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4 - Gas Giants
- Edited by Boris Galperin, University of South Florida, Peter L. Read, University of Oxford
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- Zonal Jets
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- 26 February 2019
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- 28 February 2019, pp 72-103
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2 - Terrestrial Atmospheres
- Edited by Boris Galperin, University of South Florida, Peter L. Read, University of Oxford
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- Zonal Jets
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- 26 February 2019
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- 28 February 2019, pp 9-45
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13 - The Great Saturn Storm of 2010–2011
- Edited by Kevin H. Baines, University of Wisconsin, Madison, F. Michael Flasar, NASA-Goddard Space Flight Center, Norbert Krupp, Tom Stallard, University of Leicester
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- Book:
- Saturn in the 21st Century
- Published online:
- 13 December 2018
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- 06 December 2018, pp 377-416
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Summary
In December 2010, a major storm erupted in Saturn’s northern hemisphere near 37° planetographic latitude. This rather surprising event, occurring at an unexpected latitude and time, is the sixth “Great White Spot” (GWS) storm observed over the last century and a half. Such GWS events are extraordinary, planetary-scale atmospheric phenomena that dramatically change the typically bland appearance of the planet. Occurring while the Cassini mission was on orbit at Saturn, the Great Storm of 2010–2011 was well suited for intense scrutiny by the suite of sophisticated instruments onboard the Cassini spacecraft as well by modern instrumentation on ground-based telescopes and onboard the Hubble Space Telescope. This GWS erupted on 5 December close to the peak of a westward jet and generated a major dynamical disturbance that affected the whole latitude band from 25° to 48°N. At the upper cloud level, following the rapid growth of the bright outbreak spot, a blunt aerodynamic-shaped head formed due to interaction of the spot with the westward zonal jet, with the winds reaching velocities of 160 m s−1 along the periphery of the arc. Eastward of the head, the disturbance progressed in the following months forming a turbulent wake or tail with growing vortices, one of them a major enduring anticyclone (called AV) with a size of ~11,000 km. Lightning events were prominent and detected as outbursts and flashes at the head and along the disturbance at both optical and radio wavelengths. The activity of the head ceased after about seven months when AV reached it, leaving the cloud structure and ambient winds perturbed. The tops of the optically dense clouds of the head reached the 300-mbar altitude level (~50 km below tropopause), where a mixture of ices was detected, including (1) a component of water ice lofted over 200 km altitude from its 10-bar condensation level, (2) ammonia ice as the predominant component and (3) a component that might be ammonium hydrogen sulfide ice. The energetics of the frequency and power of lightning, as well as the estimated power generated by the latent heat released in the water-based convection to create the observed dynamical three-dimensional flows, both indicate that the power released for much of the 7-month lifetime of the storm (~1017 Watts) was a significant fraction of Saturn’s total radiated power (~2.2 1017 W). A post-storm depletion of ammonia vapour was also measured in the upper troposphere. The effects of the storm propagated into the stratosphere, forming two warm air masses at the ~0.5- to 5-mbar pressure level altitude that later merged into a so-called “beacon” because of its 80 K temperature excess relative to its surroundings. Related to the stratospheric disturbance, hydrocarbon composition excesses were found, in particular for ethylene (C2H4), in the high stratosphere at the ~0.1- to 0.5-mbar altitude level. Numerical models of the storm dynamics explain the major observed features that essentially result from two processes: (1) a huge and sustained, moist, convective storm at the water clouds (altitude level 10–12 bar, or ~250–275 km below the tropopause) and (2) the interaction of the updraft columns with the ambient winds that generates the turbulent wake consisting of vortices and waves. Model simulations of the GWS require a low vertical shear of the zonal winds and low static stability across the weather layer where the disturbance develops. Its upward propagation into the stratosphere involves Rossby waves and their breaking and energy deposition to form the beacon and induce chemical changes.
