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TOPIC: Titan


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Titan
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This image of Titan was taken on May 21, 2011 when the cassini spacepeobe was approximately 2,309,387 kilometers away
The image was taken using the CL1 and CL2 filters.
Enceladus and Saturn rings can be seen in the background.

TITAN2B.jpg
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(67kb, 1024 1024)
Credit: NASA/JPL/Space Science Institute



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This image of Titan was taken on May 21, 2011 when the cassini spacepeobe was approximately 2,326,101 kilometers away
The image was taken using the CL1 and GRN filters.
Enceladus and Saturn rings can be seen in the background.

TITAN1B.jpg
Expand (56kb, 1024 768)
Credit: NASA/JPL/Space Science Institute



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Saturn moon's atmosphere forged by comet impacts

Titan is the only moon in the solar system with much atmosphere, and the origin of its nitrogen-rich air is a puzzle. There are several theories: volcanic activity may have belched it out, or sunlight may have broken up a primordial atmosphere's ammonia molecules. But these suggestions assume that the young Titan was a warm world, whereas measurements by the Cassini spacecraft imply that Titan has always been fairly cold.
The latest idea is that the atmosphere was created 3.9 billion years ago in a period known as the late heavy bombardment, when comets swarmed through the solar system.

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Title: Replacement and late formation of atmospheric N2 on undifferentiated Titan by impacts
Authors: Yasuhito Sekine, Hidenori Genda, Seiji Sugita, Toshihiko Kadono & Takafumi Matsui

Saturn's moon Titan has attracted much attention because of its massive nitrogen atmosphere, but the origin of this atmosphere is largely unknown. Massive secondary atmospheres on planets and satellites usually form only after a substantial differentiation of the body's interior and chemical reactions during accretion, yet Titan's interior has been found to be incompletely differentiated. Here we propose that Titan's nitrogen atmosphere formed after accretion, by the conversion from ammonia that was already present on Titan during the period of late heavy bombardment about four billion years ago. Our laser-gun experiments show that ammonia ice converts to N2 very efficiently during impacts. Numerical calculations based on our experimental results indicate that Titan would acquire sufficient N2 to sustain the current atmosphere and that most of the atmosphere present before the late heavy bombardment would have been replaced by impact-induced N2. Our scenario is capable of generating a N2-rich atmosphere with little primordial Ar on undifferentiated Titan. If this mechanism generated Titan's atmosphere, its N2 was derived from a source in the solar nebula different from that for Earth, and the origins of N2 on Titan and Triton may be fundamentally different from the origin of N2 on Pluto.
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Title: Ionisation processes in the atmosphere of Titan. III. Ionisation by high-Z nuclei cosmic rays

DOI: 10.1051/0004-6361/201015675



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Title: Titan's Obliquity as evidence for a subsurface ocean?
Authors: Rose-Marie Baland, Tim Van Hoolst, Marie Yseboodt, Ozgur Karatekin

On the basis of gravity and radar observations with the Cassini spacecraft, the moment of inertia of Titan and the orientation of Titan's rotation axis have been estimated in recent studies. According to the observed orientation, Titan is close to the Cassini state. However, the observed obliquity is inconsistent with the estimate of the moment of inertia for an entirely solid Titan occupying the Cassini state. We propose a new Cassini state model for Titan in which we assume the presence of a liquid water ocean beneath an ice shell and consider the gravitational and pressure torques arising between the different layers of the satellite. With the new model, we find a closer agreement between the moment of inertia and the rotation state than for the solid case, strengthening the possibility that Titan has a subsurface ocean.

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Titan's lakes
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Title: Titan's lakes chemical composition: sources of uncertainties and variability
Authors: D. Cordiera, O. Mousisd, J. I. Luninee, S. Lebonnoisg, P. Rannouh, P. Lavvasf, L.Q. Loboi, A.G.M. Ferreirai

Between 2004 and 2007 the instruments of the CASSINI spacecraft discovered hydrocarbon lakes in the polar regions of Titan. We have developed a lake-atmosphere equilibrium model allowing the determination of the chemical composition of these liquid areas. The model is based on uncertain thermodynamic data and precipitation rates of organic species predicted to be present in the lakes and seas that are subject to spatial and temporal variations. Here we explore and discuss the influence of these uncertainties and variations. The errors and uncertainties relevant to thermodynamic data are simulated via Monte-Carlo simulations. Global Circulation Models (GCM) are also employed in order to investigate the possibility of chemical asymmetry between the south and the north poles, due to differences in precipitation rates. We find that mole fractions of compounds in the liquid phase have a high sensitivity to thermodynamic data used as inputs, in particular molar volumes and enthalpies of vaporisation. When we combine all considered uncertainties, the ranges of obtained mole fractions are rather large (up to ~8500%) but the distributions of values are narrow. The relative standard deviations remain between 10% and ~300% depending on the compound considered. Compared to other sources of uncertainties and variability, deviation caused by surface pressure variations are clearly negligible, remaining of the order of a few percent up to ~20%. Moreover no significant difference is found between the composition of lakes located in north and south poles. Because the theory of regular solutions employed here is sensitive to thermodynamic data and is not suitable for polar molecules such as HCN and CH3CN, our work strongly underlines the need for experimental simulations and the improvement of Titan's atmospheric models.

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RE: Titan
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New Theory: Titan Shaped By Weather, Not Ice Volcanoes

Have the surface and belly of Saturn's smog-shrouded moon, Titan, recently simmered like a chilly, bubbling cauldron with ice volcanoes, or has this distant moon gone cold? In a newly published analysis, a pair of NASA scientists analysing data collected by the Cassini spacecraft suggest Titan may be much less geologically active than some scientists have thought.
In the paper, published in the April 2011 edition of the journal Icarus, scientists conclude Titan's interior may be cool and dormant and incapable of causing active ice volcanoes.

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On this day in 1655, Titan, Saturn's largest moon, was discovered by Christiaan Huygens.


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Cassini Sees Seasonal Rains Transform Titan's Surface

As spring continues to unfold at Saturn, April showers on the planet's largest moon, Titan, have brought methane rain to its equatorial deserts, as revealed in images captured by NASA's Cassini spacecraft. This is the first time scientists have obtained current evidence of rain soaking Titan's surface at low latitudes.
Extensive rain from large cloud systems, spotted by Cassini's cameras in late 2010, has apparently darkened the surface of the moon. The best explanation is these areas remained wet after methane rainstorms. The observations released today in the journal Science, combined with earlier results in Geophysical Research Letters last month, show the weather systems of Titan's thick atmosphere and the changes wrought on its surface are affected by the changing seasons.

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