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1.
The discovery of large, solid particles in the clouds of Venus is one of the most significant findings of Pioneer Venus because it means that a substantial mass of the clouds is composed of a material other than sulfuric acid. The evidence which suggests that solid particles form a distinctive size mode is reexamined. The mode is defined by a discontinuity between two size ranges of the Pioneer Venus particle size spectrometer. This discontinuity could represent a real size mode. However, it could also be an artifact of the measurement technique. R. G. Knollenberg (1984) discusses several possible instrumental effects which might have caused this discontinuity. It is hypothesized herein that such effects did occur and that the large particles are really the tail of the mode 2 sulfuric acid particle size distribution and are not a separate mode of solid particles. Using such a revised size distribution, it is shown that all of the Pioneer Venus and Venera optical data from the lower clouds can be explained with sulfuric acid droplets without introducing any solid particles. As a by-product of this analysis, it is also found that the upper clouds of Venus must contain a material with a higher refractive index than sulfuric acid. A small quantity of sulfur could account for this observation. 相似文献
2.
Observations of the lunar luminescence are reported for a dozen of specific Moon features using the line-depth method with a high resolution spectroscopic technique. The data indicate a variation of the Moon proper emission as a function of the phase angle which is interpreted as a proof of the thermoluminescent origin of this emission. 相似文献
3.
Two high value species, yellowtail kingfish (Seriola lalandi) and hāpuku (groper, Polyprion oxygeneios), have been identified as suitable new candidates for New Zealand aquaculture. This paper reviews the research by NIWA and collaborators conducted to test the biological, technological and economic feasibility of farming these two species. NIWA now has the capability to produce sufficient kingfish fingerlings per year to meet the needs of the early stages of an industry. Advances in hāpuku aquaculture have also been significant, from spawning in captivity through to the selection of juveniles for improved growth. Recently, the first spawning of captive hāpuku F1 broodstock and production of F2 eggs, larvae and juveniles was achieved. Although hāpuku larval survival remains variable, the ability to close the life cycle, and the availability of domesticated broodstock, provide a significant step forward and increase the chances of this species being commercially farmed. 相似文献
4.
Laser sounding of atmospheric sodium interpretation in terms of global atmospheric parameters 总被引：3，自引：0，他引：3
Measurements of the night-time atmospheric sodium layer have been performed over a period of 3 years, using a Lidar facility set up at the Haute Provence Observatory. A photochemical and dynamical model of the upper atmosphere between 25 and 150 km has been used to simulate the behaviour of the atmospheric sodium and to compare it with the experimental results as derived from a statistical study of the spatial parameters of the layer. Evidence is given for a sodium source at the upper levels together with the determination of minimum values of the integrated eddy diffusion coefficient between 82 and 95 km. Stratifications occurring in the layer are related to the propagation of gravity waves at the corresponding heights. Sporadic enhancements of the total column abundance of sodium during meteoritic showers are reported giving evidence for a meteoritic origin of a part of the sodium. 相似文献
5.
It is shown that the eddy diffusion limit of sodium clouds ejected by rockets can be considered as an indicator of the turbopause, and that the altitude of the turbopause varies substantially during the night.In order to achieve this, first the existence of two highly different wind regimes during the night between 95 and 110km altitude is revealed in the variation in mean kinetic energy with altitude as well as by other effects.Then, the relations between the variation in kinetic energy with altitude, the energy dissipated, and the eddy diffusion coefficient is established. Finally, by applying these results to experimental data, it is shown that the atmosphere remains turbulent up to 105 km during the first portion of the night, and that the turbopause descends to about 95 km during the second portion of the night.An explanation for this nocturnal evolution of the atmosphere is also presented. 相似文献
6.
European Venus Explorer (EVE): an in-situ mission to Venus 总被引：1，自引：0，他引：1
E. Chassefière O. Korablev T. Imamura K. H. Baines C. F. Wilson D. V. Titov K. L. Aplin T. Balint J. E. Blamont C. G. Cochrane Cs. Ferencz F. Ferri M. Gerasimov J. J. Leitner J. Lopez-Moreno B. Marty M. Martynov S. V. Pogrebenko A. Rodin J. A. Whiteway L. V. Zasova J. Michaud R. Bertrand J.-M. Charbonnier D. Carbonne P. Raizonville 《Experimental Astronomy》2009,23(3):741-760
The European Venus Explorer (EVE) mission was proposed to the European Space Agency in 2007, as an M-class mission under the
Cosmic Vision Programme. Although it has not been chosen in the 2007 selection round for programmatic reasons, the EVE mission
may serve as a useful reference point for future missions, so it is described here. It consists of one balloon platform floating
at an altitude of 50–60 km, one descent probe provided by Russia, and an orbiter with a polar orbit which will relay data
from the balloon and descent probe, and perform science observations. The balloon type preferred for scientific goals is one
which oscillates in altitude through the cloud deck. To achieve this flight profile, the balloon envelope contains a phase
change fluid, which results in a flight profile which oscillates in height. The nominal balloon lifetime is 7 days—enough
for one full circumnavigation of the planet. The descent probe’s fall through the atmosphere takes 60 min, followed by 30 min
of operation on the surface. The key measurement objectives of EVE are: (1) in situ measurement from the balloon of noble
gas abundances and stable isotope ratios, to study the record of the evolution of Venus; (2) in situ balloon-borne measurement
of cloud particle and gas composition, and their spatial variation, to understand the complex cloud-level chemistry; (3) in
situ measurements of environmental parameters and winds (from tracking of the balloon) for one rotation around the planet,
to understand atmospheric dynamics and radiative balance in this crucial region. The portfolio of key measurements is complemented
by the Russian descent probe, which enables the investigation of the deep atmosphere and surface. 相似文献
7.
