After the May 28th 2008 flyby, no notice is provided for any flyby, with any further data of note to be found into the section 'Further Flybys or Additional Pictures'Surface temperatures at Titan are at minus 290 degrees Fahrenheit (94 kelvins) as the Moon is like early Earth in a deep freeze. The surface features lakes and seas made of liquid methane and ethane, which are larger than North America's Great Lakes ( making Titan the only solar system body other than Earth known to have liquid lakes and seas on its surface), and an extensive layer of liquid water deep beneath the surface. Organic molecules abound in Titan's atmosphere, formed from the breakup of methane by solar radiation. Methane is not only in the atmosphere, but probably in the crust which make any life potential at the moon either of a methane-type, or a water-related one
-> After the May 28th 2008 flyby, no notice is provided for any flyby, with any further data of note to be found into the section 'Further Flybys or Additional Pictures'
| . October 26th, 2004 . December 13th, 2004 . February 15th, 2005 . March 31st, 2005 . April 16th, 2005 . August 22nd, 2005 . September 7th, 2005 . October 28th, 2005 . December 26th, 2005 (no report) . January 15th, 2006 (no report) . February 27th, 2006 (no report) . March 18th, 2006 (no report; dedicated to the atmosphere) . April 30th, 2006 . July 2nd, 2006 (no report) . July 22nd, 2006 . September 7th, 2006 (no report) . September 23rd, 2006 . October 9th, 2006 (no report) . October 25th, 2006 . December 12th, 2006 (no report) . December 28th, 2006 . January 13th, 2007 (no report) | . January 29th, 2007 (no report) . February 22nd, 2007 . March 10th, 2007 (no report) . March 26th, 2007 (no report) . April 10th, 2007 (no report) . April 26th, 2007 (no report) . May 12th, 2007 (no report) . May 28th, 2007 (no report) . June 13th, 2007 (no report) . June 29th, 2007 (no report) . July 19th, 2007 (no report) . August 31st, 2007 (no report) . October 2nd, 2007 . November 19th, 2007 . December 5th, 2007 (no report) . December 20th, 2007 (no report) . January 5th, 2008 . February 22nd, 2008 (no report) . March 25th, 2008 (no report) . May 12th, 2008 (no report) . May 28th, 2008 (no report) |
 | Volcano-like feature at Titan. NASA/JPL/University of Arizona |
No Global Ocean at Titan. What Does Replenish the Methane?
A study published in the June 9th, 2005 issue of the journal "Nature", and basing on the October 26th, 2004 flyby, is showing that Titan does not have any global ocean, as the moon's methane might be volcanoe-replenished. The explanation until now for the methane replenishment in Titan's atmosphere was that it was due to a global ocean. The recent flybys did not show any such ocean. Hence a 19-mile (30-km) wide feature seen in the infrared might be a large ice volcano helping in the process, and releasing a mixture of methane and water ice. The question now is what the internal heat source powering such a cryo-volcanism is. Next flybys will help to determine whether Titan is enduring any tidal forces sufficient to explain the source, or whether another source exists. Next flyby is scheduled August 22nd, 2005 (late studies following those dates, in 2008, are showing that Titan's volcanoes are spewing ammonia, methane and water in the moon's atmosphere). Methane in the atmosphere of Titan
is unstable and destroyed on geologically short timescale
 | click to a detailed view of the volcano-like feature related data. picture site 'Amateur Astronomy' based on pictures NASA/JPL/University of Arizona |
Cassini successfully performed its first scientific flyby at Titan on last Thursday October 26th, inaugurating the long series of science it will perform in Saturn's system. The probe grazed the moon by 730 miles (1,174 km) at 7:20 p.m. PDT (02:20 GMT)
The craft used a wide range of instruments to image and probe Titan and used its synthetic aperture imaging radar for the first time. The emerging picture of the surface of Titan is still undecisive. The only firm conclusion until now is that Titan's surface is young. No impact craters are seen. On the other hand it might that what is seen of Titan is completely new in the solar system.
Multiple geological processes seem to be at work at the Saturnian moon. The global picture might be one of a large, eroded plateau with a plate tectonics activity opening large, dark, streaked regions. On the other hand such streaked terrain might be due too to erosion by wind, flowing hydrocarbon liquids or even ice glaciers.
The flyby did not help to understand whether some part of the surface might be or not covered with lakes or oceans although the darker parts seen on some radar pictures might be such features.
Further data, and science, will be needed before a clear picture emerges from what has been seen. "We are glad that we have a full complement of instruments on this spacecraft because it is going to take all of them to reveal the story of Titan," Dr. Dennis Matson, project scientist for the Cassini-Huygens mission at NASA's Jet Propulsion Laboratory, Pasadena, Calif. said. Cassini it to perform an additional 44 flybys at Titan during its 4-year mission as the European ESA probe will parachute down Titan's atmosphere next January 14th 2005. This first flyby permitted too to probe the model of the moon's atmosphere ahead of the arrival of Huygens
 | Albedo features and south pole clouds. The round feature seen right is an artefact only. picture courtesy NASA/JPL/Space Science Institute |
 | The view is about 1,200 miles (2,000 km) across. The features may hint to various geological processes. Above all no impact craters are seen (distance: 211,000 miles (340,000 km), wavelength: near-infrared). picture courtesy NASA/JPL/Space Science Institute |
 | Titan at a distance of 4 88,000-63,000 miles (100,000-140,000 km) seen in a composite view of three infrared wavelengths (2 -blue, 2.7 -red, and 5 microns -green). The inset is showing the landing site for the Huygens probe. picture courtesy NASA/JPL/University of Arizona |
 | Titan during closest approach (745 miles (1,200 km). picture courtesy NASA/JPL/University of Arizona |
 | Huygens landing site and Titan's general view. picture courtesy NASA/JPL/Space Science Institute |
 | Synthetic radar aperture picture ( 994 miles (1,600 km), picture is 297 x 155 miles (478 x 250 km) wide). The dark features left might be liquid hydrocarbons. Bright features might be rough terrain as dark features might correspond to a smoother one. picture courtesy NASA/JPL |
 | Synthetic radar aperture picture (745 miles (1,200 km), picture is 155 x 93 miles (250 km x 150 km) wide). This might be a mix of ice and hydrocarbons. Bright features might be rough terrain as dark features might correspond to a smoother one. picture courtesy NASA/JPL |
 | This view is about 90 mile (150 km) square and it might that the bright feature stretching from top left to bottom right might some ancient ice flow, and that it might elevated compared to the darker regions.. picture courtesy NASA/JPL |
 | This b&w and color view might be interpreted too in terms of ice volcanism. It is about 93 by 186 miles (150 by 300 km). Titan's surface might be partly hydrocarbons, partly ice!. picture courtesy NASA/JPL |
 | On this 71 miles wide, 106 miles high radar picture (115 km x 170 km), some detailed relief features are seen. Location is 52 degrees north latitude and 73 degrees west longitude. picture courtesy NASA/JPL |  | Full-disc mosaic of Titan. The bright region, center right, is named Xanadu Regio. picture courtesy NASA/JPL/Space Science Institute |
 | It's southern summer in Saturn's system. The northern hemisphere of Titan is colder, with more haze, hence brighter. Seasonal changes in the atmosphere of Titan brings a hemisphsere slightly darker than a other. Scientists have found that the hemisphere with a winter typically appears to have more high-altitude haze, making it darker at shorter wavelengths (ultraviolet through blue) and brighter at infrared wavelengths. The switch between dark and bright occurred over the course of a year or two around the last equinox. The boundary is not level with latitude and is actually offset from the equator by about 10 degrees of latitude (image taken on Oct. 24, 2004, filter centered at 889 nanometers (methane); Titan is 675,000 miles (1.08 million km) away from Cassini). picture courtesy NASA/JPL/Space Science Institute |
 | A fine global view of cloud-enshrouded Titan. North high altitude features are seen which may be additional haze layers or wave perturbations in Titan detached haze layer (image taken on Oct. 24, 2004, near-ultraviolet; Titan is 620,000 miles (1 million km) away from Cassini). picture courtesy NASA/JPL/Space Science Institute |
 | The previous image was enhanced at the site to show Titan detached haze layer. This layer is produced by photochemical reactions. picture © site 'Amateur Astronomy' |
 | The bright large feature center and right is Xanadu as bright features at the south pole are clouds. Such clouds are moving at a few meters (yards) per second (image taken on Oct. 24, 2004, filter centered at 938 nanometers; distance unknown). picture courtesy NASA/JPL/Space Science Institute |
 | Planned image coverage during Titan flyby. Different colors highlight the different resolutions at which Cassini will image the moon. The yellow x is where the Huygens probe is to land. Xanadu is the bright, large, region right. picture courtesy NASA/JPL/Space Science Institute |
