Evidence for layered methane clouds in Titan’s troposphere

Wang, Chia C.; Atreya, S. K.; Signorell, Ruth

doi:10.1016/j.icarus.2009.11.022

Cited by 16 publications

(26 citation statements)

References 19 publications

(36 reference statements)

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“…Using a low-temperature aerosol cell of Firanescu et al (2006), Wang et al (2010) carried out experiments at conditions similar to Titan's troposphere at about 13-19 km (temperature of 78-82 K, pressure of 540-760 hPa, and methane mixing ratio of 0.02-0.03). The cell was initially filled with N 2 and CH 4 gases at the above proportion.…”

Section: Model Validationmentioning

confidence: 99%

“…The mixing process typically takes the form of exponential decay in temperature. Yet, the characteristic time constant of mixing between the plume and surrounding air and that of conduction to the wall in Wang et al (2010) are not available to us. Using the baseline experiment, we constrain the mixing time constant to be 4 s and conduction time to be 100 s (see Figure 2).…”

Section: Model Validationmentioning

confidence: 99%

“…Using the baseline experiment, we constrain the mixing time constant to be 4 s and conduction time to be 100 s (see Figure 2). In the chamber experiment (Wang et al 2010), the gas is injected from a steel cylinder in which the pressure is 3 bars and the temperature is at room temperature. The plume cools down during injection primarily due to expansion and also conduction to the wall of the injection nozzle.…”

Section: Model Validationmentioning

confidence: 99%

“…However, the microphysical schemes of these models tend to ignore the nucleation process and start the simulation with a prescribed distribution of cloud condensation nuclei, which are assumed to be either ethane ice precipitating from the lower stratosphere (Samuelson & Mayo 1997), tholin from the middle and upper atmospheres (Rannou et al 2004, or a combination of both (Barth and Toon 2003Barth & Rafkin 2007). No relevant laboratory validation was done until Wang et al (2010), who reported the formation of methane/nitrogen droplets in an aerosol chamber under a condition similar to that of Titan. This laboratory experiment provides a unique constraint for convective methane/nitrogen cloud formation in the troposphere.…”

Section: Introductionmentioning

confidence: 99%

“…This study attempts to understand cloud formation on Titan using a multi-component microphysical model, which is validated by the laboratory result of Wang et al (2010). Then we apply the model to simulate Titan's methane cloud formation.…”

Section: Introductionmentioning

confidence: 99%

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Methane-Nitrogen Binary Nucleation: A New Microphysical Mechanism for Cloud Formation in Titan's Atmosphere

Tsai

Liang

Chen

2012

ApJ

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It is known that clouds are present in the troposphere of Titan; however, their formation mechanism, particle size, and chemical composition remain poorly understood. In this study, a two-component (CH 4 and N 2 ) bin-microphysics model is developed and applied to simulate cloud formation in the troposphere of Titan. A new process, binary nucleation of particles from CH 4 and N 2 gases, is considered. The model is validated and calibrated by recent laboratory experiments that synthesize particle formation in Titan-like environments. Our model simulations show that cloud layers can be formed at about 20 km with a particle size ranging from one to several hundred μm and number concentration 10 −2 to over 100 cm −3 depending on the strength of the vertical updraft. The particles are formed by binary nucleation and grow via the condensation of both CH 4 and N 2 gases, with their N 2 mole fraction varying from <10% in the nucleation stage to >30% in the condensation growth stage. The locally occurring CH 4 -N 2 binary nucleation mechanism is strong and could potentially be more important than the falling condensation nuclei mechanism assumed in many current models.

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Section: Model Validationmentioning

confidence: 99%

Section: Model Validationmentioning

confidence: 99%

Section: Model Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Methane-Nitrogen Binary Nucleation: A New Microphysical Mechanism for Cloud Formation in Titan's Atmosphere

Tsai

Liang

Chen

2012

ApJ

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Titan's atmosphere and climate

2017

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Titan is the only moon with a substantial atmosphere, the only other thick N2 atmosphere besides Earth's, the site of extraordinarily complex atmospheric chemistry that far surpasses any other solar system atmosphere, and the only other solar system body with stable liquid currently on its surface. The connection between Titan's surface and atmosphere is also unique in our solar system; atmospheric chemistry produces materials that are deposited on the surface and subsequently altered by surface‐atmosphere interactions such as aeolian and fluvial processes resulting in the formation of extensive dune fields and expansive lakes and seas. Titan's atmosphere is favorable for organic haze formation, which combined with the presence of some oxygen‐bearing molecules indicates that Titan's atmosphere may produce molecules of prebiotic interest. The combination of organics and liquid, in the form of water in a subsurface ocean and methane/ethane in the surface lakes and seas, means that Titan may be the ideal place in the solar system to test ideas about habitability, prebiotic chemistry, and the ubiquity and diversity of life in the universe. The Cassini‐Huygens mission to the Saturn system has provided a wealth of new information allowing for study of Titan as a complex system. Here I review our current understanding of Titan's atmosphere and climate forged from the powerful combination of Earth‐based observations, remote sensing and in situ spacecraft measurements, laboratory experiments, and models. I conclude with some of our remaining unanswered questions as the incredible era of exploration with Cassini‐Huygens comes to an end.

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