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TOPIC: Titan
Blobrana


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RE: Titan
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Synthetic aperture radar images obtained in February 2005 show that Titans surface is modified by fluid flows and wind-driven deposits.
Previous synthetic aperture radar images have shown features that may be cryovolcanic in origin, such as long flows and linear features that may have formed by tectonic processes.


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The latest data argue that Titan has a young and dynamic surface that is modified by all four major geologic processes: volcanism, tectonism, erosion, and impact cratering. All surfaces of solid bodies are shaped by these four processes, and Cassini-Huygens is revealing how each has contributed to the Titan we see today.
The data show a variety of surface drainage patterns that include twisting channels 1 to 2 kilometres-wide and up to 200-kilometers-long.
There is a well-developed drainage pattern associated with a large (450-kilometer diameter) basin that has eroded part of the basins rim on the lower right of the image. These patters are in much larger scales than those imaged by the Huygens probe.
The most surprising new features revealed in the synthetic aperture images are dark lineated streaks, dubbed cat scratches, which are seen in patches throughout the whole radar swath image. The scratches are interpreted as linear/longitudinal dunes formed by wind transport.
Radar images of terrestrial dunes, such as snow dunes in Antarctica, show remarkably similar patterns. Individual scratches are 500 meters to 1 kilometre across and spaced by 1 to 2 kilometre intervals, straight or undulated, and oriented roughly east-west, suggesting a direction of prevalent winds.

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Blobrana


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RE: Titan flyby
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The upcoming September 7th 2005 encounter with Titan will focus on the moons high southern latitudes, an area where Cassinis cameras have seen some possible indications of lakes.
The plan is to obtain the first RADAR scans of this area, adding 50 percent to the coverage of the moon already collected.
Some other important objectives include continuing the long-term goal of temperature mapping, obtaining further detailed studies of Titan's interaction with Saturn's magnetosphere, as well as searching for lightning.


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This image was taken on September 02, 2005 and received on Earth September 02, 2005. Titan was approximately 2,813,409 kilometres away. The image was taken using the CL1 and CL2 filters.

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Blobrana


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Posts: 131433
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RE: Titan
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This processed image from Cassini's August 22, 2005, flyby of Titan reveals mid-latitudes on the moon's Saturn-facing side. This region has been imaged previously by Cassini, although the recent approach has improved the moderate-resolution coverage of the area.


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This view was acquired with the wide-angle camera at a distance of approximately 159,000 kilometres from Titan using a spectral filter centred on infrared wavelengths at 939 nanometres. The image scale is 9 kilometres per pixel.

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Blobrana


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This image was taken on August 21, 2005 and received on Earth August 23, 2005. The camera was pointing toward Titan that was approximately 204,629 kilometres away. The image was taken using the CL1 and CB3 filters.


This image was taken on August 22, 2005 and received on Earth August 23, 2005. The camera was pointing toward Titan that was approximately 163,341 kilometres away. The image was taken using the CB3 and CL2 filters.

-- Edited by Blobrana at 23:45, 2005-08-23

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Blobrana


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Huygens Probe site
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This image was taken with the Cassini spacecraft narrow angle camera on July 7, 2005, at a distance of approximately 1.3 million kilometres from Titan and at a Sun-Titan-spacecraft, or phase, angle of 60 degrees. The image was obtained using a filter sensitive to wavelengths of infrared light centred at 938 nanometres.
The image scale is 7 kilometres per pixel.



Titan's equatorial latitudes are distinctly different in character from its south polar region.
The dark terrain, presumably lowland, seen here does not extend much farther south than about 30 degrees south.
The successful Huygens Probe landed in such a region. The Huygens probes landing site is rotating into the dawn light here.

The bright region toward the right side of Titan's disk is Xanadu. This area is thought to consist of upland terrain that is relatively uncontaminated by the dark material that fills the lowland regions.

Near the moon's South Pole, and just eastward of the terminator, is the dark feature identified by imaging scientists as the best candidate (so far) for a past or present hydrocarbon lake on Titan. Farther east of the lake-like feature, bright clouds arc around the pole. These clouds occupy a latitude range that is consistent with previously-seen convective cloud activity on Titan.

Titan is Saturn's largest moon, at 5,150 kilometres across.