Cassini successfully flew by Titan for the second time on Dec. 13th at a distance equivalent to its Oct. 26 flyby, by 750 miles (1,200 km). This second flyby was still more atmosphere-oriented than the first. Data will be used for Huygens atmosphere models and to determine whether Cassini can safely get gloser to Titan for its next passages. Some clouds have been imaged in the southern hemisphere of Titan as a pattern of atmosphere banding has been observed. Weather exists at Titan with discrete clouds seen at mid-latitudes this time as no clouds were seen at the south pole. Further views of the surface, in regions not clearly seen before, might hint to more impact-related features at Titan although it's impossible to know for sure. Liquid methane is cycling between clouds and surface seas
 |  |
Published in the journal Nature, a study based on data collected by Cassini at Titan during the past eight months is showing the variety of surface features at Titan as it is demonstrating that Titan's lower atmosphere is "super-rotating". Picture left (click) is showing craters (a; upper two are 30-mile wide (56 km), wind-streamlined features (b), dark channels (c), faulting (d), drainage patterns due to underground springs (e), and thin surface plates broken and spread apart over an underlying dark material. Each white bar above each image is 124 mi (200 km) long. Scientists are convinced that only tectonism may have played a role for some of Titan's features, being the only known process to create large-scale, crust-related, linear boundaries. The picture right (click) is showing Titan's south pole (we have colorized it) and may suggest that rain occur at Titan's south pole only as no clouds have been seen elsewhere at the moon. On the other hand the data are confirming that, with winds at a speed as high as 75 mph (34 m/s) -that is a hurricane strength- the lower atmosphere of Titan is "super-rotating". The atmosphere, just like at Venus, is moving, eastwards, faster than the planet rotates! pictures courtesy NASA/JPL/Space Science Institute
 | Bright clouds are seen in Titan's southern hemisphere, where it's summer. picture courtesy NASA/JPL/Space Science Institute |
 | The atmosphere seen in the infrared during the Dec. 13 flyby is showing pronounced banding. picture courtesy NASA/JPL/Space Science Institute |
 | The bright region is Xanadu. Xanadu might be an icy upland area, of less contaminated ice. Brighter regions at Titan might correspond to icy upland areas, while the darker regions are lowlands where the byproducts of the atmospheric chemistry collect. picture courtesy NASA/JPL/Space Science Institute |
 | Some detailed features in the dark region West of Xanadu. picture courtesy NASA/JPL/Space Science Institute |
 | Circular features have been seen near Xanadu (center). Circle lower right is 345-mile wide (560 km) as the multi-ringed feature to the upper right is 205 miles (330 km). picture courtesy NASA/JPL/Space Science Institute |
 | The weather at Titan on Oct. 26, 2004 (left) and on Dec. 13th, 2004 (right). picture courtesy NASA/JPL/University of Arizona |
 | More, fine, haze layers -12 of them- have been found in Titan's atmosphere. Titan's orange limb is seen left. The divisions in the haze occur at altitudes of 124, 233 and 310 miles (200, 375 and 500 kilometers) above the limb. picture courtesy NASA/JPL/University of Arizona |
Cassini successfully performed its 3rd flyby at Titan, grazing the moon by 980 miles (1,577 km). This passage was about both Titan's atmosphere and terrain. Cassini radar imaging system was used for the second time, as pictures it took, overlapping with ones taken with the optical system, are bringing more details about Titan's surface, showing an impact features on one hand, and dark, linear features on the other hand. Despite these views, it's still uneasy to really figure out how Titan is really looking like. This passage provided fine views of Titan's atmosphere too
 | Planned imaging sequences at Titan for the 3rd Cassini flyby. picture courtesy NASA/JPL/Space Science Institute |
 | Detailed view (435 mi across (700 km)) of a part of Xanadu. White areas are water ice-rich as dark ones are hydrocarbon-rich. The processes which led to such divisions of the terrain are still unknown. As montainous terrain appears in small, isolated patches, the Xanadu region covers a large area and such a oldest terrain on Titan, might be remnants of the icy crust before it was covered by organic sediments from the atmosphere. picture courtesy NASA/JPL |
 | Radar image of an area near the northeast corner of Xanadu (186 mi from top to bottom, 300 km). The parallel, mostly East-West dark linear features may either be surface or sub-surface features. picture courtesy NASA/JPL |
 | A 273-mile (440 km) wide impact feature, likely created by a comet or asteroid tens of kilometers in size. This precisely may be a crater, or a part of a ringed basin. picture courtesy NASA/JPL |
 | This view in the ultraviolet is showing how Titan's atmosphere is alive. Haze different levels of concentration near the south pole might be gravity waves. picture courtesy NASA/JPL/Space Science Institute |
 | This natural color view is showing this time the slight haze layer previously seen in the northern hemisphere. picture courtesy NASA/JPL/Space Science Institute |
 | These views are showing how Cassini, past Titan, saw its night side and how the atmosphere is seen extending all the disk along, with the north pole haze layer particularly well documented. pictures site 'Amateur Astronomy' from a picture NASA/JPL/Space Science Institute |
 | Such a view is showing how Titan endures all the four major geologic processes known in planetary science, that is volcanism, tectonism, erosion, and impact cratering with faulting. Drainage patterns are seen as are what might be dunes shaped by east-west winds (upper and lower left; part of the image enhanced), 1,640 ft to 0.6 mile (500m-1-km) accross and space by 0.6 to 1.2-mi (1-2-km) intervals. Titan's surface is young! . picture NASA/JPL |
Cassini successfully performed its 5th flyby at Titan last March 31st. The craft flew the moon by at an altitude of 1,493 miles (2,402 km). It mainly targeted haze and transient clouds, as areas already imaged in October 2004 and February 2005 attained their best definition
 | This view of the fifth flyby is showing an area East of the Xanadu. picture courtesy NASA/JPL/Space Science Institute |
 | The view above has been colorized by our site and re-sized. pictures site 'Amateur Astronomy' from a picture NASA/JPL/Space Science Institute |
 | Region East of Xanadu. Straight lines South may reveal tectonics as the crater, North, is 50-mile (80 km) wide. picture courtesy NASA/JPL/Space Science Institute |
 | High haze details. picture courtesy NASA/JPL/Space Science Institute |
Cassini successfully performed its closest yet flyby at Titan last April 16th, flying by the moon at an altitude of a mere 638 mi (1,027 km). This proximity allowed Cassini to discover that the moon's upper atmosphere is filled with a larger variety of compounds than previously thought. A whole complex mixtures of hydrocarbons and carbon-nitrogen compounds were observed high in the atmosphere. This confirms that the action of the ultraviolet light of the Sun -and even of energetic particle radiation (from Saturn's magnetosphere in this particular case) is the "other way" in the Universe to produce life's buildings blocks. The way things occurred at Earth was better linked to interstellar clouds' dust and grains incoporated into comets, as biology took the relay. Its likely however that such processes like those seen at Titan might have been at work in the atmosphere of the early Earth too. A laboratory experiment by 2013 at NASA's Jet Propulsion Laboratory, Pasadena, Calif., simulating the atmosphere of Saturn's moon Titan suggests complex organic chemistry that could eventually lead to the building blocks of life extends lower in the atmosphere than previously thought, even with light filtered by the thick atmosphere of the moon. The results now point out another region on the moon that could brew up prebiotic materials. Sunlight in the Titan lower atmosphere can kick-start more complex organic chemistry in liquids and solids rather than just in gases. Such organics could thus coat rocks of water ice at the surface, or seep down to a possible liquid water layer under Titan's crust. In previous laboratory experiments, such materials called tholins by astronomer Carl Sagan, were exposed to liquid water over time and developed into biologically significant molecules, such as amino acids and the nucleotide bases that form RNA. Molecules known like 'carbon chain anions' found in Titan's atmosphere are building blocks of more complex molecules, and might even have acted as the basis for the earliest forms of life on Earth. Chemical acrylonitrile is found in the atmosphere of Titan, most likely in the stratosphere at altitudes of at least 125 miles (200 kilometers). That compound might contributes to the formation of cell membranes, a lipid bilayer which separates the inside of a cell from the outside. Eventually, acrylonitrile makes its way to the cold lower atmosphere, where it condenses and rains out onto the surface and it might also contribute there to life at most important quantities
 | East of Xanadu, 50-mile (80 km) wide impact crater seen (from left to right) in the infrared, with Cassini's radar, and in a false-color infrared image. The radar image had been taken during the Feb. 15, 2005 flyby. picture courtesy NASA/JPL/University of Arizona |
