus Orbiter magnetometer at all altitudes. Good agreement was also obtained between the calculated and observed plasma densities for altitudes below 250 km, including the electron density ledge near 190 km in magnetized ionospheres. It was found that the magnetic field in the lower ionosphere is maintained by the magnetic flux transported from the magnetic barrier region by the downward plasma motion. The model was also applied to the ionosphere of Mars in order to study the solar wind-Mars interaction and to estimate the magnitude of a possible intrinsic magnetic field on Mars. The calculation showed that even a small intrinsic magnetic field (B ? 30 nT) results in considerably larger electron densities at high altitudes than the densities measured by the retarding potential analyzers on Viking 1 and 2

1987-01-01

382

Comparison of Pioneer Venus and Venera bow shock observations: Evidence for a solar cycle variation  

International Nuclear Information System (INIS)

[en] Observations by the Venera 9 and 10 orbiters in 1975--1976 have been used in previous studies to determmine the mean location and shape of the Cytherean bow shock. In addition it has also been reported that the shock is found to be more distant from the planet above regions of the ionosheath where draped IMF field lines are oriented perpendicular to the flow as opposed to parallel. An examination of the dependence of shock altitude in the terminator plane on upstream IMF direction using 86 Pioneer Venus orbiter bow shock crossings in 1978--79 sets an upper limmit on this asymmetry of 12% or approximately half that derived earlier from the Venera data. More significantly, the mean distance to the bow shock observed by Pioneer Venus Orbiter is 35% greater than was the case in 1975--76 near solar minimum. As the growth in effective obstacle radius is an order of magnitude larger than can be accounted for in terms of varying ionopause altitude due to all causes, these results strongly suggest that Venus can absorb significantly more of the incident solar wind plasma diring solar minimum when EUV flux is low than during the current epoch in which maximum is approaching

1979-01-01

383

Existence of collisional trajectories of Mercury, Mars and Venus with the Earth.  

UK PubMed Central (United Kingdom)

It has been established that, owing to the proximity of a resonance with Jupiter, Mercury's eccentricity can be pumped to values large enough to allow collision with Venus within 5 Gyr (refs 1-3). This conclusion, however, was established either with averaged equations that are not appropriate near the collisions or with non-relativistic models in which the resonance effect is greatly enhanced by a decrease of the perihelion velocity of Mercury. In these previous studies, the Earth's orbit was essentially unaffected. Here we report numerical simulations of the evolution of the Solar System over 5 Gyr, including contributions from the Moon and general relativity. In a set of 2,501 orbits with initial conditions that are in agreement with our present knowledge of the parameters of the Solar System, we found, as in previous studies, that one per cent of the solutions lead to a large increase in Mercury's eccentricity-an increase large enough to allow collisions with Venus or the Sun. More surprisingly, in one of these high-eccentricity solutions, a subsequent decrease in Mercury's eccentricity induces a transfer of angular momentum from the giant planets that destabilizes all the terrestrial planets approximately 3.34 Gyr from now, with possible collisions of Mercury, Mars or Venus with the Earth.

Laskar J; Gastineau M

2009-06-01

384

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

Science.gov (United States)

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. PMID:11536499

Owen, T; Bar-Nun, A; Kleinfeld, I

1992-07-01

385

Integration of Radioisotope Heat Source with Stirling Engine and Cooler for Venus Internal-Structure Mission  

Energy Technology Data Exchange (ETDEWEB)

The primary mission goal is to perform long-term seismic measurements on Venus, to study its largely unknown internal structure. The principal problem is that most payload components cannot long survive Venus's harsh environment, 90 bars at 500 degrees C. To meet the mission life goal, such components must be protected by a refrigerated payload bay. JPL Investigators have proposed a mission concept employing a lander with a spherical payload bay cooled to 25 degrees C by a Stirling cooler powered by a radioisotope-heated Sitrling engine. To support JPL's mission study, NASA/Lewis and MTI have proposed a conceptual design for a hydraulically coupled Stirling engine and cooler, and Fairchild Space - with support of the Department of Energy - has proposed a design and integration scheme for a suitable radioisotope heat source. The key integration problem is to devise a simple, light-weight, and reliable scheme for forcing the radioisotope decay heat to flow through the Stirling engine during operation on Venus, but to reject that heat to the external environment when the Stirling engine and cooler are not operating (e.g., during the cruise phase, when the landers are surrounded by heat shields needed for protection during subsequent entry into the Venusian atmosphere.) A design and integration scheme for achieving these goals, together with results of detailed thermal analyses, are described in this paper. There are 7 copies in the file.

