* Astronomy

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.


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Credit: NASA/JPL/Space Science Institute

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to sustain the current atmosphere and that most of the atmosphere present before the late heavy bombardment would have been replaced by impact-induced N2.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: 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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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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