 | Series of relief features as seen during the flyby. pictures courtesy NASA/JPL/Space Science Institute, assembled by the site 'Amateur Astronomy' |
 | May 2005 view of Titan purple light-scattering haze (enhanced-color view, with the bluish-purple color of the upper atmospherirc haze matching the visible light color). picture courtesy NASA/JPL/Space Science Institute" |
 | An additional picture taken on an imaging passage of opportunity at Titan on June 4th, 2005 allowed this fine view, in the infrared, of the semi-circular, 345-mile (560-km) wide feature (right, above center), informally dubbed "the Smile". It's the brightest spot on Titan, as its origin is still a mystery. picture courtesy NASA/JPL/Space Science Institute" |
Provisional names have been recently applied to a number of features on Titan. Features seen in the region figuring a H, for example, have now names like Tsegihi, Aztlan and Quivira or "Bazaruto Facula". The recent state of the thinking about Titan is that the noteworthy absence of impact craters at the moon is an indicator that Titan's surface has been somehow re-surfaced in a distant past. As Titan does not display as much cratering that other moons of Saturn, it is mostly because its craters are getting erased. Dunes of windblown, exotic, hydrocarbon sand are slowly but steadily filling in. As 50 percent of Titan's surface has been imaged so far by early 2013, 60 craters only were spotted. Craters formed in polar regions, on a other hand, may have had wet sediments slump into them as Titan's polar regions are saturated by liquid hydrocarbons. Liquid and viscous flows (methane rivers or ice crust slow readjustment) might also contribute to the modification of Titan's craters. With the exception of the Xanadu lowland region, impact craters on Titan occur much more often in highlands. Regions with few craters likely were once sediment-saturated wetlands or shallow seas -feed through streams or cryovolcanism of liquid methane and ethane- that swallowed up evidence of impacts. Titan's craters, generally, are shallow relative to their diameter
 | Titan seen in natural colors (red, green, violet filters). Complex molecules generated in Titan's atmosphere by sunlight influence, filter down into the lower atmosphere and eventually combine to produce a orange smog. picture courtesy NASA/JPL/Space Science Institute |
 | Titan seen in the infrared allowing down to the surface features. picture courtesy NASA/JPL/Space Science Institute |
The September 7th, 2005 flyby provided detailed views of the region dubbed "the H", as it brought too radar images evidence of a shoreline and draining networks. As far as "the H" is concerned, it was provisionally named Fensal (northern branch) and Aztlan (southern) by the International Astronomical Union (IAU). The Fensal region has been seen littered with a variety of small "islands" -likely icy mounds eroded in the middle of a shallower lowland. The radar images provided by this flyby are bringing for the first time the clearest evidence for a shoreline -hence for liquid surfaces at Titan. Such a landform, along with large and long draining patterns, is bringing to further this idea that the methane of the atmosphere of Titan is falling on the surface under the form of rain. Such a liquid is then drained from the icy high plateaus down to the lowlands. The methane rain, there, transforms into liquid hydrocarbons areas. All this geological activity is somehow akin to the one seen at Earth. Methane simply replaces water
 | "The H" seen in details, with the Fensal region as the upper branch and the Aztlan region the lower. picture courtesy NASA/JPL/Space Science Institute, colorized site 'Amateur Astronomy' |
 | The shoreline seen by Cassini (the picture is 109 by 205 miles (175 by 330 km), located at 66° South and 356°. West). The bright, rough terrain left is likely a high terrain cut by channels and bays. picture courtesy NASA/JPL, colorized site 'Amateur Astronomy' |
 | Deep channels (canyons?). The channels are roughly 0.6-mile (1-km) across and perhaps 650-foot (200-m) deep. Some are up to 120-mile (200-km) long. Some angular segments leads to think that some may follow faults in Titan's crust. picture courtesy NASA/JPL, colorized site 'Amateur Astronomy' |
 | Radiating draining channels heading towards a dark lowland (region is 150 miles large (240 km) located near 48° South, 14° West). picture courtesy NASA/JPL, colorized site 'Amateur Astronomy' |
 | In this view taken Aug. 31st, 2005 a cloudy activity is seen at the south pole of Titan. Such an activity have been seen to be less in 2005 than in 2004. picture courtesy NASA/JPL/Space Science Institute |
Cassini, like planned, performed a flyby at Titan on October 28th, 2005. It radar-imaged, among others, the Huygens landing site. Relief features have been imaged too, like dunes of water ice or hydrocarbon particles, spaced by 0.6/1 mile (1-2 km). Tectonic ridges (formed by deformation of Titan's icy crust) have been seen poking up above the plains, some extending over 60 miles (100 km). It looks like -from further studies, that the dunes at Titan are mostly an equatorial phenomenon, as girdling the globe at latitudes from about 30 degrees north to 30 degrees south, with the notable exception of Xanadu. Dunes are thought to be comprised of grains derived from hydrocarbons that have settled out of Titan's atmosphere. Dunes are dynamic features at Titan. Reaching heights of more than 300 feet (90 meters), the dunes of Titan present a puzzling mystery: they seem to form in the opposite direction as Titan's steady east-to-west winds as those are not strong enough further to shape the viscous material into the massive dune shapes that are observed. The dunes might be shaped by short, rapid bursts of westerly wind which appears function of the changing position of the Sun in Titan's sky. The dunes generally may have taken as long as 3,000 Saturn years to form (the equivalent of 90,000 Earth years) as their formation might be too influenced by changes in Saturn's orbit. Giant dust storms occur in equatorial regions of Titan around the equinox, in which organic dust can be raised from large dune fields located there. Organic dust is formed when organic molecules, formed from the interaction of sunlight with methane, grow large enough to fall to the surface. Titan is slowly cooling as heat is still available from the original formation process through radioactive elements decaying. This is triggering a geological process called 'contractional tectonics' by which mountain ranges are created. By Earth, the sole example of such a process is found in the Zagros Moutains, Iran. Such a process is forces shortening and thickening the ice shell. Such a behavior is unique to Titan. Several mountain chains on Titan exist near the equator and are generally oriented west-east. The concentration of these ranges near the equator suggests a common history. Other icy moons in the outer solar system have peaks that reach heights similar but their topography comes from extensional tectonics -- forces stretching the ice shell -- or other geological processes. That model based upon the assumption that the moon's interior was only partially separated into a mixture of rock and ice. The model conditions for mountain ranges were met when assumed that the deep interior of Titan, was surrounded by a very dense layer of high-pressure water ice, then a subsurface liquid-water-and-ammonia ocean and an outer water-ice shell. Each successive layer of Titan's interior is colder than the one just inside it. The cooling of the moon thus causes a partial freezing of the subsurface liquid ocean and thickening of the outer water ice shell. It also thickens the high-pressure ice. Because the ice on the crust is less dense than the liquid ocean and the liquid ocean is less dense than the high-pressure ice, the cooling means the interior layers lose volume and the top "skin" of ice puckers and folds. As Titan formed around 4 billion years ago, the moon's interior has cooled significantly with heat now still available for geologic activity. The result was a shortening of the radius of the moon by about 4 miles (7 kilometers) and a decrease in volume of about one percent
 | Dunes as seen during the October 28th flyby. picture courtesy NASA/JPL |
 | Ganesa Macula is thought to be a cryovolcano (ice volcano), with cryovolcanism having been an important process on Titan in the past, and maybe today still. Impact craters, on the other hand, are very rare implying a young surface. picture courtesy NASA/JPL/Space Science Institute |
 | Three parallel ridges, as seen during the May 28th, 2008, might be tilted or separated blocks of broken or faulted crust, another sign of the tectonics at Titan. picture courtesy NASA/JPL |
As it performed its scheduled, April 30th, 2006 flyby at Titan, Cassini especially focused on Xanadu, this continent-size region. Most of Titan has no lakes, with vast stretches of linear dunes closer to the equator similar to those in places like Namibia on Earth. Radar pictures returned by the probe are showing a variety of reliefs, from impact craters, cryovolcanism caldeira to drainage channels and vast fields of dunes (the particulates of organics in the Titan's smog agglomerate themselves up to the size of dust grains and are the main components of the moon's dunes, or solid water ice coated with hydrocarbons that fall from the atmosphere; in any case, dunes are not made of silicates like on Earth). Another point made clear by the flyby is that what were thought to be oceans or seas in the equatorial neighbourhoods of Titan are in fact vast areas of dunes. Just like for Venus, the clouds and haze cover at Titan are not allowing to get an usual picture of the surface. Just those radar images combined to the pictures taken by the ESA probe Huygens as it touched down on Titan allow to figure out what Titan is really looking like