Schock, Alfred

1993-10-01

386

VENUS: cold prototype installation of the head-end of the reprocessing of HTR fuel elements. Activity report, 1 July 1976--31 December 1976  

International Nuclear Information System (INIS)

[en] The purpose of the VENUS Project is advance planning for the construction of a cold prototype system to incinerate HTR fuel element graphite. The Venus Project is organized into four phases between advance planning and experimental operation, corresponding to the maturity of the work. It is in the advance planning phase. Status of individual studies is given

1976-07-01

387

Experimental results from the VENUS-F critical reference state for the GUINEVERE accelerator driven system project  

Energy Technology Data Exchange (ETDEWEB)

The GUINEVERE (Generation of Uninterrupted Intense Neutron pulses at the lead Venus Reactor) project was launched in 2006 within the framework of FP6 EUROTRANS in order to validate on-line reactivity monitoring and subcriticality level determination in Accelerator Driven Systems. Therefore the VENUS reactor at SCK.CEN in Mol (Belgium) was modified towards a fast core (VENUS-F) and coupled to the GENEPI-3C accelerator built by CNRS The accelerator can operate in both continuous and pulsed mode. The VENUS-F core is loaded with enriched Uranium and reflected with solid lead. A well-chosen critical reference state is indispensable for the validation of the on-line subcriticality monitoring methodology. Moreover a benchmarking tool is required for nuclear data research and code validation. In this paper the design and the importance of the critical reference state for the GUINEVERE project are motivated. The results of the first experimental phase on the critical core are presented. The control rods worth is determined by the rod drop technique and the application of the Modified Source Multiplication (MSM) method allows the determination of the worth of the safety rods. The results are implemented in the VENUS-F core certificate for full exploitation of the critical core. (authors)

Uyttenhove, W.; Baeten, P.; Ban, G.; Billebaud, A.; Chabod, S.; Dessagne, P.; Kerveno, M.; Kochetkov, A.; Lecolley, F. R.; Lecouey, J. L.; Marie, N.; Mellier, F.; Steckmeyer, J. C.; Thyebault, H. E.; Vittiglio, G.; Wagemans, J. [SCK.CEN, Belgian Nuclear Research Centre, Boeretang 200, BE-2400 Mol (Belgium)

2011-07-01

388

Annual review of earth and planetary sciences. Volume 15  

International Nuclear Information System (INIS)

[en] Recent theoretical and experimental investigations in the fields of earth and planetary science are examined in a series of annual reviews. Topics addressed include the core-mantle boundary, application of stable C isotopes to early biochemical evolution on earth, physical processes in volcanic eruptions, three-dimensional seismic imaging, and integrated diagenetic modeling. Consideration is given to the atmospheres of Venus, earth, and Mars; terrestrial impact structures; the origin of the moon; organic geochemistry of biomarkers; models of lithospheric thinning; marine magnetic anomalies; and polar wandering and paleomagnetism

1987-01-01

389

Annual review of earth and planetary sciences. Volume 15  

Energy Technology Data Exchange (ETDEWEB)

Recent theoretical and experimental investigations in the fields of earth and planetary science are examined in a series of annual reviews. Topics addressed include the core-mantle boundary, application of stable C isotopes to early biochemical evolution on earth, physical processes in volcanic eruptions, three-dimensional seismic imaging, and integrated diagenetic modeling. Consideration is given to the atmospheres of Venus, earth, and Mars; terrestrial impact structures; the origin of the moon; organic geochemistry of biomarkers; models of lithospheric thinning; marine magnetic anomalies; and polar wandering and paleomagnetism.

Wetherill, G.W.; Albee, A.L.; Stehli, F.G.

