Rain and hail can reach the surface of Titan

Graves, S. D.; McKay, Christopher P.; Griffith, C. A.; Ferri, F.; Fulchignoni, M.

doi:10.1016/j.pss.2007.11.001

Cited by 84 publications

(72 citation statements)

References 27 publications

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“…The latent heat is smaller than that for pure methane to approximately take its reduction for a binary methane-nitrogen mixture into account 33 . Thermodynamic effects of ethane on the mixture 35 are not explicitly taken into account.…”

mentioning

confidence: 99%

Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle

Schneider

Graves

Schaller³

et al. 2012

Nature

125

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Supplementary InformationOur GCM is based on the Flexible Modeling System of the Geophysical Fluid Dynamics Laboratory (http://fms.gfdl.noaa.gov). It is similar to standard models for Earth's atmosphere, but with Titan's radius, planetary rotation rate, material properties, and seasonally varying insolation, and with a methane cycle instead of a water cycle. The GCM has similarities to the models in refs. 16, 17, but unlike those, it is 3D and eddy-resolving and has a different representation of radiative transfer and surface processes.Resolution. The GCM solves the hydrostatic primitive equations in vorticity-divergence form, using the spectral transform method in the horizontal and finite differences in the vertical 31 . The horizontal spectral resolution is T21 (corresponding to about 5 • × 5 • resolution of the transform grid). The vertical coordinate is σ = p/p s (pressure p normalized by surface pressure p s ); it is discretized with 18 unequally spaced levels 32 . The top of the model is at σ = 0; the uppermost full level has a mean pressure of 15 mbar (altitude ∼90 km). The time-stepping scheme is a semiimplicit leapfrog scheme (timestep 1600 s).

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mentioning

confidence: 99%

Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle

Schneider

Graves

Schaller³

et al. 2012

Nature

125

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mentioning

confidence: 99%

“…Tenuous tropical clouds predicted by GCM models to result from temperature variations (Rannou et al 2006) create methane cirrus of radii !0.9 mm and thus virga rather than rainfall (Barth & Toon 2004;Graves et al 2008). Microphysical models of weakly convective tropical clouds indicate the production of mainly 0.8-2.0 mm size drops (Barth & Toon 2004), too small to survive evaporation (Graves et al 2008), with few larger surface-prone particles (Barth & Rafkin 2007). Titan's slow average evaporation rate of ∼5 mm yr also argues against Ϫ1 recent heavy rainfall, since 5 mm of drizzle every 12 months, smaller than previous estimates (Rannou et al 2006;Tokano et al 2006b;Barth & Rafkin 2007), would sustain a wet surface.…”

mentioning

confidence: 99%

Titan's Tropical Storms in an Evolving Atmosphere

Griffith

McKay

Ferri

2008

ApJ

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The Huygens probe landed in a damp lake bed fed by fluvial channels, indicative of past rainfall. Such washes, interspersed with vast dunes, are typical of Titan's tropical landscape. Yet, Cassini-Huygens measurements reveal a highly stable tropical atmosphere devoid of deep convective storms, and the formation of washes in dune fields is not understood. Here we examine the effects of seasonal variations in humidity, surface heating, and dynamical forcing on the stability of Titan's troposphere. We find that during the probe landing, the middle troposphere was weakly unstable to convection, consistent with the tenuous cloud detected at 21 km. Yet the tropical atmosphere, at any season, is too stable to produce deep convective storms. Convection in the tropics remains weak and confined to altitudes below ∼30 km, unless the humidity is increased below 9 km altitude. Solar heating is insufficient to significantly humidify the tropical atmosphere. The large polar lakes are seasonably stable, and the methane column abundance measured by Huygens typical of the tropical atmosphere. Our study indicates the presence of distinct polar and equatorial climates. It also suggests that fluvial features in the tropics do not result from recent seasonal rainstorms, and thereby supports other origins such as geological seepage, cryovolcanism, or a wetter climate in the past.

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“…ISS observations of a storm-wetted surface [159] have empirically confirmed theoretical predictions that rain reaches Titan's surface [41]. The origin of the observation in question was a very widespread storm event raining onto equatorial bright terrain.…”

Section: Task 22c Ascertain Where When How Often and How Intenselmentioning

confidence: 68%

“…Microphysical modeling suggests that raindrops may reach the surface when evaporative cooling is taken into account [41]. The surface of Titan shows areas with drainage networks having various morphologies [8,26,38,81].…”

Section: Task 22b Constrain Global Circulation and Cloud Formation Bmentioning

confidence: 99%

AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

et al. 2011

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We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVI-ATR). With independent delivery and direct-to-Earth communications, AVI-ATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments-2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector-AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earthyear nominal mission. We propose a novel 'gravity battery' climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead

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Rain and hail can reach the surface of Titan

Cited by 84 publications

References 27 publications

Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle

Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle

Titan's Tropical Storms in an Evolving Atmosphere

AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

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