Basic principles describing the rotation of planetary atmospheres and data from the European Space Agency's Huygens probe led to circulation models that showed surface winds at Titan are streaming generally east-to-west around Titan's equatorial belt (at higher latitudes the average wind blows west-to-east however). Seasonal changes appear to reverse wind patterns on Titan for a short period and lasting perhaps two years. They are so strong that they are better at streaming sand dunes than the usual east-to-west winds. The dramatic, between monsoon-type wind reversal is occurring around the equinox about every 29 Earth years and caused by heat-related upwelling in the atmosphere of Titan. The winds reverse and accelerate due to that turbulent mixing. The dunes track across the vast sand seas of Titan only in latitudes within 30 degrees of the equator. They are about half a mile to 1.2-mile wide (a kilometer) wide and tens to hundreds of miles (kilometers) long being able to rise more than 300 ft (100 meters) high. The sands that make up the dunes appear to be made of organic, hydrocarbon particles. The dunes' ridges generally run west-to-east. The episodic reverse winds on Titan appear to blow around 2 to 4 mph (3.6-6.5 km/h). The threshold for sand movement appears to be about 2 mph (3.6 km/h), a speed that the typical east-to-west winds never appear to surpass. Regional variations among sand dunes size and patterns make that they vary as a function of altitude and latitude. Dune fields are the second most dominant landform on Titan, after the seemingly uniform plains, covering about 13 percent of the surface. Titan's dunes are gigantic by our standards, at 0.6 to 1.2 miles (1 to 2 kilometers) wide, hundreds of miles (kilometers) long and around 300 feet (100 meters) high. Scientists think the sand on Titan is not made of silicates as on Earth, but of solid hydrocarbons, precipitated out of the atmosphere. These have then aggregated into grains 0.04 inch in size by a still unknown process. In terms of altitude, the more elevated dunes tend to be thinner and more widely separated. This suggests that the sand needed to build the dunes is mostly found in the lowlands of Titan. In terms of latitude, the sand dunes are confined to the equatorial region between 30 degrees south latitude and 30 degrees north latitude. However, the dunes tend to be less voluminous toward the North which may be due to Saturn's elliptical orbit and the seasons in the Saturnian system. The southern hemisphere of Titan has shorter but more intense summers and is probably drier. The drier the sand grains, the more easily they can be transported by the winds to make dunes. More North, soils are holding more moisture making the sand particles less mobile. The dunes are also a significant atmosphere-surface exchange interface
 | Various reliefs seen by Cassini during its Apr. 30th, 2006 flyby at Titan. all pictures NASA/JPL |
Methane and ethane lakes at the north pole of Titan likely are the cause of the haze layers found there. With the July 22nd, 2006 flyby, Cassini was flying over Titan's north pole for the first time. The region is in Titan's winter since the mission arrived there. Such lakes are though varying in area along the seasons. Along with that, most recent analyzed data from the ESA Huyghens probe mission allow to think that a barely visible, low-lying layer of methane and nitrogen is 'manufacturing' a kind of permanent drizzle. Hence the surface of Titan mostly, likely has a muddy texture. This layer has on top of it the more larger methane ice later, which likely is yielded by an ascending atmospheric motion. Those low layers are clouding about half of the moon, as they diminish along latitude. A yearly 2 inches (5 cm) of methane rain are falling at Titan. This means relatively few, as it's spread over the year however. Such a drizzle is thought not enough to really play a role in the erosion process. Cassini, later in the mission, has seen a vast network of these hydrocarbon seas cover Titan's northern hemisphere, while a more sporadic set of lakes bejewels the southern hemisphere. Titan's hydrocarbon lakes, North, might have been seen partially frozen by early 2013. Solid methane is denser than liquid methane and would sink instead of providing for floes but interaction however between lakes and the atmosphere results in different mixtures of compositions, pockets of nitrogen gas, and changes in temperature providing for float or a crust. When the temperature is colder still however, the ice is sinking and forming blocks of hydrocarbon ice on the bottom of the lake. One Titan's lake, after that, was found about 560 feet (170 meters) deep. Cassini studies later confirmed how deep some of Titan's lakes are (more than 300 feet, or 100 meters) and their composition as larger northern seas or smaller lakes are filled with methane. The hydrology on the other hand, on one side of the northern hemisphere is completely different than the that of other side. On the eastern side of Titan, there are big seas with low elevation, canyons and islands. On the western side: small lakes perched atop big hills and plateaus. Transient lakes also exist, generally and likely shallower. The origin of Titan's lakes might be that deformation of the crust created fissures that could be filled up with liquid. Deep, steep-sided canyons on Titan are flooded with liquid hydrocarbons. A network of channels is particularly the Vid Flumina. Channels are narrow canyons, generally less than half a mile (somewhat less than a kilometer) wide, with slopes steeper than 40 degrees as canyons also are quite deep -- those measured are 790 to 1,870 feet (240 to 570 meters) from top to bottom. The discovery was made from 2013 data with a radar used as a altimeter, sending pings of radio waves to the surface to measure the height of features there. Channels might be due to uplift of the terrain or changes in Titan's sea level, or perhaps both. Slight changes in temperature, air pressure or composition at Titan can cause methane-rich liquids mix with ethane-rich ones with nitrogen less able to stay in solution, resulting in bubbles. The release of nitrogen, known as 'exsolution,' can also occur when methane seas warm slightly during the changing seasons on Titan. The mechanism could explain small 'islands' appearing and disappearing -- and then reappearing -- on Titan' seas under the form of masses of bubbles. A addition to exsolution would come from ethane freezing at the bottom of sea and also releasing nitrogen. Exsolution also occurs on Earth with carbon dioxide absorption by our planet's oceans, for example
 | A study made during the July 22nd, 2006 flyby shows that lakes may definitely be considered existing at Titan. Radar imaging are showing lakes are variable in size, and features, hence likely in origin, as they likely follow a hemispheric seasons pattern as Titan shares the cycle of seasons of Saturn: lakes expand during winter, as they shrink during summer. Summer solstice at Titan could have floating methane icebergs or other signs of warming shown, such as waves or bubbles at Titan lakes. picture courtesy NASA/JPL/USGS |
The September 23rd flyby was aiming mainly at the upper layers of Titan's atmosphere, with Cassini passing at its lowest over the satellite since the mission's beginning. No data have been released about that, as the flyby revealed too lakes at Titan
 | Lakes of ethane and methane seen at Titan. Lakes are about 12.5-miles (20-km) wide. picture courtesy NASA/JPL |
 | A larger lake (about 190 miles (300-km) in length) was observed at high latitudes around the north pole during the Oct. 9 passage. picture courtesy NASA/JPL |
Both the October 2006 flybys at Titan allowed for more data, the most prominent of which are a 100-mile long, icy-composed mountain range likely due to tectonics -akin to the mid-ocean ridges appearing at Earth. The peaks of the range are coated with different layers of organics. Dunes have been better understood too as they're likely due to sand grains made of organics
 | A view of Titan as seen during both the Oct. 9 and Oct. 25, 2006 flybys. The general view is from the first passage; the inserts from the second. picture courtesy NASA/JPL/University of Arizona |
