Storms, polar deposits and the methane cycle in Titan's atmosphere

Griffith, C. A.

doi:10.1098/rsta.2008.0245

Cited by 22 publications

(8 citation statements)

References 73 publications

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“…Unexpectedly, elongated streaks of clouds exhibiting convective behavior and often extending over several hundred kilometers were observed consistently at mid-southern latitudes (~40°S-50°S) from early in the mission until late 2012 ( Figure 1; Griffith, 2009;Rodriguez et al, 2011;Turtle, Del Genio, et al, 2011), well after the southern autumnal equinox. Isolated clouds have also been observed at lower southern latitudes.…”

Section: Observed Seasonal Cloud Patterns and Comparison To Model Prementioning

confidence: 90%

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Titan's Meteorology Over the Cassini Mission: Evidence for Extensive Subsurface Methane Reservoirs

Turtle

Perry

Barbara

et al. 2018

Geophysical Research Letters

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Cassini observations of Titan's weather patterns over >13 years, almost half a Saturnian year, provide insight into seasonal circulation patterns and the methane cycle. The Imaging Science Subsystem and the Visual and Infrared Mapping Spectrometer documented cloud locations, characteristics, morphologies, and behavior. Clouds were generally more prevalent in the summer hemisphere, but there were surprises in locations and timing of activity: Southern clouds were common at midlatitudes, northern clouds initially appeared much sooner than model predictions, and north polar summer convective systems did not appear before the mission ended. Differences from expectations constrain atmospheric circulation models, revealing factors that best match observations, including the roles of surface and subsurface reservoirs. The preference for clouds at mid‐northern latitudes rather than near the pole is consistent with models that include widespread polar near‐surface methane reservoirs in addition to the lakes and seas, suggesting a broader subsurface methane table is accessible to the atmosphere.

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Section: Observed Seasonal Cloud Patterns and Comparison To Model Prementioning

confidence: 90%

“…Isolated clouds have also been observed at lower southern latitudes. Summer midlatitude cloud activity was simulated in GCMs once moist physics was incorporated (Mitchell et al, 2006;2009;Rannou et al, 2006).…”

Section: Observed Seasonal Cloud Patterns and Comparison To Model Prementioning

confidence: 99%

Titan's Meteorology Over the Cassini Mission: Evidence for Extensive Subsurface Methane Reservoirs

Turtle

Perry

Barbara

et al. 2018

Geophysical Research Letters

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“…CH 4 concentrations near the surface are ≈50,000 ppmv, decrease to ≈15,000 ppmv in Titan's stratosphere (above 32 km) (Niemann et al., 2005), and remain uniformly mixed at that up to altitudes near the homopause region ≈850–1,000 km where diffusive separation causes the relative fraction of methane to increase with altitude up to the exobase (Bell et al., 2014; Johnson et al., 2010; Yelle et al., 2008). The major barrier to transport is an atmospheric cold trap occasionally broken by deep convective clouds of CH 4 (Griffith, 2009).…”

Section: Escape At Solar System's Planets and Bodiesmentioning

confidence: 99%

Atmospheric Escape Processes and Planetary Atmospheric Evolution

et al. 2020

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The habitability of the surface of any planet is determined by a complex evolution of its interior, surface, and atmosphere. The electromagnetic and particle radiation of stars drive thermal, chemical, and physical alteration of planetary atmospheres, including escape. Many known extrasolar planets experience vastly different stellar environments than those in our solar system: It is crucial to understand the broad range of processes that lead to atmospheric escape and evolution under a wide range of conditions if we are to assess the habitability of worlds around other stars. One problem encountered between the planetary and the astrophysics communities is a lack of common language for describing escape processes. Each community has customary approximations that may be questioned by the other, such as the hypothesis of H‐dominated thermosphere for astrophysicists or the Sun‐like nature of the stars for planetary scientists. Since exoplanets are becoming one of the main targets for the detection of life, a common set of definitions and hypotheses are required. We review the different escape mechanisms proposed for the evolution of planetary and exoplanetary atmospheres. We propose a common definition for the different escape mechanisms, and we show the important parameters to take into account when evaluating the escape at a planet in time. We show that the paradigm of the magnetic field as an atmospheric shield should be changed and that recent work on the history of Xenon in Earth's atmosphere gives an elegant explanation to its enrichment in heavier isotopes: the so‐called Xenon paradox.

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“…There is a large amount of liquid-equivalent methane vapor-a 5-m ocean worth-in Titan's atmosphere. Energetic arguments suggest that only a very small fraction of this amount-7 cm-can be evaporated by the available radiative energy in a 7.4 Earth year Titan season [42]. On the other hand, clouds have now been observed at high-and mid-southern latitudes, near the equator, and near the north polar lakes.…”

Section: Task 21b Constrain the Methane Cycle By Measuring The Globamentioning

confidence: 91%

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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Storms, polar deposits and the methane cycle in Titan's atmosphere

Cited by 22 publications

References 73 publications

Titan's Meteorology Over the Cassini Mission: Evidence for Extensive Subsurface Methane Reservoirs

Titan's Meteorology Over the Cassini Mission: Evidence for Extensive Subsurface Methane Reservoirs

Atmospheric Escape Processes and Planetary Atmospheric Evolution

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

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