A review of selected issues concerning the chemistry in Venus’ middle atmosphere

Mills, Franklin P.; Allen, Mark

doi:10.1016/j.pss.2007.01.012

Cited by 115 publications

(113 citation statements)

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“…Morphologies provide a good diagnostic tool for relating the atmospheric processes involved with the sources and sinks of the aerosols, condensates and trace gases. Chemical models developed for the Venus atmosphere include more than forty species and involve more than a hundred reactions (Krasnopolsky 2007;Mills and Allen 2007;) which are dependent on ambient conditions, further complicating analysis and interpretation in light of incomplete data and information. Venera and VeGa landers, four Pioneer Venus probes and two VeGa balloons have sampled the clouds below 62 km and obtained useful measurements, but these are proving to be insufficient for understanding the Venus clouds.…”

Section: Nightside Images Of Venus In Near Infraredmentioning

confidence: 99%

Venus looks different from day to night across wavelengths: morphology from Akatsuki multispectral images

Limaye

Watanabe

Yamazaki

et al. 2018

Earth Planets Space

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Since insertion into orbit on December 7, 2015, the Akatsuki orbiter has returned global images of Venus from its four imaging cameras at eleven discrete wavelengths from ultraviolet (283 and 365 nm) and near infrared (0.9-2.3 µm), to the thermal infrared (8-12 µm) from a near-equatorial orbit. The Venus Express and Pioneer Venus Orbiter missions have also monitored the planet for long periods but from polar or near-polar orbits. The wavelength coverage and views of the planet also differ for all three missions. In reflected light, the images reveal features seen near the cloud tops (~ 70 km altitude), whereas in the near-infrared images of the nightside, features seen are at mid-to lower cloud levels (~ 48-60 km altitude). The dayside cloud cover imaged at the ultraviolet wavelengths shows morphologies similar to what was observed from Mariner 10, Pioneer Venus, Galileo, Venus Express and MESSENGER. The daytime images at 0.9 and 2.02 µm also reveal some interesting features which bear similarity to the ultraviolet images. The nighttime images at 1.74, 2.26 and 2.32 µm and at 8-12 µm reveal features not seen before and show new details of the nightside including narrow wavy ribbons, curved string-like features, long-scale waves, long dark streaks, isolated bright spots, sharp boundaries and even mesoscale vortices. Some features previously seen such as circum-equatorial belts (CEBs) and occasional areal brightenings at ultraviolet (seen in Venus Express observations) of the cloud cover at ultraviolet wavelengths have not been observed thus far. Evidence for the hemispheric vortex organization of the global circulation can be seen at all wavelengths on the day-and nightsides. Akatsuki images reveal new and puzzling morphology of the complex nightside cloud cover. The cloud morphologies provide some clues to the processes occurring in the atmosphere and are thus, a key diagnostic tool when quantitative dynamical analysis is not feasible due to insufficient information.

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Section: Nightside Images Of Venus In Near Infraredmentioning

confidence: 99%

Venus looks different from day to night across wavelengths: morphology from Akatsuki multispectral images

Limaye

Watanabe

Yamazaki

et al. 2018

Earth Planets Space

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“…The thermal reactions of SO 3 and SO with H 2 SO 4 •• H 2 S clearly explain this anticorrelation. These thermal reactions not only provide useful mechanistic insights into an important sink of sulfur gases below 90 km in the Venus atmosphere, but may also help in understanding the mixing profiles of SO and SO 2 at higher altitudes (1,17,18,(32)(33)(34)(35)(36). At 96-km Venus atmosphere, the rates of the SO 3 hydration and the SO 3 photolysis are found to be comparable (17), which is suggestive of the fact that nearly half of the sulfur in H 2 SO 4 goes into SO 3 and produces the inversion layers of SO 2 and SO.…”

Section: Significancementioning

confidence: 99%

Elemental sulfur aerosol-forming mechanism

Kumar

Francisco

2017

Proc. Natl. Acad. Sci. U.S.A.