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Blobrana


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RE: Titan
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Saturn's moon Titan is as dry as a bone over most of its surface, suggest new infrared images from Earth.
The work supports similar observations from the Cassini spacecraft, in orbit around the Ringed Planet. And it suggests previous radar studies from the ground - which hinted the giant moon was covered in liquid methane seas - were actually detecting signs of liquid that had long since vanished.

NASA's twin Voyager spacecraft discovered in 1980 and 1981 that methane formed a relatively large component of Titan's thick atmosphere. That led to speculation that the gas was being constantly replenished from liquid methane seas, since ultraviolet radiation is thought to destroy the gas in 10 million years - a small fraction of Titan's 4.5 billion-year history.
Radar bounced off Titan using the Arecibo Observatory in Puerto Rico in 2003 strengthened this view. In 12 of the 16 sites surveyed, the surfaces appeared very smooth – on the scale of 13-centimetre radiowaves – with reflective properties that indicated those areas were covered by liquid.

The Cassini spacecraft has also observed intriguing liquid-related features. It has detected dark, river-like channels since it neared the moon in 2004. And the Huygens Probe, which was dropped down to the moon’s surface, sent back detailed photos of channels near its landing site.



But Cassini's visible and infrared cameras have failed to find the reflections expected from surface liquid. These instruments measure wavelengths of light ranging from about 0.25 to 5 microns (or millionths of a metre) long.
Now, astronomers observing 2.1-micron-long infrared light at the Keck Observatory in Hawaii have reported similar findings.
“(Before Cassini) we expected to see a large amount of liquid on the surface - perhaps 100 metres deep on average. Yet we don't see it. It's hard to understand" - lead author Robert West, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, US.

The study offers several explanations for the conflicting observations of liquid on Titan. "At one time, maybe a liquid water and ammonia mix flowed onto the surface and froze. That could be smooth on the scale of radar but rough on the scale we see" - Robert West.

Alternatively, the radar may have bounced off a relatively flat layer of organic material left over after liquid hydrocarbon rivers or seas evaporated. "That may explain the dark areas on Titan" - Robert West.

A third possibility is that organic particles in Titan's haze settled out of the atmosphere and were blown by wind into low-lying areas, forming smooth surfaces.
But the lack of widespread liquid methane raises questions about the source of methane gas in the moon's atmosphere. West says subsurface geothermal activity may heat the frozen moon and allow the gas to leak continuously into the atmosphere.

He says another, less likely, scenario is that an "outgassing event" - possibly a large impact - warmed up Titan's interior within the last 10 million years and freed methane trapped in the ice there. Perhaps even less likely again is that the methane is generated by life - Titan is exceedingly cold.

Source

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Blobrana


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During a recent pass of Saturn's moon Titan, one of more than 40 during Cassini's planned four-year mission, the spacecraft acquired this infrared view of the bright Xanadu region and the moon's South Pole.
Titan is 5,150 kilometres across.


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Southeast of Xanadu (and above the centre in this view) is a peculiar semi-circular feature informally referred to by imaging scientists as "the Smile." This surface feature is the brightest spot on Titan's surface, not only to the imaging science subsystem cameras, but also to the visual and infrared mapping spectrometer instrument, which sees the surface at even longer wavelengths. The Smile is 560 kilometres wide.

At the landing site of the successful Huygens probe mission, brighter regions correspond to icy upland areas, while the darker regions are lowlands that possess a higher proportion of the organic by-products of Titan's atmospheric photochemistry. Those results seem to confirm the long-standing hypothesis that Xanadu is a relatively high region of less contaminated ice. However, the cause of the even brighter Smile is a mystery that is still under study.

Farther south, a field of bright clouds arcs around the pole, moving at a few meters per second. Around the limb (edge), Cassini peers through Titan's smoggy, nitrogen-rich atmosphere.

North in this image is toward the upper left.

The image was taken with the Cassini spacecraft narrow-angle camera on June 4, 2005, at a distance of approximately 1.2 million kilometres from Titan using a spectral filter sensitive to wavelengths of infrared light centred at 938 nanometres.
The image scale is 7 kilometres per pixel.


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Blobrana


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The Cassini spacecraft took this image of Titan on July 07, 2005 (received on Earth July 07, 2005).


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The spacecraft was approximately 1,253,677 kilometres away. The image was taken using the CL1 and CB3 filters.

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Blobrana


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RE: Titan Lake
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NASA'S Cassini Reveals Lake-Like Feature on Titan

Scientists are fascinated by a dark, lake-like feature recently observed on Saturn's moon Titan. NASA's Cassini spacecraft captured a series of images showing a marking, darker than anything else around it. It is remarkably lake-like, with smooth, shore-like boundaries unlike any seen previously on Titan.



