Large, solid particles in the clouds of Venus: Do they exist?

Toon, O. B.; Ragent, B.; Colburn, D. S.; Blamont, J. É.; Cot, C.

doi:10.1016/0019-1035(84)90063-0

Cited by 44 publications

(28 citation statements)

References 17 publications

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“…Each of the simulations continues to show a sharp increase in aerosol effective radius near the cloud base, though the increase is a bit more subtle for the 'mid2' and 'pol1' profiles. This can be taken to be consistent with the LCPS observations, if tempered with the suggestion by Toon et al (1984) that the Mode 3 particles are actually just a larger particle tail of the existing aerosol distribution.…”

Section: Coagulation Effects On Full Domain Modelsupporting

confidence: 78%

“…Note that previous work by James et al (1997) suggested that the multimodal structure observed by LCPS could only be obtained when solubility of the CCN was taken into consideration. However, Toon et al (1984) pointed out that the most likely candidate for the involatile CCN observed by LCPS was sulfur allotropes, which Young (1983) noted are not miscible in sulfuric acid. Consequently, the Mode 1 particles cannot serve as CCN for the condensation of small sulfuric acid droplets if they are sulfur allotropes.…”

Section: Nominal Modelmentioning

confidence: 99%

“…The sulfuric acid vapor nucleates into droplets when supersaturations become large enough, and the particles observed in the upper photochemical clouds tend to be spherical droplets around 1 μm in radius (Hansen and Hovenier 1974), but an additional smaller mode is also regularly seen (Kawabata et al 1980;Wilquet et al 2009Wilquet et al , 2012. The evaporation of these droplets below an altitude of about 50 km leads to the accumulation of a reservoir of sulfuric acid vapor between about 40 and 50 km, which fuels the condensational clouds of Venus located between about 50 and 57 km, at equatorial latitudes (Toon et al 1984;James et al 1997). Below 40 km, the sulfuric acid is thermally decomposed into H 2 O and SO 3 (Krasnopolsky 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Below 57 km, three modes of particles were described by Knollenberg and Hunten (1980). However, the size resolution of the LCPS detector, while excellent 40 years ago, was remarkably crude by today's standards, leaving the characterization of the true Venus cloud particle size distribution somewhat unconstrained, For example, Toon et al (1984) suggested that a possible mismatch in the calibration of the detector ranges would have resulted in the so called Mode 3 particles being characterized as having radii slightly larger than the true particles. That is, if the largest detected particles are shifted to slightly smaller radii, then the Mode 3 distribution manifests itself as a large-radius tail of the wellestablished and well-observed Mode 2 population.…”

Section: Introductionmentioning

confidence: 99%

“…That is, if the largest detected particles are shifted to slightly smaller radii, then the Mode 3 distribution manifests itself as a large-radius tail of the wellestablished and well-observed Mode 2 population. The reader is referred to the original papers (Toon et al 1984;Knollenberg 1984) for further details.…”

Section: Introductionmentioning

confidence: 99%

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Effects of variation in coagulation and photochemistry parameters on the particle size distributions in the Venus clouds

McGouldrick

2017

Earth Planets Space

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This paper explores the effects that variation in the coalescence efficiency of the Venus cloud particles can have on the structure of the Venus cloud. It is motivated by the acknowledgment of uncertainties in the measured parameters-and the assumptions made to account for them-that define our present knowledge of the particle characteristics. Specifically, we explore the consequence of allowing the coalescence efficiency of supercooled sulfuric acid in the upper clouds to tend to zero. This produces a cloud that occasionally exhibits an enhancement of small particles at altitude (similar to the upper hazes observed by Pioneer Venus and subsequently shown to be somewhat transient). This simulated cloud occasionally exhibits a rapid growth of particle size near cloud base, exhibiting characteristics similar to those seen in the controversial Mode 3 particles. These results demonstrate that a subset of the variations observed as near-infrared opacity variations in the lower and middle clouds of Venus can be explained by microphysical, in addition to dynamical, variations. Furthermore, the existence of a population of particles exhibiting less efficient coalescence efficiencies would support the likelihood of conditions suitable for charge exchange, hence lightning, in the Venus clouds. We recommend future laboratory studies on the coalescence properties of sulfuric acid under the range of conditions experienced in the Venus clouds. We also recommend future in situ measurements to better characterize the properties of the cloud particles themselves, especially composition and particle habits (shapes).

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Section: Coagulation Effects On Full Domain Modelsupporting

confidence: 78%