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Elemental sulfur aerosols are ubiquitous in the atmospheres of Venus, ancient Earth, and Mars. There is now an evolving body of evidence suggesting that these aerosols have also played a role in the evolution of early life on Earth. However, the exact details of their formation mechanism remain an open question. The present theoretical calculations suggest a chemical mechanism that takes advantage of the interaction between sulfur oxides, SO n (n = 1, 2, 3) and hydrogen sulfide (nH 2 S), resulting in the efficient formation of a S n+1 particle. Interestingly, the SO n + nH 2 S → S n+1 + nH 2 O reactions occur via low-energy pathways under water or sulfuric acid catalysis. Once the S n+1 particles are formed, they may further nucleate to form larger polysulfur aerosols, thus providing a chemical framework for understanding the formation mechanism of S 0 aerosols in different environments. , SO 4 2− ) provide energy for different types of sulfur metabolisms in different environments. The sulfur cycle in the Archean atmosphere is also believed to have played a role in the early evolution of life on Earth (2-7). The emerging photochemical picture suggests that reduced elemental sulfur (S 0 ) and sulfate (SO 4 ) are the dominant sulfur species in the Archean (2-9). However, the latest isotope signatures of microscopic sulfides in marine sulfate deposits indicate that the ultimate source for this metabolic sulfur cycling was atmospherically derived S 0 (10). One of the most important sources of sulfur into the atmosphere is from volcanoes, and the most abundant sulfur gases are SO 2 and H 2 S. The photochemistry of these gases in the atmosphere yields elemental sulfur, sulfur particles, sulfuric acid, and oceanic sulfate. Scheme 1 illustrates the chemical processes suggested to be important in the photochemical oxidation of volcanic sulfur species in the early atmosphere of Earth.The S 0 aerosols are not only involved in the Archean life, but are also implicated in other environments (1,(11)(12)(13)(14)(15)(16)(17)(18)(19). For example, polysulfur (S x = S 2→8 ) aerosols are thought to exist in clouds of Venus and their role as the unknown UV absorber in its lower atmosphere has been discussed in the literature (14). The S 8 particles are also observed in the marine troposphere (15). Finally, the role of S 8 aerosols in explaining the early climate of Mars atmosphere has also been debated (16).Despite being of broad appeal, the formation mechanism of S 0 aerosols remains an open question. The photolysis of SO 2 and SO by UV light with λ < 220 nm has generally been invoked to explain the mass-independent fractionation (MIF) of isotope effects in the sulfur cycle during the Archean (2-9). However, the contribution of other mass-independent chemical reactions to this geologic record remains unclear. To fully understand the sulfur cycle, it is necessary to identify all sources of sulfur compounds and account for all species which can occur in the atmosphere.Results and Discussion SO n (n = 1, 2, 3) + nH 2 S Potential...

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“…catalytic schemes are indicated by the Greek letters in circles. α = Schemes (E), (G1), (G2), (G3), and (n) in this chapter and the heterogeneous oxidation of cO on aerosols [Mills et al, 2006]. β = cO + O 2 (c) scheme Mills et al, 2006].…”

Section: Contemporaneous Reviews Of Atmospheric Compositionmentioning

confidence: 99%

“…α = Schemes (E), (G1), (G2), (G3), and (n) in this chapter and the heterogeneous oxidation of cO on aerosols [Mills et al, 2006]. β = cO + O 2 (c) scheme Mills et al, 2006]. χ = Scheme (h) in this chapter and Schemes XIIab in Yung and DeMore [1982].…”

Section: Contemporaneous Reviews Of Atmospheric Compositionmentioning

confidence: 99%

“…The clouds define a transition region that reflects the competition between the middle atmosphere, dominated by photochemistry, and the lower atmosphere, dominated by thermochemistry . This region is also where lightning could occur and produce nO [Krasnopolsky, 2006a] and where heterogeneous chemistry on aerosol and cloud particle surfaces may be important [Mills et al, 2006]. Finally, the lowest scale height of the atmosphere is the region where surfaceatmosphere interactions may dominate.…”

Section: Introductionmentioning

confidence: 99%

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