The December 28th, 2006 flyby of Cassini at Titan allowed for a remarkable discovery, as the probe catched the view of a huge clouds system covering the north pole of Titan, down to a latitude of 62 degrees. Such a cloud system is believed, on one hand, to be part of the the seasonal rythm at Saturn's main moon, with it, moreover, lasting for some 25 years and some lulls of 4-5 years, as, on the other hand, the whole system might shift from the north, to the south pole! The cloud system, on the other hand, might be linked too to the lakes Cassini managed to image previoulsy in the northern regions, as, further, they are thought to be replenished, or to get dry, at intervals. Another view, acquired on Dec. 25, 2006, from a distance, is showing interesting band structure in the stratosphere of Titan, hinting to some superrotation, with the upper atmosphere rotating faster than the planet does. Another banding asymmetry is seen between a lighter North, and a darker South, as this banding might, as far as it is concerned, be better explained by a seasonal effect. Clouds at Titan are made mostly of methane as they are present in the sky more in the winter than in the summer, just like clouds on Earth. A upper level of thick atmospheric clouds is also extant, as the scattered clouds warm the surface to minus 297 degrees Fahrenheit (minus 183 degrees Celsius) only which nonetheless keeps the moon's methane lakes and rivers liquid. Like Earth's stratospheric clouds, methane clouds are extant at Titan and located near the winter pole as they are part of the cap of condensation over Titan's pole. They are due to a global circulation pattern in which warm air in the summer hemisphere wells up from the surface and enters the stratosphere, slowly making its way to the winter pole. There, the air mass sinks back down, cooling as it descends, which allows the stratospheric methane clouds to form. Other stratospheric clouds have been identified on Titan also, including a very thin, diffuse cloud of ethane, a chemical formed after methane breaks down. Delicate clouds made from cyanoacetylene and hydrogen cyanide, which form from reactions of methane byproducts with nitrogen molecules, also have been found there. Instead of stratospheric clouds over Titan's poles forming by condensation, dicyanoacetylene (C4N2) ice might form because of reactions taking place on other kinds of ice particles, researchers found by mid-2016. That would occur through a solid-state chemistry, bringing to some clouds similar to polar stratospheric clouds found at Earth. At Titan, particles have a inner layer of cyanoacetylene (HC3N) ice coated with an outer layer of hydrogen cyanide (HCN) ice. When a photon of light penetrates the outer shell, it can interact with the HC3N, producing C3N and H. C3N then reacts with HCN to yield C4N2 and H
->More About Titan Atmospheric System
Titan's surface temperature changes slowly over the course of the Saturn
system's long seasons -one year at Saturn is lasting 30 terrestrial years which each season thus lasting seven and a half years. As on Earth,
the amount of sunlight received at each latitude varies as the Sun's
illumination moves northward or southward along the Saturnian year. When Cassini arrived at Saturn in 2004, Titan's southern hemisphere was in
late summer as the equinox was reached by 2009 (which also was the season when the Saturnian system had been observed by the Voyager 1 in 1980). When Cassini reached Titan, clouds and rainfall were observed in the southern hemisphere, signaling a southern summer. Climate models predicted the rain would move to the northern hemisphere as the solstice there was to occur in 2017, but the clouds still hadn’t appeared by
2016. The maximum measured temperature on Titan
is around -292 degrees Fahrenheit (-179.6 degrees Celsius, 93.6 Kelvin),
with a minimum temperature at the winter pole only 6 degrees Fahrenheit (3.5
degrees Celsius or Kelvin) colder. This is a much smaller contrast than exists
between Earth's warmest and coldest temperatures. The difference in color between the blue high-altitude haze layer at Titan and the orange main astmophere could be due to blue haze particles likely smaller than the orange's
Titan haze is crude oil without the sulfur and made of tiny
droplets of hydrocarbons with other, more noxious chemicals mixed in. Titan’s dirty orange color comes from a mixture of hydrocarbons (molecules that
contain hydrogen and carbon) and nitrogen-carrying chemicals called nitriles. More gases are adding like the subfamily of hydrocarbons known as aromatics. Titan is the only moon in our
solar system with an atmosphere worthy of a planet. This atmosphere comes
complete with lightning, drizzle and occasionally a big, summer-downpour style
of cloud made of methane or ethane hydrocarbons. Wispy clouds of ice particles, similar to Earth's cirrus clouds, have been also reported with a pearly white appearance dislike the brownish haze, and optically thin and diffuse. Only a small amount of visible light penetrates Titan's haze which is made mostly of nitrogen, as is
Earth's. The heart of the physical processes that rain
hydrocarbons on Titan's surface and form lakes, channels and dunes is the last step of a process beginning in the highest part of Titan's atmosphere. Titan's trademark reddish-brown smog appears to
begin with solar radiation on molecules of nitrogen and methane in the
ionosphere, which creates a soup of negative and positive ions. Collisions among
the organic molecules and the ions help the molecules grow into bigger and more
complex aerosols. Lower down in the atmosphere, these aerosols bump into each
other and coagulate, and at the same time interact with other, neutral
particles. Unlike Earth's atmosphere Titan's has neither oxygen nor water . Instead, it contains small amounts of organic materials, including
members of the hydrocarbon family such as methane, ethane and propane.
More than a half-dozen hydrocarbons have been identified in gas form in Titan's
atmosphere, but many more probably lurk there as propylene was identified, a material of which plastics are made on Earth. The action, in terms of clouds, starts high in the atmosphere,
where some of the methane gets broken up and reforms into ethane and other
hydrocarbons, or combines with nitrogen to make materials called nitriles. Any
of these compounds can probably form clouds if enough accumulates in a
sufficiently cold area. The cloud-forming temperatures occur in the cold depths of Titan's
stratosphere as one thinks that the compounds get moved
downward by a constant stream of gas flowing from the pole in the warmer
hemisphere to the pole in the colder hemisphere. The influx of all this gas steals gas from the warmer hemisphere and gives the
colder hemisphere more clouds. Clouds are found both in the northern, or southern hemisphere as the cycle works function of the seasonal cycle in the Saturnian system. A huge swirling cloud, several
hundred miles across at the south pole and by 186 miles of altitude resulted from the change of season at Titan, with large
amounts of air being heated by sunlight during the northern spring and flowing
towards the southern hemisphere, for example. This fast cooling of the southern atmosphere may be a consequence of the
atmospheric circulation, which has been drawing large masses of gas towards
the south ever since the change of season in 2009, and the reduced exposure to
sunlight on Titan’s southern hemisphere. In Titan’s stratosphere, a global circulation pattern sends a current of warm
gases from the hemisphere where it’s summer to the winter pole. This circulation
reverses direction when the seasons change, leading to a buildup of clouds at
whichever pole is experiencing winter. Saturn endures 4 distinct seasons, like at the Earth, each lasting seven of our years! Such stratospheric clouds might be the equivalent of Earth's few polar stratospheric clouds that appear over Antarctica
and sometimes in the Arctic during winter forming in the
exceptionally cold air that gets trapped in the center of the polar vortex, a
fierce wind that whips around the pole high in the stratosphere. This is the
same region where Earth's ozone hole is found too.
Titan has its own polar vortex and may even have a counterpart to our ozone
hole! The vortex features raised
walls. The degree of similarity is intriguing as scientists stress the different
compositions and chemistries of the stratospheric clouds on Earth versus Titan. During a southern winter at Titan, the gas should start to flow from the North to South with most of the high-altitude ice clouds in the southern
hemisphere. With a seasonal change, astronomers do not know how will the vortex go out as on Earth, it goes out
with a bang and very dramatic. A ice cloud observed over the northern and southern pole during local winter are too linked to that pattern of warm air from one hemisphere rising high in the atmosphere
and transported to the cold pole where the air cools and sinks down
to lower layers of the atmosphere, where it forms such ice clouds, something similar to a Hadley cell at Earth which carries warm, moist air from Earth's tropics to
the cooler middle latitudes. As the spring equinox at Titan occurred in August 2009, it took until early 2012 to check that reversal shortly after the true seasonal change. The cloud's composition is still unknown as they could play at the moon the role of the ozone hole at the Earth. Global atmospheric currents are extant at Titan and change with Saturnian seasons.
Titan's atmosphere is mostly nitrogen with a trace of methane and other, more
complex molecules made of hydrogen and carbon (hydrocarbons). A rich and complex chemistry
originating from methane and nitrogen and evolving into complex molecules,
eventually form Titan's smog. The source of
Titan's methane remains a mystery because methane in the atmosphere is broken
down over relatively short timescales by sunlight. Fragments of methane
molecules then recombine into more complex hydrocarbons in the upper atmosphere,
forming a thick, orange smog that hides the surface from view. Some of the
larger particles eventually rain out on to the surface, where they appear to get
bound together to form the sand.