"I'd say this is definitely the best candidate we've seen so far for a liquid hydrocarbon lake on Titan" - Dr. Alfred McEwen, Cassini imaging team member and a professor at the University of Arizona, Tucson.
The suspected lake area measures 233 Km long by 72 km wide, about the size of Lake Ontario, on the U.S. Canadian border.

"This feature is unique in our exploration of Titan so far. Its perimeter is intriguingly reminiscent of the shorelines of lakes on Earth that are smoothed by water erosion and deposition" - Dr. Elizabeth Turtle, Cassini imaging team associate at the University of Arizona.

The feature lies in Titan's cloudiest region, which is presumably the most likely site of recent methane rainfall. This, coupled with the shore-like smoothness of the feature's perimeter makes it hard for scientists to resist speculation about what might be filling the lake, if it indeed is one.

"It's possible that some of the storms in this region are strong enough to make methane rain that reaches the surface. Given Titan's cold temperatures, it could take a long time for any liquid methane collecting on the surface to evaporate. So it might not be surprising for a methane-filled lake to persist for a long time" - Dr. Tony DelGenio, Cassini imaging team member, NASA's Goddard Institute for Space Studies in New York.

Despite earlier predictions, no definitive evidence for open bodies of liquid have been found on Titan. Cassini has not yet been in a favourable position for using its cameras to check for glints from possible surface liquids in the South Polar Region.

"Eventually, as the seasons change over a few years, the convective clouds may migrate northward to lower latitudes. If so, it will be interesting to see whether the Cassini cameras record changes in the appearance of the surface as well" - Dr. Tony DelGenio.

"An alternate explanation is that this feature was once a lake, but has since dried up, leaving behind dark deposits" - Dr. Elizabeth Turtle.
Yet another possibility is that the lake is simply a broad depression filled by dark, solid hydrocarbons falling from the atmosphere onto Titan's surface. In this case, the smooth outline might be the result of a process unrelated to rainfall, such as a sinkhole or a volcanic caldera.

"It reminds me of the lava lakes seen on Jupiter's moon, Io" - Dr. Torrence Johnson, an imaging team member at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, US.

"It is already clear that whatever this lake-like feature turns out to be, it is only one of many puzzles that Titan will throw at us as we continue our reconnaissance of the surface over the next few years" - Dr. Carolyn Porco, imaging team leader at the Space Science Institute in Boulder, Colorado, US.

Thirty-nine more Titan flybys are planned for Cassini's prime mission.
In future flybys the science teams will search for opportunities to observe the lake feature again and to look for mirror-like reflections from smooth surfaces elsewhere on Titan. Such reflections would strongly support the presence of liquids.

source

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Blobrana


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RE: Titan loch
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This view of Titan’s South Polar Region reveals an intriguing dark feature that may be the site of a past or present lake of liquid hydrocarbons.

The true nature of this feature, seen here at left of centre, is not yet known, but the shore-like smoothness of its perimeter and its presence in an area where frequent convective storm clouds have been observed by Cassini and Earth-based astronomers make it the best candidate thus far for an open body of liquid on Titan.


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If this interpretation is correct, then other very dark but smaller features seen in the South Polar Region, some of which are captured in this image, may also be the sites of liquid hydrocarbon reservoirs.

In addition to the notion that the dark feature is or was a loch filled with liquid hydrocarbons, scientists have speculated about other possibilities.
For instance, it is plausible that the 'loch' is simply a broad depression filled by dark, solid hydrocarbons falling from the atmosphere onto Titan’s surface.
In this case, the smoothed outline might be the result of a process unrelated to rainfall, such as a sinkhole or a volcanic caldera.

A red cross below centre in the scene marks the pole. The brightest features seen here are methane clouds. A movie sequence showing the evolution of bright clouds in the region during the same flyby is also available (see .gif movie).

This view is a composite of three narrow angle camera images, taken over several minutes during Cassini's distant June 6, 2005 flyby.
The images were combined to produce a sharper view of Titan’s surface.
The images were taken using a combination of spectral filters sensitive to wavelengths of polarized infrared light.
The images were acquired from approximately 450,000 kilometres from Titan.
Resolution in the scene is approximately 3 kilometres per pixel. The view has been contrast enhanced to improve the overall visibility of surface features.

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