UV spectroscopy of Titan's atmosphere, planetary organic chemistry and prebiological synthesis

Courtin, R.; Wagener, R.; McKay, Christopher P.; Caldwell, John; K-H, Fricke; Raulin, F.; Bruston, P.

doi:10.1016/0019-1035(91)90067-4

Cited by 57 publications

(35 citation statements)

References 40 publications

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“…We take the electron and ion densities listed in Borucki et al (1987), the temperature profile of Lellouch (1990), and the UV profile of Courtin et al (1991) in order to calculate these rates. To obtain f (Z ), we successively apply the equations…”

Section: The Charge Probability Functionmentioning

confidence: 99%

“…We utilize the charge balance study of Bakes and Tielens (1994), which balances the positively charged ion and electron collision rate with the UV pumped photoelectric ejection rate for submicrometer and molecular aerosols. We combine this with the seminal study by Borucki et al (1987), which defines electron and positive ion mass and density, and the study by Courtin et al (1991), which quantifies the UV field with altitude for the Titan haze.…”

Section: Introductionmentioning

confidence: 98%

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Photoelectric Charging of Submicron Aerosols and Macromolecules in the Titan Haze

Bakes

McKay

Bauschlicher

2002

Icarus

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Section: The Charge Probability Functionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Photoelectric Charging of Submicron Aerosols and Macromolecules in the Titan Haze

Bakes

McKay

Bauschlicher

2002

Icarus

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“…It had been recognized earlier that a bimodal distribution was necessary to explain the optical properties of Titan's atmosphere (Tomasko and Smith, 1982;Courtin et al, 1991;Toon et al, 1992). Fractal models of a haze composed of monomers in the upper altitudes and fractals in the lower layer e ectively respond like a bimodal distribution of particles.…”

Section: Fractal Models and Scattering Properties Of The Hazementioning

confidence: 99%

Physical properties of the organic aerosols and clouds on Titan

McKay¹,

Coustenis²,

Samuelson³

et al. 2001

Planetary and Space Science

158

117

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Titan's haze is optically thick in the visible, with an optical depth at 0:5 m of about three. The haze varies with latitude in a seasonal cycle and has a detached upper layer. Microphysical models, photochemical models, and laboratory simulations all imply that the production rate of the haze is in the range of 0:5-2 × 10 −14 g cm −2 s −1 . Given the rate of sedimentation, the total mass loading is about 250 mg m −2 . The transparency of the haze is high for wavelengths above 1 m because the haze material becomes almost purely scattering and the optical depth decreases with increasing wavelength. The particles in the main haze deck are probably fractal in structure with an equivalent volume radius of 0:2 m. The haze material is organic and, if similar to laboratory tholin, has a C=N ratio in the range of 2-4 and a C=H ratio of about unity. The haze signiÿcantly a ects the thermal balance of Titan, causing an antigreenhouse e ect that cools the surface by 9 K. Titan's faintly banded appearance suggests strong zonal winds in the lower stratosphere. Condensate clouds of ethane or methane, if present, are thin, patchy, or transient. Stratospheric clouds of condensed nitriles and (possibly) hydrocarbons appear to be associated with, though not contained entirely in, the polar shadow, suggesting abundances may vary with the season. Precipitating condensate particles from the stratosphere probably act as nucleating centers for the formation and rapid growth of methane ice particles in the troposphere, where the gas phase appears to be highly supersaturated. Once formed, fallout times for these hailstones are ∼ 2 h or less. Melting, and possible subsequent fragmentation of methane raindrops should occur at ∼ 12 km and below. Almost complete evaporation should occur just above the surface. A thin residue of ethane-enriched fog particles would then slowly settle to the surface, steadily modifying an existing surface or subsurface residue of liquid hydrocarbons. The optical properties of the haze in the 1 to 3 m spectral region and the implications for the visibility of the surface are probably the most pressing current research questions. Other key questions include the nature of the high altitude detached haze layer, altitude and seasonal changes in composition of the haze, the role of haze particles as condensation nuclei for clouds, and the nature of any condensate clouds. Published by Elsevier Science Ltd.

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“…The most likely mechanism involves meridional circulation, either directly by transporting haze particles from one hemisphere to another (e.g., Hutzell et al 1996) or by modifying the particle number density or optical properties by influencing condensation (Courtin et al 1991) and/or removal by rainout (L97). All these latter effects may play a role, but the changes we have observed are at least conceptually consistent with the haze transport mechanism, which has already been indicated by measurements of Titan's shadow: Karkoschka and Lorenz (1997) determined that the haze north of 5…”

Section: Mechanisms and Physical Modelsmentioning

confidence: 99%

Seasonal Change on Titan Observed with the Hubble Space Telescope WFPC-2

Lorenz

Lemmon

Smith

et al. 1999

Icarus

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Recent observations with the Wide-Field Planetary Camera (WFPC-2) on the Hubble Space Telescope (HST) show an unexpectedly rapid change in the atmospheric albedo contrast between the north and south hemispheres. In 1994 at blue wavelengths, the north was around 15% brighter than the south, and was expected to fall to about 12% in 1997, but has dropped to only 6% brighter. At some other wavelengths, the contrast has reversed, which was not expected until 2002. The interhemispheric contrast has a time dependence that varies with wavelength; contrast changes in blue lag behind changes in violet and yellow/red. The rapid change and the phase variation with wavelength are consistent with ground-based photometry. A physical model of the transport of high-altitude dark haze by meridional winds is a better description of Titan's behavior than the simple sinusoidal models used to date. Investigation with a radiative transfer model indicates that haze number density changes above 160-km altitude are compatible with the observed hemispheric albedo difference, and require particles >0.1 µm in radius.

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UV spectroscopy of Titan's atmosphere, planetary organic chemistry and prebiological synthesis

Cited by 57 publications

References 40 publications

Photoelectric Charging of Submicron Aerosols and Macromolecules in the Titan Haze

Photoelectric Charging of Submicron Aerosols and Macromolecules in the Titan Haze

Physical properties of the organic aerosols and clouds on Titan

Seasonal Change on Titan Observed with the Hubble Space Telescope WFPC-2

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