1987-01-01

390

Prelude to the Venus Express mission: a study of the atmosphere using infrared spectro-imaging  

International Nuclear Information System (INIS)

This thesis deals with the search for and the study of young galactic supernova remnants using the observations performed by IBIS/ISGRI, one of the two main coded-mask instruments onboard the european gamma-ray satellite INTEGRAL. This research is based on i) the study of gamma-ray lines coming from the radioactive decay of 44Ti, a short-lived nucleus (?? 86 y) exclusively produced during the first stages of stellar explosions, and ii) the study of the nonthermal continuum mechanisms which take place inside the young supernova remnants. I separate the manuscript in four main parts. The first one presents an overview of supernovae from an observational and theoretical point of view. The second part describes the INTEGRAL satellite with its instruments, the techniques used for analyzing the data collected by IBIS/ISGRI, and my personal investigations concerning different developments such as: the spectral calibration of the IBIS/ISGRI instrument, the correction of noisy pixels on the camera, the creation of background maps, and the development of an alternative pipeline useful for dealing with a large amount of data. I also present a method for imaging extended sources with a coded-mask instrument such as IBIS/ISGRI, and its first application on the Coma Cluster. The results obtained on historical supernova remnants like Cas A, Tycho, RXJ0852-4622 (Vela Junior) are presented in the third part. The first chapter of the last part is devoted to the study of the detectability of supernovae in the optical domain with a model of the interstellar extinction. The second chapter reports on the search for missing and hidden young supernova remnants in the Milky Way with the IBIS/ISGRI galactic plane survey through the 44Sc gamma-ray lines as well as with a multi-wavelength approach, from the radio domain (VLA) to the new observational window at TeV energies (HESS). I also discuss the constraints on the supernova rate and the 44Ti production in core-collapse supernovae, based on these IBIS/ISGRI observations and the 44Ca solar abundance. (author)

2006-01-01

391

The formation and hadronization of quark matter in the VENUS model; La formation et hadronisation de matiere des quarks dans le modele VENUS  

Energy Technology Data Exchange (ETDEWEB)

In studying nuclear collisions at ultrarelativistic energies one expects to detect high density regions, where a thermalized system of quarks and gluons is created, the quark gluon plasma (QGP). In the VENUS model the string model of hadronic interactions is used to provide a microscopic model for the formation of quark matter droplets. After a longitudinal expansion the hadronization of the droplets is described according to n-body phase space. There are presented the results concerning the particle production as a function of the rapidity y in a central collision S + S at 200 GeV per nucleon, for three values of the critical energy density ({epsilon}{sub c} 0.15, 1.00 and 2.00 GeV/fm{sup 3}). One can see easily the droplet influence in case of strange particles since their production is suppressed in the string fragmentation 6 refs.

Hladik, M.; Werner, K. [Laboratoire de Physique Subatomique et des Technologies Associees - SUBATECH, Centre National de la Recherche Scientifique, 44 - Nantes (France)

1997-10-01

392

Reentry response of the lightweight radioisotope heater unit resulting from a Cassini Venus-Venus-Earth-Jupiter gravity assist maneuver accident  

International Nuclear Information System (INIS)

Reentry analyses consisting of ablation response, thermal response and thermal stress response have been conducted on the Lightweight Radioisotope Heater Unit (LWRHU) for Cassini/Venus-Venus-Earth-Jupiter-Gravity-Assist (VVEJGA) reentry conditions. Sequential ablation analyses of the LWRHU aeroshell, and the fuel pellet have been conducted in reentry regimes where the aeroshell has been deemed to fail. The failure criterion for ablation is generally assumed to be recession corresponding to 75% and 100% of the wall thickness. The 75% recession failure criteria allows for uncertainties that result mainly because of the high energies involved in the VVEJGA reentries compared to orbital decay reentries. Risk evaluations should consider the fact that for shallow flight paths the unit may disassemble at high-altitude as a result of ablation or may remain intact with a clad that had been molten. Within the limitations of the methodologies and assumptions of the analyses, the results indicate that: (1) For a side-on stable LWRHU reentry, aeroshell ablation failures occur for all reentry angles. (2)For a side-on spinning LWRHU reentry, aeroshell ablation failures are minimal. (3) For the tumbling LWRHU reentry, the aeroshell survives for most angles. (4) For the thermostructural analyses, using both a 1% and 5% allowable strain, all reentry angles and orientations examined resulted in small loca