I.L. Bertaux J. Blamont M. Marcelin V.G. Kurt N.N. Romanova A.S. Smirnov 《Planetary and Space Science》1978,26(9):817-831
The dayside hydrogen exosphere was observed in October–November 1975 with a Lymanalpha photometer carried on board Venera-9 and 10. In addition to intensity measurements, the use of a hydrogen cell allowed for the first time linewidth measurements. Both intensity and linewidth measurements below 1500 km of altitude are well fitted by a single exospheric component (Tc = 500 ± 100 K, nc = 1.5 × 104 atom cm?3at 250 km). Above 3000 km, the measured linewidth increased sharply, to decrease again above 4500 km. This feature is interpreted as the signature of an additional population of “hot” atoms circulating on satellite orbits, created just behind the bow-shock by charge-exchange collisions (with an efficiency of 4%) between the neutral atoms and the solar wind protons, which became turbulent after bow-shock crossing. The density ratio of “hot” to standard population is of the order of 10% around 3500 km of altitude. 相似文献
8.
JN Kathena A Kokkalis MW Pedersen JE Beyer UH Thygesen 《African Journal of Marine Science》2018,40(3):293-302
There is global interest in providing scientific advice on optimal harvesting of all commercially exploited fish stocks. Nevertheless, many commercially important stocks lack analytical assessments. Therefore, we evaluate a data-moderate stock assessment method: the stochastic surplus production model in continuous time (SPiCT). The method was applied to two Namibian stocks: (i) the data-rich Cape monkfish Lophius vomerinus, where results are compared to a new data-rich assessment using a state–space assessment model (SAM); and (ii) the data-moderate west coast sole Austroglossus microlepis, which is an important bycatch species in the Cape monkfish fishery, but currently unassessed. The information available to the data-moderate assessment is total commercial catch, commercial catch per unit effort (CPUE), and survey CPUE. SPiCT and SAM gave largely consistent estimates of relative fishing mortality (F/FMSY) and relative exploitable biomass (B/BMSY) for the Cape monkfish stock, although with some discrepancies. Differences in the biomass estimates between the two assessments suggest that further investigation is required to understand the cause, and that some caution is necessary when considering the biomass of the stock. SPiCT shows that the west coast sole may be overexploited, although the confidence bounds were too wide for a firm conclusion. Similarity in the estimates of F/FMSY for Cape monkfish in recent years, using SPiCT relative to SAM, likewise indicates the suitability of SPiCT for managing west coast sole. 相似文献
9.
E. ŽÁČKOVÁ J. KONOPÁSEK P. JEŘÁBEK F. FINGER J. KOŠLER 《Journal of Metamorphic Geology》2010,28(4):361-379
The metamorphic evolution of micaschists in the north‐eastern part of the Saxothuringian Domain in the Central European Variscides is characterized by the early high‐pressure M1 assemblage with chloritoid in cores of large garnet porphyroblasts and a Grt–Chl–Phe–Qtz ± Pg M2 assemblage in the matrix. Minerals of the M1–M2 stage were overprinted by the low‐pressure M3 assemblage Ab–Chl–Ms–Qtz ± Ep. Samples with the best‐preserved M1–M2 mineralogy mostly appear in domains dominated by the earlier D1 deformation phase and are only weakly affected by subsequent D2 overprint. Thermodynamic modelling suggests that mineral assemblages record peak‐pressure conditions of ≥18–19 kbar at 460–520 °C (M1) followed by isothermal decompression 10.5–13.5 kbar (M2) and final decompression to <8.5 kbar and <480 °C (M3). The calculated peak P–T conditions indicate a high‐pressure/low‐temperature apparent thermal gradient of ～7–7.5 °C km?1. Laser ablation inductively coupled plasma mass spectrometry isotopic dating and electron microprobe chemical dating of monazite from the M1–M2 mineral assemblages give ages of 330 ± 10 and 328 ± 6 Ma, respectively, which are interpreted as the timing of a peak pressure to early decompression stage. The observed metamorphic record and timing of metamorphism in the studied metapelites show striking similarities with the evolution of the central and south‐western parts of the Saxothuringian Domain and suggest a common tectonic evolution along the entire eastern flank of the Saxothuringian Domain during the Devonian–Carboniferous periods. 相似文献
10.
Colin Frank Wilson Eric Chassefière Emmanuel Hinglais Kevin H. Baines Tibor S. Balint Jean-Jacques Berthelier Jacques Blamont Georges Durry Csaba S. Ferencz Robert E. Grimm Takeshi Imamura Jean-Luc Josset Fran?ois Leblanc Sebastien Lebonnois Johannes J. Leitner Sanjay S. Limaye Bernard Marty Ernesto Palomba Sergei V. Pogrebenko Scot C. R. Rafkin Dean L. Talboys Rainer Wieler Liudmila V. Zasova Cyrill Szopa 《Experimental Astronomy》2012,33(2-3):305-335
The European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an ‘M-class’ mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55?km, where temperatures and pressures are benign (～25°C and ～0.5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond. 相似文献