For the methane on Titan to account for the processes observed, it must
have existed in the atmosphere for at least several hundred million years. However,
researchers estimate Titan's current supply of methane should be broken down by
sunlight within tens of millions of years, so Titan either had a lot more
methane in the past, or it is being replenished somehow. Liquids on Titan consist of hydrocarbons, either as
wet sediments or shallow
marine or lake environments. Renewed weather activity by 2014 could signal the onset of summer
storms that atmospheric models have long predicted above Titan's north pole as a system of clouds developed and
dissipated over a large methane sea for more than two
days. Measurements of cloud motions indicate wind speeds of around 7 to 10 mph
(3 to 4.5 meters per second). As a huge storm swept across the moon's northern latitudes in late 2010, only a few small clouds were observed since. It is unknown however how such clouds are related to the seas. A wispy 'high-altitude south polar cloud' containing a toxic hybrid ice has been spotted at a altitude of about 100 to 130 miles (160 to 210 kilometers) far above the Titan's methane rain clouds of the troposphere, highlighting further the complex chemistry occurring in Titan’s atmosphere. At Titan, different types of gas condense into ice clouds at different altitudes. However, because
each type of cloud forms over a range of altitudes, it is possible for some ices to condense simultaneously and to form a mix. Each season in the Saturnian system is lasting for 7 years
 | A view of Titan's north pole huge cloud system (right) and of Titan's bands in the stratosphere (view in the ultraviolet, left). Titan's stratosphere is the hazy part of Titan's atmosphere which gives it its brownish-orange color. picture courtesy NASA/JPL/Space Science Institute (left) and NASA/JPL/University of Arizona (right) |
 | Methane clouds as seen on Titan. picture courtesy NASA |
 | Other views of the band patterns at Titan (color, left; visible violet, right). Such stratospheric patterns are due to the superrotation of the upper atmosphere at Titan. Further views are showing how this band structure tends to be of a fine kind. picture courtesy NASA/JPL/Space Science Institute |
 | Titan's south polar vortex (North is up). picture courtesy NASA/JPL-Caltech/Space Science Institute |
The February 22nd, 2007 flyby was a near-polar one. It allowed for the further sighting of dark features, which scientists think are lakes. Those ones however are so vast in dimensions that, should they proved to be really areas of liquid, they would be worth being termed 'seas'. One of the regions is about larger that the Lake Superior, in the USA, as another is barely smaller than the Caspian Sea. Other lake-like features have been observed too at Titan's South pole! All such areas, should they be confirmed being liquid would consist of liquid methane and ethane and, in an Earth-like, water-clouds cycle, they would contribute to the methane cycle at Titan
 | General (left) and detailed (right) views of sea-like features near Titan's north pole. picture site 'Amateur Astronomy' from pictures NASA/JPL/Space Science Institute and NASA/JPL |
As Cassini keeps its passages at Titan, a new global digital map has been released by the Cassini team, as, further, about 60 percent of the north polar region has been radar-mapped, showing the lakes in the regions. Scientists are now trying to know whether there are as much hydrocarbon lakes at the south pole than at the north one. Scientists think that those lakes might have been created by volcanism or a type of karstic erosion of the surface. Titan's lakes and seas are not distributed symmetrically by latitude. These reserves of liquid ethane and methane are predominantly found in the northern hemisphere, suggesting that the soil is moister toward the North due to the seasonal pattern of the Saturnian system, with the southern hemisphere of Titan has shorter but more intense summers and is probably drier. Over one season of Titan, northern lakes have then remained the same. Images suggests there were once vast, shallow seas at Titan's south pole as well at 300 by 170 miles (475 by 280 kilometers) across, and perhaps a few hundred feet (meters) deep. Ontario Lacus, the largest current lake in the South, sits inside of the dry shorelines, like a shrunken version of a once-mighty sea, or the Aral Sea at Earth. At several hundred feet (or meters) deep and fed by branching, river-like channels, some of the lakes fill and dry out again during the 30-year seasonal cycle on Saturn and Titan. Titan's lakes are reminiscent of what are known as karstic landforms on Earth. Such cycles similar to Milankovich cycles at Earth, in terms of cyclical orbital changes would cause long-term transfer of liquid hydrocarbons from pole to pole at Titan with a cycle of over 100,000 years. Prebiotic chemistry likely is impacted by that change. Given the wind-sculpted dunes Cassini has seen on Titan, scientists were baffled about why they hadn't yet seen yet wind-driven waves on the lakes and seas as winds stronger than in winter are needed, a speed that might be reached during the moon's spring and summer. A hemisphere's warming could also bring hurricanes, generally, similar to those on Earth
 | A map of Titan's north pole, showing the region filled with variously-sized lakes. picture courtesy NASA/JPL/USGS |
 | That view of Titan North Pole's lakes and seas was captured when Cassini made its last flyby to Titan. As during southern summer cloud activity had been observed over the South Pole, but only a few small clouds appeared during northern summer, which is not explained. picture courtesy NASA |
 | Glimpse of bright sunlight is reflecting off hydrocarbon seas. picture courtesy NASA |
 | Latest global map for Titan. picture courtesy NASA/JPL/Space Science Institute |
Further passages at Titan have allowed to see that large negative ions form in the upper regions of Titan's atmosphere and then move closer to the surface, likely forming the haze of Titan. Such large ions, 10,000 times the mass of hydrogen form, on the other hand, the base for additional formation of more complicated molecules, like polycyclic aromatic hydrocarbons
This passage yielded pictures of Titan's south pole. A discrepancy, generally, was noted that there are fewer methane lakes at Titan's south pole than North. It might that Saturn's orbit eccentricity exposes different parts of Titan to the same seasons than at Saturn, as different amounts of sunlight affect cycles of precipitation and evaporation, leading to the discrepancy and likely moving methane from the South to the North as the explanation shows too that, over very long time scales of tens of thousands of years, Saturn's orbital parameters vary, producing a reverse in the net transport of the material, linked to such large climate cycles at Saturn. Long-standing methane lakes, or puddles, have been found, by June 2012, existing also in the tropics of Titan, among others in the area of Shangri-La, with one with a depth of at least 3 feet (1 meter). A likely supplier of methane is a underground aquifer. Titan's liquid bodies appear to be connected under the surface in something akin to an aquifer system. Hydrocarbons appear to be flowing underneath Titan’s surface, so that nearby lakes communicate with each other and share a common liquid level. Polar lakes could be due to a global circulation with liquid methane in the moon's equatorial region evaporating and carried by wind to the north and south poles, where cooler temperatures cause methane to condense. Only once has rain been detected falling and evaporating in the equatorial regions, and only during the recent expected rainy season. A remarkable longevity has been found to the hydrocarbon lakes on the moon's surface as a model suggests the supply of the hydrocarbon methane at Titan could be coming to an end soon on geological timescale. Lakes on a other hand, evaporate very slowly as methane does. So scientists think the lakes must be dominated by methane's sister hydrocarbon ethane, which evaporates more slowly. The vast majority of liquid in Titan's lakes is thought to be replenished by rainfall from clouds in the atmosphere. Aquifers underground also participate to some lakes as materials called clathrates, forming a reservoir at the bottom of a aquifer, trap methane under the form of propane and ethane at the contact of water ice. Such reservoirs, reaching down to several miles underground, may feed into some specific rivers and lakes different from those made of methane. The lakes are also not getting filled quickly. More than 620,000 square miles (1.6 million square kilometers) of Titan's surface or almost two percent of the total, are covered with methane seas. A study by 2016 is showing how one Titan sea is replenished by fresh methane rainfall, or that the ethane ends up in the undersea crust, or that it somehow flows into a adjacent sea; Ligeia Mare was found at a depth of 525 feet (160 meters). In the atmosphere of Titan, nitrogen and methane react to produce a wide variety of organic materials of which the heaviest fall to the surface either directly or via methane rain clouds, or Titan's rivers. Nitriles and benzene, sink to the sea floor. With is methane lakes, Titan is the only other place in the solar system besides Earth that has stable liquid on its surface. A view is that the current load of methane at Titan may have come from some kind of gigantic outburst from the interior eons ago possibly after a huge impact and eventually could run out in tens of millions of years because it is not replenished, evaporating or turning into ethane and other heavier molecules
 | Fewer methane lakes are seen at the south pole. picture courtesy NASA/JPL |
 | The south pole however adorned with numerous evidence for some flowing events in the past. picture courtesy NASA/JPL |
Further Flybys or Additional Pictures
After the May 28th, 2008 flyby, no flyby is allowed a notice anymore, with any data of interest about Titan provided by a flyby stated below (a date, into brackets, allow for a better time location of the data. Data under the form of text only, as provided below, usually does not have any illustrating picture below)
