* Astronomy

This radar image, obtained by Cassini's radar instrument during a near-polar flyby on Sept. 23, 2006, is the second scene that shows clear shorelines reminiscent of terrestrial lakes.
With Titan's colder temperatures and hydrocarbon-rich atmosphere, these lakes most likely contain a combination of methane and ethane (both hydrocarbons), not water. This high-latitude opportunity confirmed scientists' predictions that lakes would be present here, consistent with calculations that suggested that hydrocarbons would be stable as liquids at the colder, high latitudes. It also showed unusual complex terrain, the origin of which remains a mystery.


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Credit: NASA/JPL/Space Science Institute

The image is illuminated by the radar from the top, and shows features as small as about 300 meters. Starting at the left (63 degrees north latitude by 255 degrees west longitude), where the terrain appears bland and dark, the swath heads northeast into a more rugged, mottled terrain, probably containing dried lakes and canyons formed by the presence of liquid hydrocarbons.
The first lake, an irregular, almost-triangular shape about 16 kilometres across at the widest point, can be seen near the bottom of the image; it appears to be fed by two channels from the south. Several more lakes can be seen about one-third of the way into the swath, near the closest approach to the pole, (north of 75 degrees north latitude), including Titan's "kissing lakes," each 20 to 25 kilometres across. Two other lakes feature narrow or angular bays, including a broad peninsula that on Earth would be evidence that the surrounding terrain is higher and confines the liquid. Continuing on, about three-quarters of the way through the swath, the terrain becomes brighter and more rugged, again indicating possible dried lakes and canyon-like structures. A long 100-kilometer series of grooves appears, likely carved by liquids. Next is an area of bright terrain with an unusual directional texture, indicating possible dunes, but brighter and perhaps different in nature than those seen elsewhere. Finally, towards the end of the swath, where the image quality is poorest, the terrain becomes mottled and difficult to interpret.

The Cassini spacecraft has imaged a banded cloud encircling the northern pole on Titan. This feature is what scientists expect to see in the stratosphere of Titan, where the atmosphere is superrotating, or moving around the moon faster than the moon itself rotates.


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Credit: NASA/JPL/Space Science Institute

Images taken using red, green and blue spectral filters were combined to create this negative view. The images were taken by the Cassini spacecraft wide-angle camera on Jan. 28, 2007 at a distance of approximately 196,000 kilometres from Titan. Image scale is 12 kilometres per pixel.

This radar image of Titan shows a semi-circular feature that may be part of an impact crater. Very few impact craters have been seen on Titan so far, implying that the surface is young. Each new crater identified on Titan helps scientists to constrain the age of the surface.


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Credit: NASA/JPL/Space Science Institute

Taken by Cassini's radar mapper on Jan. 13, 2007, during a flyby of Titan, the image swath revealed what appeared to be the northernmost half of an impact crater. This crater is roughly 180 kilometres wide. Only three impact craters have been identified on Titan and several others, like this one, are likely to also have been caused by impact. The bright material is interpreted to be part of the crater's ejecta blanket, and is likely topographically higher than the surrounding plains. The inner part of the crater is dark, and may represent smooth deposits that have covered the inside of the crater.
This image was taken in synthetic aperture mode and has a resolution of approximately 350 metres. North is toward the top left corner of the image, which is approximately 240 kilometres wide by 140 kilometres high. The image is centred at about 26.5 degrees north and 9 degrees west.

This image of Titan's surface shows the entire scene obtained by the Cassini radar instrument on Sept. 7, 2006. It includes clear examples of the longitudinal dunes, as well as one of only three positively-identified impact craters (on the far left).
Titan's longitudinal dunes, first discovered during the third close flyby of Titan in February 2005, make up most of Titan's equatorial dark regions. These run east-west, are around 1 to 2 kilometres wide, spaced 1 to 2 kilometres apart, around 100 meters high, and from 10 to over 100 kilometres long. They curve around the bright features in the image -- which may be high-standing topographic obstacles -- following the prevailing wind pattern. Unlike Earth's silicate dunes, these may be solid organic particles or ice coated with organic material.


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Credit NASA/JPL

The left (eastern-most) portion of the image also shows one of only three impact craters confirmed on Titan so far. Roughly 30 kilometres in diameter, it measures about 150 kilometres high by 190 kilometres wide, and its centre is at 70 degrees west, 10 degrees north. The difference in overall appearance between this crater, which has a central peak, and those without, such as Sinlap, indicates variations in the conditions of impact, thickness of the crust, or properties of the meteorite that made the crater. The dark floor indicates smooth and/or highly absorbing materials.