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Aug 23 22:43 2005
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
Aug 16 13:19 2005
Huygens Probe site
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
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.
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
. 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
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.
Aug 3 18:31 2005
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.
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
using the Arecibo Observatory in Puerto Rico in 2003 strengthened this view. In 12 of the 16 sites surveyed, the surfaces appeared very smooth Ė on the scale of 13-centimetre radiowaves Ė with reflective properties that indicated those areas were covered by liquid.
has also observed intriguing liquid-related features. It has detected dark, river-like channels since it neared the moon in 2004. And the
, which was dropped down to the moonís 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
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 "
" - 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.
Jul 14 20:52 2005
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.
and above the centre in this view
) is a peculiar semi-circular feature informally referred to by imaging scientists as "
." 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 (
), 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.
Jul 9 02:19 2005
The Cassini spacecraft took this image of Titan on July 07, 2005 (received on Earth July 07, 2005).
The spacecraft was approximately 1,253,677 kilometres away. The image was taken using the CL1 and CB3 filters.
Jun 28 23:50 2005
RE: Titan Lake
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.
Jun 28 19:02 2005
RE: Titan loch
This view of Titanís
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.
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 Titanís 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
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 Titanís 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.
May 13 20:49 2005
This stereographic projection of Descent Imager/Spectral Radiometer images from the European Space Agency's Huygens probe combines 60 images in 31 triplets, projected from a height of 3,000 metres above the black 'lakebed' surface.
The bright area to the north (top of the image) and west is higher than the rest of the terrain, and covered in dark lines that appear to be drainage channels.
May 13 20:48 2005
This mosaic from the Descent Imager/Spectral Radiometer camera on the European Space Agency's
combines 17 image triplets, projected from an altitude of 800 metres. The area covered is approximately 1,300 metres across (north at the top of the image). The smallest visible objects visible are less than five meters across, and the dark channels are 30 to 40 metres wide.
The images were then stitched together using one of several projection algorithms (
in this case 'gnomonic'
) to produce a full mosaic. The images used to construct this mosaic were taken on Jan. 14, 2005.
May 12 23:03 2005
The Cassini mission has made the most detailed ever study ever Saturnís largest moon,
, and its atmosphere. The results could lead to a better understanding of the conditions that existed on the young Earth.
Titanís atmosphere consists mainly of nitrogen, along with small amounts of organic material such as methane. The pressure at the surface is about 1.5 atmospheres, which is quite similar to the Earth, but the temperature is only about 90 K. At such low temperatures the methane in Titanís atmosphere could play a similar role to the water in Earthís atmosphere.
Titan's surface appears to be young, with few impact craters, according to Steve Wall of the Jet Propulsion Laboratory and co-workers who used the Cassini Titan Radar Mapper to image about 1% of the surface. They also observed a variety of geological features such as volcanoes and surface flows with evidence for porous ice. Moreover, dark patches in the radar images imply that it could contain frozen hydrocarbons
Michael Flaser of the NASA Goddard Space Flight Centre used the Composite Infrared Spectrometer on Cassini to analyse the methane and carbon monoxide in Titanís atmosphere, and found that the amount of these and other hydrocarbon molecules present, vary with season.
The atmosphere at Titanís poles in winter may be similar to the ozone hole above the Antarctic, but with different chemistry.
Other results show that the bulk composition of Titanís upper atmosphere does not seem to have changed greatly since it was measured by the Voyager 1 spacecraft more than 20 years ago. Data from an ultraviolet imaging spectrometer and a neutral mass spectrometer provide evidence for the presence of several organic species, including molecular nitrogen, methane, molecular hydrogen, argon and a host of stable carbon-nitrile compounds.
Other studies report on how Titanís atmosphere interacts with energetic particles, which come mainly from Saturnís magnetosphere. These interactions provide energy for the continuous production of complex hydrocarbons and nitriles from atmospheric methane and nitrogen. Finally, results from a magnetometer show that Titan does not have an internal magnetic field.
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