* Astronomy

Blobrana · L

RE: Titan

Blobrana · L

The best views of the hydrocarbon lakes and seas on Saturn's moon Titan taken by the Cassini spacecraft are being released today.

North polar region

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A new radar image comprised from seven Titan fly-bys over the last year and a half shows a north pole pitted with giant lakes and seas, at least one of them larger than Lake Superior in the USA, the largest freshwater lake on Earth. Approximately 60% of Titan's north polar region, above 60° north, has been mapped by Cassini's radar instrument. About 14% of the mapped region is covered by what scientists interpret as liquid hydrocarbon lakes.

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Blobrana · L

If space travellers ever visit Saturns largest moon, they will find a tropical world where temperatures plunge to minus 274 degrees Fahrenheit, methane rains from the sky and dunes of ice or tar cover the planets most arid regions. These conditions reflect a cold mirror image of Earths tropical and subtropical climates, according to scientists at the University.

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Image courtesy NASA/JPL/Space Science Institute

The above image shows the ground trace of the Titan-36 flyby on a mosaic of Titan's surface, for a period of 32 hours around closest approach. The colour of the trace indicates Cassini's altitude above the surface. Blue: > 100 000 km, green: < 100 000 km, light blue: < 50 000, yellow: < 10 000 km, orange: < 5000 km, red: < 2000 km. The point of closest approach is marked T36 (Cassini at 975 km altitude). Cassini approaches Titan over the equatorial region at 16 hours before closest approach (centre right in this image), and then continues to pass over Titan's southern hemisphere.

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Cassini Heads South on Next Titan Flyby
The Cassini spacecraft has been moving progressively over Titan's southern hemisphere and is getting ready for a Titan flyby on Oct. 2, 2007. During this flyby, Cassini's radar instrument will have a chance to image the surface.
This will be the radar instrument's southernmost flyby to date. The next few radar passes should bring the spacecraft closer to the south pole. Scientists will be on the hunt for lakes or seas to see if they are as prevalent here as they are at the north pole.

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Thirty-two days after Cassini's last flyby, the spacecraft revisits Titan for its thirty-seventh targeted encounter: Titan-36. The closest approach to the Saturnian moon occurs on Tuesday, 2 October, at 04:42:43 UT at an altitude of 975 kilometres above the surface and at a speed of 6.3 kilometres per second. The latitude at closest approach is 60° S and the encounter occurs on orbit number 50.
This encounter is set up with two manoeuvres: an Iapetus encounter cleanup manoeuvre on 17 September, and a Titan approach manoeuvre on 28 September. Titan-36 is the second in a series of outbound encounters that will last until the end of the prime mission (mid 2008), and occurs less than two days after closest approach to Saturn. This is the first in a series of seven Titan southern hemisphere encounters.

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This image of Titan was taken by the Cassini spacecraft narrow-angle camera on Sept. 2, 2007 using a spectral filter sensitive to wavelengths of ultraviolet light centred at 338 nanometers.
The northern hemisphere is currently in its Winter season.

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Credit NASA/JPL/Space Science Institute

This view was obtained at a distance of approximately 1.3 million kilometres from Titan and at a Sun-Titan-spacecraft, or phase, angle of 20 degrees. Image scale is 8 kilometres per pixel.

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The Huygens probe landed on Saturn's moon Titan in 2005, but it never encountered chilly seas of liquid methane as mission scientists had hoped it landed in a mud field.
In spite of the disappointment, scientists have recreated a turbulent picture of Titan's atmosphere using data from sensors intended to measure oceanic properties. In addition to showing Huygens probably plunged through turbulent methane ice clouds, the research may aid in the design of balloon probes for future Titan missions.

"We knew Huygens had a bumpy ride down to Titan's surface. Now we can separate out twenty minutes of air turbulence probably due to a cloud layer from other effects such as cross winds or air buffeting" - Mark Leese, a Huygens project manager at The Open University in the U.K.

Source

Blobrana · L

Title: About Titan's rotation: A forced "free" resonant wobble
Authors: B. Noyelles
(Version v2)

In Noyelles et al. (2007), a resonance involving the wobble of Titan is being suspected. This paper studies the probability of this scenario and its consequences.
The first step is to build an accurate analytical model that would help to feel the likely resonances in the rotation of every synchronous body. I n this model, I take the orbital eccentricity of the body into account, and also two terms in its orbital inclination. Then an analytical study using the second fundamental model of the resonance is being performed to study the interesting resonance. Finally, I study the dissipative consequences of this resonance.
I find that this resonance might have increased the wobble of Titan of several degrees. Thanks to an original formula, I find that the dissipation involved by the forced wobble might not be negligible compared to the contribution of the eccentricity. I also suspect that, due to the forced wobble, Titan's period of rotation might be a little underestimated by observers.
I finally use the analytical model presented in this paper to compute the periods of the free librations of the four Galilean satellites and Rhea. For Io and Europa, the results are consistent with the previous studies. For the other satellites, the periods of the free librations are respectively 186.37 d, 23.38 y and 30.08 y for Ganymede, 2.44 y, 209.32 y and 356.54 y for Callisto, and 51.84 d, 2.60 y and 3.59 y for Rhea.

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This image of Titan was taken by the Cassini spaceprobe on September 02, 2007, when it was approximately 1,319,014 kilometres away.
During the flyby Cassini imaged the Huygens probe landing site and studied the composition and geology of Titan's surface.

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Credit: NASA

The image was taken using the CL1 and CB3 filters.

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This image of Titan was taken by the Cassini spaceprobe on August 31, 2007, when it was approximately 28,491 kilometres away.

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Credit: NASA/JPL/Space Science Institute

The image was taken using the CL1 and VIO filters.