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TOPIC: Titan
Blobrana


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RE: Titan
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This mosaic of a large dark region several hundred kilometres in diameter on the moon Titan, was created by the  Cassini spaceprobe's synthetic-aperture radar (SAR).
The mosaic, built from images from the T39, T55, T57, T58, and T59 Titan flybys (between December 2007 and July 2009),  is centred near 82 degrees south, 205 degrees west, near the south pole.

titaSPregionb.jpg
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Credit: NASA/JPL

The mosaic shows that the large dark region with characteristics of a shoreline (top), with channels (right) that flow into it, is similar to potential lakes already observed on Titan, but differs from them as it does not produce a dark radar signature as those lakes.

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Blobrana


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Could there be life on Titan?
Scientists have discovered that despite its alien environment Saturn's moon Titan looks remarkably like Earth - complete with methane rivers.
Scientists have now mapped a third of the moon's surface using radar, which was able to get through the thick atmosphere and see mountain ranges, lakes and what may be volcanoes.

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Blobrana


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Titan moon resembles Earth
Saturn's smog-ridden moon Titan bears a striking resemblance to Earth despite its alien environment, a study has revealed.
Scientists have now mapped a third of Titan's surface using radar to pierce the planet-sized moon's thick atmosphere.
The probe has revealed mountain ranges, dunes, numerous lakes and suspected volcanoes.
Just as on Earth, the weather on Titan appears to have erased most evidence of meteorite craters.

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Blobrana


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The IAU has approved of the term planitia to be used for the naming of plains on Titan. All the plains will be called after planets from the Dune science fiction novels, by American author Frank Herbert.

Chusukb.jpg
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Credit: NASA/JPL

The 125-km-wide feature on Titan, located at 5.0S, 23.5W, has been named Chusuk Planitia. The feature is named after the 'Music Planet' Chusuk, the fourth planet of Theta Shalish, from the Dune series.

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Blobrana


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Titan's atmospheric methane
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Title: A primordial origin for the atmospheric methane of Saturn's moon Titan
Authors: Olivier Mousis, Jonathan I. Lunine, Matthew Pasek, Daniel Cordier, J. Hunter Waite Jr., Kathleen E. Mandt, William S. Lewis, Mai-Julie Nguyen

The origin of Titan's atmospheric methane is a key issue for understanding the origin of the Saturnian satellite system. It has been proposed that serpentinisation reactions in Titan's interior could lead to the formation of the observed methane. Meanwhile, alternative scenarios suggest that methane was incorporated in Titan's planetesimals before its formation. Here, we point out that serpentinisation reactions in Titan's interior are not able to reproduce the deuterium over hydrogen (D/H) ratio observed at present in methane in its atmosphere, and would require a maximum D/H ratio in Titan's water ice 30% lower than the value likely acquired by the satellite during its formation, based on Cassini observations at Enceladus. Alternatively, production of methane in Titan's interior via radiolytic reactions with water can be envisaged but the associated production rates remain uncertain. On the other hand, a mechanism that easily explains the presence of large amounts of methane trapped in Titan in a way consistent with its measured atmospheric D/H ratio is its direct capture in the satellite's planetesimals at the time of their formation in the solar nebula. In this case, the mass of methane trapped in Titan's interior can be up to 1,300 times the current mass of atmospheric methane.

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Blobrana


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The Cassini spaceprobe imaged the north pole of Titan, using the spacecrafts wide-angle camera on the 6th June, 2009, when it was approximately 194,000 kilometres from the moon.

titapole0809b.jpg
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Credit: NASA/JPL/Space Science Institute

The natural colour image shows the night/day terminator, and is centred at 49 degrees north latitude, 243 degrees west longitude, with the north pole rotated about 23 degrees to the left.
Image scale is 11 kilometres per pixel.

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Blobrana


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This Titan Radar Mapper image of a 100-kilometre-wide basin in the south polar region of Saturn's moon Titan was taken by the  Cassini spaceprobe on the 22nd June, 2009.
The image is centred near 76.5 degrees south latitude, 213 degrees west longitude, and covers an area of 190 x 140 kilometres.

titaBasinb.gif
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Credit: NASA/JPL

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Blobrana


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Titan's atmosphere
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Title: Impact of aerosols present in Titan's atmosphere on the CASSINI radar experiment
Authors: S. Rodriguez (AIM, L3ab), P. Paillou (L3AB), M. Dobrijevic (L3AB, Oasu), G. Ruffié (LPIOM), P. Coll (LISA), J. M. Bernard (LISA), P. Encrenaz (OP, Lerma)

Simulations of Titan's atmospheric transmission and surface reflectivity have been developed in order to estimate how Titan's atmosphere and surface properties could affect performances of the Cassini radar experiment. In this paper we present a selection of models for Titan's haze, vertical rain distribution, and surface composition implemented in our simulations. We collected dielectric constant values for the Cassini radar wavelength (~ 2.2 cm) for materials of interest for Titan: liquid methane, liquid mixture of methane-ethane, water ice and light hydrocarbon ices. Due to the lack of permittivity values for Titan's haze particles in the microwave range, we performed dielectric constant (\varepsilon_r) measurements around 2.2 cm on tholins synthesized in laboratory. We obtained a real part of \varepsilon_r in the range of 2-2.5 and a loss tangent between 10^{-3} and 5.10^{-2}. By combining aerosol distribution models (with hypothetical condensation at low altitudes) to surface models, we find the following results: (1) Aerosol-only atmospheres should cause no loss and are essentially transparent for Cassini radar, as expected by former analysis. (2) However, if clouds are present, some atmospheric models generate significant attenuation that can reach -50 dB, well below the sensitivity threshold of the receiver. In such cases, a 13.78 GHz radar would not be able to measure echoes coming from the surface. We thus warn about possible risks of misinterpretation if a 'wet atmosphere' is not taken into account. (3) Rough surface scattering leads to a typical response of ~ -17 dB. These results will have important implications on future Cassini radar data analysis.

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Blobrana


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Titan's Clouds
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Cassini Finds Titan's Clouds Hang on to Summer
Cloud chasers studying Saturn's moon Titan say its clouds form and move much like those on Earth, but in a much slower, more lingering fashion.
Their forecast for Titan's early autumn -- warm and wetter.
Scientists with NASA's Cassini mission have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. They found that the way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing -- clouds are still noticeable in the southern hemisphere while autumn is approaching.

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Titan clouds
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Cloud chasers studying Saturn's moon Titan say its clouds form and move much like those on Earth, but in a much slower, more lingering fashion. Their forecast for Titan's early autumn -- warm and wetter.

Scientists with NASA's Cassini mission have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. They found that the way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing -- clouds are still noticeable in the southern hemisphere while fall is approaching.

"Titan's clouds don't move with the seasons exactly as we expected," said Sebastien Rodriguez of the University of Paris Diderot, in collaboration with Cassini visual and infrared mapping spectrometer team members at the University of Nantes, France. "We see lots of clouds during the summer in the southern hemisphere, and this summer weather seems to last into the early fall. It looks like Indian summer on Earth, even if the mechanisms are radically different on Titan from those on Earth. Titan may then experience a warmer and wetter early autumn than forecasted by the models."

On Earth, abnormally warm, dry weather periods in late autumn occur when low-pressure systems are blocked in the winter hemisphere. By contrast, scientists think the sluggishness of temperature changes at the surface and low atmosphere on Titan may be responsible for its unexpected warm and wet, hence cloudy, late summer.

http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20090603/



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