The microphysics of the clouds of Venus: Results of the Pioneer Venus Particle Size Spectrometer Experiment

Knollenberg, Robert G.; Hunten, D. M.

doi:10.1029/ja085ia13p08039

Cited by 305 publications

(329 citation statements)

References 27 publications

Supporting

Mentioning

293

Contrasting

Order By: Relevance

“…While both are mainly composed of sulfuric acid (H 2 SO 4 ) aerosol particles, the particle size distribution is different in these layers, yielding different scattering properties. In the upper haze, particles are smaller than in the cloud deck, with typical radii from 0.1 to 0.3 μm, as expected from pure "mode-1" particles (Knollenberg & Hunten 1980;Esposito et al 1997). Following Wilquet et al (2009) and references therein, we consider an upper haze consisting of concentrated (75%) aqueous and spherical droplets of H 2 SO 4 .…”

Section: Atmospherementioning

confidence: 81%

Transmission spectrum of Venus as a transiting exoplanet

Ehrenreich

Vidal‐Madjar

Widemann

et al. 2011

A&A

View full text Add to dashboard Cite

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 μm 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 μm by Mie extinction (∼5 ppm at 0.8 μm) caused by droplets of sulfuric acid composing an upper haze layer above the main deck of clouds. These features are not expected for a terrestrial exoplanet and could help discriminating an Earth-like habitable world from a cytherean planet.

show abstract

Section: Atmospherementioning

confidence: 81%

Transmission spectrum of Venus as a transiting exoplanet

Ehrenreich

Vidal‐Madjar

Widemann

et al. 2011

A&A

View full text Add to dashboard Cite

show abstract

“…Upper haze layers based on Pioneer Venus data (Crisp, 1986) are added. The ratios among the particle modes are from Knollenberg and Hunten (1980). The maximum positive and negative deviations are also determined from the same data set; however, those for the upper haze layers are just assumed to be 50%.…”

Section: Resultsmentioning

confidence: 99%

“…2(h) is distributed to three particle modes (mode1, 2, and 3) and shown in Table 1. The ratios among each particle mode are taken from table 5 of Knollenberg and Hunten (1980). The maximum negative and the maximum positive deviations of the seven profiles shown in Fig.…”

Section: Cloud Modelmentioning

confidence: 99%

Contrast sources for the infrared images taken by the Venus mission AKATSUKI

Takagi

Iwagami

2011

Earth Planet Sp

View full text Add to dashboard Cite

A feasibility study has been carried out to look for the source of contrast that will be seen in the infrared images of Venus taken by the cameras on board AKATSUKI. This procedure used a cloud model based on the measurements of previous entry probes and radiative transfer calculations. The source of the small contrast expected in the 0.90-µm dayside image was found to be due to inhomogeneity in the cloud optical thickness, with the variations in cloud altitude and temperature having little effect. The source of the large contrast expected in the 2.26-µm nightside image was also found to be due to inhomogeneity in the cloud optical thickness. We attempted to determine the representative altitude of the cloud layers, but this could not be specified to one particular layer. The brightness expected in the 2.02-µm dayside image was found to be affected by the cloud altitude, as expected since the 2.02-µm is in a moderate CO 2 absorption band; however, it is also affected by the cloud optical thickness. The brightness expected in the 10-µm image was found to be affected mostly by temperature; however, the effects due to cloud optical thickness and cloud altitude are also important. It is necessary to use all of the information obtained at various wavelengths to gain a correct understanding of the brightness distribution of the Venus images taken by AKATSUKI.

show abstract

“…However, the occurrence is still under debate since the conventional mechanism of charge separation in terrestrial clouds requires H 2 O ice particles, which will not be formed in the Venusian atmosphere. Large solid particles of unknown composition suggested by the particle size spectrometer on the Pioneer Venus probe (Knollenberg and Hunten, 1980) might play some role.…”

Section: Clouds and Lightningmentioning

confidence: 99%

“…The global-scale meridional circulation of the atmosphere might also determine the life cycle of cloud particles and the cloud structure, because the sedimentation timescale of cloud particles with a typical diameter of a few micrometers (Knollenberg and Hunten, 1980) will be longer than the atmospheric turnover time of a few months estimated from cloud tracking (Imamura and Hashimoto, 1998;Yamamoto and Tanaka, 1998). Imamura and Hashimoto (1998) argued that H 2 SO 4 vapor is accumulated near the equatorial cloud base due to the precipitation in the equatorial upwelling and that this leads to the thickening of the lower cloud which was observed by entry probes.…”

Section: Clouds and Lightningmentioning

confidence: 99%

Overview of Venus orbiter, Akatsuki

et al. 2011

View full text Add to dashboard Cite

The Akatsuki spacecraft of Japan was launched on May 21, 2010. The spacecraft planned to enter a Venusencircling 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 nearinfrared 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.

show abstract

The microphysics of the clouds of Venus: Results of the Pioneer Venus Particle Size Spectrometer Experiment

Cited by 305 publications

References 27 publications

Transmission spectrum of Venus as a transiting exoplanet

Transmission spectrum of Venus as a transiting exoplanet

Contrast sources for the infrared images taken by the Venus mission AKATSUKI

Overview of Venus orbiter, Akatsuki

Contact Info

Product

Resources

About