The decades-long interval between storms is probably related to the insolation cycle and the long radiative time constant of Saturn’s atmosphere, and several theories for temporarily storing energy have been proposed.
12 - Saturn’s Polar Atmosphere
- Edited by Kevin H. Baines, University of Wisconsin, Madison, F. Michael Flasar, NASA-Goddard Space Flight Center, Norbert Krupp, Tom Stallard, University of Leicester
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- Book:
- Saturn in the 21st Century
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- 13 December 2018
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- 06 December 2018, pp 337-376
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Summary
This chapter reviews the state of our knowledge about Saturn’s polar atmosphere that has been revealed through Earth- and space-based observation as well as theoretical and numerical modeling. In particular, the Cassini mission to Saturn, which has been in orbit around the ringed planet since 2004, has revolutionized our understanding of the planet. The current review updates a previous review by Del Genio et al. (2009), written after Cassini’s primary mission phase that ended in 2008, by focusing on the north polar region of Saturn and comparing it to the southern high latitudes. Two prominent features in the northern high latitudes are the northern hexagon and the north polar vortex; we extensively review observational and theoretical investigations to date of both features. We also review the seasonal evolution of the polar regions using the observational data accumulated during the Cassini mission since 2004 (shortly after the northern winter solstice in 2002), through the equinox in 2009, and approaching the next solstice in 2017. We conclude the current review by listing unanswered questions and describing the observations of the polar regions planned for the Grand Finale phase of the Cassini mission between 2016 and 2017.
7 - The perspective: a panorama of the Solar System
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- By Agustín Sánchez-Lavega, Dpto. Física Aplicada, Escuela Superior de Ingenieros, Universidad del Pais Vasco, Bilbao, Spain
- Edited by Hans Deeg, Instituto de Astrofísica de Canarias, Tenerife, Juan Antonio Belmonte, Instituto de Astrofísica de Canarias, Tenerife, Antonio Aparicio, Instituto de Astrofísica de Canarias, Tenerife
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- Extrasolar Planets
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- 10 August 2009
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- 18 October 2007, pp 178-216
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Summary
We review the basic properties of the bodies constituting the Solar System as a reference for understanding the properties of the increasing number of extrasolar planets and planetary systems discovered.
Introduction
Space exploration has allowed us over the last 40 years to visit most of the different types of bodies that constitute the Solar System (which we define as comprising all those objects under the gravitational influence of the Sun). We have reached all the planets, except Pluto, and consequently most of their satellites, by means of fly-bys, orbital injection (Venus, Mars, Jupiter and Saturn), landing (the Moon, Venus, Mars and Titan) and probe sounding (Jupiter). We have sent vehicles to asteroids and comets (fly-bys), with impacts on the asteroid Eros and Comet Temple 1, and we have samples returned from the Moon, and from meteorites coming from Mars and the asteroid belt. All this has provided a large quantity of information, so the reader can find a large number of books dealing with the Solar System as a whole, or reviewing the properties of each individual constituent (Gehrels 1976, 1979; Burns 1977; Wilkening 1982; Morrison 1982; Hunten et al. 1983; Gehrels & Matthews 1984; Greenberg & Brahic 1984; Burns & Matthews 1986; Chamberlain & Hunten 1987; Kerridge & Matthews 1988; Vilas, Chapman & Matthews 1988; Atreya, Pollack & Matthews 1989; Binzel, Gehrels & Matthews 1989; Kieffer et al. 1992; Cruikshank 1995; Lewis 1997; Bougher, Hunten & Phillips 1997; Shirley & Fairbridge 1997; Beatty, Collins Petersen & Chaikin 1999; Weissman, McFadden & Johnson 1999; de Pater & Lissauer 2001; Cole &Woolfson 2002; Bertotti, Farinella & Vokrouhlicky 2003; McBride & Gilmour 2003; Encrenaz et al. 2004; Bagenal, Dowling & McKinnon 2004).