In terms of Titan's atmosphere, following equinox in August 2009, which saw the formation of a swirling vortex and a build up of exotic gases at unexpectedly high altitudes, the seasons swiftly changed at Titan. When Cassini arrived in the Saturn system in 2004, Titan sported a vortex with a ‘hood’ of enriched gas and dense haze high above its north, winter pole. After equinox in August 2009, spring arrived in the moon’s northern hemisphere while the southern hemisphere headed towards autumn. The change in solar heating was reflected by a rapid reversal in circulation direction in Titan’s single pole-to-pole atmospheric cell, with an upwelling of gases in the summer hemisphere and downwelling in the winter hemisphere. There was actually a increase in temperature at altitudes of 250-310 miles (400–500km) at the south pole despite the declining sunlight, as atmospheric gases that had been lofted to these heights were compressed as they subsequently sank into a newly forming southern vortex as the concentration kept on after. Gas molecules were measured sinking through the atmosphere at a rate of 1–2 millimetres per second. Astronomers have inferred from that that the detached haze layer of the Titan's atmosphere, at 250-310 miles (400-500km), thought to be the ceiling of Titan’s ‘middle atmosphere’ circulation which extends from pole to pole in one giant cell was not, and that complex haze molecules are produced higher up, and drop down to the 250 to 310-mile level with a change in the character of the haze perhaps as individual particles clump together. The height of such that haze layer is varying by some 70 miles due to Titan's seasonal climate cycle. Titan vortex generally, are monstrous clouds of frozen compounds in the moon’s low- to mid-stratosphere, the layer above the troposphere where active weather occurs. The south polar vortex, for example, is hovering at a altitude of about 186 miles (300 kilometers) as a massive ice cloud is lying under. Each Titan season lasts about 7-1/2 Earth's years. Titan south vortex forms like rain clouds at Earth, based upon evaporation as it is methane which evaporates at Titan. Circulation in the atmosphere transports gases from the pole in the warm hemisphere to the pole in the cold hemisphere. At the cold pole, the warm air sinks.The sinking gases –a mixture of smog-like hydrocarbons and nitrogen-bearing chemicals called nitriles– encounter colder and colder temperatures on the way down. Different gases will condense at different temperatures, resulting in a layering of clouds over a range of altitudes
The highest point on Titan is a peak at 10,948 feet (3,337 meters)-high and is found within a trio of mountainous ridges called the Mithrim Montes. All of Titan's highest peaks are about 10,000 feet (3,000 meters) in elevation. Most of Titan's tallest mountains appear to be close to the equator. Weathering processes which erode mountains on the Earth are also extant at Titan with methane rain and rivers as the process proceeds much more slowly due to that there is less energy to power erosive processes in Titan's atmosphere. Mountains could also be due to tectonics as related to Titan's rotation, tidal forces from Saturn or cooling of the crust
 | These are the global wind patterns at Titan as inferred from the dunes' observation. That might be an approximation only as winds from varied directions could combine to yield the dunes orientation (Feb. 2009) A season on Titan, in correlation with the Saturnian system, lasts about seven Earth years. Cloud activity has recently decreased near both of Titan's poles as these regions had been heavily overcast during the late southern summer until 2008, a few months before the equinox. Over the past six years, the scientists found that clouds clustered in three distinct latitude regions of Titan: large clouds at the north pole, patchy clouds at the south pole and a narrow belt around 40 degrees south. Now a seasonal circulation turnover on Titan is taking with the clouds at the south pole completely disappearing just before the equinox and the clouds in the North thinning out. According to astronomers models, cloud activity likely will reverse from one hemisphere to another in the coming decade as southern winter approaches. With spring in the northern hemisphere, bright clouds have been observed around the moon's midsection. picture courtesy NASA/JPL/Space Science Institute |
 | The complex layered hazes as seen around Titan. picture courtesy NASA/JPL/Space Science Institute |
 | A detailed view of the upper atmosphere's layers above Titan's north pole. It's still unknown whether the stuctures seen here are multiple detached hazes or waves in the atmosphere that propagate through stably stratified layers instead (picture taken on Jan. 18, 2006 at a distance of approximately 1.4 million miles -2.2 million km). Pre-biological chemistry could be enhanced at Titan through the entering in the atmosphere of oxygen atoms ejected at Enceladus through the geysers process and captured into fullerenes—hollow, soccer-ball shaped shells made of carbon atoms and then thus making their way down to the surface without further chemical contamination. In the atmosphere, those packages attach to polycyclic aromatic hydrocarbons—chemical compounds also found on Earth in oil, coal and tar deposits, and as the byproducts of burning fossil fuels as cosmic rays further are bombarding the oxygen-stuffed carbon cages and produce more complex organic materials, such as amino acids. Oxygen, generally, in a planetary system could be transported from such originating geysers across the magnetosphere and bringing water to the moons of the system. Titan smoggy atmosphere productive factory of hydrocarbons works from raw methane (a molecule made up of one carbon atom joined to four hydrogen atoms). Methane however is being continuously destroyed by sunlight and converted to more complex molecules and particles, albeit its isotopic carbon-13 methane version lasts some longer. Methane might last 1.6 billion or a mere 10 million years. Both scenarios assume that methane entered the atmosphere in one burst of outgassing, probably from the restructuring of Titan's interior as heavier materials sank towards the center and lighter ones rose toward the surface. Methane clathrates could be a way too to replenish methane availability. Such materials are found in the frigid depths of Earth's oceans, and some scientists think there could be an ocean of liquid water mixed with ammonia (acting as antifreeze) beneath Titan's water-ice crust. If this is so, methane might be released from its clathrate cages during the eruptions of proposed 'cryovolcanoes' of water-ammonia, or more simply could slowly seep out through fractures in the crust. Any large scale replenishment of methane, in any case could not have run longer that one billion years. Astronomers usually think that Titan's methane must have formed long after Titan itself with the last major methane eruption 350 million to 1.35 billion years ago, with the age of the current surface at 200 million to one billion years. The methane age from the atmosphere itself is now estimated at less than one billion years. picture courtesy NASA/JPL/Space Science Institute |
 | A vast ethane cloud was seen by Cassini at different dates just North of 50° latitude (picture A taken on Dec. 13, 2004; B on Aug. 22, 2005; C on Aug. 21, 2005; D on Sept. 7, 2005). picture courtesy NASA/JPLUniversity of Arizona |
 | The likely interior structure of Titan, deduced from gravity field data, seems to be a cool mix of ice studded with rock, though the outermost 300 miles (500 kilometers) appear to be mostly ice. A internal ocean might exist too at the lower part of the external ice layer. Titan may be much less geologically active than some scientists think as studies by 2011 state that Titan's interior may be cool and Titan geology vanished since eons. Ice volcanoes might be thus left unpowered and incapable of replenishing methane in the moon's atmosphere. Relief features at Titan might mostly due to weather, wind erosion or impact craters. Scientists find that Titan is more akin to Jupiter's Callisto, should Callisto have weather as the Galilean moon also has a cold interior. Instead of erosion by weather, scientists theorize the erosion on Callisto was caused by ground ice evaporating away. picture courtesy NASA/JPL |
 | Here is a possible new model of Titan's internal structure with Titan fully differentiated as of March 2012. A core consisting entirely of water-bearing rocks and a subsurface ocean of liquid water are present. The mantle is made of icy layers, one that is a layer of high-pressure ice closer to the core and an outer ice shell on top of the sub-surface ocean. That new model rules out a metallic core inside Titan and agrees with Cassini magnetometer data that suggests a relatively cool and wet rocky interior. As Titan's ice shell was further found varying in thickness around the moon, that suggests the crust is in the process of becoming rigid, leaving few hotspots only to provide for more methane at Titan. Gravity data collected, on a other hand, needs a high density to the ocean, hinting to that the ocean is probably an extremely salty brine of water mixed with dissolved salts likely composed of sulfur, sodium and potassium. picture courtesy A. D. Fortes/UCL/STFC |
 | A further model, by June 2012 has deduced that Titan likely harbors a layer of liquid water under its ice shell from data about how Saturn creates tides approximately 30 feet (10 meters) in height at the surface of the moon, which suggests Titan is not made entirely of solid rocky material. Such gravity measurements provide the best data available about Titan's internal structure. A subterranean ocean layer does not have to be huge or deep as a liquid layer between the external, deformable shell and a solid mantle would enable such observations. Such an ocean could serve also as a deep reservoir for storing methane. Titan's outer ice shell could be rigid as relatively small topographic features on the surface could be associated with large ice 'roots' extending into the underlying ocean as gravity measurements show that each bump in the topography on the surface of Titan is offset by a deeper root that is big enough to overwhelm the gravitational effect of the bump on the surface, acting like a iceberg extending below the ice shell into the ocean beneath. Such a thick rigid ice shell would make very difficult to have ice volcanoes or that convection or plate tectonics could recycle such a ice shell. The ocean might be water/ammonia ocean at 35 to 50 miles (55 to 80 kilometers) below the moon's surface. picture courtesy NASA |
 | The transition to northern spring brings methane rains and clouds to Titan's equatorial latitudes. Showers -or even storms- are darkening the surface of the moon as areas remain wet after methane fell on the surface. Surface temperature, on a other hand, responds more rapidly to seasonal sunlight changes than does the thick atmosphere. The precipitations affect vast expanses of dunes that dominate Titan's equatorial regions as they usually lie under a predominantly arid climate. That might explain how dry channels of Titanian landscapes most likely are cut by seasonal rains and not remains from a earlier, wetter climate. Tropical regions at Earth however feature a steadier climate however with a band of rising motion and rain clouds. On Titan, such extensive bands of clouds may only be prevalent in the tropics near the equinoxes and move to much higher latitudes as the planet approaches the solstices . picture courtesy NASA/JPL/Space Science Institute |
 | illustration of the evolution of a field of bright clouds near Titan's south pole, believed to be composed of methane, over a period of almost five hours. Pixel scale of ranges from 1.4 to 1.2 miles per pixel (2.2 to 2.0 km per pixel). The smallest features that can be discerned in the clouds are roughly 6 miles (10 km) across. picture courtesy NASA/JPL/Space Science Institute |
 | In this natural color view, individual layers of haze can be distinguished in the upper atmosphere of Titan's north pole. It is the rich and complex chemistry originating from methane and nitrogen and evolving into complex molecules, which eventually forms such a smog. The small view is showing Titan's layers near the south pole. High altitude haze layer appears blue whereas the main atmospheric haze is orange, a difference that might be due to particle size of the haze (blue haze likely consists of smaller particles than the orange one). Titan's north polar vortex, or hood, beganto flip from North to South as the southern hemisphere is getting into Saturnian winter, as off December 2011. picture courtesy NASA/JPL-Caltech/Space Science Institute |
 | Titan shifts with the seasons and even throughout the day. Ethane clouds thinned out, for example, and retreated as winter turned to spring in the northern hemisphere in 2012, as it appeared to cover the north pole completely down to about 55 degrees north latitude by late 2006. Open cell convection with air sinking in the center of the cell and rises at the edge, forming clouds at cell edges, might be involved. A daily change -the day at Titan lasts 16 Earth days- also occurs between the chilly mid-90 kelvins at dawn and significantly warmer in the late afternoon by 1.5 kelvins. Also high-altitude haze and a vortex materializing at the south pole of Saturn's moon Titan, akin to the open cellular convection that is often seen over Earth's oceans but at a high altitude instead of low, is a sign of a change of season, with the South passing to winter. That seems to be due to the circulation in the upper atmosphere moving from the illuminated north pole to the cooling south pole, causing downwellings over the south pole. picture courtesy NASA/JPL-Caltech/University of Arizona/CNRS/LPGNantes/SSI |
 | This is a artist's rendition of Titan's change in observed atmospheric effects before, during and after equinox in 2009. During the first years of Cassini's exploration of the Saturnian system, Titan sported a hood of dense gaseous haze (white) in a vortex above its north pole, along with a high-altitude hot spot (red). During this time the north pole was pointed away from the Sun. At equinox, both hemispheres received equal heating from the Sun. Afterwards, the north pole tilted towards the Sun, signaling the arrival of spring, while the southern hemisphere tilted away and moved into autumn. After equinox and until 2011, there was still a significant build up of trace gases over the north pole, even though the vortex and hot spot had almost disappeared. Similar features began developing at the south pole, which are still present today. Such observations are interpreted as a large-scale reversal in the single pole-to-pole atmospheric circulation cell of Titan immediately after equinox, with an upwelling of gases in the summer hemisphere and a corresponding downwelling in the winter hemisphere. picture site 'Amateur Astronomy' based upon a picture ESA/NASA |
 | This view of Titan against Saturn and Dione lying behind is interestingly showing how the haze layers of Titan are transparent and allow to see through. North is up. Scientists further are wondering the presence of important gases in Titan's atmosphere, such as methane and argon-40, since they do not appear to be able to escape from the core. picture courtesy NASA/JPL-Caltech/Space Science Institute |
 | That false-color view of Titan was taken using a infrared image and green and blue spectral filters which provides both a view of the surface and of a feathery band of summer clouds can be seen arcing across high northern latitudes Cette vue en fausses couleurs a été prise via une image infrarouge et deux filtres -vert et bleu- pour donner à la fois cette vue de la surface et d'une zone de nuages d'été s'étendant au-dessus des latitudes nord. picture courtesy NASA/JPL-Caltech/Space Science Institute |
 | Titan's both north polar hood is visible at the top of the image, and a faint blue haze also can be detected above the south pole at the bottom of the view too. Recent Cassini images suggest Titan's north polar vortex, or hood, is beginning to flip from North to South related to a season change. A faint glow, generally, is emanating from Titan from few in altitude in the atmosphere, at about 190 miles (300km). The process is likely due to deep penetrating cosmic rays or light emitted by some kind of chemical reaction deep in the atmosphere. Titan's nitrogen molecules in the atmosphere may also be involved. A extremely weak emission in the high atmosphere above 400 miles (700 km) in altitude is also seen with charged particles from the magnetic bubble around Saturn strip electrons off of atmospheric molecules at Titan. picture courtesy NASA/JPL-Caltech/Space Science Institute |
 | Some process involving heat may be at play on Titan, with similar terrain on Venus, where a dome-shaped region about 20 miles (30km) across has been seen at the summit of a large volcano called Kunapipi Mons. Titan terrain (left) is about 40-miles (70-km) long as it might result from rising magma, and known on Earth as a 'laccolith,' a intrusion formed by magma pushing up from below. picture courtesy NASA/JPL-Caltech/Space Science Institute |
 | The presence of a population of complex hydrocarbons in the upper atmosphere of Saturn's largest moon, Titan, that later evolve into the complex ringed hydrocarbons, or polycyclic aromatic hydrocarbons (PAHs) that give the moon a distinctive orange-brown haze, has been confirmed. Such PAH compounds aggregate into larger particles and they drift downward at the origin of the aerosol particles found in the lowest haze layer that blankets Titan's surface. Such heavy, complex hydrocarbon molecules that make up Titan's smog come to form out of the simpler molecules in the atmosphere. When sunlight or highly energetic particles from Saturn's magnetic bubble hit the layers of Titan's atmosphere above about 600 miles (1,000 kilometers), the nitrogen and methane molecules there are broken up. This results in the formation of massive positive ions and electrons, which trigger a chain of chemical reactions, producing a variety of hydrocarbons. These reactions eventually lead to the production of carbon-based aerosols, large aggregates of atoms and molecules that are found in the lower layers of the haze that enshrouds Titan, well below 300 miles (500 kilometers). The higher densities in Titan's lower atmosphere favor the further growth of these large conglomerates of atoms and molecules. PAHs are very efficient in absorbing ultraviolet radiation from the Sun, redistributing the energy within the molecule and finally emitting it at infrared wavelengths even in the rarefied environment of Titan's upper atmosphere, where the collisions between molecules are not very frequent (altitudes of the diagram in kilometers). picture courtesy ESA/ATG medialab |
 | Thanks to a recently developed technique for handling noise in Cassini's radar images, or 'despeckling,' radar images of Titan's surface may be turned much clearer since early 2015. picture courtesy NASA |
 | These six infrared images of Saturn's moon Titan represent some of the clearest, most seamless-looking global views of the icy moon's surface. They were created using 13 years of data acquired by the Visual and Infrared Mapping Spectrometer (VIMS) instrument on board NASA's Cassini spacecraft. It is the best representation of how the globe of Titan might appear to the casual observer if it weren’t for the moon's hazy atmosphere. It is quite clear from this unique set of images that Titan has a complex surface, sporting myriad geologic features and compositional units. picture courtesy NASA/JPL-Caltech/Stéphane Le Mouélic, University of Nantes, Virginia Pasek, University of Arizona |
 | From a relief and geological map drawn by November 2019, one knows that nearly two-thirds of Titan's surface consists of flat plains and 17 percent is covered in sandy dunes shaped by the wind, mostly around the equator. Around 14 percent of the surface is classified as 'hummocky' -- hilly or mountainous -- and 1.5 percent is 'labyrinth' terrain, with valleys carved by rain and erosion. There are surprisingly few impact craters, suggesting that the moon's surface is fairly young. picture @nature |
